Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Novel suspension for light aircraft
Keywords Hyperlast, Landing gear, Polyurethanes
Dynathane® elastomer from Hyperlast Limited is being used for novel suspension units in the landing gear of the Magnum aircraft, designed by Aviation Enterprises Limited of Membury Airfield in Berkshire.
We understand that Dynathane is a microcellular polyurethane that has been developed by Hyperlast specifically for noise, shock and vibration control. The chief designer of this advanced, two-person, light aircraft has been inspired by the use of similar, high-performance materials for suspension components on vehicles ranging from Formula One racing cars to state-of-the-art mountain bikes.
Aviation Enterprises has been working for seven years on the design and manufacture of the Magnum, which has some interesting and advanced features:
a low empty weight of around 350kg;
cruise speed of 160 knots with a 100hp engine; and
a range of 1,000 nautical miles.
This performance is achieved by advanced aerodynamics, including a retractable undercarriage to reduce drag. Angus Fleming, managing director and chief designer, explains that the Magnum will be approved by the Civil Aviation Authority (CAA) as a light aircraft and is a serious potential workhorse for high-speed, long distance commuting.
For this application, Hyperlast worked with Aviation Enterprises to customise the formulation of Dynathane and component shape to achieve the right physical and chemical properties. The shock absorbers comprise elastomer discs, each measuring 22in. in diameter and 2in. long. A stack of ten of these mouldings, with a thin metal plate between each, is used to provide what is described as a very simple, low cost, low weight, low maintenance and effective main undercarriage shock absorber.
Finally, the set of elastomer mouldings is compressed to carry the static load of the aircraft (25KN) with a minimum of deflection. In this case, deflection of just 4in. is achieved.
A feature of the undercarriage is that the designer has to cope with critical landing loads to meet the CAA requirements. Fleming says:
We are probably the only manufacturer using this type of elastomer as the complete shock absorber ... We have to prove the damping characteristics of the shock-absorption system. We did this with help from Ding Lou and his colleagues at Hyperlast Limited who assisted with the traditional drop-test. The results were excellent and met all our expectations.
He believes this is the first ever glass/carbon fibre epoxy composite retracting undercarriage in manufacture. The company has seven employees and has invested well over £1 million in this development with the assistance of grants from the Department of Trade and Industry (DTI).
Aviation Enterprises is looking forward to flight testing, which will lead to certification and then commercialisation of the Magnum. Working with Dynathane has opened up new opportunities for the company and it has acquired new expertise in the use of polyurethane microcellular elastomers for shock absorbency systems of light aircraft. This is one area in which it is offering a consultancy service, in the words of Fleming:
to gain from the steep learning curve we have been through in understanding the advantages and failings of the material.
Details available from: Hyperlast Limited. Tel: +44 (0)1663 746518; Fax: +44 (0)1663 746605; e-mail: firstname.lastname@example.org