60 years of the de Havilland 110 Sea Vixen

It is 60 years to the day that the de Havilland D.H.110 made its first flight at Hatfield.

For me no other type has encapsulated the era of early fast-jet test flying, British political military indecision, and the heyday of British test piloting as the 110 did. The drawn-out and late end result was a superbly, capable naval all weather fighter in the shape of the Sea Vixen.

A Brave New Fighter Is Born

The 110 was de Havillands’ submission to a January 1947 specification N.40/46 to reflect the Naval Staff operational requirements of NR/A.14 (itself the results of a meeting between D.H.s’ R.E. Bishop and Rear-Admiral M.S. Slattery, RN/MoS in 1946) calling for a two seat, twin jet, radar equipped, 30mm cannon armed, all weather fighter (FAW) for Fleet Air Arm use primarily aboard their new Audacious Class of carriers. The submitted design was close enough to be put forward for the Air Ministrys’ spec F.44/46 of August 1947, itself based on OR.227 which called for a night fighter aircraft very similar to the N.40/46 but for RAF use. In March 1948 the RAF issued a revised specification, F.4/48, which more closely reflected the 110s capabilities and refined the details of the intended service aircraft. Unfortunately for de Havilland Gloster Aircraft submitted their G.A.5 design to this latter spec.

Ronald E. Bishop C.B.E. headed the design team which also featured J.P.Phil Smith C.B.E and W.A.Bill Tamblin O.B.E., from early 1947 the D.H.110 drawings and models bore a close resemblance to the final service machine, the large swept wings, side by side turbojets and crew positioning, and probably most distinctly the twin tail booms with the tailplane mounted high up on the swept fins. Two features changed over a short period, the tailplane was trialled with both a rear and a forward swept layout, coupled with the fact that it was mounted between the booms this resulted in a strange ‘boomerang’ appearance in planform. Eventually it ended up as the straight edged affair that was fitted to all machines. The crew compartment originally bore a strong resemblance to the Mosquito night fighter layout and canopy arrangement (later refined in Vampire and Venom NFs/FAWs) and this was favoured for better crew cooperation, it was also seen that it would have to be modified to allow the successful fitment and use of ejection seats, and this is when the design evolved to the highly distinctive, though restricted (and criticised in service) later cockpit layout of a pilots fighter style canopy offset to port and radar operators position buried within the fuselage to stb’d. Envisaged engines had also changed from the Metrovick F.9 to the Rolls Royce A.J.65 (Axial Jet 6,500Ib thrust).

During the late 1940s more specifications were issued and the design was refined, however the Royal Navy dropped the D.H.110 design in favour of a Fairey submission to a new specification, N.14/49. The RAF, after several meetings and specific concerns (and Bishops’ reassurances) over the use of British AI radar as opposed to the American AN/APG-43 with its superior displays (as later used in the Javelin as AI.22) and the knock on consequences for the radar operators poor external visibility, decided to go ahead and order five prototypes of the thirteen originally envisaged when the RN were onboard with the project. Of these only WG236 and ‘240 completed.
When the first 110 was rolled out at Hatfield it presented a dramatic looking and advanced radar equipped fighter, distinguished and legendary Flight Test-pilot John Cunningham (C.B.E., D.S.O., D.F.C. & Bars) the carried out taxy trials on the 16th September 1951, and on the 26th he took off with Flight-Test observer Tony Fairbrother for a 46 minute maiden flight.

This aircraft then underwent an in-depth test programme, and alongside WG240, which first flew in 25th July 1952, conducted a set of demonstrations to RAF and USAF delegations. Both aircraft were powered by the AJ.65 which were now known as the Avon, ‘236 being powered by the early 6,500 Ib RA.3.
WG236 had a series of small aerodynamic and strengthening modifications made to it, while WG240 was rolled out as the definitive DH.110, it looked very dramatic in its all over gloss black ‘night fighter’ scheme, it was also powered by the more powerful 7,500 Ib Avon RA.7s.

Tragedy And Cancellation

The Sea Vixen story cannot be told without the mention of the tragedy at the Farnborough SBAC show of September 1952, to this day it remains the UKs’ worst air show disaster and was to have serious implications to the whole DH110 programme.
John Derry DFC had taken over John Cunningham as the fast-jet test-pilot at de Havilland, Cunningham moving over to the equally valuable Comet trials programme. He was a pilot of great renown, especially for his RAF Typhoon operations, demonstration test-flying, and of course being the first British pilot to break the sound barrier, while flying the D.H.108. He was a house hold name in an era where the test-pilot was highly revered and it seemed that new jet aircraft were appearing all the time, both were appearing in the latest movies (most notably, and ironically ‘The Sound Barrier’), the SBAC show at Farnborough was arguably the arena which showcased all of this to the public and so both the D.H.110 and Derry were highly anticipated. Throughout the show week the lighter and more powerful (not to mention the dramatic black look with white ‘de Havilland 110 Day and Night Fighter – Rolls Royce Avon’ script) of the two prototypes, WG240, had been flying the demonstrations, including laying a sonic boom for the crowds to marvel at, it suffered engine problems on the Saturday and so WG236 was substituted. After flying in a shallow dive and leaving a sonic boom it darted low across the crowd line before performing a tight turn to port, the crowd then witnessed a separation of major parts of the airframe in front of them, the cockpit came crashing to the ground in front of the crowd line, Derry and Flight test Observer Tony Richards were killed instantly, the inner wings and booms came fluttering down like a Sycamore leaf and crashed in the parked aircraft area. Crucially the engines had separated from the airframe and had continued in a trajectory into a crowd area and a car park, and it was these that had caused the deaths of 29 spectators, aswel as injuring 63 others.

There was immediate blame by the uninitiated, doubtlessly fuelled by the hype surrounding the sound barrier at the time, apportioned to the supersonic runs, however it was found through extensive manufacturers and AIB investigations to have been a complex structural failure which started in the stb’d wing outer leading edge. The wing was also found to be much weaker than initially thought, lacking in outboard forward spars and relying ion reinforced ‘D’ section leading edges. Many lessons, both for the aircraft industry and for air show guidelines were digested after this event. WG236 had made a total of 133 flights.

Within a month of the tragic accident the RAF withdrew from the DH.110 programme, and the Gloster GA.5 was chosen as the RAFs all weather fighter. It had slightly inferior performance in some respects to the 110 but crucially it could be fitted with the American AI.22 radar, alternatively with the British AI.17, and with their superior displays this allowed for a far better crew placement under a tandem canopy and two sets of eyes to be available when needed. The Javelin went on to serve the RAF until 1968.

Below, 2nd prototype WG240 in its first and very short lived natural metal sceme. (source unknown)