Aircraft Instrument Systems Flashcards
Where are the system descriptions found for annunciator indications and the meaning of the associated warnings, cautions, and advisory lights?
In the POH/AFM and the ICAs.
What fluid is used in an aircraft magnetic compasss?
A special water-clear fluid similar to kerosine.
What is the maximum amount of deviation error allowed when a magnetic compass is installed in an aircraft?
10 degrees.
Where should the compass correction card be placed?
In plain sight of the pilot, near the compass.
What is the difference between variation and deviation in a compass system?
compass variation is caused by the difference between the earth’s magnetic and geographic poles. Aeronautical charts display magnetic variation. Compass deviation is caused by all other magnetic fields aside from the earth’s magnetic and geographic poles. Deviation may be caused by magnetic fields in the aircraft.
What error is corrected when an aircraft compass is swung?
Deviation error.
What is done to a compass to correct for deviation error?
The compensating magnets in the compass are adjusted to minimize the effect of outside magnetic fields.
Where on an airport is a compass rose located?
At a location where there is little traffic and the area is free from magnetic interference caused by electrical power lines or buried pipes.
What are the three fundamental pressure-sensing mechanisms used in aircraft instrument systems?
The Bourdon tube, the diaphragm or bellows, and the solid-state sensing device.
What basic mechanism is used to measure oil, fuel, and oxygen pressures?
The bourdon tube.
What mechanical means is used to measure pressure in an airspeed indicator?
A diaphragm.
A failure of an airspeed indicator needle to move is likely caused by what problem?
A blockage in the pitot head will prevent the creation of a differential pressure.
What mechanical means can be used to measure oil temperature?
A fluid filled, sealed system comprising of a bulb and capillary tube connected to a Bourdon tube. As temperature increasses, the volume of the fluid increases and expands the Bourdon tube, which is connected to an indicator dial.
How does a thermocouple measure temperature?
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.
Why is the length of a thermocouple lead important?
Thermocouple accuracy is dependent on the resistance of the circuit. Lead lengths are designed for specific installations and should never be altered.
What type of electrical circuit is used to measure small changes of resistance in an electrical resistance temperature probe?
A wheatstone-bridge circuit.
What type of system is used to indicate the position of the wing flaps?
Usually a resistance-type remote-indicating system such as the DC Selsyn system.
What information is shown by the wing flap position indicator?
The number of degrees the flaps are lowered.
What are the gyroscopic instruments that are connected to the low-pressure pneumatic system of an aircraft?
Heading indicator
Attitude indicator
Turn-and-slip indicator
What device is used with a wet-pump vacuum system to prevent oil from getting into the deicer boots?
An oil separator.
What are two types of filters used with a pressure system for gyros?
A pump inlet filter and an inline filter.
What type of filter is used with a vacuum system for gyros?
A central air filter.
What may be causing an attitude indicator to not properly erect or display?
Gyroscopes are dependent on achieving and maintaining proper rotational speed. Failure to do so may be caused by low vacuum created by the vacuum system or motor failure in an electrically-driven gyroscope.
What type of direction-finding compass has no moving parts and easily integrates with digital systems?
Solid state magnetometers.
How does a flux gate compass operate?
The flux gate compass consists of a very magnetically permeable circular segmented core from called a spider. The earth’s magnetic field flows through this iron core and varies its distribution through segments of the core as the flux valve is rotated via the movement of the aircraft. Pickup coil windings are located on each of the core’s spider legs that are positioned 120° apart. The signal from the flux gate is passed to the flight deck via an autosyn transmitter.
What two types of pumps are used in the low-pressure pneumatic system?
A dry-type and a wet-type air pump.
What are the vanes of a wet-type air pump made of?
Steel.
What are the vanes of a dry-type air pump made of?
Carbon.