15.3

Question 1

What do the Inlets guide vanes do?

Answer 1

Straighten the airflow and direct it into the first stages of the compressor

Question 2

Is the air inlet duct an airframe part, or part of the engine?

Answer 2

Airframe

Question 3

What does the inlet vary according to?

Answer 3

The type of turbine engine

Question 4

What do turboprop and turboshaft engines have to prevent FOD from entering?

Answer 4

Screens to cover the inlet

Question 5

As aircraft speed increases, what happens to thrust? And what compensates for it?

Answer 5

It decreases so RAM air recovers it

Question 6

What recovers as much of the total pressure of the free airstream as possible? And how?

Answer 6

The inlet by trapping air molecules and compressing it

Question 7

What is “Ram recovery” or “Total pressure recovery”?

Answer 7

Added pressure at the inlet to increase pressure and airflow

Question 8

The choice of configuration to the entrance of the duct depends on what?

Answer 8

Airspeed, altitude, attitude, location

Question 9

Where are divided-entrance ducts located?

Answer 9

Military aircraft on either side of the fuselage

Question 10

What two things can a divided duct be?

Answer 10

A wing-root inlet or a scoop

Question 11

Disadvantage of divided ducts?

Answer 11

Drag

Question 12

What is a major drawback in terms of designing the entrance duct in a divided entrance?

Answer 12

Having a reasonable length with a few bends as possible

Question 13

Scoops at the side of the fuselage are used in devised entrance air inlets, where are they placed?

Answer 13

As far forward as possible

Question 14

Why are side scoops placed as far forward as possible?

Answer 14

To permit a gradual bend toward the compressor inlet

Question 15

What do turning vanes assist with in the side scoop?

Answer 15

The straighten the incoming air and prevent turbulence

Question 16

What is a major disadvantage of the divided entrance inlets?

Answer 16

After sudden manoeuvres loss of power occurs in one engine so causes a pressure imbalance

Question 17

In Variable-geometry ducts, what do the inlets act as?

Answer 17

Diffusers so they increase the static pressure but reduce velocity

Question 18

The aft section of the duct does what to ensure it’s acting as a diffuser?

Answer 18

Increases its area

Question 19

For very high speed aircraft what changes in order to compensate for the speed?

Answer 19

A variable geometry inlet duct

Question 20

What are the three methods to diffuse the inlet air and slow it down at supersonic speeds?

Answer 20

Vary the area of the area inlet duct using a ramp or wedge
Use variable bypass arrangement
The use of a shockwave

Question 21

What is the variable bypass arrangement?

Answer 21

It extracts part of the inlet airflow from the duct ahead of the engine

Question 22

Why would you use a shockwave in an engine inlet in supersonic aircraft?

Answer 22

To decrease the velocity

Question 23

What does a compressor inlet screen do?

Answer 23

Stops the engine from ingesting items

Question 24

What are the disadvantages of inlet screens?

Answer 24

Loss of pressure and they are susceptible to contracting ice.

Question 25

When are the screens retracted?

Answer 25

After take off and when ice formation is probable

Question 26

What aircraft are screens not used on? Why?

Answer 26

Turbofan because they weigh a lot and the fan blades do not damage easily

Question 27

When would you use a bell mouth compressor inlet?

Answer 27

When testing in a test cell

Question 28

What do the probes measure in a bell mouth duct inlet?

Answer 28

Pressure (total and static) and temperature

Question 29

What is the bell mouth attached to?

Answer 29

The moveable part of the test stand so moves with the engine

Question 30

What two parts is the bell mouth made up of?

Answer 30

A moving part and a non moving part so it can measure thrust

Question 31

What is the duct loss considered as in a bell mouth?

Answer 31

Zero

Question 32

What is the bell mouth mainly designed to obtain?

Answer 32

Aerodynamic frequency

Question 33

What does a bell mouth air intake look like?

Answer 33

A bell shaped funnel having carefully rounded shoulders which offer no air resistance

Question 34

How are inlets in turboprop and turboshaft heated?

Answer 34

By using electrical elements in the lip opening of the intakes

Question 35

What are deflector doors used for in turboprop and turboshaft?

Answer 35

To deflect ice or dirt away

Question 36

After the deflector doors where does the air pass through before entering the engine?

Answer 36

A screen

Question 37

What does a conical spinner do in turboprop and turbofan engines?

Answer 37

Does not allow ice to build up on the surface

Question 38

In dual spool engines, what allows the fan blades to rotate at low tip speed for best efficiency?

Answer 38

The fan is integral with the low pressure compressor

Question 39

How does the fan reduce damage from ingested foreign material?

Answer 39

It throws it radially outward and passes through the fan discharge rather than the core

Question 40

What is drawn from the engines to heat the inlet lip for anti icing?

Answer 40

Bleed air

Question 41

What prevents ice forming in the fan hub/spinner?

Answer 41

Warm air or uses a conical spinner

Question 42

What two effects can ice have on the engine inlet?

Answer 42

Disturb airflow so reduces performance on an engine leading to a compressor stall Suck in ice which can damage the blades or inlet vanes

Question 43

What do turboprops use to provide anti icing to the inlet area?

Answer 43

Warm oil or hot air

Question 44

What is hot bleed air extracted from in the inlet extracted from?

Answer 44

The compressor stage of diffuser

Question 45

What is used if it is only the cowls that require anti icing?

Answer 45

Electrical heat strips

Question 46

In what pattern is hot air sprayed?

Answer 46

High pressure pattern

Question 47

What temperature does ice form at?

Answer 47

5 degrees in dry air or 7 degrees in moist air

Question 48

What can thermal systems be divided into?

Answer 48

Bleed air Electrical heating

Question 49

What engines is bleed air extracted from?

Answer 49

High mass airflow engines from the HP compressor

Question 50

What valve is hot air passed through to provide surface heating to IGV’s, the spinner and the intake lip?

Answer 50

Pressure regulating bleed valve (anti-ice valves)

Question 51

What do anti ice valves protect against in the anti-ice system?

Answer 51

Over pressurised and limit of bleed air

Question 52

How can anti ice valve be operated?

Answer 52

Automatically via ice detection system and manually via flight deck

Question 53

Where is the air used for the aircraft intake anti icing ejected?

Answer 53

Overboard through small grilles

Question 54

Where is anti icing air ejected when used for the nose cone and IGVs?

Answer 54

Overboard or back to the LP compressor intake

Question 55

When does a solenoid operated driven air shut off valve open?

Answer 55

When a switch in a flight deck is triggered or ice detector detects a build up of ice

Question 56

Where does the anti ice system in the engine get air from?

Answer 56

Pneumatic system or directly from engine via engine anti ice valve

Question 57

What does the hot air flow through in the cowling?

Answer 57

Tiny holes in the Anti ice duct

Question 58

Where does the hot air leave the leading edge if the engine?

Answer 58

Through openings in the lower part

Question 59

In a regulator valve what is used to operate the valve when there is a valve or system failure?

Answer 59

Manual override

Question 60

What positions can the anti ice valves be locked in?

Answer 60

Open and Closed

Question 61

When the turbine engine is controlled by an ECC, it is linked to the ECC as part of what?

Answer 61

FADEC

Question 62

On turboprop and shaft engines, what do they tend to use for anti icing?

Answer 62

Electrical heat strips (electrothermal)

Question 63

When are electrical heat strips designed to operate? Why?

Answer 63

When the engine is running ONLY They can overheat without air running over it

Question 64

Are electrothermal systems constantly on when engine is running?

Answer 64

No. They are cycled on and off as required by ambient conditions