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#1. A gyro-magnetic compass or magnetic heading reference unit is an assembly which always consists of : 1- a directional gyro 2- a vertical axis gyro 3- an earth’s magnetic field detector 4- an azimuth control 5- a synchronising control The combination of correct statements is :
the system comprises the following elements:
• Magnetic Detector Unit. This is also often known as a flux valve or a flux detector.
• Heading Indicator. This is what most people refer to as ‘the compass’.
• Precession Amplifier. This may also be known as a slaving amplifier.
• Precession Motor. This may also be known as a slaving or synchronizing motor.
• Horizontal Gyro.
In simple systems, the horizontal gyro is directly connected to the compass card of the heading
indicator via a bevel gear and a drive shaft.
#2. A slaved directional gyro derives its directional signal from
The detector unit or flux valve is positioned in a part of the aircraft least affected by on-board electrical
fields (usually the wing tip or tail fin, where any aircraft generated magnetic disturbances are
at a minimum). Its function is to sense the direction of the earth’s magnetic field. It contains
a pendulous magnetic detecting element mounted on a Hooke’s Joint which enables the
detector to swing within limits of 25° about the pitch and roll axes, but allows no rotation
in azimuth. The unit itself is contained in a sealed case partially filled with oil to dampen any
oscillations created during flight
#3. The gyro-magnetic compass torque motor:
A torque motor is a key component in gyro compasses, helping to maintain the gyro’s orientation and counteract the effects of gyro wander (drift and topple). Here’s a brief explanation based on the provided information:
- Purpose of the Torque Motor:
- The torque motor generates a rotational force to correct the gyro’s orientation when it deviates from its desired position, either due to drift (azimuth misalignment) or topple (tilt from the horizontal).
- Inputs to the Torque Motor:
- Signals from levelling switches or gravity-based sensors (e.g., mercury switches) detect deviations in the gyro’s position.
- These sensors generate correcting signals based on the gyro’s relationship to the aircraft’s yaw axis or gravity.
- Working Mechanism:
- The torque motor applies force to the gyro’s yaw axis, inducing precession (a controlled, gradual rotation of the gyro).
- This precession realigns the gyro with the horizontal or yaw axis, depending on the compass system design.
- Precession Rate:
- The torque motor operates at a slow precession rate to avoid overcorrection or instability.
- This ensures the gyro remains stable during temporary conditions like turns, climbs, or accelerations.
#4. The heading information originating from the gyro-magnetic compass flux valve is sent to:
selsyn
The transmitting and receiving device is called a Selsyn Unit also called error detector
One of the advantages of the gyro-magnetic compass over the simple direct reading compass is
the facility to electrically transmit heading information to use as an input into other instruments.
The information is picked off from the drive shaft between the gyro and the compass card. The
transmitting and receiving device is called a Selsyn Unit.
The rotor of the transmitter is attached to the heading drive shaft and
rotates with it. The orientation of the rotor is therefore the heading which is to be transmitted.
The rotor is supplied with a constant primary excitation AC voltage, which induces a field in
the stators. The stators are directly connected by 3-strand wire to the 3 stator arms of the
repeater, so an identical field is reproduced there.
If the rotor of the repeater is not perpendicular to the field in the repeater stators, an AC
voltage will be induced in this repeater rotor. This is passed to an amplifier and then to a motor
to turn a shaft on which the repeater rotor is mounted. The repeater shaft will turn until no
further voltage is detected. The repeater shaft therefore follows any heading changes in the
main gyro drive shaft.
#5. The input signal of the amplifier of the gyro-magnetic compass resetting device originates from the:
#6. Heading information from the gyro-magnetic compass flux gate is transmitted to the:
selsyn
The transmitting and receiving device is called a Selsyn Unit also called error detector
One of the advantages of the gyro-magnetic compass over the simple direct reading compass is
the facility to electrically transmit heading information to use as an input into other instruments.
The information is picked off from the drive shaft between the gyro and the compass card. The
transmitting and receiving device is called a Selsyn Unit.
The rotor of the transmitter is attached to the heading drive shaft and
rotates with it. The orientation of the rotor is therefore the heading which is to be transmitted.
The rotor is supplied with a constant primary excitation AC voltage, which induces a field in
the stators. The stators are directly connected by 3-strand wire to the 3 stator arms of the
repeater, so an identical field is reproduced there.
If the rotor of the repeater is not perpendicular to the field in the repeater stators, an AC
voltage will be induced in this repeater rotor. This is passed to an amplifier and then to a motor
to turn a shaft on which the repeater rotor is mounted. The repeater shaft will turn until no
further voltage is detected. The repeater shaft therefore follows any heading changes in the
main gyro drive shaft.
