-
what procedure should be done when valve blow-by is indicated by a hissing sound when pulling the prop through?
compression testing to find faulty cylinder
-
running valve clearance on hydraulic lifters
zero
-
what does a cold cylinder indicate on a running engine
lack of combustion on that cyliner
-
what can be learned from a compression check
if valves, rings, and pistons are sealing
-
how do you repair a loose stud on a crankcase
remove the stud and check threads, may need to over size the stud
-
How do you check a cylinder for out of roundness?
T-gauge & micrometer. Or inside micrometer. Measure the cylinder at top & skirt 90 degrees apart.
-
Types of rod used in radials?
Master & articulating rod assemblies.
-
Name types of piston rings
Compression, oil control, & oil scraper.
-
What is the purpose of oil control rings?
Regulate oil film thickness on the cylinder wall.
-
Types of bearings used in reciprocating engines?
Plain, ball, and roller bearing.
-
Where are cracks most likely found on pistons?
Highly stressed areas, base of the pin bosses, junction of the head & walls, and ring lands.
-
How are ring gaps oriented?
Staggered (not aligned) to prevent blow by.
-
What is the purpose of valve overlap?
Permits better volumetric efficiency and lowers cylinder operating temp.
-
What is the purpose of crankshaft dynamic dampers?
Reduce engine vibrations.
-
What is a serviceable limit?
The part will most likely last until next TBO interval.
-
Name at least one part of an inspection after a prop strike
(Not stoppage) Engine mounts, crank case & nose section of crank case, oil & oil screen/filters for metal contamination, inspect prop shaft or crankshaft for alignment or run out.
-
What precautions should be ovserved before engine removal?
Disconnect battery, chock, tail stand, fuel valves off.
-
What is an indication of primer leaking?
Rough idle.
-
Result of incorrect ring installation?
Excessive oil consumption.
-
What are indications of induction system leakage?
Low power& uneven running.
-
Manufactured rebuilt engine history?
No history, zero time-record issued.
-
What is used to prevent valve surge?
Two or more springs are used on each valve.
-
Name the major components of a typical gas turbine
Air inlet, compressor section, combustion section, turbine section, exhaust section, accessory section.
-
What determines amount of air passing through a turbine engine
Compressor speed, forward speed, air density
-
Name two principal types of compressors currently in use
Centrifugal & axial flow
-
How are turbine blades attached to rotor disks
- 1. bulb-type root
- 2. Fir tree-type root
- 3. Dove tail-type root
-
Name 3 types of combustion chambers
- 1. Can
- 2. Annular
- 3. Can-annular
- 4. Reverse flow annular
-
Purpose of interconnect tubes between can-type combustion chambers
Flame propagation during starting
-
What prevents burning of the combustion chambers
Cooling air along the inside of liner
-
What is the unique feature of (dual) split compressor systems
Two rotor shafts, one inside the other.
-
What is carbon seals used for
Oil seals in rotor shaft bearings
-
What is the main operating difference between turbo shaft and turbo fans
Fan air bypasses engine core
-
What is the purpose of turbine engine compressor field cleaning
Remove contaminant deposits and improve performance
-
Methods used to field clean
Fluid wash and abrasive grit blast
-
Name the advantage of turbo fan over turbo jet
Additional thrust without increasing fuel flow
-
Function of axial flow turbine nozzles
Prepare airflow for driving the turbine rotor & deflect gasses to a specific angle.
-
Ways of relieving thermal stress on a turbine disk
Bleed air on the face of the disk or grooving in the turbine disk
-
Name types of compressor blade damage
Dents, galling, pitting, cracks, scratches, burrs, burns, and gouges
-
Used to mark hot and cold section parts
Dye, felt tip marker, or chalk
-
What is the effect of relative humidity on turbine power
Negligible.
-
Indications of engine out of trim
High EGT at target takeoff EPR
-
Cause fo high EGT, low RPM and high fuel flow at all EPRs
Turbine damage or loss of turbine efficiency.
-
Preparation for 100 hour
Remove cowl and clean
-
How can you visually identify an engine
Data plate
-
What may be used for 100 hour inspection
14 CFR part 43 appendix D
-
What additional inspection must be performed if a cylinder is weak
Internal cylinder inspection
-
Name at least one place where operating limits may be found
- Type Certificate Data sheet
- Engine specifications manual
- Aircrafts maintenance manual
-
How does SOAP help evaluate the condition
Identifies each wear metal and quantity present in the oil sample
-
Approval required when engine type design in changed
- (STC) supplemental type certificate
- Form 337 (field approval)
-
Why inspect engine removed from preservation
Look for corrosion
-
What is needed to inspect engine for conformity
Type certificate data sheet
-
Pub needed to check engine for normal operations
Maintenance manual
-
What is the purpose of a hot section inspection
Check integrity of hot section parts
-
Conditions under which compliance with a service bulletin is mandatory
AD (Airworthiness Directive)
-
Approved ops specs for commercial carrier
Overhaul procedures require it
-
What is fan blade shingling
Overlapping of mid span shrouds of fan blades
-
Pubs needed for over speed inspection
Manufacturers maintenance publications
-
What's required after an over temperature event
hot section inspection
-
Place where life limited parts are found?
T-sheet, Airworthiness section of instructions for continued airworthiness
-
Criteria of life limited parts? Turbines?
Cycles, hours, or calendar date
-
Accomplish at coast down after shut down of a turbo fan or jet
Listen for unusual noise
-
Why install blades at the same location where removed?
Balance of turbine wheel
-
Items in ops check after 100 hour
- Power output (idle & static RPM)
- Magnetos
- Fuel & oil pressure
- Cylinder & oil temperatures
-
Where on reciprocating fuel flow indicating system is connected to fuel system
Between pump & carburetor
-
Basic components of a fuel flow system
Pressure and indicator
-
What read out is indicated on fuel flow sys
Fuel flow in pounds or gallons per hour
-
What is pressure range on float type carburetors
3 to 5 PSI
-
Reason for monitoring fuel flow
Fuel flow is an indication of engine performance
-
Manifold pressure gauge indicates?
Absolute pressure in (in/hg.) inches of mercury
-
What directly controls manifold pressure
RPM & throttle opening
-
On a fixed pitch, what controls MAP (manifold air pressure)
Throttle control
-
What does a reciprocating tachometer indicate
Crank shaft speed
-
What does a turbine tachometer indicate
% of compressor RPM
-
What does turbine EGT indicate
Average temp of turbine discharge gases
-
How is turbine EGT obtained
Several probes at intervals around exhaust duct perimeter near turbine exit
-
What pressures are measure to get EPR
Total inlet pressure and exhaust pressure
-
What is the torque being developed in a turbo prop indicate
Shaft horsepower
-
Where should the CHT (cylinder head temperature) probe be installed on a single probe system of a reciprocating engine?
The hottest cylinder
-
What is the electrical source for CHT (cyclinder head temp)
Thermocouple
-
Where is the location of the carburetor air temp bulb
Ram air intake duct directly ahead of carburetor
-
Probable cause for severe oil pressure drop with full oil and normal oil temp
Transmitter or indicator malfunction
-
How can turbine EGT system be checked without running engine
Resistance of thermocouples & circuits
-
When checking MAP (manifold air pressure) where should prop be set
Low pitch
-
Name types of fire detect systems
- overheat
- rate of rise
- flame detectors
-
What happens in a thermocouple system on a slow overheat
Nothing, fast rise needed
-
What happens to a thermal switch fire system when it is heated enough to operate?
Contacts close and provide a ground for cockpit fire warning devices
-
What electrical power is needed for a thermocouple fire protection system
Aircraft system and thermocouple produced electricity
-
Minimum number of thermal switches needed for a thermal switch fire protection system to operate
At least one
-
What system has most complete coverage
a continuous loop system
-
Describe the operating principle of a Kidde system
Two wires are embedded in an Inconel tube and surrounded by a ceramic insulator. One is a ground wire the other is the positive. When the temp rises to a point, the wires conduct to complete a circuit.
-
Describe the operating principle of Fenwall system
Single wire is surrounded by ceramic beads in an Inconel tube. The resistance lowers with temp rise and the wire conducts to the outer tube to complete a circuit.
-
What is the purpose of extinguishing system
Dilute atmosphere around fire with inert gas
-
Two methods used to distribute agent
- perforated tubing
- discharge nozzle
-
What is an HRD system
High Rate Discharge
-
How is HRD distributed
Open end tubes
-
How long for HRD
one to two seconds
-
What group of agents is no longer being produced because of environmental concerns
Halons or Freon or Chlorofluorocarbons (CFCs)
-
What are the ingredients for fire
heat, fuel, or oxygen
-
What is the purpose of discharge cartridge? How is it activated?
Release agent fro the bottle. Electrically from the cockpit.
-
What is the purpose of the red and yellow discharge disks
Red indicates a thermal discharge; yellow indicates a normal discharge
-
What indicates low agent pressure
Gauge mounted on fire bottle
-
What is the proper method to check pressure of fire bottles
Pressure/temperature chart
-
Where can a generator rating and performance data be found
Data plate on generator
-
Ammeter/load meter indication when engine is running?
Whether generator is supplying enough current or battery is discharging (connected to + post)
-
Ammeter/Load meter indication when the engine is running?
current leaving the generator i.e. electrical load (connect to generator output)
-
What is used to control generator voltage output?
field current strength
-
What alternator component prevents batter reverse current flow
rectifier
-
Why are multiple generator systems paralleled
Insure each generator shares an equal electrical load
-
How many phases are used in modern aircraft
three
-
What determines frequency of alternator output
number of poles and rotation speed of the armature
-
How does a voltage regulator control voltage of an alternator
Regulating voltage output of the D.C. Exciter. (Field strength)
-
Name ways to maintain 400 Hz on a large turbo just/fan engines
- Constant Speed Drives
- Integrated drive generators
- variable speed constant frequency power systems (VSCF)
-
-
3 DC motors
- Series
- shunt
- compound wound
-
Name the components of starter
- motor
- gears
- automatic engage
- disengage mechanism
-
Modes of turbine engine starter-generator
works as a starter than as a generator
-
How do we size of wire
AWG (American Wire Gauge)
-
Which size is the largest 10 or 14
10
-
Maximum slack allowed between supports
1/2 or less
-
Kind of wire run close to exhaust stacks
High temp insulation
-
What is an indication of a dirty or worn communtator
Starter drags
-
What is the purpose of bonding wires
- Return current path
- prevent ESD
- protect aircraft and people from lightning discharge
-
Name the common DC motor used for starters
Series wound
-
Why?
High torque under heavy loads
-
What is the purpose of lubrication
Reduce friction
-
Name 2 important characteristics relating to viscosity
- light enough to circulate
- heavy enough to provide an oil film at temp
-
What is the most critical lube point on a gas turbine engine
turbine bearing
-
What if the oils viscosity is too thin
oil film breaks down
-
What is the function of the dispersing agent in ashless dispersant oil
Trap contaminants in suspension until filtered
-
Why must aircraft oils be relatively high in viscosity
- Large clearances
- high temperatures
- high bearing pressures
-
Why are oil tanks required to have exansion space
Expansion & air return oil (foaming)
-
What is the purpose of the oil cooler bypass valve
Direct oil around cooler to maintain operating temperatures
-
Where does the temp bulb usually sense oil temp
engine oil inlet
-
Presence of metal in filter indicates
Internal engine failure
-
Two areas where turbine engine oil filter/screens may be located
- Oil pressure system (main filter)
- scavenge system
- at or just before oil jets (last chance device)
-
Name common oil contaminants
- moisture
- acid
- dirt
- carbon
- metal
-
What type of oils are used in turbine engines
Synthetic oils
-
What can cause excessive oil consumption with no leaks
Worn or broken piston rings (reciprocating engine)
-
What is a low oil indication
low pressure and high temperatures
-
Results of an obstruction in oil cooler passages
high temperatures
-
What causes oil foaming
- diluted oil
- contaminations
- oil level too high
-
Name two types of turbine engine oil coolers
air and fuel cooled
-
What controls maximum pressure in a gear type oil pump
Relief valve
-
What is the first step to take after finding metal in an oil filter
Evaluate contamination IAW service manual
-
What is the purpose of magnetos
produce a high voltage spark across the plug gap
-
Name three major circuits of a high tension magneto
-
Name the components of a high tension magnetic circuit
- Permanent multi pole magnetic
- sof iron core
- pole shoes
-
What crank position does the ignition even occur
Specified degrees BTC on compression stroke
-
Where is the E gap position in a magneto
a few degrees beyond magnetic neutral
-
What is the purpose of a capacitor (condensor)?
prevents arcing of the points, collapses magnetic field
-
What happens when the magnetic rotor is in the E-GAP position and the primary breaker points are open
The plug fires
-
What turns ignition off
Circuit to ground is completed
-
What is the purpose of two magnetos
- redundancy
- combustion efficiency
-
Which magneto is grounded when switch is selected to "R" position?
Left
-
Name the three events required to fire a plug on a specific cylinder
- E gap
- points open
- distributor electrically aligned with cylinder
-
What does timing light indicate
Exact instant the points open
-
Main concern when preparing magneto for installation
Internal timing
-
Are turbine ignitions apt to carbon foul?
No, high energy sparks clean electrodes
-
What is the visual indication of service life of bushes in a starter generator
Amount of wear groove left on brushes
-
Function of a duty cycle in relation to turbine ignition system
Only operates for a given time, followed by a cool down period
-
Name the three main components of turbine ignition
- Ignition exciters
- high tension loads
- igniters
-
Name 3 sources of air for starting turbines
- APU
- GPU
- bleed air from running main engine
-
Do the field or armature windings receive current for starting in a starter-generator?
Both
-
2 parts of a starter generator that require periodic inspection for wear
-
What two types of carburetors are most common to small recips
-
What is the function of mixture control of float carburetor
to control fuel and air mixture
-
Action of float type carburetor accelerating system when throttle is opened with quick action
A charge of fuel will enrich mixture in the venturi to help in the transition through RPM range.
-
When does a carburetor economizer needle begin to open?
60 - 70 % of throttle position
-
What is the purpose of economizer system
Additional fuel at high power for cooling and to prevent detonation
-
Where does a pressure injector carburetor obtain fuel pressure
Engine driven fuel pump
-
What operates automatic mixture control?
A sealed bellows that expands and contracts with change in pressure or temperature
-
What is the position of pressure injector carburetor manual mixture to stop engine?
Idle cutoff
-
Three advantages of direct fuel injection
- less danger of icing
- improved acceleration
- improved distribution
- reduced overheating
- better fuel economy
-
Problem caused by excessive rich mixture at idle
Plug fouling
-
What is the indication of proper idle mixture at cutoff
Slight rise in RPM before stopping
-
Why accelerate periodically while making adjustments?
Clean out engine
-
Function of turbine engine fuel controls
Automatically satisfy engine needs
-
Name two basic turbine fuel controls
- Hydro mechanical
- electronic
-
Variables detected by turbine fuel control
- power lever position
- engine RPM
- compressor inlet temperature
- compressor inlet pressure
- compressor discharge pressure
- burner pressure
-
Two sources used for fuel heating (turbine)?
Bleed air and engine oil
-
What turbine engine components inject fuel into combustion area
Fuel spray nozzles
-
Name another type of fuel metering system other than carburetors
Direct fuel injection
-
Trimming is accomplished by one of two ways, what are they?
-
Name two major components of a supervisory electronic engine control
- ECU
- Hydro mechanical fuel control
-
What maintenance adjustments are allowed on a hydro mechanical fuel controls
- Fuel specific gravity
- idle RPM
- Maximum RPM (EPR)
-
Name two advantages of FADEC
- No trimming
- better starts
- saves fuel
- provides limit protection
- constant idle speed with changes in atmosphere and bleed air
- fully modulates the active clearance control
- more repeatable engine transients
-
What is the purpose of turbine engine driven fuel pump
Continuous supply of fuel at the proper pressure at all times
-
Two categories of turbine engine fuel pumps
constant and variable displacement
-
What type of pump is a gear type pump
constant displacement
-
What keeps a dual element constant displacement fuel pump operating if one gear seizes
Shear sections on shafts
-
What happens to excess fuel not required by the engine in a CD pump
Pressure valve bypasses excess fuel
-
What type of pump that can vary amount of fuel regardless of speed
Variable displacement pump
-
What is the purpose of the pressure portion of P&D valve
Provide primary and secondary fuel flow to dual line duplex nozzles
-
What is the purpose of the dump in the P&D valve
Drain fuel after shut down
-
Type of pump is widely used other than gear and piston
Rotary vane
-
What is the purpose of fuel boost pumps?
Supply fuel under pressure to engine drive pumps.
-
Boost pumps prevent what?
Engine driven pump cavitation and vapor lock.
-
Name the most common type of boost pump
Centrifugal pump
-
Causes of vapor lock
- low pressure
- high temperature
- excessive fuel turbulence
-
Why is vapor lock serious
Fuel flow blockage can result
-
What is the purpose of of main fuel strainers
Collect water and sediment and keep foreign matter out of carburetor
-
What unit in a turbine engine system is susceptible to ice
Fuel filter
-
Purpose of fuel selector valves
- stop fuel flow
- tank and engine selection
- cross feed and transfer
-
Safety feature in an engine fuel system micron filter
A bypass valve
-
Methods used to prevent ice in turbine fuel filters
Heat exchangers using bleed air or engine oil
-
What does the divided fuel flows of a turbine engine duplex fuel nozzle produce in the fuel?
Two spray patterns
-
What is looked for during an external inspection of engine driven fuel pump?
Leaks and mounting security
-
Name three units in a reciprocating induction system
- carburetor
- air scoop
- intake
-
What is the result of induction icing?
Power loss and erratic operation
-
Name three classes of induction ice
- impact ice
- fuel evaporation ice
- throttle ice
-
What is the common method of preventing induction ice
Heat induction air with pre-heater.
-
Causes of fuel evaporation ice?
Decrease in temperature caused by fuel evaporating in air stream
-
When is throttle ice most likely to form?
During part throttle operation
-
Name two types of supercharged induction systems
- internally driven
- externally driven
-
Function of a sonic venturi in a turbo charger system
Limit amount of airflow used for cabin pressure.
-
How does an internally driven super charger boost?
Impeller compresses the fuel air mixture after the carburetor
-
Where does the externally driven supercharger derive its power
Exhaust gases directed against some form of turbine (turbocharger).
-
Function of a waste gate?
Controls amount of gases directed into turbine of a turbo charger
-
Indication of leaking intake pipes
Engine runs rough at low RPM.
-
What is an indication of induction system obstruction
Fails to start or low power
-
What is an indication of waste gate not fully closing
Aircraft may not reach critical altitude
-
Probable cause of turbo charged engine surging?
Waste gate or controller malfunction
-
What is used for waste gate actuator power?
Oil pressure
-
Indication of carburetor heat application
Noticeable loss of power
-
What is the danger of applying carburetor heat at high power?
Detonation
-
What is an indication of dirty air inlet filter?
Loss of power
-
How does the divergent shaped air inlet affect the air flowing to the engine in supersonic flight?
Air velocity decreases, pressure increases
-
Bell mouth inlets are used on what aircraft?
Helicopters
-
How does an IPS work?
Inertia
-
Name two methods used for anti ice on inlet ducts
Bleed air and electric elements
-
Name three reasons excessive heat is undesirable?
- Affects combustion
- Weakens and shortens engine life
- Impairs lubrication
-
What provides cooling surface area on reciprocating engines?
Cooling fins.
-
What happens to heat after it's transferred to cooling fins?
Transferred to the air.
-
What is done with a cylinder with excessive broken fins?
Replace.
-
What is the principal function of cowling and baffles?
Direct air flow over cylinders.
-
What controls the amount of air flow through the cooling area of a reciprocating engine?
Cowl flaps.
-
What is an augmentor cooling system?
Uses exhaust gases to draw cooling air using a venturi.
-
What power is used to operate cowl flaps?
-
Why use augmentors?
Provide extra cooling.
-
Where should cowl flaps be positioned during ground ops
Open
-
Information needed prior to re-profiling a cooling fin?
Manufacturer recommendations.
-
Functions of engine cowl?
Streamlines and cools engine.
-
What is the purpose of cowl air seals?
Force air to circulate around and through the baffle system.
-
Why is cowl flap adjustment important?
Must be in tolerance to keep CHT in check.
-
Where must most cooling air flow to cool a turbine?
Through engine
-
What areas are cooled by air passing through the engine?
Combustion chamber and turbine section.
-
Source of bleed air vented turbine engine bearings and parts in some engines?
Compressor section.
-
What percentage of air is moved through turbines for cooling?
75%
-
What is the relationship in turbine engines to heat and power?
Higher the heat, higher the power.
-
How is bleed air used to allow higher temps in the turbine section of some engines?
Bleed air is ducted through hollow inlet IGVS and hollow first stage rotors, keeping them cool enough to prevent damage.
-
How are high temperature gases removed and disposed of in a reciprocating engine?
Engine exhaust system
-
What is the primary function of exhaust system (safety)?
Protects airframe from destructive exhaust gases.
-
Name two types of reciprocating engine exhaust systems.
- short stack
- collected systems
-
What type of exhaust systems are used on turbo charged engines?
collector
-
Material used to make exhaust shrouds?
Stainless steel
-
What draw back is overcome using collected system and turbo charging?
The loss of power due to back pressure.
-
Why is exhaust failure considered a hazard?
Results in carbon monoxide poisoning, power loss, or fire.
-
Why should lead, zinc, or galvanized marks not be made on exhaust systems?
Marks cause a change in the molecular structure of the metal when heated and causes cracks
-
Indication of exhaust leaks?
Flat gray or sooty black deposits.
-
How are internal baffles and diffusers inspected?
Disassemble as needed to thoroughly inspect.
-
What can result from failures of diffusers or baffles?
Restriction of the flow of gases.
-
What happens when a heat exchanger leaks exhaust gases into the intake system?
Loss of power.
-
Where are exhaust manifold and stack failures usually found?
Welded or clamped joints or flanges.
-
Name the common cause of turbo waste gates sticking.
Coke deposits or carbon build up.
-
Why are turbo exhaust leaks very damaging at high altitudes?
Pressure differential causes leaks with torch like intensity.
-
What are coke deposits?
Carbon build up.
-
What happens to turbine performance if the exhaust nozzle area is changed?
Performance and EGT changes.
-
Components of a typical turbine exhaust nozzle?
- Tail cone
- exhaust duct
- support struts
-
Function of a thermocouple probes in a turbine exhaust tail pipe
Measure EGT
-
What change goes a noise suppressor make on a turbo jet engine?
Converts low frequency to high frequency.
-
What are thrust reversers used for?
Decelerate after landing.
-
Name two types of thrust reversers
- Mechanical (clamshell)
- Cascade (aerodynamic)
-
Do thrust reversers equal engine thrust?
No, much less.
-
What are the hazards of reverser operations at low speed?
- Re-ingestion of hot gases
- FOD damage
-
How do you determine repair ability of propellers?
Manufacturer maintenance manual.
-
What is the purpose of props?
Blades produce a force.
-
What is a fixed pitch prop?
Built in blade angle that does not change.
-
What would be the blade angle change during a constant power drive (governer controlled)?
Increased blade angle to prevent over speeding of the engine.
-
Other than maintaining constant speed, what are two actions of a controllable prop?
-
What is the purpose of metal tipping on wooden propellers?
Protect propellers leading edges.
-
When an engine vibration is reported, what should be checked?
- Blade tracking
- Blade angle
-
What is blade tracking?
Determine blade tip positions in relation to each other.
-
What is used to check blade angles?
Propeller protractor.
-
How should aluminum blades be cleaned?
IAW manufacturer recommendations.
-
Name the two positions to balance props?
Horizontal and vertical.
-
What two forces are balanced in a propeller governor in an on speed condition?
Speeder spring and fly weight.
-
Effect of centrifugal force on light prop counter weights?
Increase propeller pitch.
-
What happens if constant speed feathering propeller when prop governor oil pressure drops to 0?
Propeller will feather.
-
Name three things a typical Constant Speed Propeller governor accomplishes?
- Boosts engine oil pressure before it enters propeller hub
- controls oil flow into propeller
- senses rotational speed of engine.
-
Systems used to control ice on props?
Fluid (alcohol) or electrical (boots)
-
What NDT should be done on propeller after blending?
MANU RECS Manufacturer recommendations.
-
What terms do "alpha" and "beta" range refer to?
Operating modes of turbo prop reversible-pitch propellers.
-
Define alpha range
Operational in constant speed mode (usually in flight).
-
Define beta range.
Zero or minimum thrust and negative thrust (ground handling or taxi).
-
What is the purpose of oil accumulator connected to propeller governors?
Provide unfeathering oil pressure.
-
How is feathering accomplished on a CSP?
Releasing oil pressure allows counter-weights and feathering spring to feather prop.
-
Criteria used to determine amount of bend damage that can be repaired?
Extent of damage and blade station.
-
What is used to remove file marks from a propeller?
Very fine sandpaper.
-
What is used to clean wooden propellers
Mild soap and water and brush
-
What does APU stand for
Auxiliary power unit.
-
Define APU
A small turbine with provisions for bleed air and electrical generation.
-
What causes the greatest demand on APUs?
Bleed air loads.
-
What is the function of an APU?
- Electrical power
- pneumatic power
- back up source of electrical power
-
What is typically used to start APU
Its own electric starter and battery
-
What speed does a turbine APU operate?
At or near rated speed regardless of load.
-
How is a heavily loaded APU nearing its max (EGT) protected?
Load control valve.
-
How is the cool down for many APUs done?
Running for a specified time after closing the bleed air valve (unloaded).
-
Where does an APU get its fuel supply?
One of the main air fuel tanks.
-
What does the cool down time do?
Stabilizes EGT.
-
APU speed is maintained by?
Fuel control (automatic).
-
Name 2 uses for APU pneumatic power?
- Engine start
- a/c
- anti-icing
-
What is the cause of thermal shock?
Shutting down loaded or no cool down period provided.
-
What powers the IGVs on APUs?
Fuel pressure.
-
Typical cool down period for APUs?
3 minutes.
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