AW52 Flying Wing

The Armstrong Whitworth AW 52 Flying Wing

This paper is a brief history of the AW 52 Flying Wing, designed and manufactured by Sir WG Armstrong Whitworth Aircraft Limited, Coventry.

It has been often stated that the AW 52 Flying Wing was the world’s first jet propelled all-wing aircraft. Unfortunately, this statement does not bear close scrutiny. The concept of the all-wing flying machine in fact goes back to the earliest pioneering days of aviation, but it was not until the 1920s and onwards that the potential advantages of such a configuration started to be seriously investigated in Germany by Dr Alexander Lippisch and the Horten brothers, Walter and Reimar. Whilst Dr Lippisch was a highly qualified aerodynamicist, working with several renowned German establishments and gaining his doctorate from Heidelberg University, neither of the Horten brothers had a formal technical background in aeronautics, which in the light of their later achievements was quite remarkable!

The experiments of Dr Lippisch initially centred on unpowered sailplanes, using a multitude of delta configurations. Eventually in 1939 Lippisch formed a design relationship with Professor “Willy” Messerschmitt and this collaboration resulted in the phenomenal rocket powered Me 163 Komet interceptor fighter, which had limited combat use at the very end of the Second World War. Apparently the relationship between Lippisch and Messerschmitt soured and became somewhat less than cordial. Dr Lippisch died in 1976.

The Me 163 Komet was a remarkable aeroplane, but an extremely dangerous one to fly. This had little to do with any defects in the airframe and everything to do with the extremely volatile fuels used in the Walter rocket motor. In fact the Komet was a very good flying machine and indeed it had to be, as when the rocket fuels were rapidly spent attaining interception altitude, it had to glide back to earth and land on a narrow projecting skid! It is said more Komet pilots were killed and injured by the aircraft itself than those lost in actual combat.

Initially working in Bonn, Walter and Reimar Horten created a delta wing design powered by two jet engines buried in the thickness of the wing section of their Horten Ho. IX machine. The Horten Ho IX was allocated the Reichsluftfahrtministerium (RLM) Number Ho229. A number of prototypes were constructed and on the 2nd February 1945 the Ho. IX V2 all-wing machine, with Leutnant Erwin Ziller at the controls, successfully flew from Oranienburg airfield, situated just North of Berlin. This undoubtedly was the world’s first flight of a true all-wing jet propelled aircraft and took place nearly three years before Britain’s equivalent AW 52. Test pilot pilot Ziller was subsequently killed on 18th February 1945 whilst flying the Ho IX V2 prototype, which crashed after a mid – air engine fire.

At the end of the war American forces – implementing “Operation Paperclip”, the prevention of German technology falling into Soviet hands – captured several Horten Ho IX prototypes and transported one, the Ho IX V3, back to the United States for evaluation. During its transportation back to America, the Ho IX V3 actually stopped off at Farnborough, where some consideration was given to fitting it with British jet engines in order that it could be test flown. This did not take place as British centrifugal jet engines were of a larger diameter than their German axial compressor equivalents. The Ho IX V3 still exists in a museum in the USA awaiting refurbishing.

Both the Horten brothers were committed members of the NSDAP (Fascist) party and although not a technician Walter was a competent Luftwaffe pilot who apparently fought in the Battle of Britain, claiming seven British aircraft shot down. Walter apparently lies in a cemetery in Baden-Baden. The author will investigate this fact more closely when he next visits Baden-Baden.

Early in the Second World War Armstrong Whitworth’s chief designer, John (Jimmy) Lloyd, started to investigate the possibilities of the all-wing concept allied to the qualities of laminar flow wings and boundary layer control. The project was allocated the type number AW 52. Laminar flow wings are aerofoil surfaces that have extremely low levels of aerodynamic friction which smooth the flow of air over the surface of the aerofoil for as long as possible, thus reducing turbulence and flow break-up to the absolute minimum. Boundary layer control is a further means of ensuring smooth aerodynamic airflow.

Aerofoil surfaces of laminar flow type are very difficult to construct and demand high standards of conformity, workmanship and finish. The smallest of excrescences on the surface of the aerofoil will destroy the laminar flow and nullify any advantages. Conventional section aerofoils normally have their maximum thickness at a point about one third of the chord taken from the leading edge, whereas laminar flow aerofoils have their maximum thickness at approximately the mid-chord position. It was eventually found by experimentation with test pieces and laminar flow wings actually fitted to different aircraft, that these aerofoils were not really practicable; the surfaces being virtually impossible to keep in a sufficiently clean and pristine condition. For example, objects as small as insects adhering to the aerofoil surface would be sufficient to lead to a degradation of the laminar flow. However, all this had yet to be ascertained.

Armstrong Whitworth’s foray into laminar flow wings commenced in 1942 with the building of a set of aerofoils for testing at the National Physical Laboratory. By September 1943 slow speed wind tunnel testing using models of the AW 52 G glider was taking place at Whitley. It was decided that a 0.6 full size flying wing glider utilising a laminar wing and boundary layer control would be built prior to the construction of the full size jet powered prototypes. The glider was provided with a fixed undercarriage to which were attached two windmills to drive the boundary layer suction pumps. The AW 52 G glider was allocated the registration RG 324. Construction of the glider commenced in the Wood Shop at Whitley in 1944, before being transferred to Baginton for completion in early 1945.

It was proposed that the AW 52 Glider RG 324 would be towed into the air by a Whitley B Mk. V Bomber, LA 951, the final aircraft of the type to come off the Baginton assembly line on 12th July 1943 and retained by the company for its own purposes. RG 324 eventually completed its first “free” glide on 2nd March 1945 and the flight was of 25 minutes duration. The Whitley’s towing function ended in 1948 and this task was then performed by Lancaster PA 366.

In parallel with the AW 52 G glider another aircraft was being readied for use with laminar wings and boundary layer control. This was Hawker Hurricane II, Z3687. This aircraft was first flown from Baginton on 23rd March 1945, with AWA’s Charles Turner-Hughes at the controls.  The original Hurricane wings were of a relatively thick section, and it would be interesting to know whether the new laminar flow wing set conferred extra speed, manoeuvrability and other improvements on the venerable but obsolescent interceptor fighter.

Although the AW 52 glider was entirely made of wood, the two turbojet powered prototypes, registered respectively TS363 and TS368, were to be of aluminium construction. The manufacture of the laminar flow wing presented considerable technical difficulties and new techniques were necessary to solve them. Instead of building the entire inner wing structure and then externally skinning it in the conventional manner, the laminar wing was built in two halves, working from the outside pre-formed skin inwards and joining the two halves to complete the aerofoil section. This ensured that the outer skin surface contour conformed to the required finished form at all times whilst being assembled in the profiled building jigs. An error not exceeding 0.002” was claimed for the completed aerofoil.

Because the Flying Wing lacked a conventional empennage (tailplane) and hence elevators, a control surface called an elevon was introduced. The elevon combined the dual functions of ailerons and elevators. Therefore, an elevon could be alternately up or down acting as an aileron, or in unison up or down as an elevator. Almost the entire trailing edge of the Flying Wing comprised elevon control surfaces, together with Fowler type flaps and spoilers. As an aside the Vulcan bomber had a very similar arrangement. In addition, the upper surface of the wing featured small suction ducts just ahead of the elevon control surfaces. These provided the boundary layer control, by sucking away air from the lowest level on the wing surface and generally assisting in minimising turbulent breakaway. An auxiliary pump driven by one of the jet engines provided the necessary suction for the boundary layer control.

The pressurised cockpit, which was slightly offset to port, accommodated the pilot and flight observer seated in tandem in a central nacelle. Only the pilot was equipped with a very early form of Martin-Baker ejection seat which preceded the company’s Mk. 1 seat. The Martin-Baker ejection seat was to gain great significance with the Flying Wing and will be discussed later in this paper. Buried in the thickness of the wing were two Rolls-Royce turbojet engines. The first prototype, TS 363, was equipped with a pair of Rolls-Royce Nene engines, each of 5,000lbs. thrust.  TS 368, the second prototype, had two Rolls – Royce Derwent engines, each of 3,500 lbs. thrust. The reason for this power downgrading is unknown – perhaps it was a question of availability or economy? It should be remembered this was a time of shortages and overwhelming national economic hardship. The aircraft’s undercarriage was of the fully retractable tricycle arrangement.

On November 13th 1947, Britain’s first jet propelled Flying Wing, TS363, took to the air with test pilot Eric G Franklin at the controls. In September 1948 TS 368 joined the test flying programme. This aircraft was subsequently transferred to Farnborough for research into airflow behaviour. The first prototype remained with Armstrong Whitworth.

The 30th of May 1949 was to be a momentous day for the entire aviation community, both in Britain and the rest of the world. On the afternoon of that day Armstrong Whitworth’s new deputy chief test pilot, John Oliver Lancaster, (known to everyone as “Jo”), was scheduled to take the first prototype, TS 363, up to evaluate its general handling in the speed range 270-350 mph. It was Lancaster’s third flight in the machine. The weather could hardly have been better, with towering cumulus clouds giving partial cover. Prior to taking off from Bitteswell, Lancaster had strapped himself into the ejection seat, almost without thinking. No one had ever used an ejection seat in an emergency and many pilots were dubious as to their worth and whether they would actually work when required. In the light of events it was fortuitous that Lancaster was the only occupant of the aircraft, as no flight observer was being carried that day.

Lancaster worked through his schedule of tests, mostly in the lower speed range at an altitude of 10,000 feet; he then put the put the aircraft into a shallow dive reaching about 320 mph at 5,000 feet. The machine then seemingly entered very turbulent air which had a profound effect on its stability, causing violent pitching, the oscillations increasing in intensity. Lancaster was violently thrown about in the cockpit and the situation became serious. After no more than a few seconds of this buffeting, although probably seeming an eternity, Lancaster decided to use the ejection seat to vacate the aircraft.

On the very early Martin-Baker seats the ejection sequence was not fully automatic, and having left the aircraft the seat had to be manually released by the free-falling pilot. Care was required by the pilot to ensure that the seat release was selected and not the chute harness release! Having released the seat the parachute “D” ring pull could be manually activated to stream the parachute. All this Lancaster accomplished satisfactorily, although the discarded seat did pass uncomfortably close to him on its way to earth.

On his own way to earth Lancaster noted he was descending close to a canal and endeavoured to steer the parachute away from the hazard. His efforts were not entirely successful although he did miss the canal, landing on his back in a nearby hedge. Slightly stunned Lancaster watched the water murmuring in the nearby canal trying to recount his ordeal. Eventually, assistance arrived in the form of a farmer named Mr. Shepherd, who took Lancaster back to his farmhouse and provided him with a well-earned cup of tea! All this occurred near the Cuttle Inn, Long Itchington in Warwickshire.

Although superficially unhurt, upon subsequent medical examination it was discovered that Lancaster had sustained a chipped shoulder joint and cracks to his first lumber vertebrae. He also had very severe bruising. It was uncertain whether these injuries were attributable to his shaking up in the cockpit or his hard landing. Nevertheless, Jo Lancaster had survived to tell the tale, the first man to use an ejection seat in Britain in an emergency. John Oliver Lancaster, DFC, C Eng, FRAeS, died at the age of 100 years on 10th August 2019.

Because of its early use of jet aircraft, Germany was the first nation to devise and exploit the use of compressed air ejection seats during the Second World War. However, these accounts are poorly documented and it was Jo Lancaster’s heroic escape, in reality, that paved the way for the use of the modern ejection seat. His was a major “first” in aviation history and was to be the precursor of many similar situations. It was also a great fillip for James Martin and his remarkable ejection seat. Since that first successful emergency ejection in 1949, well over 7600 lives have been saved to date worldwide using Martin-Baker seats. Martin- Baker seats are currently in use with 93 Air Forces. It is said that two ejections are made each week using Martin-Baker seats. Sir James Martin, the co-founder of the Martin-Baker Company and inventor of the ejection seat died in 1981, aged 87 years.

Although Jo Lancaster came to earth at Long Itchington, the AW 52, TS 363, actually crashed near Leamington Hastings, also in Warwickshire. The machine was totally destroyed. The subsequent investigation into the crash concluded that asymmetric flutter had developed in one of the end fins and this had progressed across the entire wing causing violent oscillations, whose frequency was between 1,5 and 2 cycles per second, with an angular movement of 20 degrees. The firing of the ejection seat rather strangely seems to have stabilised the aircraft and it flew on some distance before finally crashing. The Flying Wing’s controls were not particularly well harmonised, with the aileron/elevon response regarded as sluggish and heavy laterally, and over- light and sensitive fore and aft. In other words a bit of a nightmare to fly! Flying wing type aircraft, generally speaking, tend to display relatively poor lateral control characteristics. Artificial feel fitted to the controls may have improved the situation considerably, but these devices were in their infancy in the 1940s. Tail-less aeroplanes do have a propensity to be uncontrollable under certain conditions, the de Havilland DH 108 “Swallow” being a notable example. All three DH 108 prototypes crashed, killing their respective pilots, among them Geoffrey de Havilland Jr. The late Eric “Winkle” Brown, CBE, who flew more aircraft types than any other person in history, including the DH 108, described the aeroplane as, “a Killer”.  

The second prototype, TS 368, continued its work at Farnborough and was scrapped at the end of its useful life in 1954. The wooden AW 52 G glider, RG 324, remained at Baginton for many years, positioned outside the main Armstrong Whitworth office block at the top of Siskin Drive. Despite attempts to save this pioneering aeroplane it was eventually broken up. The author is not absolutely sure, and memory may be playing tricks, but he may have witnessed this act of vandalism actually taking place in the early 1960s.

References;

  • Armstrong Whitworth Aircraft, The Archive Photographs Series, Ray Williams, Chalford, 1998
  • Wings on My Sleeve, Eric “Winkle” Brown, Weildenfeld & Nicholson, 2006
  • Sir James Martin, The Authorised Biography of the Martin-Baker Ejection Seat Pioneer, Sarah Sharman, Patrick Stephens, 1996
  • The Rise and Fall of Coventry’s Airframe Industry, John Willock, WIAS Publication

Copyright  © J F Willock August 2020

This is an interesting piece of Pathe film from 1946 showing the AW 52G Glider (RG324) emerging from its hangar at Bitteswell (Old Site) and then being towed across the Lutterworth Road onto the airfield. Notice how a tread mat is placed carefully on the laminar wing to prevent any damage when accessing and exiting the cockpit and how someone avoids it and slides off the wing probably scratching the surface. The narrrowness of the Lutterworth Road is apparent, and this is the exact point that Vulcans and many other aircraft crossed from one side of the site to the other. This is precisely where the Magna Park Warehousing complex is today.

The second jet-powered A.W.52 with Derwent engines

 

Armstrong Whitworth AW-52 3-view drawing from Les Ailes 18 January 1947

 


 Testing the Martin Baker Ejector Seat