Airframe - AM.II.H.K4 & K5- Pressure and temperature indicating instruments Flashcards
1
Q
What are the three fundamental pressure sensing mechanisms used in aircraft instrument systems?
A
- The bourdon tube
- the diaphragm or bellows
- the solid state sensing device
2
Q
What basic mechanism is used to measure oil, fuel and oxygen pressures?
A
the bourdon tube
3
Q
What mechanical means is used to measure pressure in an airspeed indicator?
A
a diaphragm
4
Q
A failure of an airspeed indicator needle to move freely is likely caused by what problem?
A
a blockage in the pitot head will prevent the creation of a differential pressure
5
Q
What mechanical means can be used to measure oil temperature?
A
- a fluid filled, sealed system comprising of a bulb and capillary tube connected to a bourdon tube
- as temperature increases, the volume of the fluid increases and expands the bourdon tube, which is connected to an indicator dial
6
Q
How does a thermocouple measure temperature?
A
- The unit is comprised of two unlike metals
- As temperature increases, a small voltage is produced and sent to a temperature indicator
- The higher the temperature, the higher the voltage
7
Q
Why is the length of a thermocouple lead important?
A
- Thermocouple accuracy is dependent on the resistance of the circuit
- Lead lengths are designed for specific installations and should never be altered
8
Q
What type of electrical circuit is used to measure small changes of resistance in an electrical resistance temperature probe?
A
A wheatstone bridge circuit
