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Aviation History
1955
1955 - 1846.PDF
30 December 1955 969 THE EDGAR PERCIVAL P.9 Famous Name Returns to the Scene With a New Agricultural All-rounder The P.9 and its designer, Mr. Edgar Percival, pictured at Stapleford Tawney Aerodrome, where the machine was completed. "Flight" photographs THE story of the development of the P.9, Edgar Percival'snew agricultural aircraft (the completion of which was re-ported in Flight a fortnight ago) began in 1951, when this designer began considering the type of aircraft which might be most suitable for aerial topdressing operations in New Zealand. Mr. Percival, whose successful pre-war designs include the still- familiar and still-successful Mew Gull (this year's King's Cup winner), reached no firm conclusions until 1953, when he decided on a basic configuration and determined to study the New Zealand operating conditions at first-hand. Before leaving for New Zealand and Australia in November 1953, Mr. Percival made the initial design calculations, weight and balance calculations, a three-view g.a., and a check of die e.g. positions to make sure he could achieve what he had set out to do with the particular aircraft configuration selected. He next spent two months in New Zealand, visiting owners, operators, ground crews and repair organizations; discussing their aircraft require- ments; flying on a number of agricultural operations; and obtaining much relevant and valuable information. This was followed by a two-month visit to Australia for the same purpose, and sub- sequent visits to Fiji, Indonesia, the Malay States and India to examine the work being done in those countries. The work being performed in New Zealand convinced the designer that there was even wider scope for aircraft in agriculture than topdressing alone—provided a sufficiently versatile machine were available, and particularly if it were economical in use. The P.9 design as originally set out before Mr. Percival's journey abroad is what has now been built, with very few alterations, valuable confirmation of his design views having been obtained from the operating countries. Shortly after returning to England in April 1954, Mr. Percival gathered a small D.O. staff together, and detail work was started at the end of May. Edgar Percival Aircraft, Ltd., was formed in November 1954, to produce in quantity the P.9 agricultural aircraft. Initially the company's design office and factory were located in London; the move to Stapleford Tawney Aerodrome, near Abridge, Essex, was made in May of this year, when the fuselage tubular structure was almost complete. Since then progress has been steady, in spite of a number of setbacks caused by delivery delays. The completed aircraft was rolled out of its hangar on December 9th for engine running, and the first flight was to have taken place on December 20th. Design Philosophy.—Although the P.9 has been designed primarily as an aerial fertilizing and crop-spraying aircraft, Edgar Percival aimed to cover not only the widest field of use for agriculture but also to make the machine a practical general- purpose vehicle for operations in undeveloped parts of the world. He set out to produce as useful a piece of equipment for bush and outback flying as possible. This versatility, however, had to be achieved without losing the good features of the basic design by any compromise. For New Zealand, the main types of operations were: (1) aerial fertilizing; (2) anti-pest spraying; (3) supply-dropping to deer shooters (who are permanently employed in the mountain districts to destroy the large herds of wild deer); (4) the dropping of fence- posts and fencing material in the mountain country; and (5) transport of wool bales from remote mountain areas. In addition to meeting the important requirements of carrying as good a useful load as possible on a given size of engine and haying a good performance from small landing strips, the cardinal points of agricultural-aircraft design must include the safety of the pilot. The topdressing work as performed in New Zealand can be considered more hazardous than other forms of regular flying, and there has been much argument in the past concerning the best position for the pilot. In many aircraft at present used for fertilizing, the pilot is located between and on a level with the engine and the load. As a result, he is the "ham in the sandwich" in the event of a crash following engine failure during take-off or climb-away, especially in mountainous country. In the P.9 the pilot sits on a level which is above both the load and the engine. From the combination of the aircraft configuration and the pilot's position, a voluminous cargo space, or cabin space, results. The total cubic capacity of the cargo space and the pilot's com- partment is 235 cu ft, total floor area being 50 sq ft. This cargo space, coupled with the low loading platform of the cabin floor, Mr. Percival points out, makes the P.9 a true "flying jeep." It can be used for transporting sheep or other small animals, standard bales of wool and other goods. The cabin can be loaded through the large side or through the clamshell doors at the rear; standard 45-gal drums of petrol or oil can easily be rolled in and carried. As an ambulance aircraft the machine can accommodate two stretchers, one sitting-up patient and an attendant in addition to the pilot, while as a passenger aircraft the P.9 is a six-seater with luggage. An important factor when moving from one site to another on topdressing operations is that, in the P.9, a ground crew of three persons can be carried in addition to the pilot and the hopper. The relative importance of durability and repairability is a basic The capacious freight cabin and the overall configuration of the aircraft are apparent in this side view of the prototype P.9.
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