Explanations: Aircraft Instrument Systems Flashcards
When is an aircraft magnetic compass swung?
There is no required time interval for swinging a compass, but it is normally done whenever any new equipment has been added that might affect the compass deviation.
What is a Bourdon tube?
A pressure-measuring instrument.
It can be used to measure temperature by connecting it to a temperature bulb containing a volatile liquid such as methyl chloride. The bulb and the Bourdan tube are connected with a small-diameter copper tube and are sealed as a unit. When the temperature surrounding the bulb changes, the pressure above the volatile liquid changes.
The bourdan tube instrument whose dial is calibrated in units of temperature measures this pressure change, which relates to the temperature change.
What occurs when swinging a compass?
The compensators adjust for the magnetic interference caused by localized magnetic fields in the aircraft structure. There magnetic disturbances are called deviations, and they deflect a compass needle from alignment with magnetic north.
Why will a disconnected static pressure line cause the altimeter and ASI to read low?
If an instrument static-pressure line becomes disconnected inside a pressurized cabin, the altimeter will indiate a lower altitude. The increased static pressure inside the airspeed indicator case will cause it to read low.
How is an instrument static system tested for leakage?
A suction is applied to the static system that causes an equivalent altitude of 1,000 feet to be indicated on the altimeter. The system is sealed, and it must not leak more than 100 feet of altitude in one minute.
What is pressure altitude?
the altitude above sea level.
How is a turn coordinator able to sense both roll and yaw?
By using a canted rate gyro as its sensing element.
What are synchro trasnmitters?
Synchros are used to transmit angular data electrically from one location to another, where a high degree of accuracy is required.
How is magnetic deviation countered?
By compass swinging, a procedure in which small magnets inside the compass are turned in such a way that their magnetic field cancels the effect of the offending magnetic fields.
All work and no play makes Jack a what?
A dull boy.
What is a vacuum relief valve?
A spring-loaded, flat-disk valve that opens at a preset amount of vacuum to allow air to enter the system. If the spring is set with too much compression, the vacuum will have to be greater to allow the disk to offseat and allow air to enter the system.
What is an EFIS?
Electronic Flight Instrument System. It is a flight deck instrument display system in which the display technology used is electronic rather than electromechanical.
How is data transmitted in an EFIS?
via an avionics standard coms bus using a time-sharing basis.
What is a CRT in an EFIS?
Cathode Ray Tube; it is the display unit used in an EFIS.
What are the components in an EFIS?
It contains three subsystems:
The pilot’s display system (PDS), the copilot’s display system (CDS), and the weather radar (WX).
The PDS and CDS are identical and each contains two CRT displays, an SG (symbol generator), a display controller, and a source-select panel.
The SG’s receive input signals from aircraft and engine sensors, process this information and send it to the appropriate display.
