15.3 Flashcards
What does the inlet guide vane do
Straightens the airflow and direct it onto the first stages of the compressor
What’s the purpose of a screen on the engine
Prevent FOD
What is ram recovery or total pressure recovery and what does it do
The added pressure the inlet that increases pressure and airflow into engine
It compensates for loss of thrust due to increase in airspeed
What is the purpose of turning vanes
They are placed inside side-scoop inlet to straighten flow and prevent turbulence
What the 2 types of divided ducts
Wing root inlet or a scoop
Disadvantage of divided duct arrangement
Sudden manoeuvres provide an imbalance in ram pressure which can cause a slight loss in power
Function of an inlet duct
Provide correct amount of air into the engine inlet
In a variable geometry duct what must the engine airflow be
Below Mach 1
What do inlet ducts act as
Diffusers to decrease the velocity and increasing the static pressure
What makes a variable geometry duct VGD ‘variable’
Inside area of the configuration can be changed
How can you change the area of VGD
Introduce a restriction such as ramp or wedge in the duct
What does a variable airflow bypass arrangement do
Extracts part of the inlet airflow from the duct ahead of the engine
What’s the 3rd method to diffuse inlet air
Uses shockwaves into the airstream to decrease velocity of the airflow
What does a compressor inlet screen do
Prevent engine from ingesting items into the intake
Can be placed along the inlet duct
Disadvantage of compressor inlet screen
Loss of inlet duct pressure and subject to icing
Are screens used on the engines with titanium or steel fan blades
No , the disadvantages outweigh the advantages
When is a bell mouth compressor inlet used
During testing
What is duct loss considered as in bell mouth compressor inlet
0
How are turboprop inlets anti iced
Electrical elements in the lip opening of the intake
Best arrangement for inlet design on turboprop
Ducted arrangement
What’s the function of a conical spinner
Doesn’t allow ice build up on the surface
On high bypass turbofan engines where is the fan constructed to
Forward end of the compressor
What’s the function of the inlet cowl and where is it placed
Bolted to the front of the engine
Provides airflow path into engine
What speed should the fan blades rotate to achieve the best efficiency
Low tip speed
How does a fan reduce damage to engine
Throws fod radially outward and goes through fan discharge instead of engine
2 ways of anti icing inlets
Warm bleed air from engines and conical spinner
What 2 effects can ice have on the engine inlet
Reduce performance that can lead to compressor stall
Pieces of ice damage fan blades or inlet vanes
What combination do inlets use to keep it free from ice
Warm oil from engine oil reservoir
&
hot air from compressor/diffuser
When are heat strips used
Only when it’s just the cowl that needs anti-icing
What conditions does ice form
5 degreess in dry air
7 degrees in moist air (fog and rainy)
What engines is bleed air used on
Engines with high-mass airflow
Where is bleed air bled from
Bled off the HP compressor
What the function of anti-icing valves
Protect against over pressurisation to prevent loss of engine power
Where are anti ice valve operated
Automatically via ice detection system or manually in flight deck
How is air for the intake ejected overboard
Via small grills
What happens to air used for the cone and inlet guide vanes
Directed overboard or back into LP compressor intake
How are anti ice valves operated and selected
Selected electrically and pressure operated
Low and high duct pressure and temperature causes what
Latched relay to be tripped and locks system out until reset
What air does engine anti ice system use
Hot air from pneumatic system or directly from engine
Precaution against the doing ground tests on thermal anti-ice system
No personnel should be in the test area during ground tests
What’s the manual override function used for
Valve or system failure
What does EEC do in terms of anti icing
Controls flow of hot air into the engine inlets
What are electric heat strip systems constructed of
Electrical resistance wire embedded in layers of neoprene materials
Where are heat strips located
Lip of nacelle
What does an inlet guide vane do
Straighten airflow and direct it to the first stages of the compressor
