The Royal Navy was one of the pioneering services to utilise military aircraft in a combat role. The Royal Naval Air Service of World War I carried out limited strategic bombing of land targets including most famously against the Zeppelin works at Friedrichshafen. However, following the war the Royal Navy failed to truly capitalize on this lead and continued to view the aeroplane as merely an extension of the fleet’s firepower in naval battle as opposed to a strategic force.
Throughout the interwar period the Royal Navy’s Fleet Air Arm (which was still subordinate to the RAF until 1939) did little to go beyond the operating doctrines of World War I and so naval aircraft fell in to three roles – fighter, light bomber (including using torpedoes to attack shipping) and spotter – and all these roles were for directly supporting the fleet itself. With the belief that the battleship and the naval gun was still the dominant force on the sea the Admiralty viewed the spotter aircraft as among the most important. This belief in naval guns was highlighted in 1940 when a small force of ships including the carrier HMS Ark Royal with her squadron of fighter-bombers was attacked off Norway by Heinkel He.111 bombers. Not a single fighter was launched as the defensive batteries of the warship had higher priority over aircraft to defend the fleet. That would change very quickly.
In the mid-1930s the Royal Navy looked at ways of improving their ability to track enemy fleets and provide target data for the battleship’s guns. This resulted in Operational Requirement (O.R. 52) that produced an extremely demanding specification for a new aircraft to undertake the fleet shadowing role. The aircraft was required to have a crew of three, have long endurance and have a low stall speed in order to track the target fleet which would be travelling considerably slower than any conventional aircraft. One peculiar aspect of the specification also demanded that the aircraft must be very quiet so as to not alert an enemy ship’s crew when conducting night operations or using cloud for cover; a very primitive form of stealth technology.
Five companies responded to the specification – Airspeed, General Aircraft Ltd, Percival, Shorts Brothers and Fairey Aviation who was a major supplier of combat aircraft to the Royal Navy. In 1938 two companies, Airspeed and General Aircraft Ltd were shortlisted and commissioned to build prototypes of their designs. These aircraft were remarkably similar in their configurations.
Airspeed A.S.39 Fleet Shadower
The Airspeed A.S.39 was of a monoplane design with high mounted, semi-cantilever wings. At the time of the issuing of the specification many felt that only a biplane could achieve the necessary low speed and generate the high lift required for the mission. Airspeed countered this by mounting the engines high over the wings which meant that a greater degree of propwash passed over them during take-off thus dramatically increasing the lift generated at slow speeds. This resulted in an impressively low stall speed of just 33mph which as well as helping to track slow moving ships at sea also meant that the pilot had more time to land the relatively large aircraft aboard a carrier. To keep the aircraft as light as possible Airspeed bucked the growing trend of all-metal aircraft and built large sections of the wing and tail out of wood. Like all carrier aircraft the wings could be folded back for stowage.
Power was provided by four minuscule Pobjoy Niagara V seven-cylinder, air-cooled, radial engines. First produced in 1934, the engines were designed to run at much higher speeds than conventional engines with reduction gearing to lower the speed of the propeller. This configuration led to the propeller being mounted off centre of the main engine block. These engines were praised for their small size and weight which meant they were ideal for smaller aircraft designs. They were exceptionally smooth as well and the Niagara V version was tuned to 140hp. The four engine arrangement made the Fleet Shadower look more powerful in photographs than it actually was and top speed of Airspeed’s design was merely 126mph. Perhaps most importantly with regards to the Admiralty’s specification was that they were very quiet in their operation.
The crew comprised of three personnel: pilot, observer and radio operator. The pilot sat high up in the forward fuselage in a cabin that bears an uncanny resemblance from the side to helicopters such as the Westland Whirlwind and Westland Wessex of the 1950s. The observer was accommodated in the nose with clear-vision window panels arranged on three sides to maximise the forward vision. A third crewman was located in the rear section of the crew compartment and operated the radio equipment.
Work began on two prototypes as the war broke out but only a single aircraft was made airworthy to participate in flight trials beginning on 17th October 1940. Testing proved that the aircraft had significant stability problems due to its underpowered engines and was prone to being thrown around the sky by strong winds. This led the Admiralty to consider revising the specification to use Armstrong-Whitworth Cheetah XI engines but these were never fitted and the aircraft were scrapped in 1942.
- Crew: 3 (Pilot, observer, radio operator)
- Role: Observation/Target Spotter
- Powerplant: 4 × Pobjoy Niagara V (140 hp each)
- Maximum speed: 126 mph
- Stall speed: 33 mph
- Endurance: 6 hours
- Service ceiling: 14,700ft
- Length: 39 ft 10 in
- Wingspan: 55 ft 4 in
- Height: 10 ft 5 in
- Wing area: 469 ft²
- Empty weight: 4,592 lb
General Aircraft Ltd G.A.L.38 Fleet Shadower
The aircraft produced by General Aircraft Ltd shared a common design philosophy to Airspeed’s aircraft and had a similar configuration. It too was a high wing, four engine monoplane that made use of propwash to help achieve a low stall speed. The G.A.L.38 wing also made use of various high lift devices to further lower the stall speed and these included slotted flaps and ailerons. A recognition feature of the G.A.L.38 was its sponson based main landing gear compared to the Airspeed A.S.39 which featured rigged landing gear. The rear fuselage also had a much stubbier appearance compared to its sole rival while locations of the three crew were identical with the observer sat in a glazed nose, the pilot in a high location and the radio operator in the rear section.
The intended powerplant for the G.A.L.38 was the same Niagara V engine as on the Airspeed aircraft however there weren’t enough available for the two prototypes due to development troubles and so in order to expedite testing the G.A.L.38 was fitted with the earlier Niagara III engines that were intended for civil use and tuned to 130hp. Although only 10hp down on the Niagara V the aircraft’s reliance on propwash for maintaining flight at low speeds meant that the Niagara III powered G.A.L.38 had a marginally higher stall speed of 39mph (still impressive all things considered) compared to the AS.39’s 33mph. An interesting trade-off however was that the G.AL.38 had almost double the endurance of the Airspeed aircraft; 11 hours in total.
Flight testing of the first prototype began in 1940 and like the Airspeed aircraft it suffered from quite severe stability problems. This became such a concern that soon the aircraft was grounded and returned to the factory in order to have its three piece tail removed and replaced by a single tail unit of much larger area. Flight testing resumed in June 1941 and the results were considered quite satisfactory however by that time the whole concept of the Fleet Shadower was being dropped. General Aircraft Ltd continued testing in to 1942 before it was grounded and then scrapped.
- Crew: 3 (Pilot, observer, radio operator)
- Role: Observation/Target Spotter
- Powerplant: 4 × Pobjoy Niagara III (130 hp each)
- Maximum speed: 115 mph
- Stall speed: 39 mph
- Endurance: 11 hours
- Service ceiling: 6,000ft
- Length: 36 ft 1 in
- Wingspan: 55 ft 10 in
- Height: 12 ft 8 in
- Wing area: 472 ft²
- Empty weight: 6,153 lb
Several factors killed off the concept of the Fleet Shadower.
- The concept was conceived at a time when land based aircraft lacked the range to roam over the ocean. By 1941, bomber aircraft began to be converted for the maritime patrol role and these had much greater range than previous maritime patrol aircraft. Most significantly the superlative Consolidated B-24 Liberator became available in greater numbers and this aircraft had the range to cover the entire Atlantic Ocean. As such, tracking hostile vessels became more of a priority for the RAF.
- Radar technology negated the need for slow, quiet aircraft to shadow an enemy force. Now an enemy fleet could be tracked by aircraft and ships from a greater distance than ever before.
- Before December 1941 when Japan attacked Pearl Harbour and British possessions in the Far East, the main threat was Nazi Germany who possessed a relatively small surface fleet that rarely ventured out of its ports. The main threat was from U-Boats and from the decks of the Royal Navy’s light and fleet carriers the venerable Fairey Swordfish proved quite adequate in the ASW role and was a fully matured design already in production. It was also already operating with radar.
- When the Germans did take their ships to sea many of them had Arado Ar.196 seaplanes onboard. While these were intended for spotter duties they found a useful role shooting down the lumbering maritime patrol planes the RAF used in the early days of the war such as the Avro Anson. The slow flying (and as yet unarmed) Fleet Shadower would have been extremely vulnerable to this aircraft.
Both of these aircraft were really born of the earlier thinking of the Admiralty. Had they become available in the late 1920s then they would have been a more relevant design for Royal Navy use throughout the 30s.