|Object Type:||Signal/Data Processor|
|Object Name:||Standby Yaw Damper|
|Year of Manufacture:||1963|
|Location:||Archive Object Store|
Standby Yaw Damper
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.
In order to enhance the basic stability of the aircraft against dutch roll each autopilot system incorporates a yaw damper which is operative when the autopilot is engaged. In the event of failure of both dampers a third completely independent (Standby) yaw damper is available which may be engaged at any time. The Standby Damper drives the upper rudder surface under conditions where the ELRAT (Emergency Ram-Air Turbo-alternator) is operating.
The unit has the code 'V.A.A.S 227 (ET)' on it. This was an Elliott design and was delivered for the very first flight of the VC10 from Weybridge as yaw damping was deemed critical. This first unit was damaged on test before flight but was rebuilt in record time by the engineers at Borehamwood.