15.19 Powerplant Installation Flashcards
How are gas turbine engines divided into cooling zones?
Fireproof Bulkheads (firewalls)
What is the inner firewall assembly made from?
Either titanium or or steel
Why are tubes, electrical harnesses and controls sealed through a firewall?
It ensures external engine fires cannot enter the adjacent areas
What is the purpose of the engine nacelle?
It gives the engine aerodynamic smoothness and protects the engine from FOD damage
What is the fan reverser cowling and core cowling known as if it is one unit?
The thrust reverser cowling
What are the parts of the engine that are class 1 aerodynamic smoothness?
The critical parts, ensuring undisturbed airflow around and inside the engine
What are the parts of the engine that are class 2 aerodynamic smoothness?
Other parts of the engine such as the pylon
In a class 1 aerodynamic smoothness area, what is allowed?
Only very small dents allowed
When opening the engine, which part is always opened first?
The fan cowling
What is incorporated into the inlet cowling to reduce noise?
Acoustic linings
When installing the air inlet cowling, what must be ensured?
The two pins must fit into the corresponding holes on the engine, ensuring the correct installation position
What are the fan cowls usually made from?
Composite or sheet metal
How are the fan cowls attached to the engine pylon?
They are connected via hinges
When must you not open fan cowls?
In strong wind conditions
What must you also ensure before opening fan cowls?
The slat position, some aircraft require these to be retracted and deactivated
If the fan cowls are open, what is not permitted?
Towing of the aircraft
What are the fan reverser ducts also known as?
The C-ducts
How are the fan reverser cowlings opened?
They are opened using a hydraulic hand pump because of their heavy weight
What is Cowl Load Sharing?
The cowling has V-shaped groves and the fan has blades that give good contact to the engine fan frame
What is the issue with the engine cowlings at takeoff?
The airflow hits the cowlings at the bottom which can deform the shape causing excessive blade tip rub or tip clearance on adjacent sides. The cowlings are therefore strengthened
What fire protection systems does the thrust reverser cowling have?
- a protective coating on the inner side
- a fire seal on the connection to the fan frame
How is the core cowl attached to the engine?
Usually attached to the fan reverser cowling as one unit
What parts make up the exhaust nozzle?
- the centre body
- the exhaust sleeve
How do acoustic panels reduce noise?
They convert acoustic energy to heat energy
What are the pressure relief doors for?
They open when there is an overpressure in the compartment such as a bleed duct leak
How do the pressure relief doors work?
They are closed by springs in normal operations and this is overcome when the pressure inside the compartment exceeds a certain limit
What prevents a pressure relief panel flying away during flight?
A lanyard
What must you do before mooring or parking an aircraft?
Close all open holes to the engine carefully to prevent dirt, moisture or animals entering the engine
What are engines mounted under the wing called?
Wing mounted engines
What are engines mounted on the left/right hand aft of the fuselage called?
Side mounted engines
What is the engine pylon called, no matter where the engine is mounted?
The engine strut
How is the engine attached to the pylon?
The forward mount and the aft mount
Which mount is the engine thrust transferred to?
The forward mount only
Why are axial loads (thrust) only transferred to the forward mount?
The rear mount uses spherical bearings which can only take vertical loads (weight) and side loads and it also compensates for thermal expansion.
How are turboprop engines mounted?
With resilient rubber mounts and links to reduce vibration and torque effects
Due to the torque effect of a turboprop, what is an important design feature about the mount?
It must have a more robust construction than a comparable turbojet
For hoses, what must the printed indications include?
- Manufacture Date
- Part number
- Name
- Inspectors stamp
What type of rigid pipes are used on aircraft engines?
Corrosion-resistance steel pipes
Steel = thinner than aluminium and no excessive weight
Prior to assembly, what should be done to a rigid pipe?
It should be blown out with clean, dry air and flushed with the same (clean and filtered) fluid which will operate through the pipe
What cannot be used to blank off rigid pipes if storing them?
Paper, tape or rag
What is the advantage of using P-clips for rigid pipes?
It removes the need for separate packing if pipes run close to one another
What special quality do most pipes on an aircraft have?
They are self-bonding
When installed, what distance should pipes be from:
- Fixed structures?
- Rigid moving parts?
- Control cables?
- fixed = 6mm
- rigid = 18mm
- ctl cables = 25mm
What are feeders?
They are cables that take power from a component
What is the problem with resistance in a wire of a digital system (FADEC) cable?
It has signal loss, increased heat and can cause damage to the components
What type of connectors are present on FADEC or modern jet engines?
Bayonet design
What are the bayonet design connectors also known as?
MIL-38999 Series 3 connectors
At what intervals are wiring looms in jet engines bundle tied together?
Every 2 inches as the engine is a high vibration area
Where the wiring enters a connector, the last bundle tie must be…
No more than 6 inches from the connector
What type of wire bundle tie material is permitted for the engine looms?
Dacron lacing cord
Nylon wire ties are not permitted
What are the three methods of performing an engine change?
- bootstrap method
- overhead crane supported sling method
- uplift loader
How is the bootstrap engine change method carried out?
A beam is connected to the top of the pylon and chain hoists move the engine on/off the structure. It is slow as the pylon fairings are removed
What is the advantage of using the crane supported sling method?
It is around 30% less time consuming than the bootstrap method but has more expensive equipment
What is the advantage of using the uplift loader method?
It is around 40% less time consuming than the bootstrap method, but more very expensive equipment is required and so isn’t commonly used
What are fitted to the throttle levers to prevent movement due to vibration?
Friction dampers
When rigging flight controls and throttle levers, what should be installed for safety reasons?
A red-flagged safety pin
After flight control rigging, what must be done?
A duplicate inspection of the system and a ground run completed
What is the purpose of an engine drain?
It allows fluids to vent overboard and also allows for leak monitoring
What is the main drain outlet located on the pylon for?
It drains fuel directly overboard so that it does not collect in the pylon and eventually drip onto the engine
What is a direct drain system?
All drain lines end at the drain mast with specific holes
What is a leak rate check?
The engine is run and the leaking fluid is collected from the separate pipes to bottles and checked against limits in the AMM
What is the advantage of using a drain collector assembly attached to the drain lines?
It can check leak rates
What happens to a fuel leak from a fuel pump compared to other fuel system leaks?
It is collected and measured for its leak rate. If it’s a large fuel leak, it will overflow to a holding tank
(Other fuel leaks do not go to the collector; they go directly overboard)
How is an overflow of a fuel pump leak holding tank prevented?
RAM air is used to open a spring loaded valve (at 200kts) which pressurises the holding tank, venting the fuel overboard
How are drain collector tanks emptied?
Manually on the ground after flight to check the leakage rate
