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The Royal Aircraft Establishment at Bedford

BAC 1-11 XX105

BAC 1-11 XX105 was acquired by the Blind Landing Experimental Unit (BLEU) as a replacement aircraft for the ageing Comets (XP915 and XV144, being more representative of the type of aircraft in service with airlines at that time.

It was the fourth aircraft of the 200 series production line, and survived a crash-landing on Salisbury plain while investigating deep-stall problems. After being re-built, it entered airline service with British United Airways in 1964 as G-ASJD. It was purchased from British Caledonian in 1971 and became XX105 on the military register. There followed a period of overhaul and re-painting at BAC Hurn, and an extensive re-fit as a ‘flying laboratory’ at the Cranfield Institute of Technology (CIT) and then in-house at RAE Bedford. It was modified to allow the spoilers to be used for direct lift control and fitted with a Smiths SEP5 autopilot to provide a ‘CAT 2’ all-weather capability. XX105 took on a new red, yellow and white colour scheme, chosen within BLEU, which became well recognised by aviation enthusiasts throughout much of the world, and in spite of much pressure from RAE top brass to change to the official ‘raspberry ripple’ colours, this unique livery was retained for the rest of its life.

The unique colour scheme of the BAC-1-11-XX105

Forced Landing on Salisbury Plain

Early projects centred on the active control/fly-by-wire systems which would feature in future generations of passenger aircraft. Direct Lift Control, Relaxed Static Stability, Energy-based Control Laws and Steep/Two Segment Approach techniques for noise reduction were investigated with the aid of a programmable analogue computer that could be coupled into the automatic pilot system.

By the mid 1970s, BLEU had become ‘Flight Systems 2’ Department of RAE, and XX105 became the project aircraft for the Civil Avionics Section. The 1-11 research programme was supported by the MoD, the Department of Trade & Industry and the Civil Aviation Authority. The work was carried out in conjunction with many UK avionic companies and also with Eurocontrol and the European Commission. Projects included an evaluation of a Ground Proximity Warning System (GPWS), which was about to become a mandatory fit for all passenger carrying aircraft, and investigations into the role of Head Up Displays in civil aviation.

The two main programmes to which XW750 contributed were firstly what was known as the UK Economic Cat III programme in the period 1975 – 1980 and secondly the developments which led to the passive terrain-following system and the CO2 Laser Radar (CLARA) between 1983-2003. The passive terrain-following system and CLARA continued further development with Tornado ZA326.

By the late 1970s/early 1980s, an improved range of digital navigation aids had been installed in the aircraft, together with a Flight Management System (FMS) to exploit the improved accuracy and to investigate the potential reduction in pilot workload. Navigational accuracy measurements using different combinations of ground and airborne sensors were made using tracking radars at Aberporth. These results were used to define the ICAO required navigational performance for civil aircraft. An Electronic Flight Instrument System (EFIS) further enhanced the aircraft’s capabilities and made it ideally suitable for a wide range of European Air Traffic Management (ATM) research projects supported by Eurocontrol and the European Commission, which eventually became the main task.

The capabilities of the FMS were developed to include 4D Time Slot Following, integrated air/ground Air Traffic Management and curved approaches using Microwave Landing System (MLS) guidance. Navigational accuracy was further improved by utilising Satellite signals from the US Global Navigation System (GPS) and the Russian equivalent (GLONASS). The EFIS Navigation Display was developed to include a map presentation with both horizontal and vertical options showing aircraft position and progress relative to the 4D clearance negotiated with ATC over a Data Link, and a Taxi Mode showing all runways, taxiways and stands. A Direct Voice Input (DVI) capability was developed to investigate performance and potential benefits when used in the cockpit. The FMS, EFIS, Data Link and DVI systems were integrated to provide a low workload environment for the crew when negotiating and flying the ATC 4D clearance.

A wide range of independent projects were tested during the ATM flights. These included investigating the performance of Mode-S, UHF, VHF and HF Data Link communication systems in a variety of operational environments, testing improved fuel gauging systems and calibrating atmospheric sensors in conjunction with the Meteorological Office.

The Advanced Cockpit of the BAC-1-11-XX105

Flight demonstrations were an essential part of the work, and XX105 was renowned for always being serviceable at the scheduled time, even if the pilots and scientists sometimes had to hide experimental system failures.

Flight trials were required in a large variety of conditions and geographic locations. These included hot and cold weather, involving detachments to the Mediterranean, Greenland and Svalbard (flying as near to the North Pole as the fuel load permitted). Navigation and Flight Management System development required operation throughout most of Europe, as did demonstrations of the EFIS system, which also required a month’s tour of the USA in 1981, with an intensive schedule of demonstrations to aircraft manufacturers, airlines and aviation regulators. Needless to say, the aircraft remained serviceable throughout the tour.

With the closure of RAE Bedford Airfield in 1994, XX105 was transferred to Boscombe Down where it continued similar work until its last flight in 2003.

XX105 was rightly recognised as the most capable, flexible and reliable flying laboratory in Europe, and probably second to none in the world. She was operated at RAE Bedford from 26th March 1973 until February 1994, and then at Boscombe Down until 2003, and will be remembered with great affection by all the pilots and scientists who flew in her, and by all the engineers who looked after her with such skill and dedication.

Where is it now?

The days before Christmas 2012 saw this renowned aircraft broken up and removed from Boscombe Down in skips – a sad end to a 30 year career at the forefront of avionics research.


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