15.2 COMPRESSOR INLET DUCTS👌🏼

Question 1

What are Inlet guide vanes (IGV) used for?

Answer 1

• straighten airflow and direct it to first stages of the compressor

Question 2

The air-inlet duct is considered what part

Answer 2

• airframe part

Question 3

What do turboprop/turboshaft engines have to prevent FOD

Answer 3

• screens to cover inlet

Question 4

Simply explain where the air is taken from in a divided-entrance duct

Answer 4

• takes air from either side of fuselage

Question 5

What is sometimes placed in the side scoop inlet to assist in straightening the incoming airflow and prevent turbulence in a divided entrance duct

Answer 5

Series of turning vanes

Question 6

When a aircraft duct length is shortened in a divided entrance duct what is the disadvantages

Answer 6

Sudden flight manoeuvres cause imbalance in ram air pressure between the 2 ducts

Question 7

Explain inlet ducts (which function as diffusers) in terms of velocity and pressure

Answer 7

• decreasing velocity and increasing static pressure of air passing through

Question 8

Airflow through the engine must always be less than

Answer 8

Mach 1 (supersonic)

Question 9

What 3 methods diffuse the inlet air and slow the inlet airflow at supersonic speeds

Answer 9

• Vary area, or geometry, moveable restriction such as a ramp/wedge inside the duct
• variable airflow bypass arrangement
• use of a shockwave

Question 10

Explain compressor inlet screens

Answer 10

• prevent engine from ingesting FOD
• screens cause a loss in inlet duct pressure
• susceptible to icing

Question 11

Explain Bellmouth compressor inlets

Answer 11

• installed on engine undergoing testing
• for very high aerodynamic efficiency
• duct loss is considered 0

Question 12

What are inlets of turboprops anti-iced by

Answer 12

• electrical elements (lip opening of intake)

Question 13

What are deflector doors used for

Answer 13

• deflect ice or dirt away from intake

Question 14

Explain conical spinner

Answer 14

• does not allow ice build up on surface

Question 15

What does the fan prevent

Answer 15

• damage from ingested foreign material

Question 16

Explain inlet lip anti-icing

Answer 16

• warm bleed air circulated

Question 17

What effect does ice have on the engine inlet

Answer 17

• disturbed air flow that reduces performance of engine leading to compressor stall
• engine sucks in ice pieces

Question 18

How do turboprops provide anti-icing

Answer 18

• uses warm oil from engine oil reservoir to provide anti-icing

Question 19

Ice can form in the inlet in dry air at what temp

Answer 19

5*c

Question 20

Ice can form in the inlet in moist conditions at what temperature

Answer 20

• 7*c

Question 21

Explain anti-icing with electronic engine control

Answer 21

• once anti-icing is turned on.
• EEC controls the flow of hot air

Question 22

Do all thermal anti-ice valves have a manual override function

Answer 22

• yes

Question 23

What engines have electric heat strip systems

Answer 23

Smaller turboprop and turboshaft

Question 24

What should you ensure when using electric heat strip systems

Answer 24

Operate only when engine is running

Question 25

What is the main function of an inlet duct

Answer 25

Provide correct amount of airflow to engine inlet

Question 26

What are inlet ducts designed to function as

Answer 26

Diffusers

Question 27

For very high speed aircraft, inside area configuration of duct is changed by a mechanical device as the speed of the aircraft increases or decreases. What is this type of duct known as ?

Answer 27

‘Variable geometry’ inlet duct