FAA Powerplant oral questions ( Jeppensen)

What is the purpose of dynamic dampers on crank shafts

they reduce engine vibration

What types of barring are generally found in reciprocating engines

plain ball and roller barrings

Are the connecting rodes used in each cilender of a radial engine the same

no, they use master and articulating rod assembling

Name the different tyoes of piston rings

oil control, compression, and oil scraper

Where should piston ring gaps be installed relative to each other and why

compression ring gaps should be staggered, this prevents blow by

What could result from incorrectly installed piston rings

excessive oil consumption

What purpose do oil control rings serve

they regulate the thickness of the oil film on the cylinder walls

What is used to help prevent valve surge

two or more springs are used on each valve

What is the purpose of valve overlap

allows better volumetric efficiency and lowers cylinder temperatures

What indications are giving in the event of the leaking primer when the engine is running

the engine will not idol properly

A cold cilender is found when trouble shooting a running engine, what does this indicate

no combustion in that cylinder

When pulling a propeler through a hissing sound is heard indication valve blow by what should be performed

a compression check to identify the faulty cylinder

Wha is the purpose of performing a compression check

to determine if the valve and piston rings are sealing properly

When an engine is overhauled how is its total time effected and when an engine is rebuild how is its operating history effected

the total time on an engine must be continued and the time since major overhaul is entered into the eh=ngine log if the manufacture rebuilds the engine it granted a zero time status and is considered to have no previous operating history

What inspections should be preformed after a propler strike without sudden stoppage

inspect engine mounts, the crank case, and the nose section for damage, inspect oil and oil filter for metal, inspect the crankshaft for cracks and misalignment

Name some percautions tha should preformed prior to engine removal

disconnect the battery, turn off fuel valves, chock the wheels, install a tailstand

When inspecting a piston where are cracks most likely to be found

base of piston bosses, inside at the junction of the bore and the walls and ring lands

What does it mean if an engine part is within serviceable limits

the part is with in manufactures limits and can be used in an engine

What tools or instruments are used to inspect a cylinder barrel for out of roundness

a telescopic gage and micrometer can be used. Two readings should be taken 90 degrees to each other

What publication is used to check an engine for normal operation

manufactures m/m

A week cylinder is found during a compression check, what must be inspected

pressure is transmitted equally in all directions

What purpose does an oil analysis serve

medal particles in the oil show normal and abnormal wear in the engine

What inspection should be performed in an engine in storage

inspect to determine if there is any corrosion damage

Where would a carburetor air temperature bulb be located

in the ram air intake duct

What is the fuel pressure range on a float type carb

three to five psi

Where is the fuel flow indicting system generally connected within a carb engine

temperature and atmospheric pressure

What unit of measure is generally used to indicat fuel flow

pounds or gallons per hour

Why is fuel flow monitored

to determine fuel consumption and engine performance

What does the manifold gage indicate and how is it calibrated

measures the absolute pressure in the manifold and is calibrated in inches of mercury

What directly controls manifold pressure

throttle opening and engine rpm

During engine operation where should the propeller control be set when checking the manifold pressure

low pitch high rpm

Is the air craft electrical system required to power a cylinder head temperature gage

no, they creae there own electrical energy

What are the possible indications of an oil pressure transmitter or indicator malfunction

a serve or sudden drop in oil pressure while the oil tempature remains normal and the oil supply remains full

What does tachometer indicate on a recip engine

engine rpm

Where should the termalcouple be installed on a recip engine using a single probe cylinger head temperature system

on the hottest cylinder

Explain the main differences and advantages of Turbofan ever turbojet engines.

A Turbofan engine uses a fan to bypass some of the air around the Engine core and to provide thrust. provides more thurst without increasing fuel flow

Name the major components in a gas turbine engine.

Air inlet, compressor , combustion , turbine , exhaust , gearbox and accessory section

What determines the amount of airflow through a turbine engine.

The forward speed of the aircraft, compressor speed, and air density

Name the two types of compressors commonly used in turbine engines

Axial and centrifugal flow compressors

What is a split compressor system.

These are connected to turban section with two rotor shafts one inside the other

What are the different types of combustion chambers use in turbine engines.

Can, annular, can - annular, and reverse flow annular.

What prevents combustion chambers from burning.

Cooling air along the inside of the liner

What is the purpose of the interconnecting tubes attached between can - type combustion chambers.

For flame propagation during start

What functions do axial flow turbine nozzles perform.

They direct the airflow to drive the turbine rotor at a specific angle

How is thermal stress relieved on turbine disc.

By directing bleed air onto the face of the disc or by grooves being cut in the disc

What are carbon seals use for an turbine engines.

They are used as oil seals for rotor shaft bearings

What is shaft horsepower.

torque developed by a turboprop or turboshaft engine

Name the main components of a typical APU

A small power turbine for power and bleed air and a electrical generator

When is the greatest demand placed on an APU.

When supplying bleed air

How is an APU generally started.

With its own electrical starter and battery power

Where does the APU get its fuel supply.

From one of the aircraft's main fuel tanks

At what speed does the a gas turbine APU operate and how is this speed maintained.

At or near it's rated speed regardless of electrical or pneumatic loads and the fuel control automatically adjusts the fuel flow to maintain the rated speed

What is used to prevent a heavy loaded APU from exceeding its maximum EGT.

A load control valve modulates the pneumatic load to maintain EGT within limits

How is a APU shut down and why is this procedure used.

It is unloaded by closing the bleed air valve then ran for a specific amount of time to allow the EGT too cool and stabilize

What is fan blade shingling.

It is the overlapping of the mid span shrouds of the fan blades

When a Turbofan or turbojet engine is shut down what should a mechanic listen for during coast down.

Any rubbing sound or other unusual noises from the engine.

Why are compressor washes performed and what methods are commonly used.

To remove any contaminants from the compressor section and improve engine performance the fluid wash and abrasive grit wash are commonly used

How can you tell if it Turbofan or turbojet engine is out of trim

There will be a high exhaust gas temperature at the target engine pressure ratio for takeoff power

Name the different types of compressor blade damage that may be found during inspection.

Dents cracks, galling pitting, scratches, burrs, burns, gouges

What kind of markers can be used to mark the part in hot and cold sections during repair.

Layout die, felt tip marker, chalk

How does a relative humidity affect turbine engines.

No effect

What criteria determines replacement of life limited turbine engine components.

Cycles, hours and/or Calendar time

If turbine blades are removed from a turbine disc why should they be reinstalled in the same location.

To maintain the balance of the turbine wheel

How are gasturbine engine tachometers calibrated.

In percent of RPM

On a turbine engine what is the engine pressure ratio and what does it indicate.

It is the ratio between the total inlet pressure and total turbine exhaust pressure and it indicates thrusts developed by the engine

On a turbine engine what does exhaust gas temperature indicate and how is it obtained.

EGT is the average temperature of turbine discharge gases as obtained by thermocouples place near turbine exit

Can the EGT system on a turbine engine be checked without running the engine.

Yes, by checking the resistance of the thermocouple and circuits

Name the three components on the induction system of a reciprocating engine.

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

What could happen if the induction system became obstructed.

The engine may not be able to produce its rated power or it may not run at all.

How does induction icing effect engine performance.

It causes a reduction in power and possible erratic operation

How is induction icing categorized.

As impact eyes fuel vaporization ice and throttle ice

What is common method used to prevent induction ice in a reciprocating engine.

Raise the temperature of induction air with a preheater

What causes fuel evaporation ice.

because of the decrease in temperature resulting from evaporation of the fuel when introduced into the airstream

Is carburetor throttle ice more likely to occur at higher or lower power settings and why.

At lower power settings because the throttle is Partly closed, offering a larger surface area for ice to accumulate

what may be the indication of leaking intake pipes.

The engine runs rough at low RPM

What happens to engine power when the carburetor heat is applied.

it decreases

What could happen if carburetor heat is applied at high engine power settings.

Detonation

What are two types of supercharged induction systems.

Internally driven and externally driven

How and at what point does and internally driven supercharger boost air pressure.

An impeller compresses the fuel/air mixture after it leaves the carburetor

What is used to power a turbocharger.

Engine exhaust gas

What could result if the wastegate on a turbocharger system does not close fully.

The engine may not be able to produce its rated power at certain altitude and may not reach its critical altitude

What function does a turbocharger wastegate perform.

It controls the amount of exhaust gas either into or around the turbocharger, and controlling the boot pressure

What could cause a turbocharged engine to surge

There could be a wastegate or controller malfunction

What are the most common ways to control a wastegate.

Either mechanically with linkage to the throttle or a separate control, or by actuator that is driven by oil pressure

In a pressurized reciprocating aircraft, what component in the turbocharger system is used to limit the amount of turbocharge airflow use for cabin pressurization.

The sonic Venturi

What is the function of a divergent shaped jet engine inlet during sub sonic flight.

Velocity decreases while pressure increases

Where are bellmouth inlet ducts typically found.

On helicopter engines

How do venturi type particle separators, found on many turbine powered helicopters,function?

A Venturi is used to accelerate the airflow of incoming air and a debris through a curved intake. the debris gains too much speed to follow and is channeled away from the compressor

What are the most common methods use for anti-icing for turbine engine inlet ducts.

Engine bleed air and electric heating elements

What is the purpose of the exhaust system.

To remove the high temperature noxious gases

Name two types of reciprocating engine exhaust systems.

The short stack and the collector system

What drawback in using collector type exhaust systems is more than offset when used on turbocharged engines.

The loss of horsepower due to the exhaust system back pressure

What could result if the internal baffles or diffusers and an exhaust system fail.

The flow of the exhaust gases could be restricted resulting in a loss of engine power

What type of exhaust system is used on turbocharged engines.

The collector system

What kind of material is normally used to make muffler shrouds found in the exhaust system.

Stainless steel

How do you inspect the internal baffles and diffusers of an exhaust system.

Disassembling the exhaust system as necessary and visually inspecting the components

Why is an exhaust system failure considered a severe hazard.

It can result in a carbon monoxide poisoning, loss of engine power, or fire

What could happen if lead, zinc, or galvanized marks are made on exhaust system.

They cause a change in molecule structure, which could result in cracks when heated

What happens if the heat exchanger leaks exhaust gases into the induction system.

There is a loss of engine power

What is an indication of an exhaust gas leek.

A flat gray or sooty black deposit in the area of the leak