Air Data Pressure Sensing

Question 1

What are the basic 6 instruments?

Answer 1

1. Air speed indicator (ASI)
2. Attitude indicator
3. Altimeter
4. Turn indicator/coordinator
5. Heading indicator
6. Vertical speed indicator (VSI)

Question 2

Which of the basic 6 are pressure only instruments?

Answer 2

1. ASI
2. Altimeter
3. VSI

Question 3

What is used to sense pressure?

Answer 3

• Static vents
• Multi function probes
• Pitot tubes

Question 4

Which of the basic 6 are electro mechanical instruments?

Answer 4

• Attitude indicator
• Turn indicator/coordinator
• Heading indicator

Question 5

What are thee 2 types of instrument display?

Answer 5

• Analogue
• Digital

Question 6

What are the advantages of an analogue gauge?

Answer 6

• Easy to see rate of change
• Rotating needle moves relative to a scale, comparative

Question 7

What are the advantages of a digital display?

Answer 7

• Easy to see precise values
• Readout is a quantitive value

Question 8

What does a green band on the ASI mean?

Answer 8

Normal operating range

Question 9

What does a yellow band on the ASI mean?

Answer 9

Caution band

Question 10

What does a red mark on the ASI mean?

Answer 10

Warning mark

Question 11

What does a white band on the ASI mean?

Answer 11

Flap operating range

Question 12

What is at the upper and lower end of the white band on an ASI?

Answer 12

Lower - Vs0
Upper - Vfe

Question 13

What is at the upper and lower end of the green band on an ASI?

Answer 13

Lower - Vs1
Upper - Vno

Question 14

What is at the upper and lower end of the yellow band on an ASI?

Answer 14

Lower - Vno
Upper - Vne

Question 15

What are the 2 min threats to pressure sensing devices?

Answer 15

Blockages and leaks

Question 16

What is 1013.25hPa in mb?

Answer 16

1013.25mb

Question 17

What is 1013.25hPa in psi?

Answer 17

14.7psi

Question 18

What is 1013.25hPa in inHg?

Answer 18

29.92inhg

Question 19

Which systems commonly use psi?

Answer 19

• Engine oil pressures
• Hydraulic system pressures
• Cabin differential pressures

Question 20

What are the 5 common methods of measuring pressure?

Answer 20

• Aneroid capsules
• Pressure capsules
• Diaphragms
• Bourdon tubes
• MEMS technology

Question 21

What is an aneroid capsule?

Answer 21

Sealed, partially evacuated capsule which when exposed to ambient air compresses slightly due to atmospheric pressure being higher than the static pressure inside the capsule

Question 22

What is a pressure capsule?

Answer 22

Similar to an aneroid capsule but not sealed, atmospheric static pressure fed into capsule and compared against total pressure

Question 23

What is a diaphragm?

Answer 23

A device with 2 sides, each side with a different pressure, which moves towards the lower pressure

Question 24

What is a bourdon tube?

Answer 24

Partially flattened tube wound into a curve which will straighten under relatively high internal pressure, this drives the instrument, can be used to measure high pressures over a wide range

Question 25

What is MEMS technology?

Answer 25

Micro electro mechanical systems, convert pressures to electrical systems

Question 26

Which instruments use only static pressure?

Answer 26

- Altimeter - VSI

Question 27

What does a pitot measure?

Answer 27

Total pressure

Question 28

How is a pitot tube positioned?

Answer 28

- Parallel to the longitudinal axis - Inlet facing forwards

Question 29

What is position error?

Answer 29

Due to the location of the sensing device and the change in airflow at the sensing point, varies with AoA and speed

Question 30

What is the alternate source?

Answer 30

It is an alternate source of static pressure, usually in the cabin, used if the static vents and pipe work are not functional

Question 31

What does IMPS mean?

Answer 31

- Instrument - Manoeuvre - Position - Static system

Question 32

What are instrument errors?

Answer 32

Imperfections within the instruments, play within the linkages and friction

Question 33

What are manoeuvre errors?

Answer 33

Caused by changes in the pressure envelope around the aircraft when it manoeuvres

Question 34

What is static system error?

Answer 34

Caused by friction in the small tubes used to connect the static ports to the instruments