Removal of an Auxiliary Power Unit (APU) 1. Open APU compartment access door latches and open door. Install door support rods. Open circuit breakers and switches as needed. [Figure] 2. Remove lower support shroud. 3. Disconnect APU harness, APU starter motor, and APU generator plugs from receptacles in upper shroud. 4. Disconnect APU generator control … Read more
Aircraft reciprocating engine exhaust systems are exposed to extreme temperatures, vibration, and corrosive exhaust gases during operation. Regular inspection and maintenance help identify leaks, cracks, and other defects before they develop into serious safety hazards. This article explains recommended inspection procedures, common exhaust system failures, and maintenance practices. Exhaust System Maintenance Practices Any exhaust system … Read more
Broken copper wires can be temporarily repaired using crimped splices, terminal lugs with the tongue removed, or by soldering and potting the broken conductors. These repairs are applicable to copper wire. Damaged aluminum wire must not be repaired by temporary splicing. These methods are intended for temporary emergency repairs only and should be replaced with … Read more
The APU fire protection system is similar in design to engine fire protection systems, but there are some differences. The APU is often operated with no personnel in the flight deck and; the APU fire protection system can operate in an unattended mode on the ground with the engines not running. If there is an … Read more
In reciprocating aircraft engines, the connecting rod plays a critical role in converting the linear motion of the piston into the rotary motion of the crankshaft. Because it operates under extremely high compressive and tensile loads, its design must balance strength, rigidity, and low weight to withstand continuous stress while minimizing inertia forces. Different engine … Read more
A FADEC is a solid-state digital electronic ignition and electronic sequential port fuel injection system with only one moving part that consists of the opening and closing of the fuel injector. FADEC continuously monitors and controls ignition timing, fuel delivery, fuel-air mixture, and fuel injection as an integrated engine control system. FADEC monitors engine operating … Read more
In contemporary aircraft engines, cylinders are critical components where combustion energy is converted into mechanical motion. They must withstand high pressures and temperatures while remaining lightweight for optimal engine performance. Advances in aluminum alloy heads, steel barrels, precision cooling fins, and modern manufacturing techniques improve heat dissipation, durability, and efficiency. Proper cylinder design and maintenance … Read more
The procedures for preserving and depreserving gas turbine engines vary depending upon the length of inactivity, the type of preservative used, and whether or not the engine may be rotated during the inactive period. Much of the basic information on corrosion control presented in the section on reciprocating engines is applicable to gas turbine engines. … Read more
The turbine lubrication system is representative of turbine engines using a dry-sump system. [Figure] The lubrication system is a pressure regulated, high-pressure design. It consists of the pressure, scavenge, and breather subsystems. The pressure system supplies oil to the main engine bearings and to the accessory drives. The scavenger system returns the oil to the … Read more
The dry-sump variable-pressure lubrication system uses the same basic subsystems that the regulated systems used (pressure Scavenge breather). [Figure] The main difference is that the pressure in this system is not regulated by a regulating bypass valve. Most large turbofan engine pressure systems are variable-pressure systems in which the pump outlet pressure (oil pressure) depends … Read more
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