Polar Path Compass Coupler

Technical Information

Catalogue No: C1320
Category: Navigation/Inertial
Object Type: Signal/Data Processor
Object Name: Polar Path Compass Coupler
Part No: 16088-1A
Serial No: S071020
Manufacturer: Bendix
Division: Eclipse-Pioneer [of Bendix]
Year of Manufacture:
Width (mm):
Height (mm):
Depth (mm):
Weight (g):
Location: Archive Object Store

Polar Path ® Compass Coupler
SAE Spec. AS-399 TSO-C6b
Manufactured under one or more of the following patents:
2,614,355 2,726,457 2,776,397 2,797,384 other patents pending
Type No. 16088-1A
Wt lbs
Serial No. S071020
The Bendix Corporation
Eclipse-Pioneer Division
Teterboro, New Jersey
Made in U.S.A.
6TK 33


The automatic flight control system of the Standard and Super VC10 was designed to be capable of development to full blind landing. To meet this requirement the system had to be capable of failure survival and this includes associated services such as power supplies and flying controls. The method of autopilot failure survival chosen was to provide two monitored systems which are fail soft, i.e. there is negligible aircraft disturbance after a failure. Only one autopilot is used to fly the aircraft, and the two systems, including power supplies, are completely independent. Each autopilot has a comparison monitor which detects faults and, in flight, will disconnect the system if these faults are likely to lead to dangerous conditions. For autoflare the system provides for automatic changeover to the second monitored autopilot system, in the event of fault in the first. Under these conditions the second autopilot is primed and ready to take over. If for any reason the monitoring system fails to prevent an autopilot runaway, the control movement is limited to a safe amount by the yielding of a torque-limiting spring.

Many of the needed components were already present in the autopilot fit on the Standard VC10s, to achieve the autoland capacity the system on the Super received some additional items. The system, supplied by Elliott Brothers (London) Ltd, is based largely on components of the well-proved Bendix PB-20 autopilot, made under licence by Elliott, and interchangeable with American built components as installed in Boeing 707s. However, the system as a whole i.e., the dual autopilot concept was novel, and designed entirely by Elliott.

The Polar Path Compass System is a gyrocompass developed in the early 1950s. It uses a small gyro spinning at more than 20,000rpm and overall has a drift rate of less than 1 degree per hour (the name originates because of the ability of this unit to navigate in polar regions where a conventional compass would not work).

The unit supplies heading information to each autopilot.

This unit is missing a couple of circuit modules and the top cover.

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