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Airframe ASA/Baker's School FAA Oral Questions and Answers 100% Accurate
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Airframe ASA/Baker's School FAA Oral Questions and Answers 100% Accurate
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ASA Powerplant Oral Study Guide (All Questions)1. What is the main advantage of a horizontally opposed engine over a
radial engine for powering modern aircraft?: The horizontally opposed
engine has a much smaller frontal area and is easier to streamline than a
radial engine.
2. How many throws are there in the crankshaft of a six-cylinder
horizontally opposed engine?: Six.
3. What kind of connecting rod arrangement is used in a radial engine?: A
master rod connects the single throw of the crankshaft with a piston. All of the
other pistons are connected to the master rod with link rods.
4. Of what material are most piston rings made?: Gray cast iron.
5. What is the reason for using hydraulic valve lifters in an aircraft engine?:
Hydraulic valve lifters keep all of the clearance out of the valve operating
mechanism.
This decreases the wear of the valve train components.
6. At what speed does the camshaft turn, relative to the crankshaft speed in
a horizontally opposed engine?: The camshaft turns at one half of the
crankshaft speed.
7. What kind of main bearings are used in a horizontally opposed engine?:
Steel-backed, lead-alloy bearing inserts.
8. On what stroke is the piston of a reciprocating engine when the intake
valve begins to open?: On the exhaust stroke.
9. On what stroke is the piston of a reciprocating engine when the exhaust
valve begins to open?: On the power stroke.
10. Why are both the hot and cold valve clearances given for most radial
engines?: The hot clearance is given for valve timing purposes. The timing is
adjusted with the valves in cylinder number one, set with the hot clearance.
When the timing is set, all of the valves are adjusted to their cold clearance.
11. What is meant by a cam-ground piston?: A piston that is not perfectly
round. Its dimension parallel with the wrist pin is several thousandths of an
inch less than its dimension perpendicular to the wrist pin. When the piston
reaches operating temperature, the metal in the piston pin boss expands
enough that the piston becomes perfectly round.
12. Where is the piston in a reciprocating engine when the ignition spark
occurs?: About 30 degrees of crankshaft rotation before the piston reaches
top center on the compression stroke.
13. What is meant by a full-floating wrist pin?: A wrist pin that is not clamped in
either the piston or the connecting rod. Full-floating wrist pins are kept from
scoring the cylinder walls by soft metal plugs in their ends.
, ASA Powerplant Oral Study Guide (All Questions)
14. Why do most aircraft reciprocating engines use more than one spring on
each valve?: By using more than one spring and having the wire diameter
and pitch of the springs different, valve float is minimized. The springs have
different resonant frequencies, so at least one spring will always be exerting a
force on a valve.
15. Would excessive valve clearance cause the valves to open early or late?:
Excessive valve clearance will cause the valve to open late and close early.
16. What is the purpose of valve overlap in a reciprocating engine?: Valve
overlap allows the inertia of the exhaust gases leaving the cylinder to help the
fresh induction charge start flowing into the cylinder.
17. What type of piston rings are installed on the pistons of an aircraft
reciprocating engine?: Compression rings, oil control rings, and oil wiper
rings.
18. Why are some exhaust valves partially filled with metallic sodium?: The
metallic sodium melts at engine operating temperature and sloshes back and
forth inside the hollow valve. It picks up heat from the valve head and transfers
it into the valve stem, so it can be transferred to the cylinder head through the
valve guide.
19. What causes detonation in an aircraft engine?: Excessive heat and
pressure in the engine cylinder causes the fuel-air mixture to reach its critical
pressure and temperature. Under these conditions, the mixture explodes
rather than burns. This explosion is called detonation.
20. Why is a compression check important for determining the condition of
an aircraft reciprocating engine?: A compression check can determine the
condition of the seal between the piston rings and the cylinder walls, and the
seal between the intake and exhaust valves and their seats.
21. What is meant by the compression ratio of a reciprocating engine?: The
ratio of the volume of the cylinder with the piston at the bottom of its stroke to
the volume with the piston at the top of its stroke.
22. What are the two basic sections of a turbine engine?: The hot section and
the cold section.
23. What are the two basic types of compressors that are used in aircraft
turbine engines?: Axial-flow and centrifugal.
24. What is the purpose of the stators in an axial-flow compressor?: The
stators convert some velocity energy into pressure energy and change the
direction of the air so it is proper for the next stage of rotors.
25. What are three types of combustors used on aircraft turbine engines?:
Can-type, annular-type, and can-annular type.
, ASA Powerplant Oral Study Guide (All Questions)
26. How many igniters are there normally in an aircraft turbine engine?: Two.
27. What is main purpose of the turbine nozzle in an aircraft turbine engine?:
The turbine nozzle directs the hot gases as they leave the combustors so they
will turn the turbine wheel with maximum efficiency.
28. What is meant by a free-turbine turboshaft engine?: A turboshaft engine
that has a turbine wheel, or stage of turbine wheels, that is not used to drive
the compressor of the gas generator section of the engine. This free turbine
drives the propeller in a turboprop engine or the transmission and rotor of a
helicopter.
29. Why do some axial-flow turbine engines have more than one set of
turbines and compressors?: A two-spool turbine engine has a low-pressure
and a high-pressure compressor, each driven by its own turbine. The two
independent systems operate at the speed at which they are most efficient.
30. What kind of bearings are used to support the rotor shaft of an aircraft
turbine engine?: Anti-friction bearings, such as ball bearings or roller
bearings.
31. What is meant by a turbofan engine?: An axial-flow turbine engine in which
the first stage of compressor blades are lengthened, so they can force air
around the outside of the gas generator portion of the engine.
32. Where can you find the limits of repair allowed for the compressor
blades of an aircraft turbine engine?: In the FAA-approved service manual
issued by the manufacturer of the engine.
33. Why is it important that a turbojet engine be allowed to cool before it is
shut down after it has been operated at a high power setting?: If the
engine is shut down while it is hot, there is a possibility that the shroud will
contract around the turbine wheel and seize the rotor.
34. What is meant by a hung start in a turbine engine?: A start in which ignition
occurs, but the engine does not accelerate to a self-sustaining speed.
35. What is meant by a hot start in a turbine engine?: A start in which ignition
occurs, but the internal temperatures go high enough that they can damage
the engine.
36. What is meant by creep of the turbine blades?: A condition of permanent
elongation of the turbine blades. Creep is caused by the high temperatures
and the high centrifugal loading imposed on the blades.
37. How is the compressor of a turbine engine cleaned?: An emulsion-type
cleaner is sprayed through the engine while it is being motored by the starter
or operated at a low speed. The wash is followed by a clean water rinse. More
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