06 Machmeter

Question 1

What is the basic operation of a Machmeter:

• What feeds it
• Components

Answer 1

• Fed by both Static Pressure and Pitot Pressure
• Static pressure is fed into the case
• Pitot pressure is fed directly into a pressure capsule
• Air speed capsule: Pressure capsule, fed by Pitot pressure, located at the rear of the Machmeter
• Altitude capsule: Aneroid, located at the top of the Machmeter
• The combination of the expansion and contraction of both capsules converts to the Mach Number reading

Question 2

What is the equation of the Mach Number?

Answer 2

Mach Number = TAS / LSS

Question 3

What Errors are associated with the Mach Meter?

Answer 3

• Instrument
• Manoeuvring
• Position
• Note: Barometric and temperature errors have already been corrected by the instrument

Question 4

What is the equation for the Local Speed of Sound (LSS)?

Answer 4

LSS = 38.95 x Sqrt (Temp in K)

Question 5

What acronym can be used to work out the blockages in the feed tubes for a Mach Meter?

Answer 5

PUD SOD

Or POC SUC

Question 6

What happens to the following with an increase of temperature in the horizontal plane?

• TAS
• LSS
• Mach number
• CAS

Answer 6

• TAS increases
• LSS increases
• Mach number remains constant
• CAS remains constant

Question 7

What errors are does a combined ASI and Mach Meter suffer from?

Answer 7

• Instrument
• Manoeuvre
• Position
• Compressibility
• Density