22 Turbine Air, Exhaust & Reversers Practice Questions & Answers
Every Turbine Air, Exhaust & Reversers practice question from the FAA A&P Powerplant (AMP) Practice Test, with the correct answer and a short explanation.
Start practice test →1. During normal subsonic flight, what does a turbine engine air inlet duct do to the air before it reaches the compressor?
- A.Spins it into a vortex so the first compressor stage can bite more air
- B.Speeds it up and lowers its static pressure, acting as a convergent nozzle
- C.Holds its velocity steady while lowering its temperature for a denser charge
- D.Slows it down and raises its static pressure, acting as a divergent diffuser✓ Answer
The inlet duct is shaped as a divergent duct, so as flow area increases the velocity decreases and the static pressure rises — that is what makes it a diffuser. Airflow through the engine must remain below Mach 1 at all times, so the duct has to slow the air before the compressor face. Note the pairing that trips up most candidates: the inlet is divergent, while the exhaust nozzle is convergent.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Air Inlet Duct" (inlet acts as a diffuser)Report a problem with this question
2. A bellmouth inlet is installed on an engine being run in a test cell. Why is this inlet used when rated thrust and specific fuel consumption data are gathered?
- A.It filters the incoming air so that ingested debris cannot alter the thrust reading
- B.Its duct loss is so slight that it is considered zero, so the data are undistorted✓ Answer
- C.It throttles airflow to a fixed value so every engine is tested at the same mass flow
- D.It adds a known amount of ram pressure that is later subtracted from the recorded data
A bellmouth is a bell-shaped funnel with carefully rounded shoulders that offers practically no air resistance, so its duct loss is considered zero. Engine performance figures such as rated thrust and thrust specific fuel consumption are obtained with it because an installed aircraft inlet duct would impose losses of its own on the numbers.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Bellmouth Compressor Inlets"Report a problem with this question
3. A turboprop installation uses a compressor inlet screen. Which characteristic of such screens must the mechanic keep in mind?
- A.They are heated by engine oil and therefore cannot accumulate any ice
- B.They are standard on large turbofans because fan blades damage easily
- C.They eliminate inlet pressure loss because they smooth the entering airflow
- D.They add inlet pressure loss, ice up readily, and can fail from fatigue✓ Answer
Inlet screens reduce foreign object damage, but they add appreciably to inlet duct pressure loss, are very susceptible to icing, and are subject to fatigue failure — and a failed screen can cause more damage than no screen at all. Some are made retractable so they can be withdrawn in icing conditions. Large turbofans with steel or titanium fan blades generally do not use them because the disadvantages outweigh the benefit.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Compressor Inlet Screens"Report a problem with this question
4. Where does the heat come from that keeps ice off the inlet lip of a high-bypass turbofan installation?
- A.Exhaust gas routed forward through a duct built into the nose cowl
- B.Electrical heating elements embedded in the lip opening of the intake
- C.Hot engine oil circulated through passages formed in the lip skin
- D.Warm bleed air from the engine compressor, circulated inside the lip✓ Answer
On turbofan installations, warm bleed air is drawn from the engine and circulated on the inside of the inlet lip for anti-icing. Electrical elements in the lip opening are the method used on many turboprop intakes, which is why the two appear as distractors for each other. The fan hub or spinner is either heated with warm air or made conical so ice cannot build up and adhere.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Turbofan Engine Inlet Sections" and "Turboprop & Turboshaft Compressor Inlets"Report a problem with this question
5. Why must nearly all of the cooling air in a gas turbine engine be passed through the inside of the engine?
- A.Burning is continuous, so excess air inside must limit hot-section temperature✓ Answer
- B.The mixture is metered rich, so unburned fuel does most of the cooling
- C.Burning happens on only one stroke in four, so outside airflow suffices
- D.The case metal conducts heat so poorly that outside airflow removes none
In a four-stroke reciprocating engine combustion occurs only every fourth stroke, which eases the cooling problem, but in a gas turbine the burning process is continuous, so nearly all the cooling air must pass through the inside of the engine. If only enough air were admitted for an ideal 15:1 air-fuel ratio, internal temperatures would exceed 4,000 °F; admitting a large surplus of air holds hot-section temperatures to roughly 1,500 to 2,100 °F.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Turbine Engine Cooling"Report a problem with this question
6. How is the secondary (cooling) airflow used at the combustion chamber liner?
- A.It is trapped as a dead-air blanket between the liner and the outer case
- B.It is sprayed as a mist of atomized fuel that evaporates against the liner
- C.It is drawn from the exhaust stream and pumped forward along the liner
- D.It is a thin, fast-moving film over the inner and outer liner faces✓ Answer
Combustion chamber liners are constructed to induce a thin, fast-moving film of air over both their inner and outer surfaces, which keeps the flame off the metal. Can-annular burners are frequently provided with a center tube to lead cooling air into the burner, and in all gas turbines large volumes of relatively cool air join and mix with the burned gases aft of the burners before the flow reaches the turbine.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Turbine Engine Cooling"Report a problem with this question
7. Calibrated airflow is supplied to each of the primary zones of a turbine nacelle. Besides controlling temperature, what is that ventilation for?
- A.To supply combustion air to the burner when the ram inlet is obstructed
- B.To dry moisture off the electronic engine control before each engine start
- C.To prevent any buildup of harmful vapors from fuel and oil lines in the zone✓ Answer
- D.To raise zone pressure above ambient so outside air cannot enter the nacelle
Turbine powerplants are divided into primary zones isolated from one another by fireproof bulkheads and seals, and calibrated airflows are supplied so that temperatures around the engine stay acceptable and proper ventilation prevents a buildup of harmful vapors. That matters because the intermediate compressor case zone and the core engine zone both contain fuel and oil lines; case drains route potential leaks overboard so fluids cannot accumulate in the nacelle.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Accessory Zone Cooling"Report a problem with this question
8. A turbine engine exhaust duct insulation blanket is built from two working materials. What job does each one do?
- A.Aluminum foil is the low-conductance layer and fiberglass the radiation shield
- B.Fiberglass is the low-conductance layer and aluminum foil the radiation shield✓ Answer
- C.Silicone rubber seals the duct and the fiberglass reflects radiated heat
- D.Asbestos cloth carries the load and the steel shroud absorbs radiated heat
The blanket contains fiberglass as the low conductance material and aluminum foil as the radiation shield, under a stainless steel outer shroud — candidates routinely swap those two roles. The blanket is suitably covered so that it does not become oil soaked, because its whole purpose is to lower the temperature of nearby structure and keep fuel or oil away from hot engine parts.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Turbine Engine Insulation Blankets"Report a problem with this question
9. An airframe pneumatic system draws compressor bleed air. What does increasing that bleed extraction do to the engine?
- A.It lowers exhaust gas temperature by drawing heat out of the case
- B.It raises available thrust because the compressor is unloaded
- C.It lowers available thrust and raises exhaust gas temperature✓ Answer
- D.It has no effect, because bleed ports are sized to be self-limiting
Bleed ports are small openings in the compressor case adjacent to the stage from which air is taken, chosen where pressure is adequate but the air has not yet become too hot; the air serves cabin pressurization and air conditioning, deicing and anti-icing, pneumatic starting, and auxiliary drive units. That air represents compression work the engine has already performed, so heavy extraction costs thrust and pushes turbine and exhaust temperatures up.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, compressor bleed air applicationsReport a problem with this question
10. A technician reports a suspected duct leak in an engine bleed air system while that system is still pressurized. What is the correct action?
- A.Tighten the duct couplings with the system still under pressure
- B.Add sealant at the joint and run the engine to cure it in place
- C.Depressurize and cool the system, then troubleshoot the duct✓ Answer
- D.Trace the leak by hand while the duct is hot and pressurized
Bleed air is both extremely hot and at high pressure, so an escaping jet can burn personnel severely and damage adjacent structure, and maintenance must not be performed on a pressurized system. Shutting the system down and allowing it to cool before any hands-on troubleshooting or tightening is the only sequence that removes the hazard rather than working next to it.
Source: FAA-S-ACS-1 Aviation Mechanic Airman Certification Standards, turbine engine air systems risk management (bleed air hazards)Report a problem with this question
11. During a post-installation inspection of a reciprocating engine exhaust system, what indicates an exhaust gas leak at a clamped connection?
- A.A flat gray or sooty black streak on the pipe near the connection✓ Answer
- B.A wet oil film that collects on the underside of the exhaust pipe
- C.A bright blue heat tint spreading evenly around the whole clamp
- D.A ring of white powdery corrosion on the outside of the clamp
An exhaust leak is indicated by a flat gray or sooty black streak on the pipes in the area of the leak, and black soot around an exhaust gasket shows that the gasket has failed. Such leaks usually result from poor alignment of two mated members, so the clamps are loosened and the leaking units repositioned for a gas-tight fit before being retightened to the specified torque and safetied.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Exhaust System Inspection"Report a problem with this question
12. Why are galvanized or zinc-plated tools kept away from exhaust systems, and why is a lead pencil never used to mark exhaust parts?
- A.The residue insulates the pipe and drives the local temperature up
- B.The deposit reacts with soot and produces a false leak indication
- C.The absorbed metal changes the molecular structure and softens the part✓ Answer
- D.The soft metal peels off in flight and is ingested by the induction
The lead, zinc, or galvanized mark is absorbed by the metal of the exhaust system when it is heated, creating a distinct change in its molecular structure. That change softens the metal in the area of the mark and causes cracks and eventual failure, which is why the prohibition covers both the tools that touch the system and the method used to mark it.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Exhaust System Inspection" (maintenance precautions)Report a problem with this question
13. How is a ceramic-coated reciprocating engine exhaust stack cleaned?
- A.By light sandblasting, followed by an alkali cleaner rinse
- B.By vapor blasting with glass beads, then oiling the surface
- C.By degreasing the stack, with no sandblast or alkali cleaner✓ Answer
- D.By soaking in a hot alkali bath, then brushing off the coat
Some exhaust units are manufactured with a plain sandblast finish, but ceramic-coated stacks must be cleaned by degreasing and should never be cleaned with sandblast or alkali cleaners, which destroy the coating. Sandblasting is the attractive wrong answer precisely because it is an acceptable process on the plain-finish parts sitting next to the coated ones.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Exhaust System Inspection" (cleaning operations)Report a problem with this question
14. An exhaust component cannot be inspected visually because it is hidden by nonremovable parts. What is the recommended check?
- A.Fill it with penetrating oil, drain it, and dust it with developer
- B.Plug its openings, draw a vacuum on it, and watch a gauge fall
- C.Pressurize it to about 50 psi and listen for escaping exhaust gas
- D.Plug its openings, apply about 2 psi internally, and submerge it✓ Answer
When a component is inaccessible for thorough visual inspection or hidden by nonremovable parts, it is removed, its openings plugged, a suitable internal pressure of approximately 2 psi applied, and the part submerged in water; any leak shows up as bubbles. The pressure is deliberately low because an exhaust component is thin-walled sheet metal, not a pressure vessel.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Exhaust System Inspection" (pressure leak check)Report a problem with this question
15. About half of all muffler and heat exchanger failures trace to cracks in the heat exchanger surfaces. Why does that particular location matter so much?
- A.Exhaust gas can enter the cabin heat system, causing carbon monoxide poisoning✓ Answer
- B.Exhaust gas can enter the oil cooler, contaminating the engine oil supply
- C.Exhaust gas can enter the crankcase, raising internal case pressure
- D.Exhaust gas can enter the exhaust stack, blocking the flow of gases
Those are the surfaces used as cabin and carburetor heat sources, so a crack or rupture — usually in the outer wall — lets exhaust gases escape directly into the cabin heat system, which is a carbon monoxide hazard to everyone aboard. The same failure can also let exhaust be drawn into the engine induction system, causing overheating and power loss.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Muffler & Heat Exchanger Failures"Report a problem with this question
16. What is the principal in-flight consequence of an internal muffler failure in which baffling breaks loose?
- A.Reduced back pressure that causes the engine to overspeed badly
- B.Loss of cabin heat that leaves the induction system prone to ice
- C.Restricted exhaust flow that causes partial or complete power loss✓ Answer
- D.Uneven cylinder cooling that causes detonation on the rich side
Internal failures of baffles and diffusers cause partial or complete engine power loss by restricting the flow of exhaust gases, and if a broken piece partially or totally blocks that flow, engine failure can occur. Erosion and carburization from the extreme thermal conditions are the primary causes, with backfiring and combustion of unburned fuel inside the system as contributing factors.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Internal Muffler Failures"Report a problem with this question
17. What does an augmentor exhaust system do besides carrying the exhaust gases away from the engine?
- A.Its exhaust velocity induces extra cooling air to flow over the engine✓ Answer
- B.Its exhaust velocity draws fuel vapor out of the crankcase breather
- C.Its exhaust velocity pressurizes the carburetor heat muff for the pilot
- D.Its exhaust velocity spins a turbine that drives the cabin air blower
The augmentors are designed to produce a venturi effect, so the pumping action of the high-velocity exhaust gases draws an increased flow of cooling air through the engine compartment. An augmentor vane in each tailpipe can be moved toward the closed position to reduce the velocity of flow through the augmentor and raise engine temperature when needed.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Manifold & Augmentor Exhaust Assembly"Report a problem with this question
18. What do the tail cone and the radial struts inside a turbine engine exhaust duct accomplish?
- A.They add strength and impart an axial direction to the gas flow✓ Answer
- B.They add strength and impart a swirl to the gas leaving the turbine
- C.They meter the gas flow and set the engine pressure ratio in cruise
- D.They cool the gas flow and lower the measured exhaust temperature
The tail cone and struts add strength to the duct, impart an axial direction to the gas flow, and smooth that flow — they take the swirl out of the gas leaving the turbine rather than putting swirl into it. Just downstream, the first part of the exhaust nozzle together with the exhaust plug forms a divergent passage that reduces turbulence before the gas reaches the convergent nozzle.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Turbine Engine Exhaust Nozzles"Report a problem with this question
19. A turbine engine's exhaust nozzle outlet area is smaller than the correct value. What results?
- A.The gases turn subsonic and the nozzle stops producing any thrust
- B.Flow is choked in components upstream and engine performance suffers✓ Answer
- C.Exhaust gas temperature drops because less gas mass is in the duct
- D.Thrust is wasted because the gases leave before reaching full velocity
The exhaust nozzle acts as an orifice whose size determines the density and velocity of the gases leaving the engine, so its area is critical to thrust performance. If the opening is too big, thrust is wasted; if it is too small, the flow is choked in the other components of the engine. Adjusting nozzle area changes both engine performance and exhaust gas temperature.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Convergent Exhaust Nozzle"Report a problem with this question
20. A corrugated-perimeter or multi-tube noise suppressor is fitted to a turbojet exhaust nozzle. What does it actually change?
- A.It lowers the noise frequency so the sound carries a shorter distance
- B.It raises the noise frequency while total noise energy stays the same✓ Answer
- C.It absorbs part of the noise energy and converts that part to heat
- D.It cancels noise by mixing two exhaust streams a half wave apart
Both suppressor types break the single main jet stream into a number of smaller streams, which increases the total perimeter of the nozzle area and reduces the size of the eddies. The total noise energy remains unchanged, but the frequency is raised considerably: some of the noise moves above the range of human hearing, and the higher frequencies that remain are attenuated far faster by the atmosphere than low-frequency noise, which is the kind that carries farthest.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Engine Noise Suppression"Report a problem with this question
21. On a high-bypass turbofan with an aerodynamic blockage thrust reverser, what happens when the thrust levers are moved aft with the aircraft on the wheels?
- A.The blocker doors open, which lets hot core gas reach the cascade vanes
- B.The clamshell doors swing into the hot exhaust stream behind the nozzle
- C.The translating cowl closes, which opens the cascades to the fan stream
- D.The translating cowl opens, which closes the blocker doors into the fan duct✓ Answer
With the thrust levers at idle and weight on the wheels, moving the levers aft activates the translating cowl to open, and that action closes the blocker doors. Blocking the fan air from going aft redirects it through the cascade vanes, which send it forward to slow the aircraft; only fan air is used, because the fan produces roughly 80 percent of the engine's thrust. Returning the levers to idle opens the blocker doors and closes the translating cowl.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Thrust Reversers" (aerodynamic blockage)Report a problem with this question
22. Maintenance is to be performed inside the thrust reverser area of an installed engine. What must be done before personnel work there?
- A.The reverser must be pressurized so the interlocks stay seated
- B.The reverser must be mechanically locked out from deploying✓ Answer
- C.The reverser must be cycled once to verify the doors are free
- D.The reverser must be left in the deployed position for access
A reverser has several powered moving parts driven pneumatically, hydraulically, or electrically through gearboxes, flexdrives, and screwjacks, and the system is normally locked in the stowed position until the flight deck commands deployment. While performing any type of maintenance, the reverser system must be mechanically locked out from deploying while personnel are in the area — cycling or pressurizing it with people inside is exactly the hazard the lockout exists to prevent.
Source: FAA-H-8083-32 AMT Handbook—Powerplant, "Thrust Reversers" (maintenance safety)Report a problem with this question
Practice questions based on the Aviation Mechanic Airman Certification Standards (FAA-S-ACS-1), 14 CFR parts 43, 65, and 91, and the FAA Aviation Maintenance Technician Handbook—Powerplant (FAA-H-8083-32). This site is not affiliated with or endorsed by the Federal Aviation Administration. This bank covers the POWERPLANT written test only; the General and Airframe written tests and the oral and practical tests are separate. Torque values, running clearances, compression limits, magneto timing angles, spark plug gaps, temperature and pressure limits, servicing quantities, and overhaul intervals always come from the manufacturer's current maintenance data, the type certificate data sheet, and the applicable airworthiness directives — never from a practice test. Confirm current eligibility and testing requirements with the FAA before you test. About the A&P mechanic certificate →