OPERATIONAL LIMITATIONS.
Unlike the directional gyro, the attitude horizon has no attitude limits. If, however, pitch reaches 90°, the
“polar effect” is reached and the horizon bar display will rotate 180° to an inverted position and will again rotate
180° when the aircraft is right side up. The modern-day attitude horizon will not be damaged by such an extreme
attitude and will correct itself in a short time. There are no roll limitations to the present attitude horizon. Another
important but not widely understood operating limitation of air driven instruments is erection of the horizon bar
from a full stop and from a residual running condition. This can lead to wasted service time and invalid operating
complaints. When the gyro rotor is at rest and power is applied, the erection mechanism exerts maximum
authority and rapid, noticeable erection results. However, if power is removed from the spinning rotor (such as
when an engine is shut down while briefly discharging passengers) the gyro rotor continues to rotate at high
speed but the erection mechanism is not functional. When power is again applied to the air driven attitude horizon
the erection mechanism again begins to function. However, due to gyro rigidity because of high rotor speed,
erection of the instrument takes considerably longer than normal. In flight, the air-driven attitude horizon exhibits
small errors at roll out after a coordinated turn, skids and small pitch changes after acceleration and deceleration.
The electric attitude horizon exhibits small errors in pitch and roll out from a coordinated turn and also small
pitch changes after acceleration or deceleration. In both cases, the erecting mechanisms quickly return the gyro to
its proper position. The electric attitude horizon is considered generally more efficient in operation and less
subject to error than the air driven attitude horizon.
TROUBLESHOOTING.
Unless an obvious malfunction, such as inability to erect, spinning, or great horizon bar displacement, none of
which can be corrected by manually caging the instrument, requires repair or replacement of the instrument,
service is restricted to the instrument installation and power source. Typical installation examples of attitude
horizon malfunctions are due to such problems as: restricted air flow due to air line kinks or leaks, contaminated
air filters, deteriorating electrical grounds, sagging instrument panel shock mounts, systems regulators, faulty
vacuum/ pressure gauges.
— Note —
Air pressure must be 5.5 ± .5 psig.
Only after the system has proven to be good should the instrument be “pulled” for replacement or repair.
TURN AND BANK/PICTORIAL RATE INSTRUMENTS.
Unlike the familiar “free” gyro rotor found in the directional and attitude gyros both the turn and bank and the
pictorial rate indicator have captive gyro rotors, the axis of which are attached to the instrument housings. Since
the spinning gyro rotors are literally forced to follow airframe movement, the gyro resists changing position by
exerting precession forces created by the spinning gyro. The greater the “rate of change” the greater the
precession forces, thus, the turn and bank and the pictorial rate indicator ONLY MEASURE MOVEMENT -
NOT POSITION OR DISPLACEMENT. The gyro rotor forces of the turn and bank are presented on the
instrument face by a vertical turn needle and on the pictorial artificial horizon. Although the visual displays are
different the gyro rotor rate detection designs are the same. The gyro motor is mounted at a 6° angle to detect
both yaw and roll motion, but the 60° tilt favors the yaw axis. Due to the great sensitivity of the rate gyro, the turn
needle/ pictorial horizon displays are mechanically dumped to slow or average minute.
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
3 4 - 3 4 - 0 0
Page 34-11
Revised: May 15, 1989
2J5
PIPER AIRCRAFT
Summary of Contents for SEMINOLE PA-44-180
Page 38: ...CHAPTER DIMENSIONS AND AREAS 1B14...
Page 49: ...CHAPTER LIFTING AND SHORING 1C1...
Page 53: ...CHAPTER LEVELING AND WEIGHING 1C5...
Page 58: ...CHAPTER TOWING AND TAXIING 1C10...
Page 62: ...CHAPTER PARKING AND MOORING 1C14...
Page 65: ...CHAPTER REQUIRED PLACARDS 1C17...
Page 70: ...CHAPTER SERVICING 1C22...
Page 98: ...CHAPTER STANDARD PRACTICES AIRFRAME 1E2...
Page 108: ...CHAPTER ENVIRONMENTAL SYSTEM 1E12...
Page 189: ...CHAPTER AUTOFLIGHT 1H21...
Page 192: ...CHAPTER COMMUNICATIONS 1H24...
Page 202: ...CHAPTER ELECTRICAL POWER 1I10...
Page 228: ...CHAPTER EQUIPMENT FURNISHINGS 1J12...
Page 233: ...CHAPTER FIRE PROTECTION 1J17...
Page 238: ...CHAPTER FLIGHT CONTROLS 1J24...
Page 304: ...2A18 CHAPTER FUEL...
Page 325: ...2B17 CHAPTER HYDRAULIC POWER...
Page 357: ...2D1 CHAPTER ICE AND RAIN PROTECTION...
Page 414: ...CHAPTER LANDING GEAR 2F13...
Page 479: ...2I6 CHAPTER LIGHTS...
Page 488: ...2I16 CHAPTER NAVIGATION AND PITOT STATIC...
Page 503: ...2J7 CHAPTER OXYGEN...
Page 524: ...2K6 CHAPTER VACUUM...
Page 535: ...2K19 CHAPTER ELECTRICAL ELECTRONIC PANELS AND MULTIPURPOSE PARTS...
Page 546: ...INTENTIONALLY LEFT BLANK PA 44 180 180T AIRPLANE MAINTENANCE MANUAL 2L6 PIPER AIRCRAFT...
Page 547: ...2L7 CHAPTER STRUCTURES...
Page 582: ...CHAPTER DOORS 3A18...
Page 593: ...CHAPTER STABILIZERS 3B8...
Page 604: ...CHAPTER WINDOWS 3B22...
Page 611: ...CHAPTER WINGS 3C10...
Page 624: ...CHAPTER PROPELLER 3D1...
Page 643: ...CHAPTER POWER PLANT 3D21...
Page 667: ...CHAPTER ENGINE FUEL SYSTEM 3F1...
Page 681: ...CHAPTER IGNITION 3F16...
Page 712: ...CHAPTER ENGINE INDICATING 3H1...
Page 730: ...CHAPTER EXHAUST 3H19...
Page 734: ...CHAPTER OIL 3I1...
Page 743: ...CHAPTER STARTING 3I11...
Page 755: ...CHAPTER TURBINES 3J1...