For airfield pavement thickness design, which gear load primarily governs the structural design of the pavement?

Introduction:
Pavement thickness for runways, taxiways, and aprons is set to withstand repetitive aircraft load applications without excessive deformation or fatigue cracking. The most critical loading is typically from the main landing gear assembly, which carries the bulk of the aircraft weight during touchdown, rollout, and taxiing.

Given Data / Assumptions:

• Conventional tricycle gear arrangement.
• Main gears carry the majority of the aircraft weight on ground.
• Pavement response depends on gear type, tire pressure, and load repetitions.

Concept / Approach:

Thickness is governed by the heaviest gear configuration and its contact stress distribution. Nose/tail wheels serve steering/balancing functions and usually carry much less load; they are not the governing design case for thickness except in unusual configurations.

Step-by-Step Solution:

Verification / Alternative check:

Design guides and empirical charts (e.g., CBR, FAA layered models) target main gear footprints and repetitions (coverages) as the critical input.

Why Other Options Are Wrong:

• Nose wheel: Lower load share; not thickness-governing in standard tricycle gear.
• Tail wheel: Relevant only for tail-draggers; still lighter than main gear for thickness design.
• All the above / auxiliary bogies only: Over-inclusive or incorrect emphasis.

Common Pitfalls:

• Assuming tire pressure alone governs; load magnitude and repetition are key.
• Ignoring gear spacing and multiple wheel assemblies in stress distribution.

Final Answer:

main gears