|Object Name:||Flight Path Deviation Indicator|
|Division:||Eclipse-Pioneer [of Bendix]|
|Year of Manufacture:||circa 1965|
|Location:||Archive Object Store|
Indicator, Flight Path Deviation
The flight director instrument system on the VC10 is considered as an alternative to the autopilot for all modes except automatic flare-out and for this reason is integrated with the automatics to only a limited extent. It derives its attitude and compass signals respectively from the main vertical gyros and Polar Path compasses and takes radio information from either group of radio receivers.
These signals are electrically separated from the autopilot as far as is practicable. The system is of necessity duplicated in that each pilot has his own course deviation indicator and horizon
director indicator but only a single flight steering computer is provided. The attitude displays have independent absolute monitors consisting of circuits which check the vertically of the gyro and the continuity and operation of the transmission system. Failure warning is by a flag in the horizon indicator. Additionally there are comparator units between the horizon displays and between the compass systems which illuminate warning lights in the event of a difference between the two sides. Comparison is effected mechanically through torque synchros so that electrical isolation between the systems is maintained.
The course deviation indicator has a rotating compass card behind a fixed aircraft silhouette and lubber line. A marker and digital counter may be used to set desired course against the compass
card and a heading marker is provided. Linked with the course marker and occupying the centre of the dial is a left/right needle which provides simple VOR/ILS deviation information. It rotates with the course marker to give a semi-pictorial indication of the relationship of the aircraft to a VOR or ILS beam. A normal glide-slope deviation needle remains horizontally aligned. The pilot thus has a "straight" plan-position indicator and a computing director instrument.
The Ref. No. 6TK4543009 is on the instrument which was probably built by Elliotts under licence from Bendix. The Instrument was repaired at Rochester in July 2005.
From the early days of the company it had been hoped to enter the civil aircraft flight control field, in order to reduce dependence on military projects, The opportunity to take this step came in the late 1950’s with the planning of the Vickers 'VC 10' for which Elliott Brothers secured an order to provide a complete automatic flight control system. From the outset, the 'VC 10' system was planned to make provision for fully automatic landing of the aircraft. For certification ever to be possible an extremely high standard of reliability was essential, and even in the case of failure of the equipment it was a requirement that the aircraft must not be subjected to violent manoeuvres. After a detailed study of possible alternatives, the solution chosen was to duplicate the whole of the major system, one half to be operative while the other was to be 'standing by', with a changeover mechanism of the utmost reliability to permit instant switching from one to another. By 1960 the basic development was substantially complete and the requirements for automatic landing were being explored in detail with full 'autoland' capability available from January 1963. Successful development of the 'VC 10' system resulted in the opportunity to supply broadly similar equipment for the British Aircraft Corporation 'BAC 111', which has been produced in substantial numbers. 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, was 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.