Powerplant Theory and Maintenance Lecture Notes

A comprehensive set of flashcards covering key concepts from the lecture on powerplant theory and maintenance, focusing on engine types, components, functions, and maintenance protocols.

Conventional reciprocating engines classification

Classified according to cylinder arrangement (in-line, V-type, radial, or opposed) or method of cooling (liquid-cooled or air-cooled).

Types of piston rings

Compression rings, oil control rings, and scraper rings.

Oil control rings purpose

Control the thickness of the oil film on the cylinder walls.

Incorrectly installed piston rings result

Excessive oil consumption.

Common piston rods in radial engines

Master and articulating rod assembly.

Bearings in reciprocating engines

Plain bearings, roller bearings, ball bearings.

Indication of valve blow-by

Hissing or whistle when pulling the propeller through, indicating a compression issue.

Multiple springs on valves purpose

Eliminate valve surge at certain speeds and reduce danger of breakage.

Valve overlap purpose

Allows better volumetric efficiency and lowers cylinder operating temperatures.

Inspection of valve springs

Should be cleaned, visually inspected for overheating, cracks, broken ends, and compression strength.

Sodium-filled valve stems purpose

Excellent heat conductor that helps dissipate heat from valve head to stem.

Engine sudden stoppage causes

Striking an object or internal damage causing engine seizure.

Inspection after a propeller strike

Check engine mounts, crankcase, nose section for damage and oil for metal particles.

Crankshaft dynamic dampers purpose

Overcome forces causing crankshaft deflection and torsional vibration.

Detonation definition

Explosive burning of fuel-air mixture caused by exceeding critical temperature and pressure limits.

Cold cylinder indicator

used to locate cylinders with lower than normal temperature.

Components of a gas turbine engine

Air inlet, compression section, combustion section, turbine section, exhaust section, accessory section.

Types of turbojet compressors

Centrifugal flow and axial flow.

Types of combustion chamber systems

Can type, can-annular type, and annular type.

Interconnector tubes function

Spread flame to non-ignited combustion chambers during engine start.

Cooling of can-type combustion chamber walls

Achieved using louvers for air cooling.

Compressor blade damage types

Dents, scratches, gouges, burns, pitting, cracks.

Diffuser section location

Between compressor section and burner cans, changing air velocity to static pressure.

Stress rupture cracks location

Leading or trailing edge of turbine blades.

Compressor blades attachment

Fitted into disks by bulb-type or fir-tree type roots, locked with screws or pins.

Turbofan advantage over turbojet

Additional thrust without increasing fuel flow.

Turboprop vs turbojet difference

Turboprop has more turbine stages and drives a propeller.

Turbofan engine defined

Similar to turboprop but with a duct-enclosed axial flow fan.

Effect of humidity on turbojet/turbofan power

Negligible.

Common types of thrust reversers

Mechanical blockage type (clam shell) and aerodynamic blockage type (cascade).

Split compressor system purpose

Requires two concentric shafts for compressors due to turbine stages.

Relieving thermal stress on turbine disk

Achieved by bleeding cooling air onto disk face.

Out-of-trim turbojet indications

High exhaust gas temperature (EGT) at target engine pressure ratio (EPR).

Preparation for 100-hour inspection

Remove inspection plates, clean aircraft and engine.

Guide for a 100-hour inspection

FAR Part 43, Appendix D.

Weak cylinder compression inspection

Requires internal cylinder inspection.

Engine operating limitations location

Found in Aircraft Specifications or Type Certificate Data Sheet.

Identify an aircraft engine location

On the engine identification plate affixed at an accessible location.

Publication for engine inspection conformity

Engine Specifications or Type Certificate Data Sheet.

FAA approval for design change not needing new Type Certificate

Supplemental Type Certificate required.

FAA approval for change in operating principle

New Type Certificate needed.

Importance of turbine blade location after removal

Necessary for balance of the turbine wheel.

Operational check items after inspection

Power output, magnetos, fuel and oil pressure, cylinder and oil temperature.

Life limited components replacement criteria

Cycles, hours, or calendar time.

Where to find a list of life limited parts

Type certificate data sheet or Airworthiness Limitations Section.

Engine fuel flow system units

Transmitter and an indicator for each engine.

Fuel flow transmitter location

Mounted in the fuel line between engine driven pump and carburetor.

Readout indication on fuel flow system

Calibrated to record fuel flow in pounds or gallons per hour.

Reason for monitoring fuel flow

Determines if engine is operating at correct fuel-air mixture.

Manifold pressure gauge function

Measures absolute pressure in intake manifold in inches of Mercury.

Broken manifold pressure gauge line effect

Will cause gauge to indicate atmospheric pressure.

Reciprocating engine tachometer function

Indicates crankshaft speed (rpm).

Turbine engine tachometer indication

Indicates percent of compressor rotor rpm.

Turbojet EPR defined

Ratio of total turbine discharge pressure to total inlet pressure.

Cylinder head temperature gauge electric source

Connected to a thermocouple attached to the hottest cylinder.

Carburetor air temperature bulb location

Located in the air intake passage to the engine.

Turbine engine EGT check without operating engine

By checking resistance to thermocouples and circuits.

Thermocouple installation in single probe cylinder head

On the hottest cylinder.

Fire detector types

Overheat detectors, rate-of-temperature-rise detectors, flame detectors.

Thermocouple detector system slow overheating effect

Will not give warning if slow overheating occurs.

Kidde continuous loop detector system operation

Uses ceramic core resistance change to provide current during temperature rise.

Thermocouple fire detector power source

Produced power to close relay, followed by aircraft electrical system flow.

Thermal switch fire detector system description

Energizes lights when thermal switch closes at specific temperature.

Thermal switches connection in circuit

Connected in parallel but in series with warning light.

Common cause of false fire warning

Dents or kinks causing short in continuous loop detector.

Methods to discharge fire extinguishing agents

Mechanical and electrical methods.

Turbine engine extinguishing system release method

Discharge valves operated by electrically discharged cartridges.

Low pressure indication method in fire extinguisher

Low-pressure warning light in cockpit.

Yellow and red discharge plugs purpose

Yellow for normal discharge, red for thermal discharge.

Fire-extinguishing agent distribution methods

Perforated tubing or discharge nozzles.

Fire extinguishing agent function

Dilutes atmosphere to prevent combustion.

HRD fire extinguishing system defined

High Rate of Discharge system.

HRD system agent distribution method

Delivered from open-end tubes.

HRD system discharge agent time

Takes 1 to 2 seconds.

Generator brush seating method

Shape brushes to provide maximum contact with the commutator using sandpaper.

Generator rating location

Stamped on generator nameplate.

DC generator three-unit regulator components

Voltage regulator, current limiter, reverse current cutout.

Voltage control method for alternators

Speed of rotation and number of poles.

Frequency maintenance for alternator

By constant speed drive (CSD) unit.

Types of DC motors

Series, shunt, compound.

DC motor components

Armature, field, brushes, frame.

Starter-generator system function

Acts as starter motor and generates power at self-sustaining speed.

American Wire Gauge (AWG) system definition

Wire size designated by gage number based on cross-sectional area.

Open wiring definition

Any wire not enclosed in conduit.

Lubricant purpose in aircraft engine

To reduce friction between moving parts.

Important oil property for reciprocating engines

Viscosity.

Factors in determining oil grade

Operating load, rotational speeds, and operating temperatures.

Oil flow control valve purpose

Regulates oil flow into or around oil cooler.

Main oil contaminants

Gasoline, moisture, acids, dirt, carbon, metallic particles.

Oil temperature measurement location

Inlet line between oil tank and engine for dry sump; after oil cooler for wet sump.

Metallic particles on oil screen indication

Suggests internal engine failure.

Oil foaming causes

Diluted, contaminated oil or too high oil level.

Blocked oil cooler indication

High oil temperature.

Inadequate oil supply indications

Low oil pressure and high oil temperature.

Turbine engine oil type

Specially developed synthetic oils.

Types of oil coolers in turbine systems

Air-cooled and fuel-cooled oil coolers.

Oil flash point definition

Temperature where oil gives off ignitable vapors.

Oil fire point definition

Temperature where vapor supports a flame.

Engine oil functions

Lubrication, cooling, sealing, cleaning.

Aircraft engine oil weight

Approximately 7.5 pounds per U.S. gallon.