Title: Flying duck for developing countries
Author: David Woolley
Flying duck for developing countries
David Woolley describes the Land Development Aircraft, a back-to-front prototype designed by David Lockspeiser which could revolutionise communications in the third world
The first flight of a privately developed aircraft is a sufficiently rare event these days to attract attention. When the aircraft concerned is as unusual in shape as the Land Development Aircraft, it is worthy of closer examination. Configuration of an airframe is a clue to the use for which the aeroplane is intended; why then the use in this case of a canard or tail-first design?
The Land Development Aircraft has been thought up by David Lockspeiser, a pilot with British Aircraft Corporation. In its prototype form, a 70 per cent scale model of the intended production version, which is designated LDA-01, it first flew from the BAC airfield at Wisley, Surrey, last August. Bush flying in the remoter areas of the world is the particular use for which the LDA has been designed. Aviation is becoming increasingly important for communications in the developing countries, but its demands are rather different from those of aviation in Europe or North America. Rugged simplicity must be the design philosophy for an aeroplane which will be operated away from airfields, repair shops and spare-parts stores.
Coupled with a stout heart one looks for a forgiving temperament in such an aircraft. Handling qualities should be such that a pilot of average skill can fly it with minimum fatigue and maximum regularity in exacting conditions.
All of which brings us back to the unusual shape. The canard is an old idea, but one which has never really caught on except with certain high-performance military aircraft. It has been adopted for two main reasons. First, it makes for an inherently stable aircraft in which the permissible fore-and-aft range for the centre of gravity is about three times as great as that of a conventional aircraft, according to Lockspeiser. This range has an important effect on stability, and in many designs a restricted range causes complications with payload distribution and may limit the commercial usefulness of the design. In outback operations easy and flexible loading is obviously an advantage.
The second reason is simplicity. The fuselage of the LDA is of simple box construction, while the two mainplanes and the forward plane are in fact three identical and interchangeable wing surfaces. Not only is there only one type of wing surface in the spare-parts inventory, therefore; provision has also been made for a spare unit to be transported on the aircraft itself. There are few aeroplanes so designed to be able to carry all their own spare parts with them to remote airstrips.
Cargo carrying is perhaps the LDA's chief role, and to this end it is equipped with a removable container which attaches to the belly of the fuselage. Payload of the full-size developed aircraft is to be one ton. Advantages claimed for the detachable container include a quicker turn-round time, faster conversion of the aircraft to other roles, carriage of a wider variety of loads, and the instant jettisoning of the load in an emergency (a feature usually only associated with crop-spraying aircraft).
Carriage of passengers is also envisaged, together with relief work in distressed and disaster areas - the latter a concept involving the transport of supplies into the area and the evacuation of stretcher cases from it. The LDA has also been designed for agricultural spraying and dusting operations, and if it lives up to its promise of good handling qualities in the air and on the ground, coupled with strength and reliability, should prove ideal for the job. Agricultural work demands constant low-level flying; this is helped by a cockpit designed for maximum forward, sideways and downward vision. Aerial survey reconnaissance and supply dropping are also envisaged. Moreover the full-sized LDA should be able to carry a small four-seater car or boat, thus enabling the pilot to take with him a complete transport system.
The LDA-01 prototype is fitted with an 85 bhp piston engine for test purposes. The full-scale LDA would probably be powered by a Lycoming engine developing 340 bhp. In this configuration it is estimated that it would take off in a distance of 470ft, and clear a 50ft-high obstacle within 870ft. The landing run would be 360ft. Cruising speed would be 132 knots, and range 350 nautical miles. It would cost about £10 000 at 1971 prices.
An unusual feature is the use of a four-wheel undercarriage. The front wheels are steerable, and designed to allow the aircraft to be taxied quickly and accurately astride its waiting payload container. With a wide track - 12ft - the arrangement should make for good stability on the ground, and low-pressure tyres should be valuable in coping with rough airstrips. The fuselage is built of 3/4in square 22-gauge tubes of T.35 steel, welded on a flat jig, and covered with fabric. The cargo container is made of steel and light alloy, but could be constructed in glass-fibre or other materials. The wing surfaces are of conventional light-alloy construction.
The LDA clearly represents an original approach to the needs of bush flying. Lockspeiser's next hurdle, given a clear run for the test programme, is to finance production. But with this simple design it is envisaged that local production under licence in various areas of the world will be possible - which should make the project attractive to the less-developed countries.
A possible future project is to adapt the existing basic configuration to a 12-14 seater with two engines mounted on stub wings either side of the fuselage. The evolution of the LDA will be watched with interest.
The canard or tail-first layout of the LDA makes for good handling qualities, simple construction and excellent view from the cockpit. The unusual four- wheeled undercarriage is designed for stability and manoeuvrability on rough airstrips and enables the aircraft to straddle its containerised load. The LDA-O1 seen in these pictures is a 70 per cent scale model built for test purposes. It first flew in August
The 85 bhp engine of the prototype, above, will give way to a 340 bhp engine in the full-scale developed version. View downwards from the cockpit, top right, is excellent. A detachable cargo container, above right, speeds reloading, and for easy maintenance many of the components, right, are interchangeable. A comfortable cockpit opposite, should help to make the LDA a pilot's aircraft