Flightdeck Friday – Fleet Air Arm Edition: The Sea Vixen

Twin engines generating over 14,000 lb of total thrust powering the aircraft to a max speed of 710 mph at low altitudes and a service ceiling of 55,000 ft; provisions for a crew of two – one of whom was dedicated to work the powerful air intercept radar that was integrated into a weapons system controlling rockets and bombs, and envisioned for use by naval and air forces. A description of the F4H-1 Phantom? Nope – that was still almost a decade away from reality. This was the De Havilland DH-110, designed from Specification No.40/46, issued in 1947 and now flying in late 1951.

The DH-110 was one of the most advanced aircraft to take the skies in 1951. Stemming from Specification N.40/46, which called for a twin-jet naval night fighter to replace the de Havilland Sea Hornet piston fighter, with a top speed of at least 500kt from sea level to 20,000ft and a maximum all-up-weight of 30,000lb, the cutting edge design incorporated swept wings, a high mounted tail on twin booms, full hydraulic-powered flight controls and side-by-side seating for the pilot and radar operator in the broad fuselage mandated by use of the twin Rolls Royce Avon engines. Why twin booms? After all, across the Atlantic the Americans had adopted twin engines (albeit anemic ones) quite well in a conventional design, buried in the wing roots of the McDonnell XFH-1 Banshee. In part, this was a continuation of De Havilland’s experience with the Venom and Vampire aircraft where the engine exhausts were on the aircraft centerline (unlike the Banshee) minimizing the off-centerline thrust effects of an engine-out condition. The other benefit was the shorter distance the exhaust gases had to travel with less resultant loss of thrust (one of the reasons McDonnell chose the wing root mounting). The resultant design had striking aesthetics, giving the appearance of a graceful manta ray in flight. It was also exceptionally maneuverable (another requirement of the specification) and demonstrations flown by De Havilland’s chief test pilot, John Derry, displayed the big fighter’s promise.

Tragically, that promise would be delayed when the first prototype crashed during a flight demonstration at Farnborough on 6 Sep 1952, almost one year after its first flight. Like so many other prototypes and developmental aircraft in the 1950’s, the DH-110 crash was the result of a combination of unanticipated aerodynamic loads from transonic flight on airframe structures designed for subsonic flight. In this case, the wing structure used for the Vampire and Venom proved to be incapable of sustaining the forces from a supersonic dive followed by a rolling pullout. The outer wings detached from the aircraft and the rest of the aircraft broke apart in midair, killing the pilot and R/O as well as an additional 31 spectators on the ground.

Even before the tragic accident though, the Admiralty had chosen to withdraw from the program, citing concerns about the advanced designs of the aircraft (chiefly the prospect of swept wings and carrier operations, views, to be fair, that were mirrored on the other side of the Atlantic as well). For inexplicable reasons, the RAF decided to go with Gloster’s Javelin, itself a radical design (and one which would prove full of developmental issues). Overlaying all this was a government bent on the “butter” side of the guns vs. butter equation, coming on the heels almost 30 years of war or near-war conditions. Funding was significantly scaled back and forces drastically reduced. A 1950 White Paper even went so far as to speculate that the day of the manned aircraft had passed (ed: sound familiar? –SJS). Still, De Havilland pressed to resume flight trials and the Royal Navy relented, eliciting interest enough in mid-1953 that a wholly re-engineered package offered by de Havilland was accepted in the form of a decision to purchase a single navalized prototype. Capitalizing on company funded work during the interregnum; over 280 engineering change proposals were applied to what became the Sea Vixen Mk 20X which flew on 20 June 1955. Among the changes were uprated Rolls Royce Avon engines (rated at 11,230 lb st) with larger inlets, a longer nose to house the radar, new tail, provisions for CV-ops (catapult spools and tailhook), Fowler flaps instead of airbrakes and a slab-type tailplane (aka “flying tail”).

Showing somewhat more resolve than earlier in the decade, an order was placed in February 1955, before flight of the navalized prototype, for the first ten production aircraft, designated Sea Vixen FAW.1. Being a production model, these included armament fitments that had provisions for 4 x Blue Jay (later Firestreak) IR AAM’s, 2 x Microcell launchers each housing 14 folding fin rockets (in place of guns). Wing hardpoints allowed the carriage of up to 24 x 3” ground attack rockets, 150-gal fuel tanks or a Buddy-store, 1,000 lb bombs or the Bullpup missile. Like the DH-110, the R/O and pilot sat abreast, with the former buried down in the fuselage (referred to as the “coal hole” by the crews), the better able to work with the radar scopes of the period.

First flight for the FAW.1 was 20 Mar 1957 and trials with the FAA began at the Intensive Trials Unit, based at NAS Yeovilton in November 1958. IOC came with No 892 Sqdn, commissioned in July 1959 and first deployment came with the HMS Ark Royal in March 1960. Vixens eventually equipped the other all weather squadrons 890, 893 and 899 for a total of 114 aircraft delivered by 1963 when production shifted to the FAW.2. The chief difference between the two marks was the upgrade of the weapons system to support the Red Top IR missile which provided an all-aspect capability missing from the Firestreak. The other notable external feature was an enlargement of the booms supporting the tail to incorporate the area-rule concept and in the process, gained additional internal fuel capacity.

Operationally, the Sea Vixen’s primary mission was all weather air defense and practiced all manner of intercepts from 500 ft to FL400. As it was a multi-mission aircraft (strike fighter?) its bag of tricks also included close air support, war at sea strikes and, of course, tanking via the buddy store. While it never saw combat, the Sea Vixen still participated in a number of show of force events that included an appearance by HMS Victorious off Kuwait in 1961 when Iraqi president Kassem threatened to invade and annex the country. Sea Vixens also figured prominently in action over Tanganyika in January 1964, when Vixens from HMS Centaur flew air cover for marines landing to support government troops and RAF transports bringing supplies and equipment. But the end of conventional CV’s was looming large. The 1966 Defence White Paper cancelled the navy’s hoped-for new carrier CVA-01 (along with many other defense projects, including the RAF’s highly advanced TSR.2 strike aircraft). The RAF, claiming global reach, asserted their ability to reach any spot on the globe as easily as the navy’s carrier force. And yet, these ‘obsolete’ carriers were called on once again when Rhodesia declared independence – the RN being tasked to prevent oil from reaching the country. Ironically, the aircraft the RAF chose over the DH-110, the Javelin, suffered a number of embarrassing problems when they deployed to the area and proved completely ineffective. The Sea Vixen’s final mission of note was to oversee the withdrawal of British forces from Aden in 1967. By 1972 almost all of the Sea Vixens had been withdrawn from service, replaced by the F-4K Phantom FG.Mk.1.

Operations with the Sea Vixen were not without cost. Between 1962 and 1970, fifty-one aircrew were lost in thirty accidents in the aircraft. To be sure, the 1950’s and 60’s saw their fair share of aircraft and aircrew losses because of the exploratory nature of operating jet aircraft in the less forgiving trans- and supersonic realms, as well as the very real challenges operating high performance jet aircraft in the CV environment provided. For the Sea Vixen, many of the losses could be attributed to the Glow Worm mission and the accompanying risks and challenges it posed from both an aeronautical adaptability standpoint for the pilot as well as poor cockpit ergonomics.

The Sea Vixen was a remarkable aircraft whose history revolved around the phrase “if only…” If only the Admiralty had not lost its nerve in 1951 and pressed ahead with the radical new aircraft which was a world-beater… If only the government in Whitehall had not been so bent on disassembling the military in its quest for funding social programs… If only it had reached IOC at an earlier time than coincident with the American F-4…what might have evolved? At one point the Sea Vixen was under serious consideration by several NATO countries to meet their all weather interceptor needs. But the deck was stacked against it. By the time it reached operational capability, it was already being overshadowed by aircraft with greater performance and promise for growth. Today there are a surprising number of survivors in various states of assemblage and at least a one still flying.

Specifications (Sea Vixen FAW 2)

General characteristics

* Crew: 2: pilot, radar operator
* Length: 55 ft 7 in (16.94 m)
* Wingspan: 51 ft 0 in (15.54 m)
* Height: 10 ft 9 in (3.28 m)
* Wing area: 648 ft² (60.2 m²)
* Empty weight: 27,950 lb (12,680 kg)
* Loaded weight: 41,575 lb (18,860 kg)
* Powerplant: 2× Rolls-Royce Avon Mk.208 turbojets, 50 kN (11,000 lbf) each

Performance

* Maximum speed: Mach 0.91 (690 mph, 1,110 km/h) at sea level
* Range: 790 mi (1,270 km) with internal fuel
* Service ceiling 48,000 ft (15,000 m)
* Rate of climb: 9,000 ft/min (46 m/s)
* Wing loading: 64.2 lb/ft² (313 kg/m²)
* Thrust/weight: 0.54

Armament

* Missiles: 4× Red Top or Firestreak air-to-air missiles
* Bombs: 2× 500 lb (230 kg) bombs

Resources:

Note: There are many fine websites dedicated to a particular aircraft, but one of the absolute gems is the Sea Vixen site run by Martyn H. Dean, himself a former Sea Vixen pilot (and from whence many of the above photos were sourced).  If one is looking for a template for a website dedicated to an aircraft, this is the one.

Gunston, Bill.  Fighters of the Fifties.  Specialty Press: Osceola, WI, 1981.
Green, William.  The World’s Fighting Planes. Doubleday & Co: New York, 1965
Thunder and LIghtnings: Sea Vixen
Condors49ers: DeHavilland Sea Vixen
DeHavilland - Sea Vixen
De Havilland Sea Vixen