B - Pressure sensing (17-05-18) Flashcards
What is guage pressure?
The differential pressure relative to ambient air or difference between 2 pressures
What is an aneroid capsule?
A partially evacuated, sealed capsule.
What is a leaf spring?
A piece that helps capsules maintain their original shape after expanding or contracting.
What are bellows?
Essentially the same as capsules but for higher pressures.
What are diaphrams in terms of measuring pressure?
A barrier that moves with changing pressure.
What are bourdon tubes?
A tube that unravels with an increase in pressure (high pressure devices, like hydraulic devices.)
What is a transducer?
A component that transforms pressure readings into an electronic signal.
What kind of pressure is exerted by ambient air?
Static pressure
What kind of pressures make up total/pitot/impact/stagnation pressure?
Dynamic and static
What kind of pressure does movement of flow cause?
Dynamic pressure
What is the difference between pitot and pressure heads?
Pressure heads also contain static ports whereas pitot heads only contain the pitot tube.
How does a pitot tube deal with water entering the tube and how does this effect its readings?
A small drainage hole is included which releases water and this is calibrated out by the manufacturer.
How to pitot tubes deal with icing?
They have a heat element which melts ice
Where are pitot tubes located for large jet aircraft?
On the side of the fuselage forward of the wing.
Where are pitot tubes located for light aircraft?
Below the wing
Where must static ports be placed?
They must be placed at right angles to the flow.
What is done to eleminate static port errors due to side slip or yaw?
Static ports are cross coupled so that the extra dynamic pressure into the upstream static port is countered by the suction out of the downstream static port.
What kind of aircraft have static ports/vents?
Large aircraft
What kind of aircraft have static heads (pressure heads)?
Light aircraft.
What kind of errors are static ports subject to?
Instrument error
Maneouvring error
Position/pressure error
IMP
What is instrument error and what can we do about it?
The error associated with manufacturing defects.
We can use a correction card provided by the manufacturer to account for it.
Or the ADC will account for it for us.
What is position/pressure error and what can we do about it?
The error associated with airflow over the static ports causing a small amount of suction, reducing the pressure reading.
We can account for it with correction cards from the manufacturer or via te ADC.
What is maneouvre error and what can we do about it?
The difference in pressure reading due to the changing airflow over the static port during a maneouvre (mainly pitch).
We can only limit the maneouvres we do.
