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M.L. Aviation Utility / ML.1

ml-utility-proto
ML Utility Prototype


In 1955 ML Aviation at White Waltham designed and produced a portable flying machine called the ML Utility ML.1. Given the serial number XK776, the aircraft featured an inflatable rubberised fabric wing and quick release fittings enabling the aircraft to be rigged and de-rigged fairly quickly.

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Over the period of a year, the prototype fuselage was redesigned from the box like structure, to a slimmer, longer structure with tandem seating fir a pilot in the front, and passenger. The tricycle undercarriage, with swivelling nosewheel, changed from wheels on a horizontal axle to rear wheels mounted on legs.

The 65 hp McCulloch pylon mounted pusher of the prototype was changed in the Mk.1 to a Walter Mikron in a cowling faired into the rear of the fuselage. Fuel was a mix of methanol, benzole, and petrol. Cruising speed increased from 45 mph to 58 mph.

The inflatable rubberised-fabric wing, of delta planform, was cleaned up. The basic structural method was retained with the upper and lower surfaces being connected by a number of porous fabric diaphtrams running spanwise and maintaining a symmetrical aerofoil profile developed from NACA 0024. After initial inflation on the ground, the wing is maintained at its correct internal pressure, under 1 lb/sq.in, by an electric pump and relief valve. The prototype had a windmill operated pump.

Control was by inflated elevons over almost the full span of the trailing edge, operated by cable from an inverted control column mounted on the fuselage superstructure. Vertical stabilising surfaces fitted near the wingtips replaced the central fin of the prototype.

The whole wing can be deflated and packed in a bag. The wing is attachedto the superstructure by a series of toggles, and flying wires lead from patches on the wing undersurface to points on the fuselage and undercarriage members.

Despite evaluation by the British Army Air Corps at Middle Wallop further production was not taken up. The flight characteristics were unusually slow and the machine was then stored until saved by the Army Air Corps museum.

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This was an experimental 2-seat observation aircraft built in 1957 for the Army. Fuselage consisted of a canvas bathtub type fuselage reminiscent of some later microlight aircraft.
XK776 was the first of three inflatable wing aircraft flight tested between 1954 & 1960. It went to Cardington on 27/11/69, and is now preserved at the Museum of Army Flying at Middle Wallop.

Utility Mk.1 Prototype
Engine: 65 hp McCulloch

Utility Mk.1
Engine: Walter Mikron III
Span: 35 ft 0 in
Overall length: 23 ft 3 in
Overall height: 10 ft 6 in
Wing area: 400 sq.ft
Dry weight: 450 lb
Fuel: 85 lb
Pilot weighht; 180 lb
Passenger weight: 180 lb
Baggage weight: 40 lb
Total weight: 935 lb
Max speed: 68 mph
Cruise: 58 mph
Stall: 30 mph
Rate of climb: 740 fpm
Takeoff distance: 210 ft
Endurance: 2 hr 30 min
Ceiling: 5000 ft
Root chord: 17 ft 6 in
Tip chord: 5 ft 9 in
Wheelbase: 7 ft 1 in
Track: 5 ft 4 in

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