Question 82Gas Turbine - 1st Asst/Chief

The correct answer is D) Play between the surfaces of the teeth in mesh. Gear backlash refers to the small amount of play or clearance between the engaging teeth of two mating gears. This clearance allows the teeth to disengage and move slightly without causing damage to the gear mechanism. Backlash is a necessary design feature to account for manufacturing tolerances and thermal expansion of the gears. The other answer choices do not accurately describe gear backlash. Option A refers to parallel gears, which are not the focus of backlash. Option B describes clearance between non-meshing gears, which is not the definition of backlash. Option C describes radial play, which is a separate design consideration from the tangential play that defines backlash.