A.Jackson Avro Aircraft since 1908 (Putnam)
By 1918 successful development of the in-line engine was already ending the long career of the rotary. The in-line was not only less complex and more easily maintained, but less extravagant in fuel and oil. It was not therefore surprising that A. V. Roe’s ingenious civil adaptations of the 504K embraced an economical engine of this type, particularly as tens of surplus thousands were to be had at give-away prices.
Experiments began at Hamble in October 1919 with the Avro 545 G-EAPR, an experimental 504K with 90 h.p. Curtiss OX-5. This American eight cylinder Vee watercooled engine needed spiral tube radiators on each side of the front cockpit in the manner of the Avro Type E prototype of an earlier era. Such an installation, with its heavy and potentially troublesome plumbing, would not have appealed to private owners and final choice fell on the aircooled 80 h.p. Renault, a similar engine which drove a four bladed wooden airscrew.
Designated Avro 548, first flown at Hamble by H. A. Hamersley late in 1919, flown to Farnborough for checks on January 13, 1920 and certificated in the following March, the first Renault Avro G-EAPQ was a 504K with the dual control removed to carry two passengers in tandem behind the pilot. Fuel, entirely gravity fed, was carried in a large centre section tank and a false decking covered the large rear cockpit so that each occupant had his own windscreen. This machine was the only Avro 548 to have external elevator control wires running from cranks above the lower wing root. Silver overall with polished cowlings, it graced the Avro stand at the Olympia Aero Show, London, in July 1920 without markings as the ‘Avro Tourist’. The third Avro 548, G-EALF, was available for demonstration flights at Hendon during the Show and on July 28 F Lt. Leslie flew Prince Alfonso d’Orleans to Farnborough in it.
The trade slump killed any potential market, and a projected trainer version (Avro 553) was shelved, but the prototype was repainted in wartime drab for Capt. E. D. C. Herne who used it for a photographic survey of the whole of England, the entire coastline of Belgium and France as well as all the major Belgian inland towns. When King George V visited Belfast, ’PQ was flown 700 miles from Croydon to Belfast and back in one day, yet total repairs after 30,000 miles in 18 months amounted to only ?2 for a set of control cables, and 3d. for a valve spring. W. G. Pudney afterwards acquired it and ran a joyriding business at Croydon throughout 1922.
Three other Avros 548s built at Hamble were without the false decking and had a large, double rear cockpit. One was sold in Uruguay and another, G-EAFH (formerly K-147, 504K test bed for the 170 h.p. A.B.C. Wasp I), spent 1921 at Swansea with the Welsh Aviation Company and won all three races at the Croydon Meeting of September 17, 1921 piloted by F. G. M. Sparks. When the firm went into liquidation, pioneer private owner Dr. E. D. Whitehead Reid of Bekesbourne, Canterbury, bought it for a mere ?12 10s., converted it to two seater and flew it in and out of fields on his professional rounds until 1927. G-EAFH then returned to joyriding, first at Squires Gate and in 1931 at Southport sands with the Giro Aviation Co. Ltd., finally crashing there on May 31, 1935 during a low altitude aerobatic display. A. V. Roe and Co. Ltd. built only three other 548s, dual trainers G-EBIT - ‘IV for the North Sea Aerial and General Transport Co. Ltd. Reserve School at Brough in 1924.
The majority of Avro 548s were conversions made by outside firms such as the Aircraft Disposal Co. Ltd. which produced ten at Croydon. Only the first of these, G-EAYD, resembled Avro’s prototype with three separate cockpits. The remainder included five for Reserve Training at Stag Lane by the dc Havilland School of Flying Ltd., one of which was the former Avro Transport Company 504K G-EAAL. Named “Vida”, the latter eventually passed into private ownership at Stag Lane. G-EBPJ, privately owned in 1926 by Nigel Norman, served the Norfolk and Norwich Aero Club at Mousehold 1927-28; and ’PO went to Newcastle Aero Club at Cramlington in the same year.
Surrey Flying Services Ltd. built three; G-EBAJ for airborne radio telephony experiments by Marconi’s Wireless Telegraph Co. Ltd. at Croydon; G-EBBP for private owner Sir Derwent Hall Caine (which later in 1922 reverted to the company for instructional use); and dual trainer G-AABW in 1928. The only difference between these and the genuine Avro-built 548 was the bulged under-cowling. When Marconi ceased experiments in 1926, G-EBAJ joined the rapidly expanding fleet of the Henderson School of Flying Ltd. at Brooklands. A. B. H. Youell flew it at the next year’s Bournemouth Easter Meeting, winning the Business Houses Handicap on April 16, 1927 at an average speed of 74 m.p.h. On October 1 that year it took a prominent part in welcoming home the victorious Schneider Trophy team by flying round Croydon with suitably inscribed yellow banners attached to a crude metal framework. The Henderson School and its successor, the Brooklands School of Flying Ltd., owned nine 548s, six of which they built from spares. Although primarily intended for instructional work, the 548s always went joyriding at coast resorts such as Skegness and Canvey Island in the summer. Two, G-EBRD and ’SC, shipped to South Africa for a pleasure flying season in 1927-28, took part in Cape Town’s first air display on December 11, 1927.
The most important Henderson 548 was G-EAJB, one of Avro’s original 1919 civil 504Ks which had been used at Filton for some years by the Bristol Aeroplane Co. Ltd. as a Lucifer engine test bed. Standard 504K shock absorbers now replaced the special oleo units used at Bristol but 'JB retained the 504N-type ailerons with curved trailing edge. The only other Avro 548 so fitted was Henderson’s second machine G-EBRD, built for South Africa.
In 1925 Maj. F. B. Halford of the Aircraft Disposal Co. Ltd. modernised the 80 h.p. Renault by fitting redesigned cylinder heads and valve gear which raised the power output to 120 h.p. This engine, the Airdisco, was fitted into one of the company’s surplus 504K airframes to create the first Avro 548A. Registered G-EBKN, it had greatly improved all-round performance and became the lively mount of Shoreham private owner A. G. Head. Not to be outdone in publicity by A. V. Roe and Co. Ltd., donors of an Avro 504R to the Lancashire Aero Club in July 1926, the Aircraft Disposal Co. Ltd. simultaneously presented the club with one of their 548 conversions G-EBOK. Soon afterwards, on October 2, T. Neville Stack flew ’OK to victory in the Yorkshire Open Handicap Race at Sherburn, beating the Brough 548As G-EBIT and ’IU. Together with 7F, these had been re-engined with Airdicos but were sold to joyride concerns in 1928 along with ’OK. G-EBIV went to Surrey Flying Services Ltd., Croydon, while 5IT and 7?7 joined ’OK at Squires Gate and there became even better known than the 504K.
The last two British 548s, G-ABMB and ’SV, were built at Barton by Berkshire Aviation Tours Ltd. in 1931 for the Giro Aviation Co. Ltd., their sole cross country flying being the delivery flight to Southport where they worked the beaches for several years. Both were replaced by D. H. Fox Moths in 1934-35 but remained fully rigged in the hangar at Hesketh Park until 1938.
A few Avro 548 conversions were also made overseas. The Canadian Aircraft Co. Ltd. of Winnipeg, importers of six 80 h.p. Renaults in April 1920, built three machines and retained two for charter flying. The third was converted for the McCall Hanrahan Aero Service of Calgary but crashed in less than a fortnight. In 1928 they also built the Hawk-Clark Y-Avro Mallard G-CASY for W. P. A. Straith, using an old 504K fuselage (believed G- CAAQ) with a 75 h.p. Rolls-Royce Hawk engine and Clark Y section wings. In Australia Matthews Aviation Ltd. replaced the Dyak in G-AUBG by an Airdisco; and G-AUBK, flown by E. W. Percival in the Australian Aerial Derby with an 80 h.p. Renault on May 6, 1922, also later received an Airdisco. The only other example, G-AUEW, started life as a Clerget 504K, but was modified progressively to 548 and 548A by E. W. Beckman and Courier Aircraft Ltd. of Brisbane 1926-27.
Specification and data
A. V. Roe and Co. Ltd., Newton Heath, Manchester; and Hamble Aerodrome, near Southampton, Hants.
The Aircraft Disposal Co. Ltd., Croydon Aerodrome, Surrey
Berkshire Aviation Tours Ltd., Barton Aerodrome, Manchester
The Canadian Aircraft Co. Ltd., Winnipeg, Manitoba, Canada
The Henderson School of Flying Ltd., Brooklands Aerodrome, Surrey
Surrey Flying Services Ltd., Croydon Aerodrome, Surrey
(Avro 545) One 90 h.p. Curtiss OX-5
(Avro 548) One 80 h.p. Renault
(Avro 548A) One 120 h.p. Airdisco
Span 36 ft. 0 in.
Length 29 ft. 5 in.
Height 10 ft. 5 in.
Wing area 330 sq. ft.
Weights and Performances:
Avro 545 Avro 548 Avro 548A
Tare weight 1,241 lb. 1,338 lb. 1,460 lb.
All-up weight 1,829 lb. 1,943 lb. 2,150 lb.
Maximum speed - 80 m.p.h. 91 m.p.h.
Cruising speed 70 m.p.h. 65 m.p.h. 84 m.p.h.
Initial climb - 350 ft./min. 400 ft./min.
Ceiling - - 11,200 ft.
Range 210 miles 175 miles 300 miles