Powerplant Installation, Lubrication, Ignition, Starting and Propellers
Installation and systems
Know the engine installation: mounts and firewalls, cowling and cooling, induction and exhaust, fuel control unit, and the accessories driven by the engine (vacuum pump, alternator, hydraulic pump). Lubrication uses a dry-sump system with a pressure pump, scavenge pump, oil cooler, filter and bypass valve; oil pressure and temperature are the key indications, and low pressure with normal temperature is a different diagnosis from high temperature with normal pressure.
Ignition and starting
Piston engines use magnetos (independent of the electrical system) with two plugs per cylinder for redundancy and better combustion; turbine engines use igniter plugs and a starting sequence (starter, ignition, fuel on, light-off, idle). Traps: assuming a magneto check failure is minor (a dead magneto means loss of redundancy); and forgetting that a turbine start must be monitored for hung start or hot start.
Propellers
Fixed-pitch, variable-pitch and constant-speed propellers; the governor senses rpm and adjusts blade angle to hold selected rpm; feathering reduces drag after engine failure, and reverse pitch provides braking. Know the traps: propeller overspeed with a failed governor is corrected by reducing power and oil pressure effects; and a windmilling propeller can be feathered only if oil pressure or an accumulator is available.
Worked example: during the run-up, the engine dies on the left magneto. Reasoning: the right magneto is not firing or its plug lead is faulty. Do not fly; the engine has lost ignition redundancy.