Baker's A&P Oral

What is the purpose of insulation on the exhaust duct of a turbine engine?

To reduce the temperature of the structures, and to eliminate the possibility of fuel or oil coming into contact with the hot parts of the engine.

What is the function of an APU air inlet plentum?

To stabilize the pressure of the air before it enters the compressor.

What should you adjust if a pilot request 50 more RPM on an aircraft equipped with a constant speed propeller?

Adjust the governor's prop-lever set screw.

How is the APU rotated during start up?

With an electric starter.

What can cause the waste gate to stick?

A buildup of carbon.

When is most of the load placed on an APU?

When the bleed air is open.

What is the meaning of propeller blade "back" and "face"?

The curved side of the propeller is the blade back. The flat side is the blade face.

To prevent rotor seizure "shock cooling", how long should an APU idle before being shut down?

3 to 5 minutes.

What type of fuel pump is generally used with large reciprocating engines?

A Positive Displacement Rotary Vane Type pump.

What tool is used to determine propeller blade angle?

A Protractor.

What type fuel pump can be made to vary the fuel flow at any speed?

A Variable displacement pump.

What type of propeller has the blade angle built into the propeller and cannot be changed?

A fixed pitch propeller.

How is ice cleared in some aircraft induction systems if the carburetor heat is too low to clear the ice?

A fluid such as alcohol, anilol, or mersol is sprayed into the induction system ahead of the carburetor.

What should be done to cylinders when too much of the cooling fin area is broken off?

The cylinder should be replaced because it cannot cool properly and a hotspot will develop.

Where are exhaust manifold and stack failures more likely to occur?

At welds, flanges, or clamped points in the system.

Describe the Augmenter System.

Augmenters consist of two pairs of tubes running from the engine compartment to the rear of the nacelle.

Where does an externally driven supercharger get its power?

By the exhaust gasses that are directed against a turbine.

What is the most common means of regulating the cooling air flow through a reciprocating engine?

By the use of Cowl Flaps.

How is the engine fuel system protected from ice formation?

By the use of fuel heaters.

Why do you put the blades of a counterweight propeller into high pitch before stopping the engine?

Because in this position, the piston is protected from dirt and moisture in the air.

What are the main reasons that excessive heat in a reciprocating engine is undesirable?

Because it shortens the life of the engine parts, impairs lubrication, and affects combustion.

Why is a micron fuel filter provided with a bypass valve as a necessary safety factor?

Because the small openings in this type of filter make it very susceptible to clogging.

What is the source of air directed to engine bearings for cooling?

Bleed air from the compressor section of the engine.

What type of fuel control unit is used in a turbine engine?

Both hydro mechanical and electronic fuel control units are in use today. However, the most common fuel control unit is the hydro mechanical type.

How are ceramic coated exhaust stacks cleaned?

By Degreasing.

How does an internally driven supercharger get its power?

By a high speed impeller driven through a gear train from the crankshaft.

Before shut down, how would APU cooling be accomplished?

By closing the bleed air valve.

How is feathering accomplished on a constant speed counterweight propeller?

By releasing governor oil pressure on the counterweights.

What is the most common type of fuel boost pump?

The electrical driven centrifugal type pump.

What is a common cause of the waste gate unit malfunctioning in a turbocharger system?

Carbon buildup, causing the waste gate valve to stick in the closed position.

What are the aerodynamic forces and loads acting on a rotating propeller blade?

Centrifugal force, aerodynamic twisting, centrifugal twisting, torque bending, and thrust bending forces.

What is the usual cause of muffler and heat exchanger failures?

Concentrated areas of thermal stress, or vibration stress.

Turbine engine fuel pumps may be divided into what two distinct system categories?

Constant displacement and Variable displacement.

What category is a turbine engine driven gear type pump?

Constant displacement.

What is the danger of using carburetor heat when operating at high power settings?

Detonation and possible engine failure.

What power sources are used to operate the cowl flaps?

Electrical power, Hydraulic power, or Manually.

What type of visual indication can usually be seen in the area of an exhaust leak?

Exhaust leaks usually have flat gray or sooty black carbon streaks on the pipes in the area of the leak.

Why do you disassemble and inspect the collector type exhaust?

Exhaust system failure can result in carbon monoxide poisoning of crew and passengers.

What positions are used on a balance stand to check a two bladed propeller for static balance?

First the vertical position, and then the horizontal position.

What types of systems are used for deicing propellers?

Fluid or electrical deicing systems.

What should be looked for when inspecting an engine driven fuel pump?

Fuel leaks and security of mounting.

What regulates fuel scheduling during APU start and under varying pneumatic bleed and electrical loads?

Fuel scheduling is maintained automatically by the APU fuel control system.

What method is used to prevent or remove induction system ice in a reciprocating engine?

Heated Air.

Do the counterweights on a constant speed propeller increase or decrease the blade angle?

Increase.

What are two general classifications of superchargers used in reciprocating engine induction systems?

Internally driven, or externally driven supercharger systems.

What factors are affected if the area of the exhaust nozzle of a turbine engine is changed?

It affects engine performance and the exhaust gas temperature.

What is the purpose of an oil cooler bypass valve?

It allows the thick oil to bypass the cooler when the oil is cold.

What effect does induction system icing have on engine performance?

It can cause an engine to act erratically and lose power, and may possibly quit.

What are the possible hazards of exhaust system failure?

It can result in carbon monoxide poisoning, or partial or complete loss of engine power and an aircraft fire.

What is the purpose of an engine driven fuel pump?

It delivers a continuous supply of fuel at the proper pressure at all times during engine operation.

What is the purpose of a distribution impeller in a radial engine?

It is designed to break up the fuel globules into finer particles for better distribution to the cylinders.

What is blade tracking?

It is the process of determining the position of the tips of the propeller blades relative to each other.

What is the purpose of a mixture control in a float type carburetor?

It is to control the fuel-air mixture as air density changes with altitude changes.

What is the purpose of a reciprocating engine exhaust system?

It is used to remove heat and noxious gasses from the engine nacelle.

What is the purpose of an engine cowling?

It reduces drag and forms an envelope around the engine, which forces the airstream between the cylinders to cool them.

What are three general causes of vapor lock?

Low fuel pressure, high fuel temperatures, and excessive fuel turbulence.

What engine indication can be the result of a dirty air filter?

Low power.

What type of exhaust system is used on turbocharged engines?

The exhaust collector system.

What engine variables are sensed by a hydro mechanical fuel control?

The fuel control senses power lever position, rpm, compressor inlet pressure temperature, burner pressure, or compressor discharge pressure, and EGT or TIT.

Can fixed pitch propeller's pitch be changed?

No, they are fixed at a specific pitch angle.

When should cowl flaps be kept in the fully open position?

Normally during all ground run operations.

What type of power is used to control the position of the turbocharger waste gate on some engines?

Oil pressure to an actuating piston.

What is the primary function of the load compressor on APU's equipped with a free turbine and load compressor?

To provide bleed air for aircraft pneumatic systems.

What happens when lead, zinc, or galvanized marks are made on an exhaust system?

The mark is absorbed by the metal when heated and causes a change in the molecular structure that weakens the metal.

What is the purpose of the bypass valve in the engine driven fuel pump?

The bypass valve provides a path around the pump vanes for starting the engine, and to allow fuel to bypass the pump in case of a pump failure.

What type of exhaust system creates a higher exhaust back pressure?

The collector system.

What areas of a turbine engine are cooled by the secondary air passing through the engine?

The combustion chamber and the turbines.

Why are cones installed on splinted shafts with a propeller?

The cones center the propeller on the shaft as they are forced toward each other by the tightening of the retaining nut.

What is the purpose of Strainers in a fuel system?

Prevent foreign matter to enter the carburetor.

What types of materials are used to make insulation blankets for turbine engines?

Stainless steel, layers of aluminum foil, fiber glass, and silver foil.

When operating at high loads, what is the speed of an APU?

The APU remains at or near rated speed regardless of the load condition.

What are the three mayor parts of a reciprocating engine induction system?

The Air Scoop, Fuel Delivery System, and Intake Manifold.

What other engine characteristics are designed to aid in engine cooling besides cooling fins?

The Engine Cowling and Baffles.

What part of a gas turbine engine fuel system is very susceptible to the formation of ice?

The Fuel Filter.

What publication should be referred to before re-profiling cylinder cooling fins?

The Manufacturer's Service, or Overhaul Manual.

What are two types of Reciprocating Engine Exhaust Systems?

The Short stack system and the Collector system.

What are the two types of propeller configurations?

The Tractor type and the Pusher type.

What unit regulates the amount of exhaust gasses to the turbine of a turbocharger?

The Waste Gate.

Where does the APU fuel supply normally come from?

The airplane's main fuel supply.

What is the purpose of a Slinger Ring on some propeller installations?

To receive deicing fluid for the propeller.

What is the effect of the pneumatic power when being used in conjunction with maximum APU shaft power output?

The pneumatic loading will be automatically modulated to maintain a safe EGT.

What happens to the excess fuel not required by the engine in a constant displacement pump?

The pressure relief valve opens and the fuel is routed back to the inlet side of the pump.

What type of exhaust system is generally used on low powered non supercharged engines?

The short stack system.

What is the typical relationship between an aircraft's APU generator and the engine driven generator?

They are identical.

Where are the fuel spray nozzles located in a turbine engine ?

They are located either externally or internally on the combustion chamber in such a way that the fuel can be sprayed into the combustion area.

What are the two most commonly used carburetors in small reciprocating engines?

They are the float-type carburetor and pressure-type carburetor.

What is the purpose of using boost pumps in a fuel system?

They are used to supply fuel to a pressure carburetor during engine starting and in case of engine driven pump failure. However, the main function of a boost pump to keep the pressure on the suction side of the engine driven pump from becoming low enough to permit the fuel to boil when operating at high altitudes.

What is the purpose of fuel selector valves?

They provide a means of shutting off fuel flow, crossfeed for tank and engine selection and for fuel transfer.

What should be used to clean aluminum and steel propeller blades and hubs?

They should be washed with a suitable cleaning solvent using a brush or cloth.

What is the purpose of the waste gate on a turbocharged exhaust?

This valve controls the amount of exhaust gases forced through the turbo charger turbine. When the waste gate is fully closed all gasses must pass through the turbine.

When changing metal bushings on a wooden propeller assembly, a thorough inspection of the bolt holes should be accomplished. Why?

To check for elongation of the holes.

What is the purpose of a propeller?

To create thrust and either pull or push the airplane through the air.

What is the purpose of Blast Tubes?

To direct jets of cooling air to accessories of the engine that have high heat concentrations.

What is the purpose of the Fins on engine cylinders?

To increase the surface area of the cylinder for cooling.

Why is the "Open and Close" adjustment during installation of cowl flaps important?

To keep the cylinder head temperature within allowable limits.

What are the probes in a turbine exhaust pipe used for?

To measure EGT and pressure.

What is the purpose of the metal tipping on a leading edge of a wooden propeller?

To protect the propeller form damage caused by foreign object damage.

Name the heat sources for the operation of fuel heaters used in turbine engines.

Turbine engines use heat exchangers to heat the fuel and prevent the possibility of ice crystal formations. Fuel lines are routed through the fuel heater, which uses a heat source, either bleed air, or engine lubricating oil. If bleed air is used as a heat source it is called an air-to-liquid heat exchanger. When oil is used, it is a liquid-to-liquid heat exchanger.

Carburetor throttle ice is most likely to form when the throttle is in which position?

When the throttle butterfly is in the partially closed position.

Can you use automotive gasoline in a reciprocating engine in place of Avgas?

Yes, if you have an STC.