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
It was the 4th aircraft off 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.
Forced landing on Salisbury Plain
Unique colour scheme
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.
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.
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
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
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.
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.