AVRO 504N

(Monochrome Photograph showing - Avro 504Ns of No. 601 (County of London) Squadron of the Royal Auxiliary Air Force, which were used for training volunteer pilots in 1929.)

By 1919 rotary engines had reached the limit of their development thus production ceased and they were superseded by radial engines which had greater potential.

In 1920 Armstrong Siddeley (A.S.) designed a 7 cylinder air-cooled radial that initially produced 150 hp (110 kW)and was later increased to 180 hp (134 kW) with the Mk.IV in 1928.

By the mid-1920s the 504K was obsolete as it was the sole remaining rotary powered machine in service with the RAF.

In order to maintain production of the 504 Avro anticipated the need to replace its rotary with a new radial engine. Thus they developed the 504N, which was distinguished by the A.S. Lynx, improved undercarriage and two 162 gallon(74 Litre) external wing mounted fuel tanks.

Following extensive trials, in March 1927, the RAF placed it's first order for 100 machines. Ten further orders totalling 572 aircraft followed before production ended in 1932. The 504N was also widely sold abroad.

AVRO 504R 'Gosport'

(Monochrome Photograph - An Argentinian built Avro 504R Gosport, No. 31, distinguished by it's pale-blue/white/pale-blue roundel national markings. The Mongoose engines were fitted with a Townend ring cowl which was peculiar to Argentine construction.)

The last variant of the Avro 504 was the 504R 'Gosport', basically a 100 hp. Gnome Mono-soupape rotary fitted to a lightweight airframe.

The first two machines G-EBNE and G-EBNF were produced in early 1926, the second of which was presented to the Lancashire Aero Club then based at Woodford.

Ten of these early Gosports were also supplied to the Argentinian Air Force. However, by this time the rotary engine was obsolete and trials with three more modern radials was undertaken by Avro who eventually standardised production on the 150 hp. (110 KW.) 5cylinder air cooled Armstrong Siddeley Mongoose.

It is understood that the Estonian Air Force purchased 12 Mongoose 504Rs and Peru 6.

The Argentinians appear to have been very pleased with their rotary powered Gosports as they consequently negotiated a licence to assemble a further 100 Mongoose powered machines.