The Avro 557 Ava
World War I had completely changed the world’s perspective on the aeroplane as a weapon of war. Whereas before it was seen as little more than a tool for reconnaissance, now it was directly challenging age-old beliefs about the superiority of armies and navies. Nevertheless, the Royal Air Force (RAF) was still fighting for its continued existence and in order to prove its worth it had to show that it had the potential to truly affect the future battlefield. For Chief of the Air Staff, Lord Hugh Trenchard this was no easy feat as the RAF was constantly strapped for cash in the face of peacetime cuts.
Both the Army and Navy lobbied for abolishment of the RAF now that the war was over and to have their respective air arms reinstated but Trenchard and his political supporters put up a staunch defence. In order to prove the RAF’s worth, Trenchard was careful but ambitious about his service’s reequipment program in the 1920s hoping to make the most out of what little he had. One such role he envisioned the RAF undertaking was the defence of Britain against surface warships using air launched torpedoes. During the war, Britain had suffered humiliating attacks by German battleships which shelled coastal towns like Scarborough, Hartlepool and Whitby and those who supported the RAF believed that aircraft could prevent further attacks using both speed and firepower to intercept the raiders out at sea. Trenchard went further adding that in his opinion, combat aircraft had the potential to render the battleship entirely obsolete.
In 1922, the Air Ministry issued specification 16/22 aimed at acquiring an aircraft to fulfil the challenging role. Like the specification that produced the Avro Aldershot which was at that time undergoing flight testing, it was conceived around a possible war breaking out with France which was now the only real European superpower able to threaten Britain with Germany being crushed by the Treaty of Versailles and Austro-Hungary having broken up. The specification called for an aircraft capable of carrying a 21-inch (533mm) torpedo to a target around 500 miles from its base allowing it to attack shipping as far as Denmark and the entrance to the Baltic Sea. This was no easy feat since the 21-inch torpedo was over 3,000lbs in weight but Trenchard believed this weapon was the bare minimum needed to sink a battleship. To increase the type’s usefulness, the specification also stipulated that the aircraft was to be used as a bomber and carry the equivalent weight in bombs.
Avro and Blackburn Aircraft were both shortlisted to produce prototypes for testing with Avro’s project being led by the talented Roy Chadwick. Both companies had to work under a strict veil of secrecy however since at that time there were calls for world-wide disarmament and it was believed by some that an aircraft capable of sinking a battleship might be perceived as contrary to this. Initially, Chadwick opted for a single engined design centred around the 1,000hp Napier Cub engine which Avro had been testing on the original Avro Aldershot prototype. Blackburn adopted the same engine for their design but eventually Chadwick dropped it in favour of producing a twin engined design equipped with individually less powerful engines that combined produced even more power; something the Air Ministry was looking more favourably upon.
Chadwick’s design was for a three-bay biplane of wooden construction with a biplane tail that had a triple rudder arrangement. The two uncowled engines were mounted close to the fuselage but forward of the main wing resting on pylons that extended down to their relative undercarriage. Chadwick settled on the Rolls Royce Condor III V12 engine which churned out 650hp to power the type. The aircraft was to have a crew of five with two pilots sat in an open cockpit located at the top of the forward fuselage slightly ahead of the propellers. The navigator/bomb aimer worked in the enclosed cabin during the flight but could occupy a “dustbin” gun turret that retracted down from beneath the aircraft when it was under attack. The aircraft also had two dedicated gunners with one located in the extreme nose and the other in a dorsal position behind the wings. Each gunner was equipped with a single .303in Lewis machine gun. The main offensive armament was carried on racks underneath the fuselage between the two innermost undercarriage wheels.
The first prototype of the new aircraft was completed in 1924 and given the in-house number 557 and the serial number N171 before the name “Ava” was assigned to it. The origin of the name is unclear but it is likely a derivative of the Latin word “Avis” which means “bird”. Avro test pilot Bert Winkler was at the controls during the type’s first flight and being a man of rather short stature, he had to be propped up in the seat with a few cushions to allow him to see forward over the nose. Not long in to the test program, the central rudder was removed as it was deemed unnecessary. Work also began on a second prototype, N172, which was to be of all-metal construction reflecting this growing trend amongst aircraft manufacturers.
Meanwhile, Blackburn Aircraft had begun test flying their own aircraft to meet the Air Ministry’s specifications known as the Cubaroo – a name likely inspired by its powerful Napier Cub engine. Despite the Air Ministry emphasizing a preference for a twin-engined design, Blackburn submitted their single-engined Cubaroo which was at that time the largest single-engined military aircraft in the world. Despite this fact, flight trials showed that it had good flight characteristics although Blackburn would suffer a temporary setback when the prototype crash landed in January 1925.
As work on both aircraft continued, the grey clouds of cancellation began to form over their respective aerodromes. Naval observers of the project argued that these relatively large and lumbering aircraft would offer an easy target to the newer anti-aircraft guns being fielded aboard surface warships around the world. They also argued that they would be vulnerable to interception by modern carrier aircraft equivalent to the Royal Navy’s Fairey Flycatcher which was significantly faster than either the Ava or the Cubaroo when carrying their torpedo.
In 1924, the Fleet Air Arm was formed within the RAF to handle shipboard operations and this new branch argued for smaller torpedo-carrying carrier aircraft to fulfil essentially the same role as was envisioned for the Ava and Cubaroo. These aircraft would be equipped with the 1,800lb Mark.VIII torpedo so could be smaller, faster and tougher to shoot down with defensive fire. The Air Ministry agreed and had rescinded specification 16/22 by 1926 rendering both the Ava and the Cubaroo surplus to requirements. With the veil of secrecy having been lifted, Avro demonstrated N171 during the 1926 Hendon Air Pageant while at the same time continued work on the second prototype which would not be completed until 1927, flying for the first time on April 22nd. In terms of design, the only difference between the two prototypes was that the second prototype had more rectangular shaped wing tips than the first prototype.
Avro quickly began scouring the Air Ministry’s order books for a requirement that the all-metal Ava could possibly fulfil and settled on the recently issued B19/27 which was designed to produce a replacement for the Vickers Virginia and Handley Page Hinaidi bombers. With some more development, the Ava could just about squeeze in to this requirement which demanded a night bomber capable of carrying a 1,500lb bombload, 920 miles from its base at an average speed of 115mph. However, Avro faced stiff competition from Bristol, Fairey, Handley Page and Vickers all of whom were working on newer designs with Fairey even offering up a new monoplane design in the shape of the Fairey Hendon. The Air Ministry weren’t interested and the Ava joined the list of Avro’s failed attempts to produce an operational bomber.
Length: 58 ft 3 in (17.75 m)
Wingspan: 96 ft 10 in (29.51 m)
Height: 19 ft 7¾ in (5.99 m)
Empty weight: 12,760 lb (5,788 kg)
Max. takeoff weight: 19,920 lb (9,036 kg)
Powerplant: 2 × Rolls-Royce Condor III water cooled V-12, 650 hp (485 kW) each
Maximum speed: 115 mph  (100 kn, 185 km/h)
3 × 0.303 in (7.7 mm) Lewis Guns (Nose, dorsal and retractable ventral positions)
1 × 21 in (553 mm) torpedo or 4 × 550 lb (250 kg) bombs