The Fairey Hendon
night-bomber and its projected developments.
Fairey Hendon in flight. Note the white markings on top of the wing; these outlined the panels that gave access to the bomb cells and fuel tanks. A small door on each side of the fuselage gave access to the top of the wings for maintenance.
When the Fairey Aviation Company first flew their revolutionary Fox biplane bomber in 1925 they gave thought to using the prototype to gain the world distance record. Nothing came of this plan directly but the Air Ministry must have been intrigued by the possibilities because in 1927 they asked Fairey to design an aircraft specifically to get the world distance record. This brought forth the Fairey Long-range Monoplane, two of which were built. The first of these first flew in November 1928 and it made the first non-stop flight to India in April 1929 but tragically crashed during an attempt on the distance record in a flight to Cape Town in December 1929. In October 1933 the second Fairey Monoplane succeeded in gaining the record with a flight to Walvis Bay in South West Africa (modern Namibia).
In designing the Hendon, Fairey capitalised on the technology they developed to build the huge, internally-stressed, monoplane wing for their record-breaking Long Range Monoplane (seen above). Little did they know, that in only a couple of years, that technology would be made obsolescent by new, stressed-skin techniques from the USA.
The thick monoplane wing that Fairey were developing for their long-range machine seemed to have a lot of scope for further development. So, in parallel with the Long-range Monoplane, they designed a twin-engined aircraft for the Air-Ministry B19/27 night-bomber specification of 1927. Initial studies had conceived an aircraft with folding wings to be more easily accommodated in the hangars of the period but the design evolved into a larger aircraft. When it emerged from the factory for its first flight in November 1930 the prototype carried a pilot in an enclosed cockpit, a bit of a novelty at the time. To ensure a good view of the ground the cockpit was offset to port (like the cockpits in the later Sea Vixen and Canberra B8 jets). A navigator/ radio operator was accommodated in the fuselage behind the pilot and there were three gun positions, one each in nose, tail and dorsal positions. The tail and dorsal gun positions were accessed by metal catwalks, suspended in the framework of the fuselage. The aircraft was powered by two Bristol Jupiter radial engines enclosed in some of the first NACA cowls to be used on British aircraft. Apparently, Fairey had hoped to use the new Bristol Pegasus radial engine on the new aircraft, but none were available in time. The Hendon had its mainwheels enclosed in "trouser" fairings but the engines were located inboard of these when initially built.
The Fairey Hendon prototype in its original configuration with Bristol Jupiter radial engines enclosed in NACA cowlings. Note the engines are inboard of the main wheels in their trouser fairings. Those heavily dented fairings look more fragile than those on the production aircraft. There looks to be very little gap between the tips of the propellers and the fuselage.
The prototype K1695 did taxying tests on 17th and 18th November 1930 and then on the 20th November took short test hops into the air before taking to the air properly on the 25th November 1930. Testing continued until the prototype overshot and crashed on the 31st March 1931, fortunately, there were no casualties. The airflow around the cowled radial engine was suspected of causing a disturbed airflow over the tail and so when the prototype was rebuilt it was given Rolls-Royce Kestrel water-cooled engines instead. These were installed further out on the wings, directly above the trouser fairings of the undercarriage. The enclosed cockpit was also removed at this time. The rebuilt aircraft did not fly again until November 1931. At first, a finned radiator mounted on the top surface of the wing was tried, but this did not work well, so underslung radiators were fitted instead. It was found that with the new Kestrel engines the prototype was some 7 mph slower than with the original Jupiter radial engines. The rebuilt aircraft also incorporated "wash-out" on the wings to make the stall start at the wing-root, giving some feedback to the pilot and ensuring the ailerons stayed effective until touchdown was achieved.
Fairey Hendon Prototype K1695 with a Handley Page Heyford behind, the aircraft that secured the B19/27 order. Notice the extensive bracing struts needed on the tail and the strut from the wing to the undercarriage .
The prototype took part in competitive trials at Martlesham Heath in early 1932 against the Handley Page Type 38 "Heyford" (the Vickers "Vanox" biplane also built to B19/27 had already been rejected). The Air Ministry ended up ordering the Handley Page Type 38 Heyford bomber (this was despite the prototype HP38 crashing during the evaluation). The production version of the Heyford was renamed the "Type 50". This is often presented as a lack of vision by the Air Ministry, rejecting a modern monoplane design in favour of an "old-fashioned" biplane. However, this is a view clouded by modern prejudices and preconceptions. In performance terms, there was little to choose between the Fairey monoplane and the HP Heyford. They had about the same top speed (depending on which mark of Kestrel engine was fitted to both aircraft) and had very similar range and ceilings, but the biplane could lift a greater weight of bombs (2,500 Ib (1,134 kg) normal payload but up to 3,500 lb (1,588 kg) in overload condition). Most importantly the biplane had a much lower landing speed, essential for the small grass airfields the RAF then used. Without the benefit of flaps, the Fairey bomber had a high landing speed (for the time) of 68 mph. This was some 13 mph higher than the Heyford, a crucial difference. With the high accident and casualty rate the RAF experienced at the time, and no prospect of a major war foreseen, it is only natural the Air Ministry should opt for the safer design. This was somewhat ironic since Fairey were a pioneer in the design of flaps and had used an early version of them on some of their WWI designs. The Fairey monoplane might look more "modern" but the metal structure of both the fuselage and wings were covered in fabric, a far cry from the multicellular stressed-skin metal structures that would start to be built within only a few years. The internal structure, needed to give the cantilever wing strength, added greatly to the weight of the aircraft and dictated a very thick wing. Large parts of the Hendon's structure had to be built of steel for strength rather than lightweight aluminium. This added weight and drag negated any advantage over traditional biplane design. In the late 1970s, I met an old RAF fitter who had worked on the Hendon. He said it was... "Not so much a monoplane, more a biplane with the gap between the wings filled in!"
Another photo of the prototype, notice the second pilot position added behind the first. The prototype was continuously modified and almost every photo of it shows some change in configuration.
The Air Ministry must have liked some elements of the Fairey design because they paid for it to undertake tests with RAF squadrons. Then in January 1933, they paid for it to be modernised before an extensive service trial with No 10 Squadron, after which it was modernised yet again prior to another full test at Martlesham Heath in April 1934.
Crew entering a production Hendon bomber. Note the metal three-bladed propellers. The engines are directly above the main undercarriage wheels. The raised rear canopy shows this to be one of the aircraft modified with dual-controls. A 10-foot ladder was the only means of entry into the Hendon, unless you got a step-ladder and took a flying leap into the rear gunner's position! You can clearly see that the Hendon is not suitable for transporting troops, as claimed in contemporary descriptions.
Of course, while all this had been going on the political climate of Europe had changed considerably. Hitler had come to power in Germany and although the full scale of German rearmament was still not apparent tensions were growing daily. At the same time developments in commercial aircraft design in the USA had started to make biplanes look old-fashioned. As part of its rearmament plans, the RAF expanded the size of many of its existing airfields and construction work began on new large airfields better able to accommodate the longer take-off and landing runs of monoplanes like the Hendon. So after the re-evaluation at Martlesham Heath, the Air Ministry issued B20/34 and ordered 14 production aircraft to be called "Hendon", enough to equip a single squadron. The order was placed in mid-1934. This would seem a very low-risk ploy by the Air Ministry to quickly get some "modern-looking" aircraft into the shop window to deter aggression, even though their structure and performance were hardly any different to their biplane contemporaries and they had a very small bombload. The RAF already had much more advanced bombers on order and Fairey had fully investigated the new stressed-skin aircraft designs from the USA and was working on the Battle and P4/34 bombers. Shortly after this initial order was placed, the revelation of the increased rate of German rearmament panicked the Air Ministry into ordering more Hendons and they went as far as allocating serial numbers for another 61 aircraft (4 dedicated dual-trainers and 57 bombers). This additional order was soon cancelled as the replacement AW Whitley night-bomber promised much higher performance, as did the Handley Page Harrow medium-bomber. Even the single-engined Vickers Wellesley was faster, had a longer range and higher ceiling with a comparable bombload.
A dramatic painting of Fairey Hendons in action as painted by Frederick Blakeslee for the American "Dare-Devil Aces" magazine in 1936. The painting shows the aircraft in the configuration of the prototype rather than the production machines. He has upgraded the gunners to twin machine guns. The description inside the magazine stressed that the performance of these aircraft was a closely guarded secret.
The production aircraft saw the reintroduction of the enclosed cockpit and this was extended rearwards to give a tandem position for the navigator to sit and get a view outside. On some of the aircraft, this position was fitted with dual controls and a raised canopy to give a better view ahead. Aircraft so fitted served as trainers for pilots converting to the type while still retaining full operational capability. More powerful Kestrel VI engines driving metal three-bladed propellers were fitted. Perhaps most noticeably an enclosed manually-operated front turret was fitted to protect the gunner from the blast of the airflow. The tail and dorsal positions were still open although both incorporated a small retractable windshield to give a bit of protection.
Above: the two styles of cockpit. On the left is the normal cockpit, on the right is the dual-control tandem cockpit with the raised rear portion.
The bomb load and fuel capacity of the Hendon were linked. The Hendon had two large fuel tanks of 250 gallons (1,136 litres) each, accommodated behind the engines in the thick wings with additional small 20 gallon (91 litre) gravity feed tanks directly behind each engine. However, with a full fuel load, the aircraft could not lift the full bombload. So if the full bombload of 2,548 lb (1156 Kg) was to be carried fuel had to be limited to 394 gallons which gave a combat radius of 680 miles (1,094 Km). If the full internal fuel load of 540 gallons was carried then only a reduced bomb load of 1,600 lb (725 Kg) could be carried to a radius of 950 miles (1,529 km). If no bomb load was carried and additional overload fuel tanks were installed in the bomb cells a ferry range of 2,500 miles (4,023 km) was expected.
Fairey Hendon in flight.
The Hendon did not have a central "bomb bay". Instead, it had a series of ten large "bomb cells" that spanned the wing and fuselage between the two engines. Behind those were another six smaller bomb cells in the wing. The Hendon had removable panels on the top of the wing to give access to these bomb cells from above to help with winching the bombs into place. The small bomb cells could accomodate the new 100 lb (45 Kg) anti-submarine bombs or the older 112 lb (50 Kg) and 120 lb (54 Kg) bombs of WW1 design. The larger bomb cells were big enough to accommodating 1,000 Ib (454 Kg) or 500 lb (227 Kg) bombs but the Hendon was incapable of taking off with such bombs in all the cells. If 1,000 lb bombs were to be carried then only two would be loaded in the two central bomb cells under the fuselage (even then the fuel load would have to be restricted). If 500 lb bombs were to be carried then it would be limited to only four in the two cells under the fuselage and the two cells under the wing closest inboard, with the same restriction on fuel-load. The Hendon could carry ten of the smaller 250 lb bombs in the large bomb cells and this would probably have been the favoured loadout. The Hendon also had the provision to carry two of the ubiquitous "light series" bomb-racks externally to accommodate small 24 lb (11 Kg) Cooper bombs or incendiaries (up to 4 on each rack).
Above: Diagram of the underside of the production Hendon showing the 10 large bomb cells (red) and the 6 small bomb cells (blue).
Contemporary descriptions of the Hendon usually claim "15 to 20 fully equipped troops can easily be transported". That is a frankly ridiculous statement (although it depends on how you define "easily"). The only access to the interior of the Hendon was through a hatch in the nose (see photo above) which required a 10 foot (3m) ladder. Once onboard only a limited area around the pilot, navigator and radio operator positions had a proper "floor". The rest of the length of the Hendon had only a narrow catwalk. Any troops carried in a Hendon would have found it a very uncomfortable ride with an awkward entry and exit, especially if loaded down with weapons and other equipment. They would have had to be thoroughly briefed not to damage the thin fabric covering of the fuselage or touch any of the exposed control cables. The unheated interior of the Hendon would have been very cold in winter or if flown at altitude.
A contemporary postcard illustration of the Fairey Hendon by AFD Bannister. He is usually noted for his accuracy but in this case, he seems to have invented an enclosed turret for the dorsal position (at least no photograph of such an installation exists). Note the pilot and navigator in tandem under the enclosed cockpit canopy.
In service, the Hendon would normally be crewed by 4 people. There would be the pilot in the enclosed cockpit. Behind and in tandem with the pilot to get a good view would sit a second pilot who carried out the duties of navigator, he had access to a chart table with fold-down seat inside the fuselage and he would also be expected to go forward to act as bomb-aimer and front-gunner. Then the radio operator sat in the fuselage facing backwards just behind the cockpit. If the aircraft was attacked, the radio operator would go back and take up the dorsal-gun position. Finally, in the tail was the dedicated tail-gunner. On flights of limited duration the pilot himself would take on the duties of navigation and the second pilot's place would be taken by an airman observer who could man the front gun, be the bomb-aimer and handle charts for the pilot.¹ On training missions, it would not be unusual to carry one or two more crewmen to get extra experience (and bump up their flying pay).
Above is a poor quality image of the interior of a production Hendon; looking forward from the radio operator's position. The pilot sat on the raised platform on the left, you can just make out part of the instrument panel in front and there is a large control wheel on the left (trimming wheel perhaps?). Notice the foldable seat for the navigator on the right, it looks exactly like the foldable seat for the flight engineer on the Lancaster of a decade later. There are additional instruments above it on a panel on the fuselage side on the right. Up a step and forward are the front gun and bomb-aiming position. You can see the exposed control cables running along the left-hand side. Hardly a space suitable for the transport of troops.
The Hendon prototype K1695 rebuilt to production standard (the serial number is visible under the wing on the original photo). The thickness of the wing is particularly evident in this view.
The cockpit canopy of the Hendon can be deceptive; looking at this view in isolation you would swear it was placed centrally on the fuselage.
But if you look at this view of the same aircraft from the other side and compare it with the previous image you can clearly see the cockpit is offset to one side.
A wider view of the aircraft. Again, the thickness of the wing is evident.
The Hendon entered service with Number 38 Squadron at Mildenhall at the end of 1936, some 6 years after the first flight of the prototype (a bit of a record at the time but quite good compared to the Lockheed F-35!). The faithful prototype was upgraded and also served with the squadron. It is interesting to note that Mildenhall was probably the largest RAF airfield at the time, giving ample room for the long landing space required by the Hendons, with their lack of flaps and tendency to "float" down the runway. At one stage some of the Hendons were detached to form the nucleus of the newly reformed 115 Squadron at Marham (another airfield recently expanded), but the aircraft were returned to 38 Squadron when 115 received Handley Page Harrows as replacements. The Hendons only saw service for two years, until the end of 1938, when the squadron re-equipped with Wellingtons. During that time only two Hendons were written-off because of crashes (both at Marham). One of these (K5094) was an aircraft "hijacked" by two groundcrew for a lark; it was fitted with dual-controls and crashed because they both tried to control it at the same time. Fortunately, no one was injured.
The first production Hendon (K5085) in flight, showing off the all-over "NIVO" finish with "B" type roundels and large black serials under the wings.
Throughout their service, the Hendons were painted overall in a very dark green-grey "Night Invisible Varnish, Orfordness" (NIVO) a colour used for night-bombers by the RAF dating back to World War One. There is no photographic evidence of them ever adopting the disruptive camouflage introduced in the late 1930s. Roundels were "type B" red/blue with large black serial numbers under the wings and small black serial numbers on the rear of the fuselage and rudders. Some Hendons carried dull red stripes or diamonds on the undercarriage trouser fairings.
After withdrawal from frontline service, the primitive internal layout of the Hendon, with its narrow catwalks and awkward entrance hatch, did not lend itself to transport or "flying classroom" duties. Its lack of flaps would have made the dual-control aircraft unsuitable for use as pilot trainers for the new generation of bombers entering service. So the Hendons were retired to ground-instruction duties. It is possible that the Kestrel engines stripped from them were rebuilt and upgraded for use in Miles Master trainers. The last flight by a Hendon took place in early January 1939, 8 months before the start of WW2 in Europe. The biplane Handley-Page Heyford outlasted it in RAF service; the Heyfords seeing service until 1941 as gunnery and bombing trainers and as glider tugs.
Specification (Hendon Mk 2 production version)
Max speed: 155 mph (249 kph)
Cruising Speed: 133 mph ((214 kph)
Service ceiling: 21,400 ft (6553 m)
Range and bomload: See text above.
Defensive armament: 3 x .303 Lewis guns. One each in nose, tail and dorsal positions.
Serial numbers: Prototype K1695, Production K5085 to K5098. Cancelled order K5768 to K5771 (dedicated pilot trainers) and K6555 to K6612 (bombers).
The Hendon 6-stage development programme
Fairey had a history of the progressive development of designs to keep them up to date. The best example of this is the Fairey III series which started during the First World War with the IIIA and evolved through the B, C, D and F and then onto the Gordon and Seal that were still in service at the start of World War Two. When they first designed the Hendon, they were, of course, completely unaware of the revolution in multicellular stressed-skin wing design that was only years away (the Northrop Alpha that pioneered this type of design entered service in 1931). So it was natural for them to think of ways the Hendon could be progressively improved to meet future needs. The Fairey archivist ID Huntley described a brochure that was meant to be shown with slides that outlined the progressive improvement and refinement of the Hendon in 6 stages. Each stage would be an improvement that could be easily introduced on the production line. Unfortunately, the sole drawing that survived illustrates only the final "6th stage" aircraft, a four-engined, low-wing bomber with retractable undercarriage and enclosed turrets. It retains the offset cockpit of the Hendon and seems to be powered by RR Kestrel engines. The drawing does not show if flaps were to be incorporated.
The "6th Stage" 4 engined Hendon development.
At first glance, this design seems amazingly similar to the Avro Lancaster, but appearances can be deceptive. This "Superhendon" still had a heavy fabric-covered airframe, low-powered Kestrel engines (giving only a third the power of the Lancaster's Merlin engines), manual (rather than power-driven) turrets only armed with a single gun apiece. The bombload quoted was only the same as the Hendon, 2,548 lb (1156 Kg), tiny compared to aircraft like the Lancaster Halifax and Stirling. For deterrence value, it might have looked good in the "shop window" in 1936-38 but, it's hardly an aircraft you would choose to go to war in during the 1940s.
Above and below: What a Stage-6 "Superhendon" might have looked like in service.
¹The ranks, duties and training of the aircrew of British bombers were changed considerably in the late 1930s and early 40s. Read "Observers and Navigators" by CG Jefford for a full understanding.
Fairey Aircraft Since 1915 : by HA Taylor,. Published by Putnam. ISBN 0-370-00065-X.
The Fairey Hendon : a two-part article by ID Huntley in the January and February 1974 editions of Aircraft Illustrated magazine. The February edition includes an excellent scale plan that shows the layout of the bomb-cells.
RAF Bomber Command and its aircraft 1936-1940 : by James Goulding and Philip Moyes, first published in 1975, reprinted in 2002 by Ian Allan publishing. ISBN 07110 0627 X.
The British Bomber since 1914 : by Peter Lewis, published by Putnam. ISBN 0 370 10040 9.