Chapter 3 - Vertical Speed Indicator

Question 1

Purpose of the VSI?

Answer 1

Purpose: to convert static pressure
changes into a mechanical movement.

Question 2

what is 1 m/s in ft/min?

Answer 2

1 m/s ≈ 200 ft/min

1m = 3.281 feet

Question 3

What VSI errors are there?

Answer 3

I M P + LAG

Instrument - Manufacturing imperfections, including friction in the linkage.

Manoeuvre - Due to turbulence in the pressure heads.

Position - Due to brief changes in pressure at the static vents, mainly when changing pitch attitude.

LAG - The pointer takes a few seconds to steady because of the time taken to build
up a steady pressure difference when climbing or descending.

Can be controlled by calibration

Question 4

A VSI that is blocked will read?

Answer 4

Static blockages always cause the needle to return to zero.

If the blockage occurs in the climb or descent, the VSI indication will gradually return to zero.

If the blockage occurs in level flight, the indication will remain at zero.

Question 5

VSI Leak errors, unpressurised and pressurised AC?

Answer 5

Question 6

How does an Instantaneous VSI overcome lag?

Answer 6

To overcome lag, it includes an accelerometer and DASHPOT which responds quickly to altitude changes.

Question 7

Instantaneous VSI errors are?

Answer 7

Turning

During steep turns, increased “G” force causes an initial false climb indication. The turn should be flown with reference to the altimeter.

Over Sensitivity

The instrument is over-sensitive whilst flying in turbulence. Fly the aircraft smoothly and do not chase the needles.

Question 8

What is an IVSI?

Answer 8

Instantaneous VSI

Question 9

What is an IVSI fitted with?

Answer 9

DASHPOT or Accelerometer