Artificial Horzion Flashcards
AH
The artificial horizon (AH) provides the pilot with information in terms of the aircraft’s attitude
both in pitch and roll.
Composition
vertical tied Gyro(Earth)
2 degree of freedom
symbol of airplane fixed
rotor turn in the local H plane
Pitch
The pitch-up movement has rotated the case together with the attached outer gimbal ring about the lateral axis YY
Limitation +- 60
Roll
the rigidity of the vertical gyro provides the stable attitude reference. A rolls on longitudinal axis the instrument case and the
gull-wing will rotate about the stabilised gyro rotor and gimbal system.
limitation 110 in roll
Error air
Pitch error acceleration nose up decell nose down
Roll error acc right turn decell left turn
Turning error air
Turning through 90°: Under-reads bank angle Pitch error – indicating a climb
Turning through 180°: Bank angle correct Pitch error – indicating a climb
Turning through 270°: Over-reads bank angle Pitch error – indicating a climb
Turning through 360°: Bank angle correct Pitch angle correct
Electrical AH
Greater rigidity due to its faster spin rate. This greater rigidity results in increased accuracy due to reduced errors.
The vertical gyro is still tied by earth’s gravity, but by mercury / levelling switches and torque motors .
how work EAH
levelling switch is not level, the mercury liquid ball moves from its central position and drive its torque motor that provides the force which is precessed to return the gyro axis to the vertical.
There are two levelling switches, one to sense pitch and one to sense roll, they activate the pitch and roll torque motors respectively to move back the
vertical as soon as it starts to wander.
Acceleration error on EAH
Acceleration errors are minimal following reasons:
- The high rotor speed results in very high gyro rigidity and therefore very low precession rates
- The rotor housing is less bottom heavy therefore roll error is reduced while accelerating
- Pitch and roll cut-out switches.
