POWERPLANT INSTALLATION Flashcards
What are powerplants divided into cooling zones by means of?
Fireproof bulkheads (firewalls)
Made from steel, titanium or thermoplastics.
What does the engine nacelle do?
Give the engines a necessary aerodynamic smoothness and protects engine components from damage.
What size dents are allowed in class 1 aerodynamic areas?
Only very small dents.
What gives undisturbed airflow around the pylon?
Fairings.
What part of the air intake can be heated to prevent build up of ice?
Nose lip.
Spray duct distributes hot air.
Why does the inner barrel have acoustic linings?
Reduce noise radiation from the fan.
What are index pins for?
Ensures the engine cowl can only be installed in the correct position.
What part of the engine covers the accessory gearbox?
Fan cowling.
What is the fan cowling usually made of?
Sheet metal or composite materials.
How many latches is the lower part of each fan cowling fastened to the opposite cowling?
3 or more.
What ducts do the fan air pass through in the fan reverser cowling?
C ducts (because of shape)
What is the fan reverser cowling made of?
Steel or titanium
Composites for skin only
How can the fan reverser cowling only be opened?
Hydraulic pressure.
What is cowl load sharing for fan reverser cowling?
Uses V shaped grooves and blades that give good contact to the engine fan frame.
Which cowling has 2 passive fire protection features preventing fire from hot sections reaching other areas of the aircraft.
Fan reverser cowling.
What is the fire seal on the fan reverser cowling connection to the fan frame made of?
Titanium with heat resistant silicon layer
What is the core cowling always made of?
Metal, covers hot section.
What 2 components is the exhaust nozzle made up of?
Centre body
Exhaust sleeve
What engines have reduced exhaust signature?
High bypass fan engines. Turbines extract most energy from gas stream.
How do acoustic panels reduce noise?
Noise absorbing materials convert noise energy to heat energy.
What materials are used for low temperature and high temperature areas in the acoustic panel?
Low- lightweight composites
High- fibrous-metallic materials
What is the noise absorbing material made up of in acoustic panels?
Perforated metal or composite facing skin, supported on honeycomb structure.
What size are acoustic panels?
Air intake- 1 inch thick
Inner fan case and outer casings- 1-1.5 inch thick
Exhaust cone- 0.5 inch thick
What does the compartment ventilation exhaust discharge?
Air that was used to cool core engine cases.
How is the pressure relief door usually held shut?
Closed by a spring.
What does a lanyard do in the pressure relief valve?
Prevents panel from flying away.
How are holes usually covered to prevent anything entering?
Plastic covers fixed with strips or tape, special plastic plug for exhaust nozzle.
What are engines under the wing called?
Wing mounted engines.
What is the pylon where all engines are fitted on?
Engine strut.
How many mounts is the engine usually connected to the pylon by?
2
Forward mount- to fan frame
Aft mount- to turbine frame
What do the engine mounts do?
Transfer all forces from the engine to the pylon.
What axis does the engine weight act in?
Vertical axis (known as z axis)
Carried by forward and aft mounts.
What axis does the engine thrust act in?
Longitudinal axis (also called x axis)
Axial force, only supported by forward mount.
What axis do side loads act in?
Lateral axis (also known as y axis)
Generated by flight manoeuvres, transferred by forward and aft mount.
Why is thrust only transferred by the forward mount?
The axial thermal expansion of engine (can be more than 20mm) must not generate force to mounts.
How is the forward mount connected to the pylon by?
4 attachment bolts.
Vertical engine loads
On the forward mount, how are thrust and side loads transferred?
Shear pins.
What construction is the support beam for forward engine mount?
Fail safe.
Loads can be shared between remaining 2 connections if one breaks.
What type of anti-vibration mounts are used on turboprop?
Resilient rubber mounts.
Need to be inspected for heat and fluid deterioration
What is PTFE used for in hoses?
High pressure applications.
-54 to 223 celsius and on most fluids.
The does the use of steel for pipes permit?
Use of thinner walls, no excessive weight gains.
What are feeders?
Cables which take power to and from a component.
What design are most connectors found on modern aero engines?
Bayonet design.
How are wiring looms and bundles secured?
Dacron lacing cord.
(Nylon tie wraps not permitted)
As engines high vibration areas, no more than 2 inches apart.
What is the bootstrap method for engine change?
Uses a beam attached to the top of the pylon with quick release pins.
Standard method for all wing mounted engines.
Requires a long time.
What is the crane supported sling method?
More expensive equipment but about 30% less time than bootstrap.
Sling connected with 2 chain hoists.
What is the uplift loader method of engine change?
Expensive special equipment. (Not commonly used)
Fastest time (40% faster than bootstrap)
Why are friction dampers fitted to the throttle lever assembly?
Prevent movement from vibration.
What are the components of an engine drain system?
Drain lines
Module assembly where all drain lines end
What is the lower part of a drain system called which puts the fluids overboard?
The drain mast
What typical areas would you find component leaks?
- pylon
- fuel operated VBV and SVS actuators and servo valves
- oil tank scubber
- fuel oil heat exchanger
Where can drain lines be found?
- drive pads of the HMU
- Starter
- IDG
- fuel oil and hydraulic pumps
How is a fire risk in the pylon drain outlet minimised?
The most important outlet drains fuel directly overboard
Ensures fuel can’t be collected anywhere and drip on engine
What is a direct drain system?
Drain lines which end with a specific hole in the drain mast.
(Fuel lines on left, oil lines on right)
How can you identify which system a leak has come from on a direct drain system?
Follow the fluid mark directly to the designated hole.(tells you which system it’s from)
How do you do a system leak rate check on the drain systems?
Disconnect drain lines from the drain mast and fit small plastic bottles to it. Do engine leakage run
What is the purpose of a drain collector system?
Uses separate collectors to catch leaks for individual accessory gear box components
On drain collector assemblies, where do leaks which aren’t from the accessory gear box go?
Directly to the drain module assembly.
What is the system process if there is a leak in the fuel pump?
- Fuel pump collector
- If full overflows to holding tank
- Overflow again, to drain mast
Why should an overflow of the holding tank not occur?
As it is emptied during flight
How are holding tanks emptied during flight?
Ram air enters front side of drain mast, at 200 knots ram air pressure opens spring loaded valve and pressurises tank
(Fluid forced out)
How do you empty collectors?
Manually by a spring loaded drain valve
Used to check leakage rate of accessory drive seal
How do you check the leakage rate of an accessory drive seal?
Drain collectors with manual spring loaded drain valve. Measure fluid. Next flight compare the fluid leakage against collected fluid.
