Engine Exhaust and Reverser Systems practice questions

Answer: B) High-velocity, high-temperature exhaust gas leaving the tailpipe

Behind a running turbine engine, the main hazard is the hot, high-velocity exhaust (jet blast). It can injure people and damage equipment, while the suction hazard is at the inlet.

• AIncorrect. Strong suction is a real hazard, but it is at the engine inlet in front of the engine. Exhaust flows away from the nozzle and does not pull people toward it.
• BCorrect. Even at idle, jet exhaust is hot and fast enough to knock a person down, cause burns, and throw debris into equipment.
• CIncorrect. Ignition exciters are shielded high-voltage units. They do not create a radiation danger zone behind the engine.
• DIncorrect. A normally operating engine does not vent oil mist into the exhaust. The breather discharges only small amounts of mist, and those are not the reason for the danger area.

Answer: D) To speed up the gas

• AIncorrect. That is afterburning.
• BIncorrect. It speeds it up.
• CIncorrect. This is not the purpose.
• DCorrect. A converging nozzle speeds up the exhaust to produce thrust.

Answer: D) Carbon causes heat cracking

• AIncorrect. This is not the reason.
• BIncorrect. The concern is damage, not visibility.
• CIncorrect. The concern is carbon contamination.
• DCorrect. Carbon from graphite can cause intergranular corrosion and cracking when heated.

Answer: A) To protect adjacent structure and components from radiated heat

Insulation blankets around the turbine hot section and exhaust duct contain radiated heat. This keeps surrounding structure and components from heat damage.

• ACorrect. Insulation blankets contain the heat of the hot section and exhaust duct. This protects nearby structure, wiring, and components from radiant heat damage.
• BIncorrect. Extinguishing agent is stored in containers and sent through discharge lines. Insulation blankets do not hold or deliver any agent.
• CIncorrect. Bleed air leaks are prevented by ducting, seals, and clamps, not by heat-insulation blankets around the hot section.
• DIncorrect. The blankets are wrapped around the outside of cases and ducts and have no contact with the rotating turbine blades. Blade vibration is controlled by blade and disk design.

Answer: A) The reverser lock is not confirmed stowed and locked, raising the risk of an unwanted in-flight deployment

A reverser 'unlocked' indication in flight means a reverser lock is not confirmed stowed and locked. This is a stow or lock fault that raises the risk of unwanted in-flight deployment.

• ACorrect. The unlocked indication comes from the reverser lock sensors and shows that a lock is not confirmed engaged. An unlocked reverser in flight greatly increases the chance of unwanted deployment, so this is treated as a stow or lock fault.
• BIncorrect. Reverser deployment is commanded on the ground after touchdown, not in cruise. An unlocked indication in flight is a fault, not normal operation.
• CIncorrect. Isolating hydraulic pressure to the reverser in flight helps keep it stowed. A normal stowed and locked reverser does not show an unlocked indication.
• DIncorrect. Overheat and fire conditions are reported by the separate fire and overheat warning system, not by the reverser lock indication.

Answer: A) To prevent an uncommanded reverser deployment in flight, which could cause loss of airplane control

Thrust reverser stow locks, often with an independent additional lock, keep the reverser from deploying in flight, which could make the airplane uncontrollable. They are a flight-safety feature, not a ground-handling or power-limiting device.

• ACorrect. The stow locks keep the reverser from deploying in flight. FAA rules (14 CFR 25.933) and airworthiness directives, such as one requiring an additional reverser locking system, address the controllability hazard of in-flight deployment.
• BIncorrect. These locks hold the reverser stowed, not deployed. During rollout the actuation system keeps the reverser deployed.
• CIncorrect. Reverse power is limited by throttle and reverser lever interlocks and air/ground logic, not by the mechanical stow locks.
• DIncorrect. For maintenance, technicians install separate deactivation or lockout devices according to the maintenance manual. The stow locks are not a maintenance convenience.

Answer: B) Air/ground (squat) switch logic that enables deployment only with weight on the landing gear

Ground-only thrust reversers are usually armed through air/ground (squat) switch logic. The squat switch senses weight on the landing gear, so the reverser cannot deploy in flight.

• AIncorrect. Engine oil pressure is about the same in flight and on the ground, so it cannot tell whether the airplane is airborne.
• BCorrect. The squat switch senses when the landing gear strut is compressed. The reverser control circuit allows deployment only when the airplane is on the ground.
• CIncorrect. Fuel flow goes to the flight-deck indication. Low fuel flow also happens at idle in flight, so it cannot work as an in-flight lockout.
• DIncorrect. A synchronizer matches propeller rpm between engines. It plays no part in arming or locking out a thrust reverser.

Answer: A) Actuators driven by engine bleed air or by aircraft hydraulic pressure

Clamshell thrust reverser doors are moved by powered actuators, usually pneumatic ones using engine bleed air, with hydraulic actuators on some installations. The reverse thrust lever in the flight deck controls them.

• ACorrect. Clamshell doors are typically moved by pneumatic actuators running on compressor bleed air, or on some installations by hydraulic actuators. The flight deck reverse thrust lever controls the actuators.
• BIncorrect. Engine oil pressure is used to lubricate and cool the bearings and gears. It is not the power source for clamshell reverser actuators.
• CIncorrect. The doors must be moved and held against large exhaust gas loads. That needs powered actuators, not direct mechanical linkage from the reverse thrust lever.
• DIncorrect. Exhaust gas loads are something the actuators and locks must resist. They are not used to drive the doors, and springs alone cannot command deploy and stow.

Answer: A) Removing the heater shroud that surrounds the muffler's outer shell

Muffler cracks often hide under the cabin heat shroud, so the shroud has to come off before the muffler can be fully inspected or properly pressure-tested.

• ACorrect. The heat shroud hides most of the muffler's outer surface, where cracks and burned areas form. FAA guidance says to remove carburetor heat, cabin heat and preheat shrouds for a proper inspection and pressure test.
• BIncorrect. Port gaskets are checked when stacks come off at the cylinder. Removing them gives no view of the muffler shell under the heat shroud.
• CIncorrect. FAA guidance calls for removing the shrouds when pressure-testing the exhaust system so the muffler can actually be seen and checked. With the shroud on, leaks and cracks stay hidden.
• DIncorrect. The muffler and shroud can be reached once the cowling is open. Pulling the engine is not a normal part of a muffler inspection.

Answer: C) Straightens the flow

• AIncorrect. The compressor does that.
• BIncorrect. That is an afterburner.
• CCorrect. It forms a diffusing passage that straightens and smooths exhaust gas.
• DIncorrect. That is a reverser.