Instruments Flashcards
What drives the vacuum pump for a vacuum driven gyro?
The engine in a modern aircraft or a venturi tube in some older ones
Displacing a spinning gyro with a yaw causes it to respond with what?
A roll
The pressure gauge for the vacuum pump should indicate what pressure?
4.5-5.4 in Hg
Why do we use a gyro and why do we also have a compass?
To keep the card’s azimuth oriented North regardless of the direction of the aircraft. A magnetic compass will bounce about in turbulence but a gyro is more stable. The gyro is set by the compass before takeoff.
What is the role of the turn indicator?
It uses the gyro to indicate the aircraft’s rate of turn. It shows a standard turn rate (3degrees per second= 180 degrees/min). It is elect rically powered so that it operates even if the vacuum pump fails and you lose the artificial horizon. However, unlike the artificial horizon it won’t tell you the pitch.
Describe the role of the pitot tube and the static vent
The pitot tube points towards the relative airflow and uses it to inflate a balloon which expands into a cavity. The pressure in the cavity remains static as the cavity vents air from around the balloon via the static vent which is aligned such that it is at right angles to the airflow. The balloon inflation is used to measure airspeed.
What are the colours of the arcs on the airspeed indicator and what do they represent?
White: flap operating range (Vso - Vfe)
Green: Normal operating range (Vsi-Vno)
Yellow: Caution range (Vno-Vne)
Red line: never exceed speed (Vne)
Can you fly in the yellow ark and if so under what circumstances?
Yes, If there is no turbulence and you make no abrupt control changes.
How does the vertical speed indicator work?
It meaures the rate of change in the static pressure (the pressure outside the balloon in the cavity of the altimeter)
What’s a good rate of descent?
500ft/minute
How does the altimeter work?
It is similar to the airspeed indicator but withiut a pitot tube. The pressure in the balloon remains constant so its inflation measures changes in static pressure.
What is the rate of change of pressure with height?
1mb per 30 ft.
What is standard sea level pressure in barr?
1.01325
If you accelerate to the east or west in the southern hemisphere, what happens to the compass?
It indicates a turn to the south due to the way the needle is suspended. South Accelerate, North decelerate SAND
Overshoot north, undershoot south (ONUS)
When you turn through north or through south, what error occurs in the rate at which the compas turns?
Too fast through north -nippy north
Too slow through south -sluggish south
