B. Turbine Engines

How are the four strokes of a reciprocating engine similar to the sections of a turbine engine? (AM.III.B.K1)

Intake = air inlet section, compression = compressor section, ignition and power = combustion and turbine sections, exhaust = exhaust section.

What type of turbojet engine is commonly used in commercial aviation due to lower noise and better fuel consumption? (AM.III.B.K1)

High-bypass turbofan engines.

What four types of gas turbine engines are used in aircraft? (AM.III.B.K2)

Turbofan, turboprop, turboshaft, and turbojet.

What are the two types of turbine compressors? (AM.III.B.K3)

Centrifugal flow and axial flow.

What is meant by trimming a turbine engine? (AM.III.B.K4)

Adjusting the fuel control so the engine develops the correct idle and trim speed RPM.

What type of equipment should be used to determine that a turbine engine is performing up to the standards specified by the engine manufacturer? (AM.III.B.K4)

A JetCal analyzer/trimmer has all of the instrumentation and cables to determine the EGT, EPR, and other parameters specified by the engine manufacturer.

What is meant by a hot-section inspection? (AM.III.B.K5)

An inspection of the hot section of a turbine engine. The hot section includes the combustors, the turbine, and the exhaust system.

What is meant by on-condition maintenance of a turbine engine? (AM.III.B.K5)

The monitoring of the engine performance at regular intervals and determining when maintenance is required based on certain operating parameters specified by the engine manufacturer.

What checks of a turbine engine are necessary to verify preflight condition? (AM.III.B.K5)

a. Inspect the cowling and all air inlet areas and attachment of the engine to the airframe.

b. Inspect the inlet guide vanes and the first stage of the compressor or fan blades.

c. Check for unusual noise when the compressor is rotated.

d. Inspect the rear turbine and exhaust system.

e. Check the quantity of the lubricating oil for the engine and the constant-speed drive unit.

f. Check the ignition system for operation by listening for the sparks.

What engine instruments are monitored during the start of a turbine engine? (AM.III.B.K6)

Tachometer, oil pressure, and internal gas temperatures.

What checks are performed after the installation of a turbine engine? (AM.III.B.K6)

After starting and idle speed is obtained, the engine should stabilize, and engine instrument values are monitored. Takeoff thrust is checked by adjusting the throttle to obtain a single, predicted reading on the engine pressure ratio indicator. The manufacturer's procedures and limitations must be followed during all engine operations. After engine shut down, inspect the engine for fuel and oil leaks and general condition.

What engine fault could cause a turbine engine to have high exhaust gas temperature, low RPM, and high fuel flow at all engine pressure ratio settings? (AM.III.B.K7)

Possible turbine damage and/or loss of turbine efficiency due to excessive wear.

What would be the indications of an engine bleed-air valve malfunction? (AM.III.B.K7)

Engine has higher-than-normal exhaust gas temperature during takeoff, climb, and cruise. RPM and fuel flow are higher than normal.

What is the primary purpose of bleeding air off the compressor section? (AM.III.B.K8)

To unload the compressor at low speeds and to control the flow of air to the combustion burners.

What is the secondary purpose or use of bleed air? (AM.III.B.K8)

Bleed air is used in a variety of aircraft systems including cabin pressurization, heating and cooling, deicing and anti-icing systems, pneumatic starting of engines and auxiliary drive units, and vortex dissipaters.

How is a turbine engine preserved for long periods of inactivity? (AM.III.B.K9)

The methods will vary depending on the manufacturer and the length of inactivity. Common practices include draining the lubrication system and flushing with preservative oil. The engine fuel system may also be drained and filled with preservative oil, including the fuel control. Before the engine can be returned to service, the preservative oil must be completely flushed from the fuel system by motoring the engine and bleeding the fuel system. Always follow the manufacturer's instructions when performing any preservation or de-preservation of gas turbine engines.

Where are most APUs located in modern jet transport aircraft? (AM.III.B.K10)

In the tail cone of the fuselage.

What is the function of an APU? (AM.III.B.K10)

An APU provides electric power and compressed air when the main engines are not operating.

What are two sources of compressed air from an APU? (AM.III.B.K10)

From bleed air from the APU turbine compressor, or from a load compressor driven by a free turbine in the engine.

Where in maintenance information based on the ATA-100 system would you find instructions for inspecting and servicing the engine of an airborne APU? (AM.III.B.K10)

In section 49-20.

How is most of the troubleshooting done for a modern APU? (AM.III.B.K10)

By the fault codes generated by the FADEC.

What ensures that an APU will not be shut down while it is too hot? (AM.III.B.K10)

The APU fuel control incorporates an automatic time-delay feature that closes the bleed air valve to remove most of the load and reduce the APU temperature before it is shut down.

What prevents the APU exceeding its safe operating limits when the bleed air valve is wide open? (AM.III.B.K10)

The FADEC monitors the load and regulates the fuel going to the APU to prevent it from exceeding its safe limits.

What document would you use to find the safety procedures to follow when replacing an igniter plug in an APU engine? (AM.III.B.K10)

The maintenance manual for the APU.

What adjustments and rigging are accomplished on a turbine engine? (AM.III.B.K11)

The primary rigging on a turbine engine involves the adjustment of power control levers and cables, followed by careful adjustment of the fuel control unit to trim the engine for the correct idle speeds and to obtain maximum thrust.