Cierva Low Volume Production

(Avro Type 574) Single seat autogyro with four blade rotor to Air Ministry Specification 3/26, Based on the Spanish-built Cierva C.6, the aircraft was basically an Avro 504K fuselage and tailplane (with larger, horn-balanced elevators), with wider than standard undercarriage (still fitted with a central skid) and fitted with a four-bladed articulated rotor mounted on a pylon of steel tubes. Ailerons were mounted well outboard of the fuselage on wire-braced faired steel tube booms. One 130 h.p. Clerget 9Bb powerplant. The C.6C was later modified with stub wings and wide track undercarriage, similar to the C.6D.

Specification
Rotor Dia	Length	Span *	Empty Wt	Max AUW	Minimum Speed	Maximum Speed	Range	Service Ceiling
36 ft 1 in	34 ft 4 in		1490 lb	2275 lb	15 mph/ 13 kn	87 mph/ 76 kn
11 m	10.46 m		676 kg	1032 kg	24 kph	140 kph

Span * = span of stub wing

(Avro Type 575) Two seat civil variant of the C.6C, also to Air Ministry Specification 3/26. After initial flights, new stub wings featuring ailerons were fitted, along with a new wide track undercarriage with vertically oriented oleos mounted on the stub wings just inboard of the ailerons, strut-braced back to the upper longerons and wire braced to the lower, with no cross axle, but still featuring the central skid. One 130 h.p. Clerget 9Bb powerplant.

(Avro Type 576) Single seat lightweight autogyro with cable braced four blade rotor and featuring stub wing ailerons, to Air Ministry Specification 4/26. The new design of fuselage was a slim, plywood covered, square section box structure with curved rear decking. The tailplane featured an elongated 'comma' type rudder with no fin. It featured a wide track oleo undercarriage and outrigger ailerons, attached to the lower longerons, with inverted V-bracing to the upper. A four-bladed articulated rotor was mounted on a pylon of three steel tubes. The fuselage design was later used for the Avro Avian I. One 70 h.p. Armstrong Siddeley Genet I powerplant.

Specification
Rotor Dia	Length	Span *	Empty Wt	Max AUW	Minimum Speed	Maximum Speed	Range	Service Ceiling
30 ft	24 ft 6 in	16 ft	816 lb	1073 lb
9.14 m	7.47 m	4.88 m	370 kg	487 kg

Span * = span of stub wing

Single seat lightweight autogyro with cable braced four blade rotor and strut braced ailerons, to Air Ministry Specification 4/26, designed by Harold Bolas at Parnall and Co. The rotor pylon was a complicated six strut structure in front of the cockpit. The rectangular tailplane was fitted with horn balanced elevators. Unlike the Avro machines, a well rounded fin was fitted. The undercarriage was initially a typical cross axle type, but this was later replaced by one of wider track. One 70 h.p. Armstrong Siddeley Genet I powerplant.

Specification
Rotor Dia	Length	Span *	Empty Wt	Max AUW	Minimum Speed	Maximum Speed	Range	Service Ceiling
30 ft	22 ft 8 in	17 ft		1100 lb
9.14 m	6.91 m	5.18 m		499 kg

Span * = span of stub wing

Two seat autogyro, similar to the C.10. One 120 h.p. A.D.C Airdisco powerplant.

Two seat autogyro with with a fully enclosed cockpit, designed by de Havilland with the exception of the C.19-type 3-bladed rotor assembly supplied by the Cierva Company. The front portion of the fuselage was a welded steel tube structure based on the D.H.80A Puss Moth, while the rear portion was of wood construction. A streamlined triangular pylon over the cabin contained a gravity-feed fuel tank and supported the rotor high enough for the blades to clear the truncated tail. The pilot and passenger sat in tandem inside a small cabin - some sources state the design was originally for two passengers as the Puss Moth, but the narrowness of the cockpit makes this clearly impossible. The aircraft featured stub wings with upturned tips to aid lateral stability, along with a tricycle undercarriage. Originally fitted with no fin and rudder attached directly to the stern post, this proved inadequate and adorsal fin was added, plus end plate fins in the tailplane. One 120 h.p. de Havilland Gipsy III powerplant.

Specification
Rotor Dia	Length	Span *	Empty Wt	Max AUW	Minimum Speed	Maximum Speed	Range	Service Ceiling
34 ft	23 ft 8 in	19 ft 6 in	1280 lb	1800 lb	25 mph/ 22 kn	110 mph/ 96 kn	350 mi	9150 ft
10.36 m	7.21 m	5.94 m	581 kg	816 kg	40 kph	177 kph	563 km	2789 m

Span * = span of stub wing

Single seat autogyro built by Comper Aircraft, the fuselage and engine installation resembling that of the Comper Swift. It featured a fixed-spindle, folding three blade cantilever rotor and an engine drive for rotor spinup, stub wings and, initially, tail surfaces with a single fin and rudder, later modified to incorporate three vertical surfaces. One 80 h.p. Pobjoy R Cataract powerplant.

Five seat enclosed cabin autogyro with three blade direct control cantilever rotor. The basic fuselage structure was a Warren girder layout of square section steel and aluminium tubing, with duralumin and wood stringers and formers to create an oval section. The tail unit consisted of a two piece strut braced tailplane of duralumin tubing and pressings, the port half having inverted aerofoil to counteract the torque affect of the propeller. There was a large dorsal fin, a larger ventral fin and two endplate fins on the tailplane, canted outwards to avoid the rotor. The whole structure was fabric covered. One 550 h.p. Armstrong Siddeley Panther IIA powerplant.

Specification
Rotor Dia	Length	Span *	Empty Wt	Max AUW	Minimum Speed	Maximum Speed	Range	Service Ceiling
50 ft	38 ft		3221 lb	4150 lb	21 mph/ 18 kn	162 mph/ 141 kn	280 mi
15.24 m	11.58 m		1461 kg	1882 kg	34 kph	261 kph	451 km

Span * = span of stub wing

(Possibly also designated C.31) Although a design of Cierva-Lepère in France, this machine was built by Westland Aircraft Ltd in England, so is included here for completeness.
Two seat, side by side direct control cabin autogyro, with a fabric covered fuselage of welded steel tube. The tailplane featured no elevators, but had endplate fins in additional to the fuelage mounted dorsal and ventral fins. One 90 h.p. Pobjoy Niagara III powerplant.

Two seat experimental helicopter to Air Ministry Specification E.16/43 to investigate a powered tilting hub-controlled rotor with automatic collective pitch control, and torque reaction control using jet efflux, the first example of the NOTAR (NO Tail Rotor) concept. The machine initially featured a highly streamlined fuselage, totally enveloping the structure, but following damage sulfered in a ground-running accident, a maior rebuild was then necessary. Early in the flight programme, the front fuselage structure was cut back and a much smaller but longer rear fuselage added. At this time, however, there was still a fairly enveloping front fuselage back to the beginning of the tail boom. Further modification of the front fuselage led to most of the fuselage structure and rotor pylon covering being discarded. Some sources refer to these varied configurations as the W.9A and W.9B, but there appears to be no official confirmation of these designations.
In its original format the rear fuselage ended in an upward curve, at the top of which was a jet efflux duct, canted to port. In the later configurations the duct was set at right-angles to the line of the fuselage, but still at the extreme end of the tail boom. Initially there was no fin, but, probably by first flight, a tall, slender fin was added. Engine cooling air from a fan driven by the engine was ducted along the inside of the tail boom, joined and heated by the engine exhaust gases and ejected through the tail ‘pipe’. Two horizontal shutters at the fan intake controlled the efflux of air to control the reactive thrust. The initial fixed pitch fan and shutters were inadequate and were replaced by a multi-bladed variable pitch fan coupled to the rudder pedals to vary the jet velocity.
The main rotor system of the W.9 stemmed from theoretical and experimental work undertaken earlier in the war by Weirs. It was styled the Aerodynamically Stabilised Rotor and the whole rotor was carried on one rotating universal joint or gimbal. A swash-plate connected to the pilot's contol was linked to the blades to effect change of pitch in the cyclic sense. One 205 h.p. Gipsy Six Series II powerplant, taken from the Weir W.6 helicopter.

Specification
Rotor Dia	Length	Height	Disc Area	Empty Wt	Max AUW	Maximum Speed*	Range	Service Ceiling
36 ft	36 ft 9 in	10 ft	1017 sq ft		2647 lb	116 mph/ 101 kn
10.97 m	11.2 m	3.05 m	94.48 m2		1201 kg	187 kph

* Estimated