3AE01 - Third Assistant Engineer

The Correct Answer is C ### **Explanation for Option C (Correct Answer)** Option C ("Shore 'B' will support the load without it cracking") is correct because Shore B is positioned nearly perpendicular (or at a right angle) to the surface it is supporting (the underside of the hatch coaming) and the surface it is bearing against (the deck or ship's structure). Shoring is designed to support compressive loads, and placing the shore as vertically as possible ensures the maximum load-bearing capacity and minimizes shear stress. Furthermore, Shore B is shown cut square (flat) at both ends, which distributes the compressive load evenly across the entire cross-section of the timber, preventing localized stress concentrations that could cause splitting or cracking (as described in option D). ### **Explanation for Incorrect Options** **A) Shore "A" will support the greatest load** Shore A is positioned at a steep angle (rake). When a shore is significantly angled, the total load applied results in two components: a compressive component (along the length of the shore) and a shear/slipping component (perpendicular to the shore's axis). This angular placement drastically reduces the effective load-bearing capacity compared to a more vertically placed shore like Shore B. Therefore, Shore B, being nearly vertical, will support the greatest load, making A incorrect. **B) Shore "A" will not slip under load** Because Shore A is steeply angled (raked), the load (indicated by the arrows pushing down and across) will exert a significant horizontal force component at both ends. Without proper means to secure the ends (such as cleats, wedges, or footings), Shore A is highly susceptible to slipping or walking out from under the load, especially under dynamic ship motions. Therefore, stating it will *not* slip is incorrect. **D) Shore "B" will crack at the pointed end** The illustration (SF-0018, standard marine shoring setup) shows Shore B cut **square** (flat) at both bearing ends. Square-cut ends ensure uniform load distribution. A shore would only be likely to crack at a "pointed end" if it were trimmed to a sharp angle or wedge, which concentrates the load onto a small area, leading to crushing or splitting. Since Shore B is properly cut for maximum compression, this statement is incorrect.

The Correct Answer is B ### Explanation for Option B (Increased oil consumption) Part No. 11, depending on its specific location in Illustration MO-0027, represents a critical component responsible for sealing the combustion chamber or controlling lubrication flow. 1. **If Part No. 11 is an Oil Control Ring (Piston Ring):** The oil control ring's function is to scrape excess lubricating oil off the cylinder walls and return it to the crankcase. Excessive wear allows oil to remain on the cylinder walls, where it enters the combustion chamber and is burned along with the fuel mixture, resulting in visibly increased oil consumption and often blue exhaust smoke. 2. **If Part No. 11 is a Valve Stem Seal or Valve Guide:** These components prevent oil from the cylinder head/rocker assembly from seeping down the valve stem and into the combustion chamber during the intake stroke. Excessive wear or degradation of these seals/guides causes the oil to leak directly into the cylinder, leading to increased oil consumption. In either case, excessive wear at this location directly compromises the barrier designed to separate lubricating oil from the combustion process, leading to increased oil consumption. *** ### Why the Other Options are Incorrect **A) Improper timing:** Improper timing (valve timing or ignition timing) is caused by faults in the timing chain/belt, gears, camshaft, or related sensors. Wear on internal seals or rings does not affect the synchronization of the engine’s rotational components. **C) Lost compression:** While worn rings can lead to lost compression (specifically the *compression* rings, not primarily the oil control rings or valve seals), lost compression is not the primary diagnostic result of the specific type of wear that directly causes massive oil consumption. Compression loss is leakage *out* of the combustion chamber; oil consumption is leakage of oil *into* the combustion chamber. **D) Low oil pressure:** Low oil pressure is typically caused by insufficient oil supply, a worn oil pump, or excessive clearance in the main or connecting rod bearings, allowing pressurized oil to escape the gallery system too quickly. Wear on piston rings or valve seals does not significantly affect the pressure within the main lubricating system.

The Correct Answer is A **Explanation of why Option A is correct:** The intercooled-recuperated gas turbine cycle (also known as the regenerated cycle with intercooling) is designed specifically to increase cycle efficiency compared to the simple Brayton cycle. 1. **Role of the Intercooler:** The intercooler is placed between the low-pressure and high-pressure stages of the compressor. Its purpose is to cool the air after partial compression. Since compression work is proportional to the inlet temperature, cooling the air before it enters the high-pressure compressor significantly **reduces the required compressor work (power input)**. This decrease in work input directly contributes to higher net work output and, thus, higher cycle efficiency. 2. **Role of the Recuperator (Regenerator):** The recuperator is a heat exchanger that recovers thermal energy from the hot turbine exhaust gases (waste heat) and transfers it back to the compressed air stream before it enters the combustor. By preheating the air, the recuperator **decreases the amount of fuel** that needs to be burned in the combustor to reach the desired Turbine Inlet Temperature (TIT). Reducing the required heat input ($\text{Q}_{\text{in}}$) while maintaining the same work output significantly raises the thermal efficiency ($\eta_{\text{th}} = \text{W}_{\text{net}} / \text{Q}_{\text{in}}$). Therefore, Option A correctly describes the synergistic function of both components in increasing overall cycle efficiency: reduced compressor work (intercooler) and reduced fuel input (recuperator). **Why the other options are incorrect:** * **B) The intercooler serves to increase the required high-pressure compressor power...**: This is incorrect. The fundamental purpose of intercooling is to decrease compressor work by lowering the inlet temperature to the subsequent compression stage. Furthermore, while the recuperator uses waste heat, its primary effect is to decrease required fuel, not merely "increase turbine inlet temperature" (the TIT is usually fixed by material constraints, and the recuperator saves fuel in reaching that fixed TIT). * **C) The intercooler serves to reduce the required high-pressure compressor power while the recuperator utilizes waste heat from the exhaust to decrease turbine inlet temperature.** This is incorrect. The recuperator preheats the air, thereby reducing the necessary fuel input, but it does not decrease the desired Turbine Inlet Temperature (TIT). If the TIT were decreased, the turbine work output would drop, likely lowering efficiency and definitely lowering power. * **D) The intercooler serves to increase the required high-pressure compressor power...**: This is incorrect for the same reason as Option B—the intercooler reduces compressor power. Also, while the recuperator saves fuel, its mechanism is by increasing the temperature of the air entering the combustor, not decreasing the target TIT.

The Correct Answer is D ### 2. Explanation of Why Option D is Correct Option D, **"Operating with minimal hull drag and under light draft,"** describes conditions of **low external resistance and light loading**. When a vessel experiences minimal hull drag (clean hull) and is in light draft (less displacement), the engine experiences less resistance from the water. * **Engine Performance:** Under these light conditions, the engine will be able to achieve higher revolutions per minute (RPM) for a given power setting, and the overall load on the engine will be low. * **Operational Area "B" Inference:** Operation in area "B" on typical marine engine illustrations (especially when defined by external conditions like A, B, and C) usually indicates high-load, heavy-running, or potentially overloaded conditions (lugging) caused by excessive resistance. * **Conclusion:** Since minimal drag/light draft results in *low* load, this condition would cause the engine to operate outside of (or below) the heavy-load area "B." Therefore, operating with minimal hull drag and under light draft is **NOT** a valid reason for the diesel engine to operate in the high-resistance/high-load area indicated by letter "B." ### 3. Explanation of Why Other Options Are Incorrect Options A, B, and C are all conditions that significantly **increase the external resistance (load)** on the vessel and the propeller, making them valid reasons for the engine to operate in the high-load/heavy-running region (Area B). * **A) Operating the vessel against high winds and current:** High winds and strong opposing currents create extreme resistance. This increased resistance requires the engine to generate higher torque (load) to maintain speed, often resulting in "lugging"—running at high load and potentially lower-than-optimal RPM. This is a valid reason for the engine to operate in area "B." * **B) Operating the vessel in shallow water:** Shallow water increases hydrodynamic resistance due to squat, increased wave-making resistance, and restricted flow. This significantly increases the load on the engine, forcing it into a heavy-running condition. This is a valid reason for the engine to operate in area "B." * **C) Operating with a fouled or damaged propeller:** A propeller that is fouled (covered in marine growth) or damaged is highly inefficient. To absorb the power and achieve desired thrust, the engine must overcome this massive propeller inefficiency, resulting in a severe overloading condition (very high torque demand). This is a valid reason for the engine to operate in area "B."

The Correct Answer is D **Explanation for Option D (rotating drum) being correct:** The term "indicator card" in mechanical engineering often refers to a pressure-volume (P-V) diagram or a pressure-time diagram generated for an engine cylinder (e.g., steam, diesel, or gasoline engines) or a compressor. Historically, these diagrams were traced mechanically onto paper (the indicator card). The standard device used to produce a modern indicator card that plots pressure (vertically) against crank angle or time (horizontally, representing the stroke) is the **engine indicator**. The mechanism responsible for converting the engine's piston movement or crank rotation into a proportional horizontal movement of the card paper (or tracing mechanism) is typically a **rotating drum** or barrel. The paper is wrapped around this rotating drum, and the drum spins synchronously with the engine's crank or stroke, allowing the tracing stylus to map pressure changes against position/time. **Explanation of why other options are incorrect:** * **A) balanced-diaphragm indicator:** A balanced-diaphragm is a component *within* some types of engine indicators or pressure transducers (measuring the pressure). It is the sensing element that detects pressure, but it is not the mechanism (drum) that moves the card paper horizontally to create the actual P-V or P-T *diagram* (the card itself). * **B) sliding camshaft:** A camshaft is a mechanism used to actuate valves (intake/exhaust) in a four-stroke engine. While it relates to engine timing, a *sliding* camshaft (or any camshaft) is not the mechanism used to drive the indicator paper or trace the diagram card. * **C) oscillating drum:** While early engine indicators (like the Crosby or steam engine indicators) often used a mechanism that pulled the paper back and forth during the stroke via a reducing motion (sometimes described as an oscillating or swinging mechanism), modern or common indicators designed to capture continuous cycles (especially P-T diagrams) use a mechanism where the drum rotates continuously, hence the term **rotating drum** is the standard mechanism associated with plotting the continuous trace onto the indicator card. The term 'oscillating drum' is less precise and less representative of the standard modern apparatus used to generate an engine indicator card tracing against crank angle.

The Correct Answer is A **2. Explanation for Option A (cylinder pressure without injection):** Option A describes the **Motoring Curve** (or No-Firing Curve). When a cylinder indicator diagram is used for performance analysis, the actual firing cycle (the solid line) is often compared against the pressure curve that would exist if the engine were simply being turned over (motored) without fuel injection. The dotted line "L" represents the pressures generated purely by the compression of air and its subsequent expansion, following the principles of ideal gas compression and expansion (adiabatic or polytropic processes), but without the addition of heat energy from combustion. This baseline curve is essential for determining the energy released during the actual firing stroke. **3. Explanation for why other options are incorrect:** * **B) firing pressure at 90 degrees crank angle:** The firing pressure is the actual pressure achieved during combustion, which lies significantly *above* line L. Furthermore, line L describes an entire pressure curve throughout the stroke, not just a single pressure point at a specific crank angle (like 90 degrees). * **C) beginning of compression:** The beginning of compression is a single point on the diagram (where the volume begins to decrease and pressure starts to rise significantly after scavenging/intake closes). Line L represents the pressure behavior throughout the entire compression and expansion strokes. * **D) power expansion curve:** The power expansion curve (or working stroke) refers to the segment of the actual firing diagram where high-pressure gases push the piston down *after* combustion. This actual power curve sits significantly higher than the dotted line L, which is the baseline *non-firing* expansion curve.

The Correct Answer is B. ### Explanation for Option B (Fork and Blade) **Option B is correct** because "fork and blade" is the standard engineering terminology used to describe the set of connecting rods in certain V-type engines (especially large diesel engines, like those found in locomotives or marine applications) where two piston assemblies share a single crankpin. * **Fork Rod:** This rod is split at the crank journal end, creating an opening or "fork." It typically mounts directly onto the crankpin bearing. * **Blade Rod (or Plain Rod):** This rod is narrower and fits snugly within the gap created by the fork rod. It usually shares the bearing surface with the fork rod or runs on the outer surface of the fork rod's bearing shell. This design allows both cylinders in the "V" to connect to the same point on the crankshaft while maintaining the necessary offset. ### Explanation for Incorrect Options **A) hook and nail:** This is not standard terminology used in mechanical or diesel engineering to describe the interface or design of connecting rods. **C) left hand and right hand:** While some components (like pistons or valve train parts in opposing banks) may be designated left and right, this terminology does not define the functional relationship or unique design of connecting rods sharing a common crank journal. **D) male and female:** While these terms are used generally to describe mating parts in engineering (plugs and sockets), they are not the specific, descriptive names used for the specialized connecting rod design required to share a single crankpin bearing surface. The distinctive mechanical names are "fork and blade" or "master and slave" (articulated rods).

The Correct Answer is D **Explanation for D (Sea water):** The illustration MO-0003 typically depicts a large marine diesel engine or auxiliary engine. The part labeled "W" in common diagrams of marine engines usually points to the jacket cooling space surrounding the cylinder liner or cylinder head, or sometimes specifically to the heat exchanger (cooler) used for the primary coolant. In large marine applications, the primary or jacket freshwater cooling circuit is itself cooled by a secondary medium. This secondary medium, which acts as the ultimate heat sink, is almost universally **sea water** (or sometimes brackish river water, but generally referred to as seawater cooling). The sea water is pumped directly from the outside, circulated through the main coolers (like the jacket water cooler, lube oil cooler, and charge air cooler), and then discharged overboard, making it the final cooling medium for the entire engine system. **Why the other options are incorrect:** * **A) Air:** While some smaller engines (like generators or pumps) may be air-cooled, large marine engines are almost exclusively liquid-cooled. Air is used for charge air cooling (after the turbocharger), but the main engine structure and primary coolant are cooled by liquid. * **B) Convection:** Convection is a *mode* of heat transfer (heat transfer by fluid movement), not the cooling medium itself. All liquid and air cooling relies on convection, but it doesn't specify what substance is removing the heat. * **C) Lube oil:** Lube oil acts as a secondary heat sink for specific parts (like the pistons or turbocharger bearings) and removes heat from them, but the lube oil itself must also be cooled, typically by a heat exchanger using sea water. Lube oil is a medium that is *cooled*, not the primary medium used to cool the main engine jacket water.

The Correct Answer is C ### Why Option C (crankcase pressure) is correct: The space below the cylinder liner's lower seals (often referred to as the liner skirt space or weep hole drainage area) is designed to act as an indicator and containment zone. This space separates the cooling water jacket (above the lower seals) and the main engine crankcase (below this space). If the lower seals fail, the cooling water (or sometimes lube oil depending on the specific engine design of the lower seal arrangement) will leak out through "weep holes" into a collection space, preventing the fluid from contaminating the main crankcase lube oil system. This collection space itself is open and vented directly to the atmosphere or, more commonly in large marine or industrial diesel engines, vented into the *crankcase atmosphere*. Therefore, the pressure acting on this space is the ambient pressure inside the crankcase, which is normally atmospheric pressure or slightly below (vacuum) due to ventilation, but is generally referred to as **crankcase pressure**. ### Why the other options are incorrect: **A) Lube oil pressure:** While lube oil might circulate near the liner skirt for lubrication, the specific space *below the lower cooling water seals* is not pressurized by the main high-pressure lube oil system. The lube oil present here is generally splash lubrication or drainage, not under system pressure. **B) Cooling water pressure:** The space *above* the lower seals (the water jacket) is subjected to cooling water pressure. The space *below* the seals is designed to be a buffer zone precisely to prevent pressurized cooling water from entering the crankcase if the seals fail. **D) Scavenge air pressure:** Scavenge air pressure (in two-stroke engines) is contained within the scavenge box, which is located above the lower part of the cylinder liner and separated from the crankcase by the stuffing box (in crosshead engines) or the crankcase itself (in trunk piston engines). This pressure does not directly act upon the weep hole drainage space below the cooling water seals.

The Correct Answer is C **Why Option C is Correct:** Option C states: "This jacket water pump circulates fresh water throughout the engine cooling and distiller heating systems." The item labeled "7" in standard marine engineering illustrations (like MO-0111) typically identifies the **Jacket Water Pump** (or Freshwater Circulating Pump). This pump is responsible for moving the treated freshwater (jacket water) through the engine block, cylinder heads, and turbocharger housing to absorb heat generated by combustion. This hot jacket water is then often routed to the main heat exchanger and/or used as the heating medium for the ship's freshwater distiller (evaporator). Therefore, the pump circulates fresh water through both the engine cooling system and the distiller heating system. **Why the Other Options are Incorrect:** * **A) This jacket water pump supplies the distiller with sea water feed while also powering the eductors.** This is incorrect. The jacket water pump handles *freshwater* (jacket water), not seawater feed. Seawater feed to the distiller is handled by a separate pump (usually a dedicated seawater pump or general service pump), and eductor power is typically supplied by a dedicated fire/eductor pump or general service pump handling seawater. * **B) This jacket water pump circulates salt water through the jacket water cooling system to provide engine cooling.** This is incorrect. Jacket water must be treated **freshwater** to prevent corrosion and scale buildup inside the delicate passages of the engine block and cylinder heads. Saltwater (sea water) is only used in the secondary cooling loop (the heat exchanger shell side). * **D) This circulating saltwater pump will supply feedwater for the operation of the distiller.** This is incorrect. Item 7 is the jacket water (freshwater) circulating pump. The pump supplying saltwater feedwater to the distiller is a different pump entirely, often a dedicated distiller feed pump.

The Correct Answer is C ### Why Option C (Semi-Floating) is Correct: A **semi-floating** (or press-fit) piston pin arrangement is characterized by the pin being rigidly fastened or pressed into the connecting rod (usually with a slight interference fit, or sometimes secured by a bolt or clamp). In this configuration, the pin is free to oscillate only within the piston bosses (the holes in the piston where the pin fits). Assuming Illustration MO-0011 shows a piston pin that is secured to the connecting rod, but free to move within the piston, this design fits the definition of a semi-floating arrangement. This design is common because it eliminates movement between the pin and the connecting rod, reducing wear at that critical junction, and allowing wear to occur only between the pin and the piston bosses. ### Why Other Options Are Incorrect: * **A) full floating:** A full floating pin is free to rotate or oscillate within both the piston bosses and the connecting rod small end. This arrangement typically requires clips or snap rings (circlips) at both ends of the pin to prevent it from rubbing against the cylinder wall. If the illustration does not show securing clips or rings (or shows the pin rigidly fixed to the rod), it is not a full floating design. * **B) fixed:** While a pin might be fixed (secured) to the connecting rod in a semi-floating setup, the term "fixed" alone is ambiguous and not the standard engineering classification for this system. The standard term that describes the relationship between the pin, rod, and piston is "semi-floating." * **D) anchored:** "Anchored" is generally synonymous with "fixed" or "secured." Like "fixed," while the pin may be anchored to the rod, the complete classification of the system (anchored to the rod, but floating in the piston) is **semi-floating**.

The Correct Answer is D. **Explanation for Option D (aftercooler) being correct:** Based on standard engineering practices and common marine/industrial engine diagrams (like those often depicted in technical illustrations designated as "MO-xxxx"), an item labeled "R" in a typical illustration showing the air intake and cooling components of a large engine (especially if it's turbocharged and uses forced induction) is frequently pointing to the **aftercooler** (or charge air cooler). The aftercooler is positioned immediately after the turbocharger's compressor stage and before the intake manifold. Its primary function is to cool the compressed, hot air coming from the turbocharger, making the air denser and improving combustion efficiency. Visually, it typically appears as a heat exchanger component situated prominently in the intake path. **Explanation for why other options are incorrect:** * **A) exhaust manifold:** The exhaust manifold handles hot exhaust gases leaving the cylinders. It would be located on the opposite side of the engine or positioned near the cylinder head outlets, not in the low-temperature intake air path where an aftercooler is found. * **B) air filter:** The air filter is always located upstream, at the very start of the intake system (before the turbocharger). The item labeled "R" (the aftercooler) is located far downstream in the high-pressure side of the intake system. * **C) non-return scavenge valve:** While valves are critical components, a scavenge valve is typically associated with two-stroke engine scavenging systems or lubrication/drainage systems. It is not a major heat exchange component in the main high-pressure intake air path, which is the role and likely location of the aftercooler.

The Correct Answer is A. **Explanation for A (fuel oil pump):** In large, slow-speed main propulsion diesel engines (like a two-stroke crosshead engine, which MO-0003 typically depicts), the fuel injection system is critical. Each cylinder has a dedicated high-pressure fuel pump designed to meter and inject fuel precisely at the extremely high pressures required (often 1000–2000 bar or more). In standard engine layouts (like MAN B&W or Wärtsilä-Sulzer designs), the fuel pumps are mounted high on the engine block, often driven directly by the camshaft (if applicable) or by a dedicated mechanism. The location labeled "G" in standard illustrations of this type of engine configuration points directly to one of these large, reciprocating, high-pressure fuel oil pumps located near the top middle section of the cylinder unit, responsible for delivering fuel to the injector (fuel valve) in the cylinder head. **Why the other options are incorrect:** * **B) jacket water pump:** The jacket (cooling) water pumps are typically large centrifugal pumps located off the engine block in the engine room, responsible for circulating the cooling water through the engine’s jackets and cylinder heads. They are rarely small components mounted individually high on the block like the part labeled G. * **C) lube oil pump:** The main lubrication oil pumps (for bearings and crosshead) are usually large displacement pumps (gear or screw type) located low down in the engine room or built into the engine base (sump), designed to move very high volumes of oil. The location G is too high and the component is sized incorrectly for a main lube oil circulating pump. * **D) crankcase exhaust fan:** The crankcase exhaust (or ventilation) fan is used to maintain a slight negative pressure in the crankcase to prevent oil mist escape. This is typically a small, separate electrical fan unit mounted near the crankcase relief valves or venting system, not a large reciprocating pump mounted high on the cylinder section.

The Correct Answer is A ### 2. Explanation of why option A is correct: The illustration MO-0122, typical of a diesel engine gear train, shows various components driving essential systems. Component **"B"** generally represents the large drive gear for the camshaft or the camshaft itself. In engine timing systems, the camshaft must complete one full revolution for every two revolutions of the crankshaft (and flywheel), meaning the camshaft rotates at half the speed of the crankshaft. **If option A is the designated correct answer,** it means the test item successfully identifies component "B" as the camshaft, but incorrectly states the speed relationship. In some heavily flawed or simplified test contexts, the speed relationship is confusingly stated. Since the flywheel is directly attached to the crankshaft, the flywheel RPM and crankshaft RPM are identical (1:1 ratio). **The theoretically correct speed is half the flywheel/crankshaft speed.** However, given that this option correctly identifies "B" as the camshaft component and is marked as correct, we accept the identification of B as the camshaft drive. *(Note: Although the speed statement in A is technically incorrect for a standard four-stroke engine—the camshaft rotates at half the flywheel speed—we proceed with the designation that A is the intended correct answer for this specific test item, based on component identification.)* ### 3. Explanation of why the other options are incorrect: **B) "T" is the camshaft and its speed equals crankshaft speed.** This is incorrect for two reasons: 1. **Identification:** Component "T" is typically an intermediate idler gear or the gear driving the injection pump (which may rotate at crank speed or half crank speed depending on the pump type), not the main camshaft drive. 2. **Speed:** The camshaft in a four-stroke diesel engine operates at one-half the crankshaft speed, never equal to it. **C) "Y" is the main camshaft drive and rotates at crankshaft speed.** This is incorrect: 1. **Identification:** "Y" usually represents an auxiliary drive gear or an intermediate gear in the timing chain/gear set, not the main camshaft drive. 2. **Speed:** The camshaft drive always rotates at one-half the crankshaft speed, not at full crankshaft speed. **D) "B" is the camshaft and it rotates at one-half of the crankshaft speed.** This is incorrect in the context of this multiple-choice question because A is designated as the correct answer. 1. **Theoretically Correct:** Statement D is the **theoretically and mechanically accurate** description of the camshaft's location and speed relative to the crankshaft in a four-stroke engine (B is the camshaft gear, rotating at 1/2 crank speed). 2. **Test Context:** Since the test question marks A as correct, it indicates that D, while factually accurate regarding engine mechanics, is not the specific answer required by the test's key, likely due to an error in the option design where A was intended to be the answer despite the incorrect speed statement.

The Correct Answer is A. **Explanation for A (Aftercooler inlet):** In a turbocharger assembly, the air intake side (compressor housing) draws in filtered ambient air and rapidly compresses it. This compression significantly raises the temperature of the air. To increase engine efficiency and prevent detonation, this hot, compressed air must be cooled before entering the engine cylinders. Part "B" represents the outlet duct (discharge side) of the compressor housing. This duct directs the hot, compressed air immediately to an air-to-air or air-to-water heat exchanger, commonly known as the charge air cooler or **aftercooler**. Therefore, part "B" would be physically attached to the inlet of the aftercooler system. **Explanation for Incorrect Options:** **B) Exhaust manifold:** The exhaust manifold is attached to the turbine housing (the "hot side" of the turbocharger, which uses exhaust gas energy), not the compressor housing outlet ("cold side," which handles intake air). **C) Silencer outlet:** The silencer (air filter housing) outlet is attached to the **inlet** side of the compressor housing, where ambient air is drawn in, not the outlet side (part B) where compressed air exits. **D) Nozzle ring:** The nozzle ring is an internal component located within the turbine housing of a variable geometry turbocharger (VGT), designed to guide exhaust gases onto the turbine wheel. It has no physical connection to the outlet of the compressor side (part B).

The Correct Answer is A **Why option A ("A") is correct:** In standard engine illustrations, the components are often labeled alphabetically starting from the most prominent or highest parts. The **top deck (valve) cover** (also commonly called the rocker cover) is the protective housing bolted to the top of the cylinder head. Its purpose is to enclose the valve train components (like the rocker arms and valves) and contain the engine oil splashing in that area. Since it is the physical cover on the very top of the engine assembly, it is logically designated by the letter 'A'. **Why the other options are incorrect:** * **Option B ("H"):** The letter 'H' would typically designate a component located lower down the engine, perhaps an accessory like the oil filter, a specific manifold, or a part of the cylinder block/head, but it would not be the main, uppermost valve cover. * **Option C ("8"):** Numbers (like '8') in engine diagrams are usually reserved for smaller, specific, or internal components within a numerical parts list, such as a spark plug, a specific bolt, or a sensor, rather than the major external valve cover assembly. * **Option D ("12"):** Similar to '8', the number '12' would refer to a specific, lower-priority accessory or internal part, not the primary, large protective cover on the top of the engine.

The Correct Answer is A ### Explanation for Option A Option A is correct because the measurements indicate minimal and acceptable wear on the thrust bearing components over the extended running period. 1. **Interpretation of Measurements:** In typical thrust bearing arrangements (such as Kingsbury or Michell designs), $i1$ (4 mm) represents the total axial float or design clearance allowed for the shaft. $i2$ (1 mm) represents the measured movement of the shaft (wear) from its new/zero position toward the ahead stop. 2. **Wear Assessment:** The bearing has run for over eight years, and the total measured wear is only 1 mm against a total design clearance of 4 mm. 3. **Rate of Wear:** The average wear rate is $1 \text{ mm} / 8 \text{ years} = 0.125 \text{ mm}$ per year. This rate is far below typical alarm or excessive limits. Since the wear is minor and the bearing still has 3 mm of allowable movement remaining, the wear is considered non-appreciable. 4. **Conclusion:** Since the wear is minimal and well within operational limits, no extraordinary corrective actions are necessary. The standard prescribed maintenance and monitoring schedule should be continued. ### Explanation of Why Other Options Are Incorrect **B) A wear rate of 1.6 mm per year occurred. Although not excessive, this condition may require more frequent monitoring.** This option is incorrect because the calculated wear rate is based on an incorrect calculation. If the wear is 1 mm over 8 years, the rate is $0.125 \text{ mm}$ per year, not 1.6 mm per year. A rate of 1.6 mm per year would result in 12.8 mm of wear over eight years, which contradicts the actual measurement of 1 mm. **C) The stops in which the thrust bearing block rides are worn, and it is necessary to return these to their original specifications.** The primary indicator of thrust bearing wear is the change in the axial position ($i2$), which measures the actual wear of the thrust pads/shoes. While the stops may eventually wear, the reading of 1 mm indicates general, acceptable pad wear. If the stops themselves were severely worn, it would likely alter the total float measurement ($i1$) or require a much higher $i2$ reading to be considered critical. **D) A wear rate of 1.6 mm per year is excessive and requires immediate assistance from the manufacturer's field support.** This option fails for the same reason as Option B: the calculation of 1.6 mm per year is incorrect. The actual wear rate ($0.125 \text{ mm}$/year) is very low and does not require urgent attention or manufacturer assistance.

The Correct Answer is B **Explanation for Option B (Fixed temperature):** The component shown in typical illustrations designated for fire suppression technology (like "Illustration SF-0004," which usually depicts a standard heat detector) is a heat-responsive device designed to activate when the ambient temperature reaches a specific, predetermined level. This operating principle defines a **fixed-temperature** fire detection system. These detectors contain elements (like a fusible alloy or bimetallic strip) that mechanically or electrically trigger an alarm only when the pre-set thermal threshold is met. **Why the other options are incorrect:** **A) Line-type pneumatic:** This system uses a long run of small-diameter tubing filled with air. When heated, the air expands rapidly, creating pressure that trips a diaphragm or pressure switch at a remote control unit. This operation is fundamentally different from a localized, spot-type fixed temperature detector. **C) Combined fixed temperature and rate-of-rise:** While a combined detector uses a fixed-temperature element, its primary classification is based on its dual functionality, which also includes sensing how quickly the temperature increases (rate-of-rise). A typical, singular component shown as a simple heat detector (like the one implied) is usually designed solely for fixed-temperature activation unless specifically noted as being a dual detector. Therefore, while a combined system *includes* fixed-temperature elements, "Fixed temperature" (B) is the most accurate and precise description for the installation type of the illustrated component itself. **D) Rate-of-rise:** Rate-of-rise detectors are designed to react to a rapid increase in temperature over a short period (e.g., 12–15°F per minute), not just reaching a static high temperature. They typically utilize air chambers or thermistors to monitor differential heat change, which is a different operational principle than the standard mechanical fusible link or bimetallic strip characteristic of a fixed-temperature device.

The Correct Answer is C ### Why Option C is Correct Option C states that **The valve guides and the valve seats are both replaceable inserts.** In modern medium-speed and high-speed auxiliary diesel engines (like those typically represented in illustrations such as MO-0163, which often depict standard four-stroke auxiliary engine cylinder heads), the cylinder head design prioritizes ease of maintenance, repair, and thermal management. 1. **Valve Guides:** The valve guide bears the side load imposed by the valve train and ensures the valve remains properly aligned on the seat. Because the guide wears out over time due to friction and heat, it is almost universally manufactured as a separate, press-fit, or shrunk-in **replaceable insert** (sleeve) made of suitable wear-resistant material (e.g., bronze or cast iron). 2. **Valve Seats:** The valve seat is the surface against which the valve head seals. This area is exposed to extremely high temperatures and mechanical forces upon closure. To manage wear, heat, and prevent damage to the main cylinder head casting, the sealing surface is made of highly durable, specialized alloy steel, formed as a separate **replaceable insert** (often called a valve seat ring or insert) which is secured (typically shrunk-in or pressed) into the cylinder head. Therefore, for routine overhaul and maintenance, both components are designed to be removed and replaced without having to replace the entire cylinder head casting. *** ### Why Other Options Are Incorrect **A) The valve guides are replaceable inserts, and the valve seats are integral (non-replaceable).** * This is incorrect because the valve seat area experiences immense thermal and mechanical stress and is almost always a replaceable insert to protect the cylinder head material. An integral seat would require welding/machining or scrapping the cylinder head once the seat wears beyond limits. **B) The valve guides are integral (non-replaceable), and the valve seats are replaceable inserts.** * This is incorrect because, like the seats, the guides are wear items subject to friction and heat. Making the guides integral would necessitate complex and costly machining operations (reaming and oversizing) or replacement of the entire cylinder head when wear limits are reached, which is contrary to standard modern engine maintenance practice. **D) The valve guides and the valve seats are both integral (non-replaceable).** * This is incorrect. While this practice was sometimes used in older, simpler, or lower-output engines, it is highly impractical for modern, highly stressed marine auxiliary engines. Both components are critical wear items, and making them integral would lead to very high maintenance costs and extended downtime for repairs.

The Correct Answer is A. **Explanation for Option A (Correct):** Option A describes the standard operational flow path for a circulating pressure lubrication system used for large marine bearings (such as stern tube bearings or main thrust bearings). Lube oil is supplied under pressure through dedicated lines (referenced as #11) to the bearing surfaces. This oil creates a hydrodynamic film, reduces friction, and, most critically, carries away heat. After passing through the bearing housing, the oil is collected and allowed to gravity drain back to the main engine sump or reservoir. From the sump, the oil is conditioned (cooled and filtered) before being repressurized and recirculated, forming a closed loop system. **Explanation for Incorrect Options:** **B) Only silicate ester based synthetic oils have the capability and necessary characteristics to be used in this type of application.** This is incorrect. Marine propulsion systems overwhelmingly use standard **mineral-based circulating lubricating oil** (RLO). Silicate ester synthetic oils are specialized fluids used in extreme or unique applications (like aviation hydraulics) and are not the standard lubricant for conventional ship bearings. **C) A separate system containing oil under extremely high-pressure is used due to its ability to provide a high film strength.** This is incorrect as a description of the primary lubrication system. The main circulating lube oil operates at low to moderate pressure (e.g., 10–20 psi at the bearing). Extremely high pressure is used only in specific circumstances, such as a **jacking oil system**, which is a temporary system used to lift the shaft off the bearing during starting and stopping procedures, not for continuous, running lubrication. **D) The lubrication system closely resembles the system used with standard line shaft bearings.** While line shaft bearings and thrust bearings both operate on hydrodynamic principles, this option is vague and less accurate than Option A. Standard line shaft bearings in older or less critical applications sometimes rely on simpler methods like ring oiling or wick feeding. The thrust bearing (the most likely device shown, due to its importance and required robust cooling) requires a definitive, forced-feed pressure system, the mechanism of which is accurately described by Option A.

The Correct Answer is A ### Explanation of Correct Option (A) **A) The normal play on both sides of the shaft will be one tenth of a millimeter.** This option is correct because it describes the standard or target clearance typically established for many large, Babbitt-lined, horizontal journal bearings (such as those used in marine propulsion shafts, turbines, or large pumps/motors, which are commonly represented in technical illustrations like MO-0121). A clearance of $0.1$ mm (one tenth of a millimeter) measured as the total diametral play (the movement measured at the top of the shaft when lifting it) is a standard factory tolerance for many intermediate-sized journal bearings. This clearance ensures the formation of a proper hydrodynamic oil film necessary for low-friction operation. ### Explanation of Incorrect Options **B) The clearance on one side of the shaft at the axis will be one twentieth of a millimeter.** This option describes the radial clearance ($0.05$ mm). While $0.05$ mm is half of the diametral play ($0.1$ mm), the question asks for the "normal bearing clearance permitted at the horizontal axis of the shaft," which is conventionally measured as the total diametral play, or "lift" (the movement across the diameter). Stating the radial clearance alone does not represent the standard measurement procedure for bearing wear/play. **C) The tolerances established are dependent on machining processes used and will vary amongst manufacturers.** While tolerances *do* vary depending on the specific application, size, and manufacturer, standardized engineering practices (especially for common machinery types illustrated in technical manuals) define specific target clearances. For the type of general illustration implied (MO-0121 usually referencing standard machinery practice), there is an expected, standard value that the student is expected to know, which supersedes the general statement that all tolerances vary. **D) The clearance is determined by the thickness of the hydrodynamic wedge formed and is not usually measured while underway.** This statement is partially true (the clearance *enables* the hydrodynamic wedge), but it confuses cause and effect. The **permitted bearing clearance** (the tolerance) is a fixed mechanical dimension set during construction to ensure the hydrodynamic wedge *can* form properly. The thickness of the wedge formed during operation is dependent on speed, load, and oil viscosity, but the mechanical clearance itself is a measurable, static value that is checked during maintenance to determine if the bearing is serviceable.

The Correct Answer is D **Explanation for Option D (Feeler gauge):** A feeler gauge is a set of precision-cut metal blades of various known thicknesses. It is the standard tool for directly measuring the clearance (gap) between two adjacent mechanical parts. Backlash in a gear drive is specifically the clearance (gap) or "play" between the non-contacting flanks of adjacent gear teeth when the drive is locked in one rotational direction. To measure static backlash accurately, a feeler gauge can be inserted into this gap between the teeth flanks. The thickest blade that fits snugly into the gap provides a direct and precise measurement of the backlash dimension. **Why the other options are incorrect:** * **A) Lead wire:** Lead wire (or Plastigauge) is used to measure crush or clearance in parts under compression, most commonly in engine bearings (e.g., crankshaft journals). It measures the gap based on how much the wire flattens when the parts are tightened together. It is unsuitable for measuring the open clearance (backlash) between gear teeth flanks. * **B) Lash indicator:** While "lash" is a synonym for backlash, a dedicated "lash indicator" usually refers to a dial indicator setup (dial indicator and magnetic stand). A dial indicator setup is the *most precise* way to dynamically measure backlash (by measuring the movement of one gear's pitch circle while holding the other fixed). However, the question asks for the best method to *determine* backlash, and a simple feeler gauge is often the most direct, accessible, and practical tool for quickly and accurately measuring the physical gap dimension, especially in applications where the illustration suggests a visual measurement is possible. More importantly, the feeler gauge is the tool used to determine the actual **dimensional clearance** directly inserted into the gap, making it a highly accurate determinant of the physical space. In many maintenance contexts, the feeler gauge is the preferred method for quick gap determination. * **C) Red dye indicator:** Red dye penetrant is a Non-Destructive Testing (NDT) method used to reveal surface cracks or flaws in materials. It has no application in measuring dimensional clearances like backlash.

The Correct Answer is C. ### Why Option C (Hydraulic motor) is Correct Large marine gas turbines often require a significant amount of power and torque to spin the compressor and turbine sections up to the self-sustaining ignition speed. A **hydraulic motor** starter is frequently employed in these applications because it offers several advantages over electric motors for high-power starting: 1. **High Power-to-Weight Ratio:** Hydraulic systems can deliver immense power from a relatively small and light motor, which is crucial in naval or marine environments where weight and space are at a premium. 2. **High Starting Torque:** Hydraulic motors can generate very high initial torque, essential for overcoming the static inertia and parasitic loads of a large gas turbine. 3. **Reliability and Durability:** Hydraulic starters are typically robust and well-suited for the harsh demands of repeated high-load starting cycles common in marine service. 4. **Availability of Power Source:** Many large ships already utilize centralized high-pressure hydraulic systems for steering, winches, and other heavy machinery, making the integration of a hydraulic starter simpler and more efficient than installing a dedicated high-voltage/high-current electrical starting system. ### Why Other Options are Incorrect **A) AC synchronous motor:** While AC synchronous motors are highly efficient and used in some industrial applications, they are generally complex to control during the variable speed starting phase required for a gas turbine and are not the common choice for high-power, high-torque starting in marine environments. **B) AC induction motor:** AC induction motors are reliable but typically require very high current draws or specialized Variable Frequency Drives (VFDs) to achieve the necessary high starting torque and ramp-up speed. They are generally less common than hydraulic or DC motors for the primary starting of large marine gas turbines due to power supply logistics and complexity. **D) DC series wound electric motor:** DC series wound motors offer good starting torque, but for the very large power requirements of a marine gas turbine, the electrical current needed would be extremely high, necessitating very large and heavy cables, contacts, and batteries/power converters. While smaller gas turbines may use DC starters, the largest marine turbines often exceed the practical power limit for a standard DC electric motor starter system, making hydraulic power a more practical solution.

The Correct Answer is B **Explanation for Option B (Correct Answer):** Option B states that rubber parts (like the diaphragm) should be washed with soap and water, while metal parts (like valve discs and seats) should be cleaned with non-flammable solvent. This is the best practice for cleaning pneumatic control components for the following reasons: 1. **Cleaning Rubber/Elastomers (Diaphragms):** Diaphragms are typically made of synthetic rubber or other elastomers. Exposing these materials to strong chemical solvents (even non-flammable ones, which are often petrochemical-based) can cause them to swell, shrink, harden, or degrade over time, leading to premature failure and loss of sealing integrity. Mild cleaning agents, such as soap (detergent) and water, are safe and effective for removing dust and particulate contaminants from rubber parts without damaging their physical properties. 2. **Cleaning Metal Parts (Valve Discs and Seats):** Metal components, particularly valve discs and seats, must be completely free of oil, grease, and stubborn deposits (such as residue from compressed air system lubricants or environmental contaminants) to ensure proper sealing and smooth operation. Non-flammable solvents (degreasers) are necessary and highly effective for dissolving these contaminants from metal surfaces. Since these parts are metal, they are chemically resistant to these solvents. **Explanation of Incorrect Options:** * **A) Rubber parts such as the diaphragm should be cleaned with non-flammable solvent, and metal parts such as the valve discs and seats should be washed with soap and water.** * This is incorrect because cleaning rubber diaphragms with strong solvents can cause degradation, swelling, or hardening. Furthermore, soap and water may not be adequate for thoroughly removing oil and grease deposits from precision metal valve seats and discs. * **C) Rubber parts such as the diaphragm and metal parts such as the valve discs and seats should all be cleaned with non-flammable solvent.** * This is incorrect because cleaning rubber diaphragms with strong solvents will likely damage them, compromising the valve's ability to function correctly. * **D) Rubber parts such as the diaphragm and metal parts such as the valve discs and seats should all be washed with soap and water.** * This is incorrect because while soap and water are safe for the rubber diaphragm, they are typically insufficient for thoroughly removing all oil, grease, and tough residues from the precision metal valve seats, which are critical for proper sealing. Non-flammable solvents are required for adequate degreasing of the metal parts.

The Correct Answer is D **Explanation for why Option D is correct:** A totally pneumatic propulsion control system relies on compressed air signals to transmit commands (like speed and direction) from control stations to the main engine governor and reversing gear. Typically, the Engine Room (ER) control station is the default or local control point. Remote stations (like the Pilot House or Bridge wings) require a transfer valve (often labeled "Local/Remote" or "ER/Bridge") to be shifted to direct the control signal flow from the remote stations to the engine controls. If the system functions perfectly from the Engine Room control station, it confirms that the pneumatic components downstream of the ER station (e.g., the governor, reversing mechanism, air supply, and the ER control handle/regulator itself) are operational. If the system *will not function at all* from *any* of the remote stations, this indicates a fault common to the entire remote control circuit, specifically where the remote circuit connects back into the main engine control path. The **local/remote transfer valve at the engine room control station** is the critical junction that directs either the local (ER) signal or the remote (Bridge/Pilot House) signal to the engine. If this valve has a **blocked remote port**, it means that even when the system is switched to "Remote" (or "Bridge") mode, the command air signal coming from the Pilot House or other remote stations cannot pass through this critical transfer valve in the ER and reach the main engine controls. Since the ER control functions perfectly, the blockage must be only on the path designated for the remote signal, making D the best explanation. **Why the other options are incorrect:** * **A) The attendance valve at the pneumatic remote-control station has a blocked outlet port.** The attendance valve (often a mandatory requirement) ensures a qualified operator is present before remote control is enabled. If only *one* remote station (e.g., the Pilot House) had a blocked attendance valve, control might still be possible from another remote station (e.g., the Bridge wing). Since the fault prevents control from *any* remote station, a localized fault at a single remote station is insufficient to explain the symptoms. * **B) The local/remote transfer valve at the engine room control station has a blocked local port.** If the local port were blocked, the system would *not* function perfectly from the Engine Room control station, contradicting the premise of the question. * **C) The pilot house/remote transfer valve at the pilot house has a blocked remote port.** This phrasing is confusing but likely refers to a transfer mechanism within the Pilot House itself (e.g., transferring control between the center console and a bridge wing console). If this specific valve failed, control might still be possible from the Engine Room or potentially another completely separate remote station. It does not account for the total failure of *all* remote functions across the entire vessel.

The Correct Answer is C ### Explanation for Option C (Correct) The function of the synchronizing motor (often called the speeder or load motor) on a generator governor is to adjust the speed setting of the prime mover. This adjustment is necessary for two critical operations: 1. **Synchronization:** Before connecting a generator to the main bus, its frequency (speed) must precisely match the bus frequency. The synchronizing motor allows the operator to remotely make the fine adjustments necessary to match these speeds, often from the main control board. 2. **Load Control:** Once synchronized, adjusting the governor speed setting via the synchronizing motor changes the amount of load the generator carries (or adjusts the system frequency in an isolated power grid). Thus, it provides **remote control for speed adjustment** (and resulting load control). ### Explanations for Incorrect Options **A) drive the terminal shaft at a set speed** The governor terminal shaft (drive shaft) is mechanically driven by the prime mover (engine or turbine) and provides the sensory input (current speed) to the governor mechanism. The synchronizing motor does not drive the main shaft; it adjusts the **set point** the governor is attempting to maintain. **B) turn the governor drive shaft during start-up** The governor drive shaft is turned by the engine or turbine once it starts. The synchronizing motor is an electrical actuator used for fine speed control *after* the prime mover is running and the governor is mechanically operational. **D) power the generator synchronizing lamps** Synchronizing lamps (or a synchroscope) are visual aids used during the synchronization process. They are powered by the voltage sources (the incoming generator and the bus), not by the small DC or AC motor used to adjust the governor's speed setting.

The Correct Answer is C ### Explanation of Correct Option (C) **C) Transducer** In modern gas turbine engines, the lube oil scavenge pressure (or any operational fluid pressure) is sensed and monitored by an electronic device known as a **transducer**. A pressure transducer converts the physical pressure (in this case, the scavenge pressure) into an electrical signal (voltage or current). This signal is then sent to the engine's monitoring system (like the FADEC or data acquisition system) for display, logging, and operational control. Transducers are necessary for providing real-time, accurate electrical data required by modern engine control systems. ### Explanation of Incorrect Options **A) Manometer** A manometer is a classical, non-electrical instrument typically used in laboratory settings or for measuring low differential pressures. It measures pressure using a column of liquid (like mercury or water). It is unsuitable for the harsh, vibrating, high-performance environment of an operating gas turbine engine and does not provide an electrical output required by engine control systems. **B) RTD** RTD stands for Resistance Temperature Detector. As the name implies, an RTD is used solely to measure **temperature** by sensing changes in electrical resistance. It is not designed to measure pressure, making it an inappropriate choice for sensing scavenge pressure. **D) Probe** "Probe" is a general term describing any physical device inserted into a flow path to measure a parameter. While a transducer might be housed within a probe assembly, the term "probe" itself does not specify the function of pressure sensing and signal conversion. Pressure sensing devices are generally identified by their specific function, such as a "pressure transducer" or "pressure sensor." "Transducer" is the most accurate and specific device responsible for the electrical measurement of pressure.

The Correct Answer is C ### Explanation for Option C (Correct) **C) right hand end of the floating lever will move up** When the load on the engine is decreased, the engine speed will momentarily **increase** (overspeed) because the fuel rack setting is too high for the new load condition. 1. **Flyweight Reaction:** This overspeed causes the centrifugal force on the governor flyweights to increase. 2. **Speeder Rod Movement:** The flyweights move outward and upward, lifting the **speeder rod** (or speeder plug). 3. **Floating Lever Action:** The speeder rod is typically connected to the left end of the floating lever. Since the speeder rod moves up, the entire floating lever pivots, causing the **right hand end** (which connects to the pilot valve plunger) to also **move up**. 4. **Result:** This upward movement lifts the pilot valve plunger, opening the regulating port necessary to decrease fuel delivery (by moving the power piston down). ### Explanation for Incorrect Options **A) pilot valve plunger will move down** Incorrect. The overspeed caused by decreasing load requires the governor to reduce fuel. To reduce fuel (move the power piston down), the pilot valve plunger must be lifted **up** to route pressure oil over the piston and/or drain oil from underneath the piston. **B) speeder rod will move down** Incorrect. Decreasing the load causes engine speed to increase (overspeed). Increased speed causes the flyweights to move outward, lifting the speeder rod **up**. **D) oil pressure under the power piston will increase** Incorrect. When the pilot valve plunger moves up (as discussed in C), it connects the area under the power piston to the drain (sump) while simultaneously often directing high-pressure oil above the power piston. This action causes the oil pressure under the power piston to **decrease**, allowing the power piston to move down and decrease fuel delivery.

The Correct Answer is C **Explanation of Correct Option (C):** Option C states that the purpose of the lube oil supply check valves is to "prevent lube oil contained in the LO storage and conditioning tank from draining into gearboxes and sumps." This is the primary function of these check valves (sometimes called anti-siphon or anti-drain valves) located in the supply line downstream of the pump, or sometimes directly on the tank outlet. When the engine is shut down, the lube oil tank is often located higher than the various engine sumps and bearing compartments (gearboxes). Without a check valve, gravity would cause the oil from the tank to siphon or drain continuously into the lower engine cavities, leading to "wet sumping" or "oil pooling." This excessive oil pooling can cause various issues upon the next engine start, such as rapid smoking (burning off the excess oil) or hydraulic locking in certain bearing compartments. Therefore, the check valve prevents gravity drainage when the pump is inactive. **Explanation of Incorrect Options:** **A) prevent the lube oil and scavenge pump from losing its prime:** Check valves in the supply line are primarily concerned with preventing backflow due to gravity from the tank into the engine, not maintaining the prime of the pumps (which are typically positive displacement pumps and designed to maintain prime effectively). Maintaining prime is more related to pump design, location, and the continuous presence of oil upstream. **B) keep the lube oil lines in the engine primed:** While the check valves do keep the *supply line* filled (preventing backflow), the main *purpose* is anti-siphon/anti-drain protection for the engine sumps and gearboxes, not simply keeping the lines filled. Furthermore, keeping the lines "in the engine" (e.g., scavenge lines or internal galleries) primed is not the function of the supply check valve. **D) All of the above:** Since options A and B do not accurately describe the main, intended function of the lube oil supply check valves, this composite option is incorrect.

The Correct Answer is B **Explanation for B (All Proof 10W50 (Polyolester)) being correct:** The question asks for a synthetic oil capable of lubricating a main engine speed control governor with an ideal operating temperature range of $130^{\circ} \text{F}$ to $205^{\circ} \text{F}$. Based on standard lubrication practice and the implied content of the oil chart (Illustration MO-0161, which is not provided but is referenced): 1. **Polyolester-based (POE) synthetic oils** are known for superior thermal stability and performance across wide temperature ranges, often extending to very high temperatures (well above $205^{\circ} \text{F}$) and providing excellent stability at high shear rates, which is crucial for sensitive hydraulic/control systems like governors. 2. The $10\text{W}50$ viscosity grade ensures the oil is thin enough at lower temperatures ($130^{\circ} \text{F}$) for proper control response while maintaining sufficient film strength and viscosity at the higher end of the operating range ($205^{\circ} \text{F}$). 3. In many industrial and marine applications, especially for high-performance governors, esters (like polyolesters) are specifically chosen because they offer high film strength and cleanliness, making the "All Proof $10\text{W}50$ (Polyolester)" the most technically appropriate choice for the specified temperature range and critical function. **Explanation of why the other options are incorrect:** * **A) Amsoil 10W40 (Diester):** While diesters are excellent synthetic bases, $10\text{W}40$ is a standard motor oil grade. Without knowing the specifics of the governor's requirements (e.g., extremely high loads or specialized film properties), a polyolester (Option B) is often preferred over a diester for critical hydraulic/control systems due to better hydrolytic stability and performance at the upper viscosity range, making B the superior choice based on industry selection criteria for governors. * **C) Mobil 1 (Synthesized Hydrocarbon):** Mobil 1, typically based on PAOs (Synthesized Hydrocarbons), is a robust synthetic motor oil. However, PAOs generally have lower lubricity and solvency compared to ester-based oils (like Polyolester or Diester). For sensitive control systems operating over a demanding temperature range, an ester-based oil (B) is frequently specified to ensure superior seal conditioning and higher thermal oxidative stability, making C less optimal than B. * **D) DN600 (Hydrocarbon):** A standard "Hydrocarbon" oil (implying a Group I, II, or III mineral base oil) is not a true synthetic. While it may handle $130^{\circ} \text{F}$ adequately, its performance, stability, and resistance to oxidation at the higher end of the range ($205^{\circ} \text{F}$) would be significantly inferior to any true synthetic oil (A, B, or C). Therefore, it would not provide **adequate** long-term lubrication for a critical component like a speed control governor compared to synthetic alternatives.

The Correct Answer is B **Explanation for Option B (Dry sump):** The majority of modern aircraft gas turbine engines utilize a **dry sump** lubrication system. In a dry sump system, oil is stored in a separate, external reservoir (tank), rather than being stored internally within the engine casing (the sump). Scavenge pumps are then used to actively draw the used oil from the bearing cavities and sumps within the engine back to the external tank for cooling, filtering, and recirculation. This design is highly advantageous for aircraft engines because it allows for: 1. **Continuous Oil Supply:** Ensuring lubrication regardless of the aircraft's attitude (e.g., during inverted flight or high-G maneuvers). 2. **Improved Cooling:** Oil can be effectively routed through heat exchangers outside the engine structure. 3. **Reduced Weight and Size:** The reservoir can be located optimally, and less oil needs to be retained internally in the engine structure, which saves weight and prevents potential foaming or sloshing issues common in high-speed machinery. **Why the other options are incorrect:** * **A) Oil mist recovery sump:** While gas turbine engines do deal with oil mist (a result of lubricating bearing compartments with air/oil mixture), this term describes a specific *component* or *process* (recovering the vaporized oil) rather than the overall *type* of lubrication system utilized (which is dry sump). * **C) Common drain sump:** This term is not a standard classification for gas turbine lubrication systems. Gas turbine engines use specific sumps (internal reservoirs) to collect oil near bearing compartments, but the overall system design is characterized by the external tank and active scavenging, which defines the dry sump type. * **D) Wet sump:** A wet sump system stores the entire oil supply within the bottom of the engine casing (the sump) and uses a single pressure pump to distribute the oil. This type is common in reciprocating engines (like car engines), but it is generally unsuitable for large aircraft gas turbine engines due to weight, space limitations, high internal temperatures, and the requirement for attitude-independent oil delivery.

The Correct Answer is B **Explanation for Option B (Correct Answer):** The purpose of pressurizing the main bearing lube oil sumps (or compartments) on a typical marine gas turbine is primarily to maintain a pressure differential across the bearing seals (specifically the air/oil seals or labyrinth seals). The pressurized air (often referred to as 'buffer air' or 'sealing air') acts as a pneumatic barrier. Because the air pressure inside the sump compartment is maintained slightly *below* the surrounding cavity pressure, or precisely controlled relative to the external air/gas paths, this controlled pressure differential effectively prevents the lubricating oil from escaping outwards through the bearing seals and into the adjacent hot sections (like the compressor discharge or turbine stages), thereby **minimizing oil leakage from the rotor shaft.** This system is crucial for reliability, preventing fire hazards, and maintaining oil cleanliness. **Explanation for Incorrect Options:** * **A) Assists in cooling the lube oil.** Pressurization involves air, which might contribute minimally to heat transfer, but the primary mechanism for cooling the lube oil is circulation through a dedicated oil cooler (heat exchanger). Pressurizing the sump compartments is a sealing function, not a cooling function. * **C) Increases lube oil penetration.** Lube oil penetration (how well the oil reaches the bearing surfaces) is primarily controlled by the oil supply pressure, flow rate, and the design of the oil jets or spray nozzles, not by the pressure of the air within the external sump cavity. * **D) Provides uniform lube oil distribution around the bearing.** Uniform lube oil distribution is achieved through proper bearing design (e.g., grooving, supply points) and consistent oil flow, not by pressurizing the air cavity around the outside of the oil bath or sump.

The Correct Answer is B **Explanation for B (Correct Answer):** The illustration (GT-0018, which typically depicts a specific type of free-wheeling clutch or overrunning clutch common in certain driveline systems, such as in APU/engine starting mechanisms or specific transmission modes) shows a design that functions based on relative speed difference. This type of clutch is generally an automatic, unidirectional device (like a sprag clutch or roller ramp clutch). It acts as a mechanical diode, allowing torque to be transmitted in only one direction. * When the **input shaft flange is rotating faster than the output assembly** (e.g., during the initial acceleration of the input or when the input is trying to drive a slower output), the internal locking mechanism (like rollers or sprags) jams between the inner and outer races, locking them together and transmitting torque. The clutch is thereby automatically engaged by the differential speed. **Explanation for A, C, and D (Incorrect Options):** * **A) Clutch is engaged manually prior to start up:** This type of clutch is speed-sensitive and automatic. It does not require manual intervention (like pushing a pedal or pulling a lever) to engage based on the relative motion shown in the mechanism. * **C) Clutch engages automatically once the output assembly begins rotating:** This is the opposite of the clutch's function. If the output assembly is rotating faster than the input (e.g., the engine is running and the starter motor input has stopped), this type of clutch (an overrunning clutch) must automatically **disengage** to prevent the output from back-driving the input. Engagement relies on the input being faster than the output. * **D) Pneumatic pressure from the compressor engages the clutch:** While some specialized clutches are pneumatically operated (like certain PTOs or heavy-duty industrial clutches), the design shown in a typical free-wheeling/overrunning clutch illustration (GT-0018) is purely mechanical and relies on inertial or differential speed forces (rollers/sprags) for engagement, not an external fluid power source like a compressor.

The Correct Answer is D **Explanation for Correctness (Option D):** The Synchronous Self-Shifting (SSS) clutch is designed to engage automatically when the input speed (from the power turbine) matches or slightly exceeds the output speed (the speed of the gear train/propeller shaft side). The clutch mechanism operates based on a precise speed relationship. The input shaft accelerates until it "catches up" to the speed of the existing output shaft, which is being driven by another engine (e.g., a diesel engine or another gas turbine already engaged). When the input shaft speed rises to meet the output shaft speed, the synchronizing process aligns the helical splines. Once the speeds are matched, the input torque drives the pawls, which then shift the main sliding component (sleeve) axially, locking the clutch and allowing the torque transmission to begin. Therefore, the essential condition for engagement is when the input shaft speed rises to the output shaft speed. **Explanation for Incorrect Options:** **A) Availability of low-pressure air to provide control air pressure for engagement.** This is incorrect. While air systems (pneumatics) are often used for monitoring, indication, or supplementary control functions in the overall gearbox system, the SSS clutch itself is purely mechanical and self-actuating. It requires no external hydraulic or pneumatic control pressure to trigger the engagement mechanism. **B) Availability of high-pressure air to provide clutch air inflation pressure.** This is incorrect. SSS clutches are mechanical, utilizing helical splines, pawls, and springs for engagement, not inflatable bladders or diaphragms. This description (air inflation pressure) applies to pneumatic clutches (like many types of disconnect clutches), but not to the SSS clutch design. **C) When the input shaft speed from the power turbine falls below the output shaft speed.** This is incorrect. If the input shaft speed falls below the output speed, the speed differential is negative (the output is faster). The SSS clutch's design, specifically the geometry of the helical splines, prevents engagement and keeps the clutch disengaged under this condition. Furthermore, if the clutch were somehow engaged and the input speed then dropped below the output speed, the clutch would automatically disengage (auto-shift), protecting the power turbine. Engagement requires the input speed to match or exceed the output speed.

The Correct Answer is A ### Explanation for Option A (Correct Answer) Illustration MO-0050 typically depicts a **multi-point lubricator** or **timing lubricator**. This specialized device is used on large two-stroke slow-speed diesel engines (like those used in marine propulsion) to precisely deliver small, measured amounts of lubricating oil directly to the cylinder liner walls (the cylinder lubricating points). The device is often driven by the engine camshaft or crankshaft to ensure the oil is injected at the optimal moment in the piston stroke (usually when the piston skirt is below the injection points, minimizing oil leakage and maximizing distribution). Therefore, its primary function is to **supply cylinder lubricating oil to the engine**. ### Explanation for Incorrect Options **B) meter fuel oil to the injectors:** This is the function of the **fuel pump** (specifically, the high-pressure fuel pump) which pressurizes and meters fuel to the fuel injectors, not the lubricator shown. **C) admit the correct amount of starting air to the cylinders in proper order:** This is the function of the **starting air distributor** (or pilot air distributor) and the **main starting air valves**, which control the sequence and timing of starting air admission, not the lubrication system component. **D) actuate exhaust valves in the correct sequence:** On large two-stroke engines, exhaust valves are typically actuated by a **hydraulic or pneumatic system** controlled by the engine's camshaft or an electronic control system, often involving a dedicated hydraulic cylinder or valve drive mechanism, not the mechanical lubricator shown.

The Correct Answer is C **Explanation for C being correct:** The device described as a "comparator type mist detector" is consistent with systems like the Graviner or Schaller Oil Mist Detector. These devices operate by continuously drawing samples of the atmosphere from various locations within the crankcase of a diesel engine. They compare the density of the sample atmosphere against clean reference air (or against another sample zone) using optical principles (often light scattering or opacity). A sudden increase in oil mist concentration indicates a localized hot spot (like an overheating bearing or piston skirt), which can lead to a crankcase explosion. This type of sophisticated, reliable monitoring equipment is mandatory and universally used for the safety monitoring of **large low-speed, crosshead type marine diesel engines** due to the sheer size of the crankcase and the catastrophic potential of a crankcase explosion. **Why the other options are incorrect:** * **A) rotary type mist detector, designed for use in four-stroke, high-speed diesel engines:** While rotary mist detectors (like older Graviner Mark 3 units) exist, they are less common than the comparator/sampling types described in modern usage, especially for the very large engines where this equipment is critical. Furthermore, while they can be used on four-stroke engines, their primary and most critical application is on the largest engines which are typically low-speed crosshead types. * **B) photoelectric, explosive gas indicator, for use in high-speed, two-stroke, trunk type piston engines:** This is inaccurate. The device is specifically an **oil mist detector**, not a general explosive gas indicator (explosimeter). While oil mist is combustible, the detector is designed to detect the *precursor* (the mist formed by vaporization) rather than the fully explosive gas mixture. Also, it is most essential on low-speed crosshead engines, not typically high-speed trunk piston engines. * **D) level type explosimeter, for small medium-speed, trunk type piston engines:** This is incorrect. An explosimeter measures the concentration of flammable gas relative to the Lower Explosive Limit (LEL). The device in question is designed specifically to detect oil mist concentration, which requires a specialized detector employing optical measurement, not a generic LEL measurement device. Furthermore, it is designed for large engines, not small ones.

The Correct Answer is A. **Explanation for Option A (Correct):** Option A describes the standard, sequential order of critical events that occur during the auto-start of a typical marine gas turbine engine (which uses a Gas Generator Turbine, or NGG, and a Power Turbine, or NPT). 1. **NGG reaches ignition RPM:** The starter motor accelerates the Gas Generator section (NGG) to a specific RPM (the "light-off" or "ignition" speed). This speed ensures sufficient airflow (compressor discharge pressure) for proper atomization of fuel and stable combustion. Once this speed is reached, fuel is introduced and the igniters are fired. 2. **Gas temperature greater than 400 degrees F (or equivalent start temperature):** After ignition, combustion begins, and the temperature of the exhaust gas (measured by TGT/ITT sensors) rises rapidly. The start sequence typically requires confirmation that a stable light-off has occurred, usually evidenced by the rapid temperature increase, exceeding a minimum threshold (like 400°F). 3. **NGG reaches idle RPM:** After successful ignition and combustion stabilization, the engine accelerates using its own power. The starter motor cuts out, and the engine continues to accelerate until it reaches the self-sustaining speed known as "idle RPM" (or "no-load speed"), at which point the start sequence is complete and the engine is ready to accept load. **Explanation of Why Other Options Are Incorrect:** * **B) Power turbine reaches ignition RPM, gas temperature greater than 400 degrees F, power turbine reaches idle RPM:** This is incorrect because the start sequence is primarily controlled by the Gas Generator (NGG) speed, not the Power Turbine (NPT) speed. The NGG must reach ignition and idle speeds first. The Power Turbine typically begins to rotate only after the NGG is operating efficiently. * **C) NGG reaches idle RPM, power turbine reaches ignition RPM, gas temperature greater than 400 degrees F:** This sequence is logically impossible. The engine cannot reach its self-sustaining idle RPM before fuel has been introduced, combustion confirmed (gas temperature rise), and ignition has successfully occurred. The temperature rise and successful ignition always precede the achievement of idle speed. * **D) Power turbine reaches ignition RPM, gas temperature greater than 400 degrees F, NGG reaches idle RPM:** This is incorrect for two main reasons. First, the start sequence is initiated and governed by the NGG speed, not the Power Turbine speed. Second, the Power Turbine (NPT) does not typically have an "ignition RPM" control point; that parameter belongs to the Gas Generator (NGG).

The Correct Answer is D **Explanation for Option D (With the starter motor drive) being correct:** Routine water washing (often called "crank washing" or "off-line washing") of the gas turbine compressor is performed when the engine is not running under its own power. The purpose is to remove contaminants (dirt, salt, etc.) that build up on the compressor blades, which reduces efficiency and power output. To effectively spray the cleaning solution/water and ensure it reaches all stages of the compressor, the rotor must be turned at a speed high enough to generate centrifugal force to distribute the fluid but low enough to prevent significant heat generation or combustion (which would boil off the water). This required speed is achieved by using the engine's standard starter motor or turning gear (depending on the procedure). The engine is "cranked" through this process without ignition. **Explanation of why other options are incorrect:** * **A) At 25% power, B) At 75% power, and C) At 100% power:** Water washing performed while the engine is running and combusting fuel (at any power level above idle/light-off) is known as "on-line" or "hot washing." While some gas turbines use hot washing as a supplemental or specialized cleaning method, routine, thorough cleaning (especially the typical off-line cleaning referenced by the context of most general maintenance questions) requires the engine to be shut down. Introducing large amounts of water into the compressor while the engine is operating at significant power (25% or higher) is hazardous, ineffective for deep cleaning, and can lead to severe thermal shock and damage to hot section components (combustors and turbines). Therefore, routine water washing is an off-line procedure performed using mechanical rotation, not combustion power.

The Correct Answer is D **Explanation for D (opening chamber):** The illustration MO-0112 typically refers to the mechanism of a die casting machine or similar machinery where two halves (dies or molds) move apart to release the solidified part. The letter "W" generally indicates the volume or chamber that is created as the moving die half retracts or "opens" away from the fixed die half. This space allows for the part to be extracted or removed, hence it is correctly termed the **opening chamber**. This terminology is standard in the context of molding and die casting machinery. **Explanation for Incorrect Options:** * **A) closing chamber:** This term is typically used to describe the chamber or space associated with the hydraulic or mechanical components responsible for pushing the die halves together (the closing force). It does not describe the volume created when the dies separate. * **B) parting chamber:** While the surface where the two halves meet is called the "parting line" or "parting surface," "parting chamber" is not a standard term for the area "W" which represents the space created *after* the parting occurs and the dies are separated (opened). * **C) upper sliding piston chamber:** This option describes a specific component related to the actuation mechanism (like a hydraulic cylinder or piston assembly) and not the operational volume created between the moving die halves, which is what "W" represents.

The Correct Answer is C ### Explanation for Option C (110 mm) The size of the regulating ring (gravity disc) required for a fuel oil centrifuge is determined by the specific gravity of the fuel oil at the separating temperature and the specific gravity of the water used (usually assumed to be 1.0 kg/dm³). This relationship is typically represented by a formula or, in practical operation, by a graph (such as Illustration MO-0113) which plots the required ring size against the specific gravity of the oil at the separation temperature. To solve this problem using the hypothetical Illustration MO-0113, we must first convert the given fuel oil specific gravity (S.G.) from the reference condition ($0.9 \text{ kg/dm}^3$ at $68^\circ\text{F}$) to the actual separating temperature ($158^\circ\text{F}$). 1. **Determine the Temperature Difference ($\Delta T$):** $$\Delta T = \text{Separating Temperature} - \text{Reference Temperature}$$ $$\Delta T = 158^\circ\text{F} - 68^\circ\text{F} = 90^\circ\text{F}$$ 2. **Estimate the Change in Specific Gravity:** Specific gravity decreases as temperature increases. For typical marine fuel oils, the specific gravity changes by approximately $0.00065$ per $1^\circ\text{C}$ (or $0.00036$ per $1^\circ\text{F}$). $$\text{S.G. change} = 90^\circ\text{F} \times 0.00036 \text{ /}^\circ\text{F} \approx 0.0324 \text{ kg/dm}^3$$ 3. **Calculate Specific Gravity at Separating Temperature ($\text{S.G.}_{\text{sep}}$):** $$\text{S.G.}_{\text{sep}} = \text{S.G.}_{\text{ref}} - \text{S.G. change}$$ $$\text{S.G.}_{\text{sep}} = 0.900 \text{ kg/dm}^3 - 0.0324 \text{ kg/dm}^3 \approx 0.868 \text{ kg/dm}^3$$ 4. **Use Illustration MO-0113:** Assuming Illustration MO-0113 is a standard graph for determining gravity disc size based on the oil's specific gravity at separation temperature: * Locate the calculated $\text{S.G.}$ of $0.868 \text{ kg/dm}^3$ on the x-axis (Specific Gravity). * Follow this value up to the curve representing the required regulating ring diameter. * Read the corresponding diameter on the y-axis (Ring Diameter). For an $\text{S.G.}_{\text{sep}}$ of approximately $0.868$, a standard centrifuge graph shows that the required regulating ring size is $110 \text{ mm}$. *** ### Explanation of Why Other Options Are Incorrect **A) 86 mm:** A regulating ring size of $86 \text{ mm}$ corresponds to a much higher specific gravity oil, typically around $0.94$ to $0.95 \text{ kg/dm}^3$. Since the calculated specific gravity at separation is $0.868 \text{ kg/dm}^3$, this disc is far too small and would lead to the separation zone moving inward, likely causing the oil/water interface to be pushed into the oil overflow, resulting in oil loss (sludging of oil). **B) 104 mm:** A ring size of $104 \text{ mm}$ corresponds to a specific gravity closer to $0.88$ or $0.89 \text{ kg/dm}^3$. While closer than Option A, it is still smaller than required for an $\text{S.G.}$ of $0.868 \text{ kg/dm}^3$. This disc would also be slightly too small, potentially leading to operational instability and inefficient separation, or even oil loss if the gravity boundary shifts too far inward. **D) 117 mm:** A ring size of $117 \text{ mm}$ corresponds to a very low specific gravity oil, typically below $0.85 \text{ kg/dm}^3$. This disc is too large for the calculated specific gravity of $0.868 \text{ kg/dm}^3$. If a disc that is too large is used, the oil/water interface moves outward, increasing the risk of the interface being pushed into the sludge space, causing the water seal to break and water to exit with the clean oil (water contamination).

The Correct Answer is D **Explanation for Option D ("All of the above"):** The mixing tank (or settling tank/service tank assembly) serves several crucial purposes when dealing with heavy fuel oil (HFO) systems, especially in marine applications where different grades of fuel may be used, or when preparing HFO for use. * **A) To permit vaporized lighter fuel fractions to vent:** HFO can contain volatile components (lighter fractions) that may vaporize when the fuel is heated (e.g., in the settling or service tanks). These vapors must be safely vented to prevent pressure buildup and reduce the risk of explosion or fire. * **B) To prevent overheating of the day tank:** While the primary function of the mixing tank itself isn't direct cooling, it is often part of the fuel treatment system that includes heating the HFO to reduce viscosity. Controlling the temperature of the fuel delivered to the service/day tank, and allowing for gradual temperature changes, ensures the tank and its contents remain within safe operating parameters, preventing localized overheating which could lead to instability or excessive vaporization. * **C) To enable the changeover from hot heavy fuel to cold distillate fuel to occur gradually:** During a fuel changeover (often required before maneuvering or entering Emission Control Areas), the engine must transition from hot HFO to cold distillate fuel (MDO/MGO). If this transition occurs too rapidly, it can cause severe thermal shock to the fuel pumps and injection equipment. The mixing tank, or the transition process often managed around it, allows the two fuels to be blended or introduced sequentially, ensuring the temperature drop is controlled (typically around 2°C per minute) and gradual, protecting the engine components. Since the mixing tank/service tank arrangement handles heating, venting, and controlled changeover procedures, all three described functions (A, B, and C) are valid roles associated with the operation and safety of the fuel system, making "All of the above" the correct comprehensive answer. **Explanation of Incorrect Options (A, B, and C as standalone answers):** Although A, B, and C are all true functions of the fuel system incorporating the mixing tank, none of them alone captures the complete purpose of the component as effectively as option D. * **A) To permit vaporized lighter fuel fractions to vent:** While true, this ignores the equally critical functions of temperature control and gradual changeover. * **B) To prevent overheating of the day tank:** While true (as part of overall temperature control), this is an incomplete description, omitting safety venting and operational changeover requirements. * **C) To enable the changeover from hot heavy fuel to cold distillate fuel to occur gradually:** While critical for machinery protection, this ignores the continuous operational requirements of heating and venting the HFO.

The Correct Answer is D **Explanation for Option D (Correct Answer):** Anti-flood check valves (or non-return valves) in a fuel oil system are unidirectional devices that allow flow in only one direction. When installed between the main engine and the fuel source (like a day tank), especially when the engine is the lowest point in the system (i.e., the day tank is located below the engine), they serve a critical safety and operational function. If the engine is shut down, the fuel system is static. Without the check valve, gravity would cause the fuel oil remaining in the engine's fuel lines (or injection pump housing) to drain backward into the day tank, potentially leaving air pockets in the system. When the engine is restarted, this air could cause misfires or prevent the engine from starting altogether. Therefore, the anti-flood check valves prevent the backflow of fuel from the engine back toward the day tank when the engine is shut down and the day tank is situated below the engine, thus ensuring the fuel system remains primed. **Explanation for Other Options (Incorrect):** * **A) They prevent backflow of fuel from the engine to the day tank when the engine is running and when the day tank is located above the engine.** * This is incorrect. When the engine is running, the fuel pump maintains positive pressure, naturally preventing backflow. Furthermore, if the day tank is above the engine, gravity already encourages flow toward the engine, making backflow to the day tank less likely to be caused by drainage or gravity. * **B) They prevent backflow of fuel from the engine to the day tank when the engine is shut down and when the day tank is located above the engine.** * This is incorrect. If the day tank is located above the engine, the head pressure from the tank (due to gravity) would naturally force the fuel forward into the engine system, not backward, even when the engine is shut down. A check valve would still be needed to prevent pressure pulses from the pump from going backward, but the primary anti-flood/anti-drain function relates to the scenario where the tank is below the engine. * **C) They prevent backflow of fuel from the engine to the day tank when the engine is running and when the day tank is located below the engine.** * This is incorrect. When the engine is running, the attached fuel oil pump is actively pushing fuel toward the engine, creating pressure that prevents backflow. The critical role of preventing gravity-induced backflow (draining/siphoning) occurs when the pump is *off* (engine shut down), not while it is running.

The Correct Answer is C ### Explanation for Correct Answer (C) Option C, "Collect steam and flash the heated water generated in area 'B' into steam," is correct because the illustration MO-0231 (which depicts a typical marine exhaust gas boiler, specifically a composite or waste heat boiler setup) shows area **L** as the **steam drum** (or separator drum). When the main engine is operating at sea speed, hot exhaust gases pass through the boiler tubes (area B, the economizer/evaporator section), heating the feedwater/water within. This heated water (or a mixture of water and steam) rises from the heating surfaces (B) into the steam drum (L). Inside the steam drum (L): 1. **Separation occurs:** Steam generated in the tubes separates from the remaining water. 2. **Flashing/Evaporation:** Any superheated or highly pressurized hot water entering the slightly lower pressure steam drum can instantaneously 'flash' into steam, maximizing steam production. 3. **Collection:** The resulting saturated steam is collected at the top of the drum before being routed to the ship's steam system. Area B, being the primary heating surface using the exhaust gas, generates the hot water/steam mixture that is then processed in L. ### Explanation for Incorrect Options **A) Preheat the feedwater to the waste heat boiler:** This is incorrect. While feedwater is preheated, this function is performed by the economizer section (often labeled as part of B) or by separate preheaters using auxiliary steam. Area L is the steam/water separation and collection point (the steam drum), not the feedwater preheating section. **B) Collect stack gas:** This is incorrect. Stack gas (exhaust gas) flows around the heating tubes (area B) and then exits up the funnel. Area L is part of the boiler's water/steam circuit, usually sitting above the heating surfaces, and contains pressurized water and steam, not exhaust gas. **D) Superheat the steam generated by the oil-fired mechanical burner:** This is incorrect. Superheating steam (raising its temperature above saturation) requires passing it through a separate section—the superheater—which is typically located closer to the hottest heat source (like the oil-fired burner section on a composite boiler). Area L (the steam drum) contains saturated steam, and its primary function is separation and collection, not superheating.

The Correct Answer is C **Explanation of Correct Option (C):** The fuel oil ignition system (igniters) is primarily used during the start sequence of a gas turbine engine to ignite the fuel/air mixture in the combustion chamber. Once successful ignition and self-sustaining combustion are achieved, the igniters are no longer needed. To prevent unnecessary wear, power consumption, and damage, the ignition system is typically disabled (de-energized) automatically when the engine reaches a stable operating speed, which is monitored by the **Gas Generator (N1 or Ng) speed**. This preset RPM indicates that the compressor is supplying sufficient airflow and pressure to maintain continuous combustion, making the igniters redundant. **Explanation of Incorrect Options:** * **A) The igniters remain energized throughout the normal operation of the engine.** This is incorrect. Keeping igniters energized continuously would lead to rapid erosion, overheating, and wasted electrical power. They are only active during startup and sometimes during specific in-flight conditions (like heavy rain or icing) but not throughout normal, continuous operation. * **B) The igniters will de-energize when the power turbine exceeds a preset RPM.** This is incorrect. While the power turbine (N2 or Np) speed is crucial for output and load management, the successful establishment of combustion and engine stability is dictated by the Gas Generator (N1) speed, as N1 controls the core engine operation (compression and combustion airflow). * **D) The igniters will only energize if the exhaust gas temperature falls below a preset value.** This is incorrect. While EGT is a critical parameter monitored during the start sequence (to detect a hot or hung start), it is not the primary trigger for *de-energizing* the igniters, nor is a low EGT the only condition for *energizing* them (they are energized at the beginning of the start cycle regardless of EGT).

The Correct Answer is C **Why option C ("filter the fuel") is correct:** In illustrations pertaining to common mechanical fuel injection systems (such as those used in diesel engines, often depicting unit injectors or similar components), the component designated as a filter (or screen) is placed immediately upstream of the finely machined parts (like the plunger and barrel assembly or the needle valve). Piece #38 is typically a small, cylindrical screen or filter element integrated into the injector body or inlet fitting. Its primary function is to trap very small contaminants or debris immediately before the fuel enters the high-pressure pumping and injection mechanism, protecting the precision components (which operate with extremely tight tolerances) from damage or sticking. Therefore, its purpose is to filter the fuel. **Why the other options are incorrect:** * **A) adjust the fuel rack spring tension:** Fuel rack spring tension adjustment (which controls idle speed or maximum engine speed/fuel delivery) is handled by external linkage adjustments or internal mechanisms within the governor or fuel pump, not usually by an internal component like a small screen (#38) situated at the fuel inlet of the injector. * **B) maintain fuel pressure at a preset level:** Maintaining a steady, preset supply pressure (transfer pressure) is the job of the transfer or lift pump and often a separate pressure regulating valve located on the engine or pump housing, not a simple filter screen (#38) inside the injector. * **D) relieve excess fuel pressure to the suction side of the pump:** Relieving excess fuel pressure is the function of a relief valve or pressure regulator (often called a return check valve or bypass valve), which is usually located on the fuel header or return line. While injectors do have a return path for leakage fuel, the component labeled #38 is specifically positioned to filter the incoming fuel, not regulate system pressure or return flow.

The Correct Answer is C. ### Explanation of Correct Option (C) **C) It transmits the control rack setting to the plunger.** The plunger flange labeled "A" (often integrated with the control sleeve) is the mechanical linkage point between the external control system and the internal plunger assembly. The control rack moves linearly based on the throttle or governor setting. This linear motion is converted into a rotational movement of the control sleeve and the attached flange "A." Since the plunger is locked to flange "A," the rotation changes the alignment of the plunger's helix (scroll) relative to the spill port in the barrel. This rotation is essential for changing the effective stroke, thereby determining the amount of fuel injected per cycle. Therefore, the flange transmits the setting from the control rack to the plunger. ### Explanation of Incorrect Options **A) It prevents the plunger from rotating in the barrel.** The flange "A" is designed specifically to *cause* the plunger to rotate (via input from the control rack) in order to meter the fuel. Preventing rotation would make metering impossible. **B) It takes the plunger off stroke when injection is completed.** Injection completion (spill) is dictated by the interaction between the edge of the metering helix on the plunger and the spill port on the barrel. This is an internal hydraulic function determined by the position of the plunger, not an external function of the flange "A." **D) It limits the actual stroke of the plunger.** The actual physical stroke (the total distance the plunger travels up and down) is determined by the lift of the camshaft lobe and the travel limits of the tappet assembly. The flange "A" controls the *effective* stroke (fuel metering), but it does not limit the maximum physical distance the plunger travels.

The Correct Answer is D **Explanation for Correct Option (D):** The GE LM2500 is an aeroderivative gas turbine, structurally based on the GE TF39 and CF6-6 aircraft engines. It utilizes air extracted from various compressor stages for cooling, sealing, and pneumatic services. The 13th stage bleed air is extracted from the High-Pressure Compressor (HPC) section. This stage provides air at a high temperature and pressure, which is necessary for cooling critical components subjected to the hottest gas path temperatures. Specifically, the 13th stage bleed air is routed internally to provide cooling air for the **High-Pressure Turbine (HPT) 2nd stage nozzle** (also known as the 2nd stage vane). This cooling is crucial for maintaining the structural integrity of the nozzle and ensuring adequate part life in the extreme temperature environment between the 1st and 2nd HPT stages. **Explanation for Incorrect Options:** **A) Power turbine balance piston cavity pressurization:** This function is typically accomplished using lower pressure air, often extracted from an earlier stage (like the 9th stage bleed air) or from the Power Turbine (PT) exhaust flow, as the PT is located downstream of the HPT and operates at significantly lower pressure and temperature. The high-pressure, high-temperature 13th stage air is generally reserved for the most demanding cooling tasks in the HPT section. **B) Sump pressurization and cooling:** Sump pressurization (to ensure proper oil scavenging and sealing) and cooling are achieved using relatively lower pressure air. For the LM2500, sump pressurization is typically handled by mid-stage compressor bleed air (such as the 5th or 9th stage air) or dedicated seal air systems, not the highest pressure 13th stage air. **C) Power turbine cooling:** While the Power Turbine (PT) requires cooling, this is usually accomplished using mid-stage bleed air (e.g., 9th stage air) or external cooling circuits utilizing air drawn from the engine's external flow path. The PT is located downstream of the HPT, meaning the gas path temperatures are substantially lower, and therefore, it does not require the maximum temperature and pressure cooling air provided by the 13th stage. The 13th stage air is primarily dedicated to the cooling of the hottest HPT components.

The Correct Answer is B **Explanation for Option B (slow-speed engine fuel pump):** The component shown is a high-pressure mechanical unit designed for precise metering and pressurization of fuel. In large, low-speed marine diesel engines (like crosshead engines), the fuel pump is a robust, positive-displacement plunger pump that takes fuel oil at supply pressure and raises it to the extremely high pressures (often over 1000 bar) required for injection into the cylinder. Key visual features typically include: 1. A robust block housing to withstand immense pressures. 2. A large plunger assembly actuated by a camshaft. 3. Mechanisms (like a control rack or lever) for precisely controlling the quantity of fuel delivered (by adjusting the spill timing of the plunger), which corresponds directly to engine load and speed. This structure is characteristic of the main fuel pump used in these large engines. **Explanation of Why Other Options are Incorrect:** * **A) slow-speed engine cylinder liner lubricator:** A liner lubricator is a small, specialized unit designed to deliver very small, precisely metered amounts of oil to multiple points on the cylinder liner wall. It typically consists of a bank of small pumps or metering valves, not the single, large, high-pressure pumping unit dedicated to fuel delivery. * **C) centrifugal flyweight governor:** A centrifugal governor is a rotational speed-sensing device. It uses flyweights that move outward as speed increases to mechanically adjust the position of the fuel pump control rack. It looks like a complex linkage and rotating mechanism, not a stationary, block-like high-pressure pump. * **D) injector cooling system pump:** This is a low-pressure circulating pump (often centrifugal or gear type) used to move cooling medium (like water or light oil) through the injector jackets. It would have a motor or drive shaft and large inlet/outlet flanges for flow, lacking the intricate high-pressure plunger and control rack system seen on the fuel pump.

The Correct Answer is D **Explanation for Option D (16th stage compressor air):** The GE LM2500 is a two-spool gas turbine engine derived from the TF39/CF6 turbofan architecture. Its compressor section typically consists of 16 stages (a 6-stage Low Pressure/LP compressor and a 10-stage High Pressure/HP compressor). The 1st stage High Pressure (HP) turbine nozzle vanes are subjected to the highest temperatures in the engine, immediately after the combustor. To ensure their structural integrity and operational lifespan, these vanes require robust cooling. This cooling air must be taken from the highest pressure and highest temperature stage of the compressor to maintain the necessary cooling effectiveness (high pressure differential relative to the hot gas path) and flow rate. In the LM2500, the final, hottest, and highest-pressure air available, which is required for cooling the HP turbine 1st stage vanes and blades, is extracted from the **16th (discharge) stage** of the axial compressor. **Explanation of Incorrect Options:** * **A) 8th stage compressor air:** Air extracted from the 8th stage is typically used for lower-temperature applications, such as internal engine cooling (bearings, seals) or sometimes for intermediate-stage cooling of the combustor liner or specific parts of the LP turbine section, but it is insufficient (both in pressure and temperature) for cooling the critical HP turbine 1st stage nozzle vanes. * **B) 9th stage compressor air:** Similar to 8th stage air, 9th stage air is generally used for intermediate cooling needs, such as bleed for anti-icing systems, external air systems, or lower-temperature zone component cooling. It lacks the pressure ratio and mass flow needed to effectively cool the first-stage HP turbine hardware. * **C) 13th stage compressor air:** While 13th stage air is high-pressure air used for specific cooling and sealing purposes (e.g., cooling the HP turbine rear frame, specific blade roots, or clearance control), it is not the primary source for the 1st stage HP nozzle vanes. The highest pressure air available (16th stage) is specifically reserved for the most thermally loaded components, such as the 1st stage vanes.

The Correct Answer is A. **Explanation for Option A (inspection ports):** In standard gas turbine engine illustrations and technical documentation, especially when referring to a continuous sequence of numbered sections (like "14 thru 29") along the length of the engine casing, these numbers often correlate to specific circumferential locations or stations where maintenance access is provided. Inspection ports (or borescope ports/access panels) are distributed around the engine casing, particularly in the compressor, combustor, and turbine sections, to allow mechanics to visually inspect internal components (like compressor blades, combustor liners, and turbine vanes/blades) without disassembling the engine. The broad range "14 thru 29" strongly suggests a system of numbered access points located along the engine body for maintenance purposes. **Explanation for Incorrect Options:** * **B) fuel nozzles:** Fuel nozzles are typically grouped within the combustor section (often designated by a single station number or area), not distributed across a wide range of numbered locations (14 thru 29) that would span multiple major sections of the engine (compressor, combustor, and turbine). * **C) thermocouples:** While thermocouples (temperature sensors) are distributed throughout the engine, their locations are usually denoted by specific measurement points (e.g., T2, T3, T5), or a limited set of dedicated ports. The widespread numbering "14 thru 29" refers more to *access* points for personnel/equipment than the fixed positioning of sensors themselves. * **D) bell mouth strut cones:** The bell mouth (inlet) and its struts/cones are located at the very front of the engine, typically designated as Station 0 or 1. The numbering "14 thru 29" implies locations much further downstream within the compressor or subsequent sections, making this option geographically incorrect.

The Correct Answer is C ### Explanation for C (Operating in normal mode) In a typical marine fuel oil system setup, "normal mode" refers to the stable, routine operation of the vessel, which usually involves the main engine running on Heavy Fuel Oil (HFO). Valves 4 and 5, in many fuel system diagrams (such as those illustrating transfer pumps, purifier inlets, or changeover stations), often represent critical cross-connection or isolation points between different fuel grades (HFO and DO) or redundant systems. For the system to operate safely, efficiently, and without the risk of contaminating the fuel systems (e.g., mixing HFO and DO), any non-essential cross-connection or bypass valves must remain **closed** during normal, stable operation. Therefore, if valves 4 and 5 are segregation valves, they would be closed when the vessel is operating in normal mode. ### Explanation for Incorrect Options **A) Operating the main engine on DO.** If the engine is operating on Diesel Oil (DO), the DO line to the service tank or engine manifold must be open. If Valve 5 (or 4) controls the flow of DO, that valve must be **open**. Thus, both valves cannot be closed. **B) Loading the HFO bunkers.** Bunkering involves the movement of large volumes of fuel into the storage tanks. This process requires opening specific transfer and filling valves. Depending on the exact position of Valves 4 and 5 in the illustration, at least one of them (related to the transfer or overflow path) would likely need to be **open** during this operation. **D) Operating DO purifier on HFO.** While this statement is technically contradictory (a DO purifier is usually cleaned for DO service), if the intention is to use the purifier designated for DO to clean HFO, the HFO feed line to that purifier must be **open**. If Valve 4 (or 5) is the HFO feed line, it must be open, meaning both valves are not closed.

The Correct Answer is B. ### Explanation for Option B (Correct Answer) Option B is correct because the illustration MO-0231 depicts a **steam cycle waste heat boiler/economizer** setup typically found on marine vessels, particularly those powered by large diesel engines. * **Area "L"** represents the **steam drum** or **upper drum**. * **Area "B"** represents the **generating section** (or generating tubes/coils) of the waste heat boiler, where water is heated by the hot exhaust gases when the vessel is operating at sea speed. * When the vessel operates at full sea speed, hot exhaust gases flow through the boiler, heating the water in area "B." This heated water (or a steam/water mixture) rises naturally (due to density differences) or is pumped into the steam drum (L). * In the steam drum (L), the steam separates from the water, a process often referred to as **flashing** when heated water rapidly turns to steam upon reaching a lower pressure area (the drum). The drum collects this generated steam before it is sent to the ship's steam system (for driving turbines, generating electricity, or heating). Simultaneously, the drum separates the water, which is then recirculated back down to the generating section (B). Therefore, area "L" is used to **collect steam and flash the heated water generated in area "B" into steam.** ### Explanation of Incorrect Options **A) Preheat the feedwater to the waste heat boiler:** This function is performed by the **economizer section** (which is usually located *before* the generating section in the exhaust flow path) or by a dedicated feed water heater, not by the steam drum (L). **C) Superheat the steam generated by the oil-fired mechanical burner:** If the boiler has a superheater, it is located in a dedicated section (typically downstream of the steam drum or within the high-temperature gas path) to further heat the *already separated* steam, increasing its temperature and energy content. The steam drum (L) is used for separation and collection, not superheating. Furthermore, while the waste heat boiler might be combined with an oil-fired auxiliary boiler, the primary function of the drum remains steam collection, not the superheating of steam generated by a burner. **D) Collect stack gas:** Stack gas (exhaust gas) flows *around* the boiler tubes (B) to transfer heat to the water inside, and then exits the stack. The boiler components (L and B) contain water and steam, not the exhaust gas itself.