Power-plan Oral Question

Define the term operating flexibility in regards to aircraft engines.

the ability of an engine to operate smoothly at all speeds from idle to full power

How are conventional reciprocating engines classified?

by cylinder arrangement or by cooling method.

What are the different types of piston rings?

Compression rings, oil control rings, and scraper rings.

What are the main causes of a cylinder having low compression?

Broken piston rings, rings are not properly sealed, burnt valves, and poorly seating valves.

What is the purpose of the oil control rings?

to control the thickness of the oil film on the cylinder walls.

What may be the result of installing piston rings incorrectly?

Excessive oil consumption.

What type of piston rods are commonly found in radial engines?

A master and articulating rod assembly.

What type of bearings are in general use in reciprocating engines?

Plane, roller, and ball bearings.

Plane bearings are generally used for crankshafts, camshafts, and connecting rods.

Roller bearings are used primarily as crankshaft main bearings.

Ball bearings are used for supercharger impeller shafts, crankshaft thrust bearings on large radial engines.

What is the indication of valve blow by?

hissing or whistling sound when turning the propeller by hand

What is the purpose of using more than one spring for valve closing?

To prevent valve surge and float.

What is the purpose of valve overlap?

for better volumetric efficiency and lowers the cylinder operating temperatures.

Describe the inspection you would give the valve springs during engine overhaul.

should be cleaned thoroughly, then visually inspected for evidence of overheating, cracks, broken ends, and compression strength.

What is the purpose of using valves with sodium filled stems?

Sodium is an excellent heat conductor and helps transfer heat from the valve head to the stem, where it is dissipated into the cylinder head.

What causes engine sudden stoppage?

By striking an object or internal engine damage

What type of inspection must be made after sudden stoppage of an engine?

Most manufacturers require complete engine tear down and inspection.

What is the purpose of the crankshaft dynamic dampers used in aircraft engines?

to reduce crankshaft deflection and torsional vibration

How would you make a runout check on a crankshaft that is still installed in the engine?

Remove the propeller, place a dial indicator on the crankshaft, rotate the crankshaft, and check runout limits

What is detonation?

Detonation is the explosive, uncontrolled burning of the remaining fuel-air mixture in the cylinder after normal ignition.

What cylinder is engine to magneto timing based on?

The number one cylinder, timing is usually set for around 30° BTDC of the compression stroke.

What is engine sudden speed reduction?

This happens when the propeller strikes an object but the engine continues running, requiring a thorough inspection

What can be learned about the condition of an engine by studying the results of a compression check?

From a cylinder compression check, you can determine if the valves, piston rings, and pistons are adequately sealing the combustion chamber.

How can a cold cylinder be located on a double row radial engine?

infrared laser thermometer.

What instrument can be used to check bore for out of roundness?

dial indicator, telescoping gauge, an outside micrometer, or inside micrometer.

What would a cold cylinder indicate?

That there's been no combustion inside the cylinder, normally due to no ignition or clogged fuel nozzle.

Where is a crack most likely to occur on a piston?

where piston pin connects. The metal is thinnest at this location.

What should be done to a nose wheel airplane before removing the engine?

Support the tail of the airplane.

What is the running valve clearance on engines equipped with hydraulic lifters?

Zero.

What lever is used to adjust the manifold pressure in a reciprocating engine?

The throttle lever

on an engine with a fixed pitch propeller, what is the relationship between manifold pressure and RPM?

As RPM increases, manifold pressure also increases

What is an indication that primer is leaking or is open during engine operation?

The engine will not idle properly.

What should be done to repair a loose stud in an engine crankcase?

Remove the loose stud and inspect the hole for size and threads condition. It may be necessary to use a suitable oversized stud.

What is meant by an engine part being within serviceable limits?

It means that the part is within the manufacturer's limits and can be used in an engine, does not require replacement.

What are the main parts of reciprocating engine accessory section?

Case and gear drivetrain.

What is stoichiometric ratio?

15 to 1

What type of ignition systems are used on modern reciprocating engines?

Electronic ignition systems.

What type of hardware is used in reciprocating engine mounts?

Heat-treated, high-strength

What type of ring goes on a chromium piston?

Iron.

The basic induction system of an aircraft reciprocating engine consists of what components?

The air scoop, carburetor or fuel control, and the intake manifold.

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

Air scoop, carburetor or fuel control unit, and intake manifold

What effect does induction system icing have on engine performance?

reduction in power and unstable engine operation

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

By applying heated air to the induction system.

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

Anti-icing fluid (like alcohol) is sprayed into the induction system to melt and loosen the ice so it can be ingested by the engine.

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

Low power.

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

The higher air temperatures could cause detonation and possible engine failure.

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.

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

as internally driven or externally driven

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

It breaks the fuel into fine particles for better distribution to the cylinders

How does an internally driven supercharger get its power?

mechanically driven by the engine crankshaft

Where does an externally driven supercharger get its power?

from exhaust gases directed against a turbine.

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

The wastegate.

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 can cause the wastegate to stick?

carbon buildup

What are the most common ways to control a wastegate?

Most common ways are mechanical linkage to the throttle or an oil-pressure actuator

What causes fuel evaporation ice?

caused by fuel cooling the air as it evaporates

What is the function of the turbocharger wastegate?

It controls how much exhaust gas goes to the turbine.

What may be the indication of leaking intake pipes?

The engine runs rough.

What may be the indication if a turbocharger waste gate will not close fully?

The aircraft may not be able to reach critical altitude.

What could be the probable cause of a turbocharger engine that surges?

Wastegate or controller malfunction.

What is used on many turbocharged engines for the wastegate actuator power?

Oil pressure.

How does a divergent shaped jet engine inlet affect the air flowing to the engine when an airplane is in subsonic flight?

It causes the air velocity to decrease and the air pressure to increase.

Bellmouth inlet ducts are used typically on what type of aircraft?

Helicopters.

The Venturi type particle separator found on many turbine powered helicopters utilize what characteristics of matter to help remove debris from induction air?

Inertia.

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

Using cowl flaps.

What is the purpose of the fins on engine cylinders?

To increase the surface area of cylinders for cooling.

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

The engine cowling and baffles are designed to force air through the cylinder cooling fins.

How is an engine designed to provide more cooling area?

The outer surface of the cylinder is increased by use of cooling fins.

Why is the open and closed adjustment during installation of cowl flaps important?

The movement must be within tolerances to keep cylinder head temperatures within limits.

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

The cylinder should be replaced

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

during all ground run operations.

What publications should be referred to before reprofiling cylinder cooling fins?

The manufacturer's service or overhaul manual should be used to obtain the allowable limits.

What power sources are used to operate the cowl flaps?

by electrical power, hydraulic power or manually.

What is the purpose of blast tubes?

To direct cooling air to hot engine accessories and ignition components to prevent overheating.

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

Excessive heat reduces engine life, affects combustion, and reduces lubrication effectiveness.

Describe the augment system.

An augmenter system uses exhaust flow to create suction that pulls more air over the engine for extra cooling.

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

Bleed air from compressor

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

To reduce heat in nearby structures and prevent fuel or oil from contacting hot engine parts.

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

stainless steel, layers of aluminum foil, fiberglass, or silver foil.

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

The combustion chamber and the turbines.

What is the purpose of an engine cowling?

To streamline the engine to reduce drag and direct cooling air around the cylinders

What is the purpose of an oil cooler bypass valve?

It allows cold, thick oil to bypass the oil cooler.

Where should cowl flaps be positioned during ground operations?

Fully open.

What is the purpose of cowl air seals?

They force air to circulate around and through the baffle system.

Where must most cooling air flow to cool a turbine engine?

Through the inside of the engine.

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

The combustion chamber and turbine.

What is the relationship between turbine engine upper temperature limits and power produced?

The higher the engine temperature limit, the more power the engine can produce.

What is the approximate percentage of air passing through a turbine engine that is used for cooling rather than combustion?

75%.

What is the unit of measure for manifold pressure?

Inches of mercury.

Other than cooling fans, how else can you cool a reciprocating engine?

Cooling jackets.

Propeller control system is divided into two types of control. What are they?

Manual and automatic control. One for flight and one for ground operations.

What is the purpose of a propeller?

To create thrust and push the airplane through the air.

What are the two types of propeller configurations?

The tractor type and the pusher type.

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

A fixed pitch propeller.

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

It is to protect the propeller from damage caused by FOD in the air during landing, taxiing and takeoff.

What tool is used to determine propeller blade angle?

A universal propeller protractor.

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

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

What is the meaning of propeller blade back and face?

Blade back is the curved side facing away from the engine, and blade face is the flat side facing the engine.

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

with a suitable cleaning solvent using a brush or cloth.

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

vertical and then horizontal position.

Can a fixed pitch propeller's pitch be changed?

No, they are fixed at a specific pitch angle.

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

To move the cylinder inboard and protect the piston from dirt and moisture when the engine is shut down.