Avro 604, 608, 622, 627 and 654

Two seat high performance day bomber to meet Specification 12/26. A single-bay biplane, of unequal span and chord, the staggered wings were of all-metal construction, with spars and ribs of duralumin, but with fabric covering. All wing fittings were of stainless steel. The wings were.slightly swept and featured Frise-type ailerons on the upper wing only. The fuselage was a rigid structure built of duralumin sheeting riveted to a framework of L-section dural stringers. The engine mounting and variable incidence tailplane were of welded steel tubing. Initially an unbalanced rudder was hinged from a triangular fin, but this was later replaced by an aerodynamically balanced rudder on a truncated fin. All tail surfaces were of welded steel tube construction, covered with fabric. The pilots cockpit was located under the wing trailing edge, with the wing roots of the upper mainplanes tapering to give maximum view, and was provided with a fixed forward firing Vickers machine gun. The gunner was located in a seperate cockpit behind the pilot with a Lewis gun mounted on an Avro gun ring. Bomb racks were located under the lower wing, aimed by the gunner from a prone position in the fuselage bottom. The undercarriage was of the oleo and rubber compression type, with long travel, braced with radius rods to the fuselage longerons. One 480 h.p. Rolls-Royce F.XIB powerplant cooled by means of a honeycomb radiator mounted under the nose of the fuselage and housed in a tunnel. There were two fuel tanks, a main and a gravity tank, both mounted in the fuselage behind the fireproof bulkhead.

Type 604 Antelope Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
36 ft	31 ft 2 in	10 ft 9 in	377 sq ft	2859 lb	4538 lb	145 mph/ 126 kn	173 mph/ 150 kn	580 mi	22000 ft
10.97 m	9.5 m	3.28 m	35.02 m2	1297 kg	2058 kg	233 km/h	278 km/h	933 km	6706 m

Two seat fighter variant of Type 604, retaining the mainplanes, interplane and centre section struts, tail unit and undercarriage of the Type 604, but the fuselage was fabric covered over formers to produce a rounded shape. Two synchronised, forward firing Vickers machine guns plus one Lewis machine gun in an Avro low drag, rotateable mounting. One 425 h.p. Bristol Jupiter powerplant.

Two seat fighter bomber. Type 608 redesigned to take the 540 h.p. Armstrong Siddeley Panther II powerplant.

Single seat mailplane development of the Type 622. Designed for air-mail operations in Canada, designer Roy Chadwick worked in cooperation with the Canadian Government officials and Canadian Airways, Ltd. The fuselage was of welded steel tubing, divided into three sections, consisting of the engine mounting, the middle section including the mail compartment and the pilot's cockpit, and the rear section continuing from behind the pilot to the stern post. As far aft as the pilot's cockpit the fuselage was tubular strut braced, while the rear section was wire braced. The engine mounting was a triangulated welded-up steel tube structure, terminating forward in a ring to which the engine was mounted, and with four attachment points on the aft end for bolting to machined steel fittings. The fuselage forward section included an electric inertia starter and an engine-driven electric generator, and fuselage panels were of aluminium, shaped to follow the Townend ring-type engine cowling.
Directly behind the engine mounting was the section carrying the two fuel tanks, having a large rectangular one in the middle slung on steel straps, with a shaped gravity tank above it. Aft of this was the mail compartment, completely lined with duralumin-asbestos-duralumin, and providing 40 cubic ft. of clear space inside it. A folding lid of the same material opened towards the starboard side, providing a large access for loading. Directly behind the mail compartment was the pilot's cockpit, and, being situated so far aft, gave the pilot an excellent view in all directions. Cockpit heating was provided direct from the exhaust, with openings under either heel board. Special instruments included a button on the dashboard controlling the Eclipse electric inertia starter, and arrangements for releasing parachute flares for emergency landing. A receiver for the Western Electric radio beacon was situated on the floor behind the pilot's seat. The side fairings of the mid fuelage were built up of spruce and three-ply, in complete frames, which were easily detachable, readily exposing all control rods and wires, which were led outside the primary fuselage frame.
Like the Type 622, it was a single-bay biplane, of unequal span and chord, the fabric covered, staggered wings being of all-metal construction but, unlike the Antelope, the spars were constructed of high tensile corrugated strip steel and the ribs of duralumin pressings. The drag bracing was efiected with built-up girder-type compression struts and cross bracing wires. All the tail surfaces were of welded steel tubular construction, with both the rudder and elevators balanced aerodynamically, the elevators also being balanced statically, like the ailerons. The rudder and fin were unbraced, but the tail plane, which was provided with incidence adjustment, had two streamline tubular steel struts on each side. The front spar fittings also provided additional ground adjustment. The lower main planes had hinged landing lights fitted to them, operated from the pilot's cockpit. The undercarriage was similar to the Type 604 except for a balloon-type castoring tail wheel, and all were covered with streamline fairings. Attachment points were provided for a twin-float or ski undercarriage. One 525 h.p. Armstrong Siddeley Panther IIA powerplant.

Type 627 Mailplane
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
36 ft	30 ft 10 in	10 ft 10 in	381 sq ft	3077 lb	5150 lb	147 mph/ 128 kn	170 mph/ 148 kn	560 mi	19000 ft
10.97 m	9.4 m	3.3 m	35.4 m2	1396 kg	2336 kg	237 km/h	274 km/h	901 km	5791 m

Type 627 converted as a high performance testbed for the 700 h.p. Armstrong Siddeley Tiger IV powerplant. A flight observers cockpit later replaced the mail compartment.