The Avro 549 Aldershot
Having expanded exponentially over the previous four years, the end of the war in 1918 and the vicious cull of advanced aircraft projects for the still infant Royal Air Force threatened the very existence of the plethora of British aircraft manufacturers that had emerged. Even producing some of the war’s most legendary aircraft was no guarantee of survival as was proven by Sopwith who having made a name for themselves with their Camel and Pup fighters, disappeared in 1920 after entering voluntary liquidation and then having their assets absorbed by Hawker.
The name A. V. Roe (Avro), had become most associated with trainer aircraft during the war and so was less of a household name than the more glamorous manufacturers like Bristol, Sopwith or the Royal Aircraft Factory. This overshadows the importance of types such as the Avro 504 trainer to the war effort which as well as being used as a warplane in its own right, produced thousands of pilots for the front. Avro used this experience after the war to begin producing sporting aircraft for the civil market to be bought up by many of the demobilised military pilots who wanted to keep flying. This would then generate the money to keep it functioning while waiting for impending lucrative government contracts.
An early success story for the company came in the form of the Avro 534 Baby which went on to take part in numerous races and set distance records at the hands of the “Australian Lone Eagle” Bert Hinkler. On May 31st 1920 he made a non-stop flight from Croydon to Turin, a distance of 655 miles, in 9 hours 30 minutes. Another Avro Baby made the first ever flight between London and Moscow in 1922 while another example was expected to support Ernest Shackleton’s ill-fated Antarctic expedition but vital components for the aircraft failed to arrive in time before he set off.
Unfortunately, these technological successes failed to truly translate in to financial success and Avro was forced to sell off much of its land holdings it acquired during the war in order to keep the company going. In 1921, Avro secured one of the few highly coveted government contracts when it’s Avro 555 was selected to meet a requirement for a carrier-capable reconnaissance and gunnery spotting aircraft. A total of 53 Avro 555 Bisons were eventually built in two main variants and helped keep Avro’s foot in the government’s door.
In 1920, the Air Ministry began finalising the specifications for a new interim bomber to replace a number of the RAF’s wartime types still in service. The new specification was quietly centred around a possible war breaking out with France now that Germany and Austro-Hungary ceased to be any real influence on the continent. France was increasingly feeling threatened by the influence the British Empire’s economy had on the world stage much to her own detriment while Britain was suspicious of France’s resistance to disarmament efforts. As a result the specification envisioned a bomber powered by the Rolls Royce Condor engine that was capable of carrying a 1,800lb bomb in excess of 500 miles so that it could attack targets in and around Paris from bases in south-east England.
Whereas during the war, the time between drawing board to prototype to production order could be measured in just a few months there was now less urgency which allowed engineers more time to perfect their designs before construction began. It also allowed the Air Ministry to be a little more fussy about selecting designs to be funded at prototype level. Avro was one of a small number of companies who responded to the requirement which had garnered some controversy amongst RAF and aviation industry leaders over its use of only one, albeit powerful, engine when at least two was the norm for an aircraft of this type.
The thinking behind the Air Ministry’s decision was that the single-engine shape should allow for higher levels of performance while aircraft with two or more engines were often more costly, more problematic, more unreliable or in some cases their performance was simply lacking compared to single-engined types. Opponents argued however that two or more engines increased reliability and survivability in the air and that the technology was advancing to overcome these shortcomings albeit at greater expense.
Avro and De Havilland were both shortlisted and given contracts to produce prototypes for testing. Avro’s design was for a three bay biplane with wooden wings and a steel-framed fuselage covered in plywood and fabric. It had a wingspan of 68ft, a length of 39ft and was nearly 15.5ft tall sitting on four large main wheels when on the ground. The crew comprised of a pilot, navigator/bomb-aimer and up to two defensive gunners armed with .303 (7.7mm) Lewis machine guns; one in the rear fuselage and one in the ventral position although the latter position would seldom be used. As dictated by the Air Ministry, the new aircraft was fitted with the Rolls Royce Condor V-12 engine. This was a more powerful development of the earlier Rolls Royce Eagle which powered the Vickers Vimy bomber but could churn out around 650hp.
The new Avro aircraft was given the in-house number of 549 before adopting the name “Aldershot” and the prototype, J6952 made its first flight during October 1921 from Hamble Aerodrome in Southampton. There was little time to celebrate however for De Havilland’s aircraft, which was now known as the DH.27 Derby, achieved its first flight within days of the Aldershot. Testing of both aircraft began which for Avro revealed poor directional control from the tail resulting in the aircraft being taken back to the factory to have a 6ft extension added to the rear fuselage to alleviate the problem. The landing gear was also later revised which saw the two inner wheels removed.
These improvements were made to the second prototype whilst it was under construction. At this time, the Air Ministry began revising its specification regarding the offensive armament the aircraft was expected to carry. Originally it was expected to carry a single 1,800lb bomb but this was changed to either four 500lbs or eight 250lbs. Fortunately, this didn’t require major modifications and the Aldershot could carry the four 500 pounders externally while a bomb bay allowed it to carry the smaller weapons internally which decreased drag significantly.
The De Havilland Derby on the other hand had to carry all its weapons externally which hampered the aircraft’s performance that was already at a disadvantage to the Aldershot being 420lbs heavier while powered by the same engine. Comparing the two aircraft through 1921 it was obvious the Aldershot was the superior type and on January 26th 1922, Avro was awarded a contract for 15 production aircraft built to Aldershot III specification that was essentially the same as the second prototype.
With the conclusion of the test programme, it was decided to adapt the first prototype to undertake trials with the Napier Cub engine. This had the potential to be an awesomely powerful aeroengine for the time being the first in the world to churn out 1,000hp and like the Aldershot was developed in response to the Air Ministry’s interest in large, powerful single-engined bomber types. It achieved this figure with 16 cylinders arranged in an “X” pattern with the bottom rows angled more narrowly than the ones on top to ease the pressure on the crankshaft.
In order to accept the 35% more powerful engine, the Aldershot’s airframe had to be considerably strengthened and the nose section had an extra set of exhaust pipes to expel the gases from the lower bank of cylinders (Right). The original two-blade propeller was replaced with a large four-bladed prop each blade of which was 18in at its widest point.
Known as the Aldershot II, the Cub-powered aircraft first flew on December 15th 1922 and was at that time the most powerful single-engined aircraft in the world; something Avro was quick to publicise. Some of Avro’s own literature started referring to the aircraft as the Avro “Cub” although this was not officially adopted and they claimed a top speed in the region of 140mph. This was 30mph faster than the regular Condor-powered Aldershot III that the RAF was taking on charge but this speed came at the cost of reduced endurance.
The RAF began to receive their first operational Aldershot IIIs in July 1924 with the aircraft being taken on charge with No.99 Squadron based at RAF Bircham Newton. Delivery had been delayed by the adoption of the newer Condor III engine but the 15 aircraft ordered was enough for the squadron to form two separate flights during that summer. No.99 Squadron used the aircraft primarily for the night bombing role although unusually they flew in the silver colour scheme that was adopted by day units of the time.
Conceived as an interim type until more advanced aircraft were available, the Aldershot was never going to have a stellar career in the RAF but the increasing dissatisfaction with both it and the thinking behind its conception conspired to doom the aircraft to having one of the shortest frontline careers in the service’s history. Confidence in the single-engined heavy bomber concept proved short lived but even more damning was that for all its technical innovation, the Aldershot was little better (and sometimes worse) than the wartime types it was expected to replace. With the RAF deciding against any further acquisitions, No.99 Squadron would gain the somewhat unique distinction of being the only frontline operator of the type in history. They would relinquish their last Aldershots in March 1926, just 20 months after they first arrived, replacing them with Handley Page Hyderabads.
The first prototype and the sole Aldershot II, J6952 would actually outlive the production types it spawned. It continued testing the Napier Cub engine until late 1926 by which time its development was cancelled after just six engines had been built. J6952 was then re-engined once again, this time with the Beardmore Typhoon I slow-revving engine. This engine aimed to produce higher power with lower revolutions than a standard aeroengine. J6952 was redesignated as an Aldershot IV and first flew with the Typhoon on January 10th 1927. Testing showed that the new engine gave the aircraft a much smoother ride than either the Condor or Cub engines but government support for it was already fizzling out and no production order was made.
This brought an end to the story of the Avro Aldershot itself. It formed the basis for the Avro Andover flying ambulance and transport aircraft but like its forebear, the Andover was less than spectacular and only four were built. Experience gained with the Aldershot would influence some of Avro’s later design work but the aircraft itself occupies a mere footnote in aviation history.