Aircraft General Knowledge: Airframe, Systems and Powerplants
What this domain tests
This domain checks that you see the aircraft as an integrated machine: structural design philosophy, ATA system grouping, and how the powerplant is installed and controlled. Questions often ask you to classify a design feature or calculate a certified load.
Core rules
- Airworthiness loads are defined as limit load. The structure must withstand limit load without permanent deformation and ultimate load (1.5 × limit) for 3 seconds without failure.
- Fail-safe design provides alternative load paths after damage; safe-life parts are retired at a fixed life; damage-tolerant design relies on inspection to find cracks before they become critical.
- ATA 100 chapters group systems: 21 air conditioning, 24 electrical, 27 flight controls, 28 fuel, 29 hydraulic, 32 landing gear, 71 powerplant, 79 oil.
- Redundancy can be active (parallel systems), standby, or dissimilar. A single failure should not hazard the aircraft.
Worked example
An aircraft has mass 1,200 kg and a limit load factor of +3.0 g. Limit load = 3.0 × 1,200 × 9.81 = 35,316 N. Ultimate load = 1.5 × 35,316 = 52,974 N. In pounds, 1,200 kg is about 2,646 lb, giving about 7,938 lbf limit and 11,907 lbf ultimate. The reasoning is always: mass → weight → multiply by load factor → apply the 1.5 ultimate factor.
Traps
Confusing limit and ultimate load; applying 1.5 to the mass instead of the load; assuming fail-safe means no inspection; mixing kg and lb; treating the 1.5 factor as a stress margin rather than a load factor.