Avro 504B

The Avro 504B was the first version of the Avro 504 family to be designed specifically for the Admiralty, and introduced a number of changes that were later introduced on all members of the family.

The original Avro 504 had been ordered by the War Office, but the Admiralty had taken over six aircraft to use on a raid on the Zeppelin sheds at Friedrichshafen on 21 November 1914. The Admiralty was impressed enough by the aircraft to order some for itself.

Avro 504B in the air

The Admiralty wanted a version with wing spars of a greater cross section. Avro made a number of other changes on the resulting Avro 504B. It had the same long span ailerons as the 504, rather than the shorter span version on the 504A. It had a large unbalanced rudder attached by hinges to a large dorsal fin. The top longerons of the fuselage were recessed to allow curved cut-outs to be placed on the sides of the rear cockpit. It was given a strong ash tail skid, sprung with rubber cord and hinged on a pylon. This tail skid was used on all later Avro 504 variants.

Eight batches of the 504B were ordered, with production split between A.V.Roe, Parnall and Sunbeam. If all had been built there would have been 230 completed, but one Sunbeam order for 30 had some completed as the Avro 504J.

Most of the 504Bs were used as naval trainers, and late production aircraft in this role used a 80hp Gnome engine in place of the Le Rhone engine of early aircraft, removed the cut outs on the rear cockpit and could carry a Scarff ring.

A small number of Avro 504Bs saw front line service, from the RNAS station at Dunkirk. At least two (9890 and N5267) were given fixed forward firing guns using interrupter gear.

On 17 May 1915 two Avro 504Bs actually managed to intercept two separate Zeppelins. The first incident came early in the day when Flt Sub-Lt Mulock found L.Z.38, but the Zeppelin was able to climb too quickly for him to use the two hand grenades and two incendiary bombs he was carrying. Later Flt Cdr A.W. Bigsworth in Avro 504B 1009 found L.Z.39 and chased it towards Ostend. He was actually able to get above it and dropped four 20lb bombs on the Zeppelin’s stern. This caused some fire damage and forced it into a heavy landing at Evere. L.Z.39 was repaired, but eventually suffered more serious damage on 17 December 1915 and was scrapped.

At least one 504B was used in early experiments with deck landing arrester gear.

Attempts to use the type in the coastal reconnaissance role showed it had insufficient range and instead a single seat version, the Avro 504C, was developed, with extra fuel replacing the front cockpit.

Engine: Gnome or Le Rhone
Power: 80hp
Crew: 2
Span: 36ft 0in
Length: 29ft 5in
Height: 10ft 5in

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