ATL aviation design engineering consultants

+44 (0)1202 581900

Aviation Traders Limited, now trading as ATL, has been a name synonymous with pioneering and innovative aircraft modification design since 1947.

Aerostructures design

A large proportion of aircraft structures comprises thin webs stiffened by slender longerons or stringers. Both are susceptible to failure by buckling at a buckling stress or critical stress, which is frequently below the limit of proportionality and seldom appreciably above the yield stress of the material. Clearly, for this type of structures design, buckling is the most critical mode of failure so that the prediction of buckling loads of columns, thin plates and stiffened panels is extremely important in aircraft design. Part 21 design considers the buckling failure of all these structural elements and also the flexural-torsional failure of thin-walled open tubes of low torsional rigidity.

Two types of structural instability arise: primary and secondary. The former involves the complete element, there being no change in cross-sectional area while the wavelength of the buckle is of the same order as the length of the element. Generally, solid and thick-walled columns experience this type of failure. In the latter mode, changes in cross-sectional area occur and the wavelength of the buckle is of the order of the cross-sectional dimensions of the element. Thin-walled columns and stiffened plates may fail in this manner.

The aircraft design skills abundant in the UK as its origins in the early days of Airbus when Airbus design and production was under pressure from Boeing across the Atlantic.

On 29 November 1978, BAe's full partnership agreement received the official signature and the British company took a 20 percent stake in Airbus Industrie with effect from 1 January 1979.

It was now imperative that detailed work on the A310 proceeded without delay, if Airbus was not to fall behind Boeing - which had reached an advanced stage in the development of the 757 and 767 models, with the latter especially considered a close competitor. Work on a new wing had been in progress at VFW-Fokker in Germany and at BAe Hatfield. But following the re-admission of Britain, and against strong objections from Aerospatiale, responsibility for the overall design and manufacture was given to British Aerospace, with VFW-Fokker responsible for the moving surfaces. After testing several configurations in the wind tunnel, the designers decided to maintain the 28° sweepback and virtually the same span as the A300. It was found, however, that through the use of a new aerofoil section with a double curvature in the lower skin of the inner section, the wing area could be reduced by 16 percent. The increased strength also helped to produce weight savings of more than 5 tonnes.

Leading edge slats of greater chord and radius were introduced to improve take-off performance, while cruise drag was reduced by combining the two outer flaps into one, with the inner flaps changed from the original tabbed-Fowler flaps on the A300 to a vaned Fowler flap. It was also found that the outboard ailerons could be removed, producing a much cleaner wing. The pylons were designed to support all advanced technology, high bypass turbofan engines with a thrust of around 213kN (48,0001b), then available for the A310. These included the General Electric CF6-80A1 and Pratt & Whitney JT9D-7R4D1, although Airbus was prepared to fit the Rolls-Royce RB211-524D4, if requested. However, as no orders had been received by the time the first flight approached, the certification programme was carried out only with the US engines, and these remained the only ones to power the A310.

The fuselage was reshaped at the rear and cut shorter by the removal of 13 frames from that of the A300, while the fin required few modifications, except for a reduced size horizontal stabiliser. But the most striking innovation in the A310 was the application of the latest advances in avionics technology, so that the aircraft could be operated by two pilots, rather than the two pilots and flight engineer prevalent in other aircraft on both sides of the Atlantic.

ATL has grown from this kind of background to provide avionics and electrical design, structural and mechanical design including stress analysis, systems design including hydro-mechanical systems, and also design and build packages with EASA release. A list of supplemental type certificates is available on the STCs page of their website at http://www.atl.aero/index.php?option=com_content&task=view&id=34&Itemid=45

ATL

7 Brackley Close, Bournemouth Airport, Christchurch, Dorset, BH23 6SE, United Kingdom

Phone: + 44 (0)1202 581900

Fax: + 44 (0)1202 582944

Email: info@atl.aero

Internet: www.atl.aero