Powerplants and Airworthiness
What the paper tests
This domain covers turbine powerplant theory and operation - thrust production, compressor stalls and surges, fuel control, EGT/N1/N2/EPR indication, thrust reversers, APU - plus the airworthiness framework that keeps an aircraft legally flyable: type certificates, certificates of airworthiness, airworthiness directives, maintenance releases, the MEL and engine life limits.
Core rules
- Thrust falls with density altitude; the manufacturer's performance data, not intuition, gives the derate.
- EGT margin is the health indicator: a rising EGT at constant N1 means deterioration or a sensor fault.
- Airworthiness directives are mandatory; service bulletins are manufacturer recommendations that become mandatory only when an AD requires them.
- An aircraft may be dispatched with a defect only if the MEL permits it, the prescribed rectification interval is respected, and a valid maintenance release covers the flight.
Worked example
A four-engine aircraft has an oil consumption limit of 0.5 US qt/hr per engine. Over a 9-hour sector the crew adds 12 qt. Total rate = 12 ÷ 9 = 1.33 qt/hr. Per engine = 1.33 ÷ 4 = 0.33 qt/hr, inside the limit. Note the reasoning: the limit is per engine, so the total must be divided by the number of engines before comparing. A result of 0.6 qt/hr on one engine would exceed the limit even though the fleet total looked modest.
Traps
Comparing a fleet total against a per-engine limit; confusing life-limited parts with on-condition items; assuming an MEL item removes the defect rather than deferring it; quoting take-off thrust without the assumed bleeds and bleed configuration.