Geodetic Aircraft Design

Geodetic Fuselage of Vickers Wellington

When further work on airships was abandoned in Britain during 1930, Barnes Wallis was recruited by Rex Pierson to move to Weybridge, where he settled into applying his expertise in using light alloy construction to fixed-wing aircraft.

“I transferred to aeroplanes. At that time their structure consisted of a rectangular skeletal framework, the outer skin being doped fabric supported on a complicated and otherwise useless wooden framework shaped to produce a streamlined form, but with the disadvantage of adding considerably to the weight of the basic structure”

Wallis hit upon a revolutionary structural idea – rather than building an aircraft structure on the principle of a beam, which supports an external aerodynamic skin, he developed a new type of structure which had the structural members formed within the aerodynamic shape itself. This required the structural members to follow the curved outer shape of the fuselage and wings.

“With the knowledge of geodesics gained from the gasbags of R.100 in my mind, it occurred to me that I could not only abolish the wooden falsework, but could at the same time enlarge the internal skeletal structure to full streamline dimensions, by forming its members as geodesics in the surface of both wings and fuselage, thus getting a much lighter, stiffer and stronger structure than ever before”

Wallis and Pierson were the centre of the Vickers-Armstrongs design team – Pierson working on the general layout of the aircraft and Wallis designing the internal structure. During this partnership the pair designed and developed two aircraft of note that played pivotal roles within the RAF; the Wellesley and Wellington Bombers.

What is a Geodetic Design?

A geodetic (or geodesic) airframe makes use of a space frame formed from a spirally crossing basket-weave of load-bearing members. By having the geodesic curves form two helices at right angles to one another, the members became mutually supporting in a manner that the torsional load on each cancels out that on the other. In addition to being comparatively light and strong, the fact that the geodetic structure was all in the outer part of the airframe meant that the centre was a large empty space, ready to take payload or fuel.

Wellesley Bomber

Vickers Wellesley Bomber

The Vickers Wellesley Bomber originated from Air Ministry Specification G4/31 which called for a general purpose aircraft capable of bombing, reconnaissance and army co-operation. Designed by Barnes Wallis using geodetic construction, a Vickers Type 253 bi-plane won the G4/31 contest and in 1935 an order was placed for 150 machines. Meanwhile, Wallis was working on a monoplane, the Type 246, using the same construction techniques and the aircraft took to the air for the first time in June 1935.

Vickers Wellesley Bomber Cutaway

It soon became clear that the monoplane’s performance was significantly better than that of the Type 253 bi-plane. Power came from a Bristol Pegasus XX serial radial piston engine producing 925 horsepower. Performance specifications included a maximum speed of 228 miles per hour, a range out to 1,220 miles, and a service ceiling of 25,500 feet. Cruising speeds was typically around 180 miles per hour. In September 1935, the Type 253 order was replaced with one for 96 Type 246 aircraft to fulfil a light bomber role.

After a number of improvements, the first production aircraft, the Vickers Wellesley Mk I, took to the air in January 1937 and entered RAF service with No 76 Squadron at Finningley in April of that year. By May of 1938, 177 total aircraft were delivered. Three specially-modified Wellesley’s were used to set a world distance record on November 5th, 1938, traveling from Ismailia, Egypt to Darwin, Australia.

When Britain declared war on Germany in September of 1939, the Wellesley was still in service though it was clear the aircraft was obsolete. The Wellesley maintained some value in raids and general reconnaissance work in the Middle East and sorties over East Africa, which continued into September of 1942. The line was retired in full during 1944.

Wellington Bomber

Vickers Wellington Bomber

The Vickers Wellington was the primary bomber of the Royal Air Force at the start of World War 2. Designed in the mid-1930s at Weybridge, Surrey to meet the requirements of the Air Ministry Specification B9/32 for a medium-class, twin-engined, long range bomber, and first flew in prototype form during 1936. Commonly named Wimpy by its crews (after J. Wellington Wimpy, Popeye’s friend), the Wellington joined Bomber Command in 1938 and saw production numbers exceed 11,400.

Vickers Wellington Bomber Cutaway

The Wellington was powered by a mix of Hercules, Pegasus and Merlin engines throughout its service, mounted on the monoplane wings which straddled the streamlined fuselage. The whole crew complement reached up to six personnel. The Wellington’s internal bomb load capacity was limited to 4,500lb of conventional drop ordnance while defensive armament came with 7.7mm machine guns – two fitted to a forward turret, four at a rear turret, and an additional two machine guns mounted at waist positions.

The Wellington proved a vital and successful additional to the Royal Air Force’s offensive reach early in the war and excelled as a night time bomber, their primary mission being to derail German war capabilities during hard-to-defend, low-light hours. As much as the Wellington progressed throughout its time in the war, it was nonetheless becoming outclassed by the addition of new bombers to the Allied cause along with new Axis fighters used in interception sorties. Outlasting many of its 1930s-designed contemporaries, the Wellington would fly its last offensive mission in October of 1943.

“The Wellington proved such a success that our works were full up with work and Pierson and I had nothing else to go on with. We shouldn’t have been allowed to put it into the shops if we had, so I was just at liberty to think of what I wanted and I thought of what would be an engineer’s way of stopping the war”

Warwick Bomber

Vickers Warwick Bomber

The Vickers Warwick was a multi-purpose bomber of the Royal Air Force during World War 2. Designed in parallel with the smaller Wellington in January 1935 at Weybridge, Surrey, the Warwick aimed to meet the requirements of the Air Ministry Specification B1/35 for a twin-engined heavy bomber. The Warwick used Wallis’ geodesic airframe construction pioneered in the Wellesley and Wellington and was intended to make use of the more powerful engines being developed at the time, allowing the Warwick to be both faster and capable of carrying a heavier munitions payload than the B3/34 specification, which would be met by the Whitley medium bomber in 1937.

Vickers Warwick Bomber Cutaway

By the end of July, the Air Ministry was able to consider eight designs. The Vickers Warwick fitted with Bristol Hercules engines was the aircraft of choice and a prototype ordered, alongside alternative designs by Armstrong Whitworth (AW39) and Handley Page (HP55) who later cancelled both projects; preferring to work on the new specifications for medium and heavy bombers. Vickers chose to continue but construction was slowed by work on the Wellington, the lack of available engines and official expectation that the design would be surpassed by later aircraft.

The Warwick’s design was modified in 1936 for greater fuel and payload capacity and the Rolls-Royce Vulture X-24 aero engines were named as alternative powerplants and adopted in late 1938. In February 1939 it was decided to no longer proceed beyond the prototypes due to the level of work required to integrate the Rolls-Royce Vulture engine but this decision was reversed in the following January.

Vickers completed two prototypes. On 13 August 1939, the first prototype Warwick flew from Brooklands fitted with Rolls-Royce engines. The engine, also required for the Avro Manchester, was deemed unlikely to be available in sufficient numbers for the Warwick, and proved unreliable. The second prototype, flown on 5 April 1940, had originally been designed to use Napier Sabre engines, but development of the Sabre was slow, with all production capacity needed for the Hawker Typhoon fighter, so the prototype was instead fitted with the Bristol Centaurus radial engines. While the Centaurus-powered prototype was more promising, the development of the Centaurus was at an early stage and again engines were in short supply. Subsequently use of the American Pratt & Whitney Double Wasp radial was proposed. The second prototype was converted to use the engines and first flew in this form in July 1941. The Double Wasp installation was inferior to the Centaurus but an initial production order for 250 Warwicks, consisting of 150 Double Wasp-powered aircraft and 100 Centaurus-powered aircraft, was placed on 28 December 1940. Of the original 250 Warwick ordered, 219 went to Coastal Command. Another 14 were converted to transports for BOAC.