Instrumentation - Vertical Speed Indicators Flashcards
What is the key component in a VSI operation that relates to real rates of climb and descent?
The metering unit.
How does the metering unit in a VSI compensate for pressure altitude and temperature changes?
It uses a “choke” to direct air through a capillary tube and a “knife edge orifice”.
What happens to the pressure difference at height when using a VSI?
The pressure difference increases due to lower air density, but the orifice balances it by reducing the pressure difference.
How does the VSI compensate for reducing temperature?
The orifice allows the pressure difference to increase while the capillary balances it by reducing the pressure difference with decreasing temperature.
What is a VSI and what does it record?
A Vertical Speed Indicator (VSI) records the rate of change of static pressure and displays it as a rate of climb and descent.
Where is the vertical speed indicator positioned in a standard instrument layout?
Below the altimeter.
How does the IVSI improve upon a standard VSI?
It includes weights in dashpots with springs, causing immediate differential pressure because of their inertia as the aircraft starts to climb or descend.
What is a disadvantage of the IVSI in terms of aircraft acceleration?
The dashpots sense acceleration in the vertical and are also affected by acceleration in the aircraft normal axis.
What should pilots monitor when flying in turbulence using an IVSI?
Their attitude, power, and trim, and they should cross-reference the pressure altimeter during and after maneuvering.
How can vertical speed be displayed in modern transport aircraft?
Using either an electronic system driven by an Air Data Computer (ADC) or an Inertial Reference System (IRS).
What is the common unit for rates of climb and descent on a VSI?
Feet per minute, but meters per second can also be encountered.
How can you convert between feet per minute and meters per second for VSI readings?
1000 ft/min roughly equates to 5 m/s.
What additional feature might advanced VSIs have for indicating system reliability?
An off flag to indicate loss of power or an unreliable indication.
Where is the vertical speed displayed on an EFIS display?
To the right of the altitude indicator strip.
What is one major error that can occur with VSI readings?
Lag, which is a delay before the rate of descent or climb is indicated.
