VSI Flashcards
(14 cards)
What does a VSI sense?
Rate of change of static pressure
How does a VSI work in a climb?
Static pressure decreases in the capsule, the capsule contracts, climb is indicated
What determines the rate of climb indication?
The difference between the case and capsule pressures
What happens when an aircraft levels off?
Pressure in the capsule stops changing, pressure in the case will take a few seconds to catch up, once pressures equalise indication is 0
What are the errors for a VSI
I - instrument
M - manoeuvre
P - position
Time lag
What is the time lag error in a VSI?
The time taken for the needle to respond to an actioned manoeuvre
What is an iVSI?
Instantaneous VSI, uses a dash pot to artificially alter pressure in the capsule to reduce time lag
What indication does a turn error give?
False climb indication
How does turbulence effect the VSI?
Erroneous readings
What happens when there is an unpressurised leak in the static port?
Momentary rate of climb
What happens when there is a pressurised leak in the static line?
Rate of descent until pressure equalises with cabin, then the gauge only shows changes in cabin altitude
What happens if there is a static blockage?
Reads 0fpm as case and capsule display is frozen
What happens if there is a blockage in the alternate static line?
Momentary rate of climb
What is the rate of descent equation?
ROD = TAS x gradient
