Automatic landing or Autoland is taken for granted now. It has been suggested to me that an account of the pioneering work on its development, at the Blind Landing Experimental Unit (BLEU) of the Royal Aircraft Establishment (RAE), might be of interest to those with a taste for ancient history. I was at BLEU from 1955 to1958. This thread is a shortened version of a contribution I made to Wikipedia on Autoland, Sections 2.4 and 2.5 (with references). Apart from that, I hope that other contributions to this thread will help to fill in some of the gaps.
The BLEU was formed at RAF Woodbridge and RAF Martlesham Heath during 1945 and 1946. ,The terms of reference were that the unit “will operate as a satellite of the RAE and will be responsible for the development on blind approach and landing of RAF, Naval and Civil aircraft”.
The subject of blind landing had been pursued with enthusiasm from much earlier. For example, in 1916 flight tests were made by the Royal Naval Air Service of an Aircraft Height Indicator, consisting of a weight attached to a length of cord, hanging from the aircraft. When the weight hit the ground the tension in the cord was relieved, triggering a switch to light a red lamp in the cockpit, so that the pilot knew it was time to start a flare out. The basis for BLEU’s work was however the development of autopilots at RAE during the 1930s. The Mark 4 was the wartime “George”.
Before the formation of BLEU, an automatic landing was made at the Telecommunications Flying Unit (TFU) of the TRE at RAF Defford in a Boeing 247D aircraft, DZ203, early in 1945, using the American SCS 51 radio guidance system. Although accounts of that event vary in detail, it is said to have been in complete darkness, with no landing lights and all other lights obscured by the wartime blackout. There was no flare-out - the low approach speed and shallow glide angle meant that the aircraft could be allowed to fly straight onto the ground.
SCS 51 was the basis for ILS, adopted by ICAO in 1948. Trials were made at Defford of an alternative system developed there. That was radar-based, which in effect gave range and height data to add to autopilot heading, so enabling automatic landing.
Research during the first few years at BLEU led to the conclusion that the most promising approach to blind landing would be a fully automatic system, and to the definition of the requirements for such a system. ILS was used as guidance during the approach phase, but at that time was not sufficiently accurate to complete the landing. That led to the development at BLEU of an improved FM radio altimeter for height guidance, capable of resolving height differences to 2 feet at low altitude, and a magnetic leader cable system for azimuth guidance. In collaboration with Smiths Industries Ltd., BLEU also developed coupling units to derive the commands to the autopilot from the guidance signals, and auto-throttle.
Components of the system were developed separately on several types of aircraft, including the Lancaster, Viking, Devon and Albemarle. A demonstration of the techniques used was given to military and government representatives in May 1949. Partially automatic landings had been made before then, but the generally accepted date for the first demonstration of the entire system including auto throttle, in a Devon, is 3rd July 1950. Over the next 20 years, BLEU in conjunction with UK industry and the UK airworthiness authority, continued the work needed to convert the concept of those experimental demonstrations into safe, accurate blind landings by large transport aircraft. The system in use now is, I understand, basically the same as that used experimentally in 1950.
During the early 1950s, as a preliminary to the further development of the full system, automatic approach trials were carried out on Valetta, Meteor and Canberra aircraft. The Canberra, VN799 (the prototype Canberra) was acquired in 1953 but was a write-off following a crash landing in August that year due to a double engine failure, possibly caused by a fuel leak, fortunately without serious injury to the crew.
At that time, Autoland had lower priority because efforts were concentrated on other projects including rapid landing of aircraft for RAF Fighter Command, visual aids for pilots, runway approach lighting and an approach aid using DME with Barbro. That changed when Operational Requirement 947 (OR947) for automatic landing on the V-force bomber fleet was issued in 1954. At that time the V-bomber force was the UK’s main contribution to the strategic nuclear power of the west and all-weather operation was essential. There was also renewed interest in automatic landing for civil aviation. As the next step in the development, the flare-out and coupling units from the Devon were linked to a Smiths Type D autopilot and installed in Varsity WF417, a much larger aircraft, capable of carrying 38 people rather than 10 in the Devon. The first fully automatic approach and landing was made by WF417 on 11 November 1954 under calm and misty conditions. A similar system was installed in Canberra WE189 to provide the first application of Autoland to jet aircraft. Automatic approaches and landings were recorded by WE189 early in 1956 but the development was interrupted in April when the facilities at Woodbridge, which had the only suitable leader cable installation, ceased to be available to BLEU. Development of auto-flare and automatic kicking-off drift was continued at RAF Wittering, but in September that year WE189, on an approach to its base at Martlesham Heath, crashed due to engine failure . The pilot, Flt. Lt. Les Coe, and the BLEU scientist in charge of the project, Mr. Joe Birkle, were killed.
Early in 1957 BLEU moved from Martlesham Heath to a newly equipped airfield at Thurleigh, the base for RAE Bedford. The development was continued in a third Canberra, WJ992, based on the results obtained with WE189. Experimental flights in WJ992 began late in 1957. I did most of the experimental flying, variously with four RAF pilots: Sqn. Ldr. John Greenland and Flt. Lts. Alf Camp, Alan Bountiff and “Pinkie” Stark. Automatic landing with auto-throttle was achieved by March 1958. Initially there were some problems with landing nose wheel first but by June things had improved - a note from my logbook reads “not bad - about 0.7 g nicely on main wheels - kicking off drift OK“. Then a week later: “Throttles off at 50ft. Very pleasing results” and on 20 August “hands and feet off” (that was with Alan Bountiff). By October 1958, when a further demonstration was given by BLEU, over 2,000 fully automatic landings had been made, mainly in the Canberra and Varsity aircraft. The demonstration by WJ992 can still be seen in this 1958 Pathé News clip (the airborne sequences are in a Varsity):
FOG WON'T STOP FUTURE FLYING - British Pathe
The V-bomber project to install and develop Autoland on Vulcan XA899, originally classified as Secret, ran in parallel with the Canberra and Varsity work. The first automatic landings in the Vulcan were made between December 1959 and April 1960. Trials were carried out later that year and the system was accepted for military service in 1961 - the first application of the Autoland system.
The Vulcan used leader cable but that was recognised as being impractical for general use. It was also known that it could be dispensed with if improvements could be made to ILS. Some improvement resulted from a narrow beam localizer aerial system developed by BLEU during the early 1950s and by 1958 automatic landings had been made using only ILS localiser for azimuth guidance. By the early 1960s radically new aerial designs for the ILS transmitters developed by Standard Telephones & Cables (ST&C) improved ILS to an extent that leader cable became obsolete.
For many years there had been discussions between the UK Ministry of Aviation and the US Federal Aviation Agency (FAA) on guidance aids for landing in poor visibility. The Americans favoured a “pilot in the loop” technique, with improved aids for the pilot, over the fully automatic system preferred in the UK. In 1961, to gain experience with “the BLEU automatic landing system” the FAA sent a Douglas DC-7 to RAE Bedford for the system to be installed and tested. After that and further tests on return to Atlantic City, the FAA were convinced and thereafter strongly supported a fully automatic solution to the all-weather problem, later to be adopted internationally.
Up to that stage the system had been realised only as “single-lane” or single channel, without any redundancy to protect against equipment failure. During the late 1950s and early 1960s increased cooperation between BLEU, the UK Civil Aviation Authority (CAA) and companies in the aviation industry with BEA and BOAC led to the definition of safety requirements in terms of a specification for maximum tolerable failure rates. In 1961, the UK Air Registration Board (ARB) of the CAA issued a working document BCAR 367 “Airworthiness Requirements for Autoflare and Automatic Landing” which formed the basis for the definitions for weather visibility categories adopted by ICAO in 1965. In 1959, contracts were placed by BEA and BOAC to develop automatic landing, based on Autoland, for the Trident and the VC10. The Trident used a triplex system with no common elements, so that a failure in one of the three channels could be detected and that channel eliminated. “Nuisance disconnects” were an early problem with that system, eventually solved by the industry, using torque switches with a controlled degree of lost motion. The introduction of Autoland for Category 3 operation in BEA’s Trident fleet required a huge effort by BEA, Hawker Siddeley Aviation, Smiths Industries and BLEU. A triplex system was also developed by Smiths and BLEU for the RAF’s Belfast freighter.
The VC10 used an Elliott duplicated monitored system. Later, the Concorde system was basically an improved version of the VC10 one, benefiting from advances in electronic circuit technology during the late 1960s. By 1980, the Trident had carried out more than 50,000 in-service automatic landings. The VC10 accrued 3,500 automatic landings before use of the system was curtailed in 1974 for economic reasons. By 1980, Concorde had performed nearly 1,500 automatic landings in passenger service. 10 years on from the 1958 demonstration, here is Pathé again with the VC10 - giving a much better impression of the system at work:
An earlier clip, from 1965 in Varsity 665, briefly shows the autopilot itself:
BLEU (renamed the Operational Systems Division of RAE in 1974) continued to play a leading role in the development of aircraft guidance systems, using a variety of aircraft including DH Comet, BAC 1-11 and HS 748 (to replace the Varsities, which had been the main “work horses“ for BLEU experiments for more than a decade) and VC-10 until the closure of RAE Bedford in 1994.
The development of the system for the Caravelle during the 1960s is another story, unknown to me, and I hope there will be contributions on it.