CHAPTER ONE

VENOM FIGHTER DEVELOPMENT

Early in the development of de Havilland’s first jet fighter design, the DH 100 Vampire, the company had made plans to replace the standard 3,000lb-thrust Goblin turbo-jet engine with the more powerful Halford H2 engine. The company’s Engine Division had seen the potential of the Goblin engine and concluded that a new version, capable of producing at least 5,000lb thrust, would be required for future fighter development. The most direct method of achieving this increased thrust (without a major redesign of the engine) was to raise the maximum speed by providing a higher rate of mass airflow through the engine. This was obtained by increasing the diameter of the engine’s singlesided centrifugal impeller from 31 to 36 in; this in turn raised the air mass flow from the 60lb/sec. of the Goblin to 88lb/sec. Under this arrangement an unusually high pressure ratio of 4.67:1 was also produced. One feature that contributed to the compactness of the new engine was the dimpling of the steel cone which allowed the combustion chamber ‘cans’ to be arranged close to the axis of the engine; this brought the overall diameter down to 53 in, only 3 in more than the Goblin; the number of combustion chambers was also reduced from sixteen to ten, with each chamber being fed by a coupled pair of diffuser outlets. The new engine weighed approximately 500lb more than the Goblin and, although initially called the Halford H2, in 1943 de Havilland’s renamed its improved engine the Ghost.

Two prototype Ghost engines were built in 1944 and 1945; the second was subsequently redesigned to allow it to run at increased temperatures and so a give higher thrust rating. The construction of the Ghost resembled that of the Goblin in main essentials. The engine was built round a single rigid rotating component with bearings at the front and rear only, supported by a conical steel ‘backbone’ member, and with a compressor and diffuser casing in two sections to which the single-entry air intakes were attached. A spill-flow burner capable of producing a very fine atomised spray of fuel at altitude was also fitted, as was a Rotax twin breech, cartridge–operated turbo-starter system and a high-energy igniter system controlled by an automatic sequence operated from the cockpit.

In October 1945 a Ghost engine ran at 4,400lb thrust on the test stand and by December was developing its rated output at 5,000lb of static thrust. Unlike the Goblin, the Ghost was designed with an eye to civil as well as military needs, and in June 1948 it became the first British turbo-jet to attain full approval for civil operation with fare-paying passengers under Air Registration Board regulations. Early installations included the DH 106 Comet, a modified version of the Vampire and the SAAB J.29 jet fighter. Over 2,000 Ghost engines would eventually be built for the early Comet 1s as well as for the Venom and Sea Venom fighters for the RAF and Royal Navy, for the licence-built RM2 for Sweden, and for the Swiss Venoms and the French Aquilon naval fighters.

While the Vampire F.Mk.II and the proposed ground-attack Vampire F.Mk.IV would be fitted with Rolls-Royce Nene turbojets, de Havilland’s announced that its latest designs – the Vampire Mk.7 (which was subsequently abandoned) and the FB.Mk.8 (which, it was suggested, would eventually replace the Vampire FB.5 ground-attack aircraft) would be fitted with Ghost engines. To take advantage of the increase in thrust required from the new engine and to raise the permissible Mach number, the company revealed that the Vampire FB.Mk.8 would feature a revised ‘thin wing’, with the thickness/chord ratio reduced from 14 to 10 per cent and a leading edge taper of 17 degrees 6 minutes. The concept of a swept and thinner wing section had been an integral feature of the DH 108 tail-less research aircraft, which had been designed and built to investigate the behaviour of the swept-wing design. Although all three prototype aircraft had been lost in flying accidents during the trials programme, a great deal of important information had been gathered with regard to the development of the swept-wing layout to increase performance.

The British government showed little interest in de Havilland’s latest project. However, on 23 March 1948 the Engine Division’s modified Vampire TG278 (which had been used for the high-altitude development of the Ghost engine) established a new world height record of 59,446ft. Seizing the opportunity to exploit his new design (and no doubt influenced by the fact that the Air Ministry had decided to select the Gloster Meteor IV as the standard interceptor fighter for the RAF, thereby relegating the Vampire F.III to a less spectacular role), de Havilland’s Chief Designer R.E. Bishop immediately forwarded the company’s proposal for the ‘Thin Wing Vampire’ to the DMARD. In his letter Bishop remarked that his proposed Vampire F.Mk.8 differed from the earlier marks by having a thin wing, which would be stressed to carry underwing weapons and a jettisonable fuel tank at each tip. A Ghost 103 gas turbine engine producing 5,000lb of static thrust, new engine mounts and cowlings, redesigned air intakes and a strengthened tailplane were also features of the new design; the cockpit and canopy, however, would remain unchanged from the original design, as would the internal fuel capacity of 330 gallons. Bishop went on to confirm that a Vampire fitted with a Ghost engine had been undergoing a series of flight trials and that the limiting Mach number of the new fighter at altitude was expected to be at least 0.85 (585mph), compared with 0.79 for the Vampire. He also suggested that, since the operational requirement of the aircraft remained unchanged (i.e. as a single-seat interceptor fighter with the alternative role of a ground-attack fighter-bomber), the intention was to introduce the Vampire F.Mk.8 into service by way of modifications to existing aircraft; Mod. 700 would incorporate all the changes from the Vampire FB.5. DMARD considered Bishop’s design to be basically sensible, with no severe design or aerodynamic problems, and further commented that if a decision was made to proceed with a prototype contract, production could begin within two or three years.

Bishop also sent a copy of the brochure to the Air Ministry, outlining the firm’s development estimate. By June the CS(A) had responded by confirming its confidence in Bishop’s proposal and advising that the decision to proceed with the new design should be taken. In a later memorandum the Air Ministry intimated that its decision was partly based on the fact that the company might possibly continue with the project regardless, with a view to selling the new aircraft to other countries.

On 1 October 1948 DMARD informed the company that a contract for two prototypes (which had by now been given the new type designation DH 112) had also been approved by the CS(A) against Specification Vampire 1/P/2 with Modification Vampire/700 installed. At the end of the month the contract was formally approved at a cost of £180,000, and two Vampire FB.5 airframes, VV612 and VV613, were allocated from the production line at Preston for conversion, with both aircraft ready for collection in early 1949. They were transferred to Hatfield in mid-February.

On 2 September 1949 the first prototype, VV612, took to the air from Hatfield, piloted by John Derry. Four days later the ‘Thin Wing-type Vampire’ was officially renamed the Venom and made its public debut at the SBAC air display at Farnborough. In a spectacular display of demonstration flying, John Derry put the prototype through its paces and thrilled the crowd with a succession of loops, slow rolls and his trademark ‘Derry Turn’ – an inverted reverse turn. Until his tragic death in the DH 110 prototype at Farnborough a few years later, Derry was responsible for much of the test-flying of the Venom prototypes and was delighted with the aircraft’s impressive performance in regard to general manoeuvrability at medium altitudes, climb rate and operational ceiling. He did express concern, however, about problems with aileron flutter, and the tendency for the aircraft to experience a violent wing drop in high-speed dives above Mach 0.84.

On 14 September 1949 Specification 15/49/P was issued to cover the design and construction of the ‘Thin Wing Vampire to Operational Requirement 277’, which was written around the aircraft to incorporate all the agreed modifications. The specification also called for wing-tip drop-tanks to be fitted and the tailplane to be strengthened; although an armament load of either two 500lb or two 1,000lb bombs or eight 60lb rockets was required, the installation of ejection seats was not considered essential; it added that an initial order for 196 aircraft (sic) had already been placed. Two weeks after the specification had been issued, the decision to proceed with the Vampire F.Mk.8 – or ‘Ghost Vampire’ – was given by DOR(A) on the basis that it would replace the Vampire types at present in service with the RAF.

John Wilson, a contemporary of John Derry, joined de Havilland’s as an experimental test pilot in 1948 and was initially concerned with the flight development programme of the Vampire series. He later became involved in the Venom project, beginning with the Venom prototype in January 1950, the Venom NF.2 – in which he made the first flight in August 1950 – and the Sea Venom NF.20 in April 1951. During the period to May 1956 he made a respectable 738 test-flights in Venom aircraft.

I spent many more hours flight-testing the Venom than I did the Vampire. The ‘thin-wing Vampire’ was a brute to develop and, apart from the Venom FB.4 with its powered ailerons, never became a good aircraft. The Venom wing was not really ‘swept-back’ as were the MiG-15 and F-86 Sabre: the planform being dictated more by the need to move the centre of pressure aft to accommodate the heavier Ghost engine.

During my first test-flight of VV612, I noted in my flight-test report that it was decided to carry out a combat climb to 50,000ft, during which longitudinal stability deteriorated with altitude, and at 45,000ft the lack of stability was the most noticeable characteristic of the flight. Levelling off at 50,000ft, speed was built up in a shallow dive to Mach .80, when dive brakes were extended. Tab flutter was noted of considerable amplitude, with some aileron movement. At Mach 0.842 nose-up trim change occurred with right wing drop, which was held up with aileron, while nose-up pitch was corrected with elevator to maintain the aircraft in compressibility. Aileron response at high Mach numbers was good, crisp but rather heavy. Two landings were made and a noticeable right wing low was noted when the flaps were fully down. Impressions of the test-flight were that, although the aircraft handled much more crisply than the Vampire, the stick force had increased and the feel of the wing decreased, especially at low level.

Following a period of company trials that included stability, flutter and high-altitude handling checks, VV612 was issued to the A&AEE at Boscombe Down in May 1950 for the official handling and stability trials. It was replaced at Hatfield by the second prototype, VV613, which took to the air for the first time on 23 July. By this time both aircraft were fitted with wing fences to reduce the spanwise airflow normally associated with swept wings, thereby avoiding tip stall. John Wilson again:

I flew the prototype again in March 1950 to compare the handling characteristics following the addition of tailplane extensions, wing fences, new aileron torque tubes and re-balanced tabs. It was immediately obvious in the climb that there was a considerable increase in stick force stability, and although there was a tendency to ‘Dutch Roll’ at 40,000ft the aircraft still had positive stability – a marked improvement over the previous flight. At 45,000ft the aircraft was unstable at climb speed, deteriorating to a fair degree of instability at 48,000ft. On levelling off and increasing speed it was noticed that, at 0.75M and above 46,000ft the aircraft became stable, with stability increasing progressively with a Mach number up to 0.83M indicated. Increasing speed in the dive gave an unpleasant rapid and sudden nose-up pitch at approximately 0.86 Mach, which can hardly be called satisfactory, as there was no warning and a large positive acceleration. Misting and poor visibility limited the low-level handling, but it was immediately apparent that there was a great need for a ‘g’ suit. At 440 knots IAS there appeared to be no great change of trim. Aileron response was crisper than before but the rate of roll at this speed was not very rapid.

On 8 July 1949 an initial production order for 200 Venom FB.1s – Contract no. 6/Acft/3627/CB.7(a) – was placed with de Havilland’s, the funding for which had been authorised by the Treasury the previous March. Construction of the first order would be shared by the Hatfield, Chester and Ringway factories; Hatfield, however, was only to build the first sixteen Venom airframes because of its priority work on the Comet airliner, and the assembly line was soon switched to Chester. The first batch of aircraft was issued with the serial numbers WE255–WE483, with deliveries beginning in June 1951.

In December 1950 a second order for 85 Venom FB.1s was placed, followed by a further order for 400 aircraft in the following February. In a letter to the Air Council, the CS(A) confirmed that all orders for 1,159 (sic) Venom fighters had been placed with both de Havilland’s and the Bristol Aeroplane Company at Filton, and that by May 1954 the monthly production rate would be at a peak of 104 aircraft. The letter, however, pointed out that the Venom had been chosen before it was subjected to any rigorous flight-testing, and that it had been shown to possess some unacceptable characteristics that would introduce limitations in its role as a highspeed fighter aircraft. Doubts were also being expressed at this time as to the long-term future of the Venom following the decision not to produce the type under licence in Italy as NATO’s standard fighter-bomber. This subsequently resulted in the production contracts being amended and the number of aircraft on order being reduced. In August 1953 the third order for 400 aircraft was cut back to 90, while orders for a further 461 Venoms placed with the Bristol Aeroplane Company were all cancelled.

Between May 1950 and September 1951 both VV612 and VV613 and the first production aircraft, WE255, were flight-tested at Boscombe Down, where subsequent reports confirmed the problems found during the company’s early test programme and were highly critical of the Venom’s characteristics. The major criticisms and recommendations included the following:

• The rate of roll was considered poor without tip-tanks and deplorable with them fitted. This was partly remedied in subsequent aircraft by increasing the span of the spring tabs.

• Longitudinal stability at high altitude was unsatisfactory; this was subsequently improved by a forward shift of the centre of gravity.

• Aileron tab ‘buzz’ was generated by the operation of the air brakes, which was associated with severe tip-tank oscillation. The report recommended that the ailerons should be re-rigged in the slightly ‘up’ position.

• The high Mach number characteristics were also considered unsatisfactory because of a violent nose-up pitch at high and medium altitudes and rudder buffet at low altitudes. The latter was considered to be potentially dangerous: if the Mach number was increased sufficiently at high altitude then control of the aircraft would be lost owing to the almost simultaneous onset of aileron and elevator ineffectiveness. An investigation of ailerons with thickened trailing edges to improve their effectiveness at high Mach numbers had already begun and these would have to be, of necessity, power-operated. As an interim measure, until this system had been developed, several types of artificial warning for impending critical conditions were suggested: these included an audible warning, automatic operation of the air brakes or a stick shaker.

• Wing drop prior to the stall was excessive. Treating the wing surface with filler reduced this problem, though subsequent deterioration led to a more permanent filler being used and an improved basic wing shape being recommended.

• Airbrakes were insufficiently effective and caused aileron buffet.

• The absence of ejection seats was condemned.

In December 1950 VV612 was passed to de Havilland Engines at Hatfield to begin development flying of a Ghost engine fitted with reheat, following plans made by DOR(A) to install the system into the Venom night-fighter to improve its high-altitude performance. Earlier flight trials with a Vampire fitted with the system had shown that, within the limits of the tailpipe, such an engine was capable of giving up to 30 per cent thrust augmentation, thereby raising the static thrust to 6,700lb. In an attempt to control the area of the exit nozzle of the tailpipe to provide the desired turbine temperature and pressure conditions under both normal and augmented engine operation, development was given over to both two-position and rectangular-type, fully variable nozzles. Trials had been originally carried out during 1949 with a similar system fitted to the Goblin engine of a Vampire (VV454), and had been continued when it was fitted to a Ghost the following year. To accommodate the reheat system the tailpipe of the Venom was extended and in this form the aircraft was exhibited for the first time at the 1951 Farnborough Display by test pilot Chris Beaumont. A contemporary report of its display concluded: ‘When requiring thrust augmentation from this quite unobtrusively installed fitment, the pilot presses a button which operates the high-pressure fuel cock, and pushes a lever to ignite the extra fuel. The resulting noise is that of a gargantuan blowlamp, but the flame is less apparent than in earlier experimental installations.’ In March 1952 the scheme to fit the Venom night-fighters with reheat was dropped, chiefly on the grounds of cost. By this time VV612 was already nearing the end of its useful life. It did, however, make a final public appearance at Farnborough that same year and a further report subsequently recounted that:

This Venom FB.1, adapted for two-position DH afterburning, is silver finished and carries red bands on its wings outboard of the booms. Whereas on the reheat Venom last year the necessary modification appeared somewhat elementary, if not crude, the afterburner has now been faired into the nacelle with notable smoothness. The power boosting installation, incidentally, is primarily intended for the two-seater Venoms and Sea Venoms. R. Plenderleith was the demonstration pilot, and the most effective of his manoeuvres was his run-in with dive brakes extended, followed by retraction of the brakes and immediate opening up to full boosted power, with the afterburner glowing and emitting the characteristic cacophony.

In December 1954 VV612 was struck off charge and ended its days as a ground target on the firing ranges at Shoeburyness.

By April 1951 VV613 had been fitted with a modified tail unit and ailerons and was issued to the A&AEE for an assessment, but there was found to be no substantial improvement on the first prototype. The stalling and airbrake features criticised during the earlier trials persisted, with the additional characteristic of aileron tab ‘buzz’ at speeds above 390mph. Although the ailerons were found to be lighter, the rate of roll remained poor for an interceptor fighter, and the stalling characteristics of both aircraft were considered to be similar in that the stall was preceded by a starboard wing drop. Further trials with wing tanks fitted showed all the defects of the previous test: increased starboard wing drop prior to the stall and aileron tab ‘buzz’ producing a rapid oscillation of the tip-tank. The tanks also caused an appreciable reduction in the rate of roll and a slight reduction in the limiting Mach number. VV613 was to spend the next two years at Hatfield on a programme to remedy the problem of wing drop and aileron tab flutter, before being relegated in August 1953 for use as an instructional airframe at RNAS Arbroath.

In July 1951 the first production Venom, WE255, was flown to Boscombe Down to join the test programme on a series of gunnery trials. Before its release, de Havilland’s had carried out a number of modifications in an attempt to rectify the problems found with the second prototype. The aileron tab ‘buzz’ and associated tip-tank movement, together with the tendency for wing drop during landing, were partially cured by rigging the ailerons in the ‘up’ position and using a filler to smooth the surface of the port wing tip. These refinements were nevertheless still considered unacceptable, and the gunnery trials were subsequently discontinued when the high Mach number characteristics of the aircraft were thought to be potentially dangerous between 30,000ft and 40,000ft because of the magnitude of the nose-up pitch. Uncontrollable wing dropping at high altitude still occurred, and the use of filler on certain parts of the wing surfaces was also criticised.

During the first half of 1952 further tests with four early production aircraft (WE257, WE258, WE259 and WE260) to investigate the variations in the stalling and high Mach characteristics of individual aircraft resulted in a number of recommendations that included the fitting of wing-tip slats to improve the stalling characteristics and the installation of a ‘stick shaker’ to indicate an impending stall. As a longer-term measure more effective power-assisted controls were required in the hope that flight to even higher Mach numbers would be possible and the loss of control eliminated. Corresponding handling trials conducted with the first two aircraft (WE257 and WE258) to be fitted with production-type 78-gallon wing-tip tanks proved to be satisfactory and they were subsequently recommended for service use.

Between July 1951 and August 1952 the Venom’s official gunnery acceptance trials were carried out at Boscombe Down, using three aircraft, WE255, WE258 and WE259. Following an intensive air-firing programme, during which 117 sorties were flown and over 55,000 rounds fired in a variety of operational conditions, the installation was cleared for service use. Rocket-firing trials were also completed at the same time, with eight 3in, 60lb RPs carried on both conventional rails and in double-tier stowage under each of the wings. Two aircraft (WE258 and WE259) had Mod. 227 incorporated, which removed the trailing edge strip from the rudder and rudder tab; this improved the lateral and directional characteristics during the tests but did not appear to affect the oscillatory stability. Dives from various levels were carried out during the tests and it was found that, except at high Mach numbers, the carriage of the RPs did not affect the handling characteristics of the aircraft. Nor did the carriage of the wing-tip tanks affect the launching or firing of the RPs. The only major criticism of the aircraft in the rocket-firing role was of the excessively heavy elevator stick forces at low altitude, which prevented full advantage being taken of the attainable airspeeds.

The armament trials programme received a slight setback on 25 November 1952 when one of the Venoms (WE258), while returning from a bomb-handling sortie at Porton, collided with a Vickers Valetta in the circuit at Boscombe Down. Although the passengers and crew of the transport aircraft were uninjured, the pilot of the Venom, Sqn Ldr C.G. Clark, was unfortunately killed.

During the summer of 1952 a number of refinements were made to WE272 in an attempt to improve the stalling characteristics of the Venom. These included: Mod. 241, to introduce 10lb lead balance weights in the nose of the wing-tip tanks to eliminate wingtip tank oscillation; Mod. 242, to install small, fixed wing-tip slats inboard of the tip-tanks to improve the stalling characteristics of the aircraft; and Mod. 251, to replace the round trailing edge strip of the aileron spring tabs with a flat section strip to eliminate aileron tab ‘buzz’. Following a series of aileron flutter tests at Hatfield, the aircraft was then flown to Boscombe Down in August 1952 where, over the next eight months, further handling tests were carried out to evaluate the modifications. The subsequent report concluded that they had proved highly successful on this particular aircraft but that simultaneous tests carried out with another, similarly modified, aircraft had shown that the original handling characteristics still occurred and that further work with power-operated flying controls was essential.

EJECTION SEATS

One constant demand throughout the Venom’s development trials was for the fitting of an ejection seat, but this proved to be a source of numerous problems for the design team at de Havilland’s. As far back as 1946 preliminary studies had shown that such a seat could not be installed into a standard Vampire cockpit without considerable alterations to the cockpit and airframe structure, so the requirement had been temporarily dropped. By May 1950 the Martin-Baker Company had redesigned their basic ejection seat structure and successfully fitted it into a Vampire fuselage at their factory at Denham. To confirm that the cockpit arrangements were suitable for the Venom, a further Vampire (VZ835) was allocated to the trials programme and modified to represent an operational aircraft. A meeting held at Hatfield the following January discussed the various alterations made to the MB.1E seat, which included modifications to the seat guide rails, the fitting of a shorter stroke jack and the inclusion of special foot rails owing to the proximity of the control column torque link. The face of the headrest pad should also be brought forward. Further requirements included an increase in the travel of the footrest tubes to ensure that the pilot’s thighs were protected during ejection and the possible provision for head armour.

In January 1953 WE315 was delivered to Christchurch and became the first Venom to be fitted with an ejection seat, remaining with the company as a trials aircraft until late 1955. By this time, however, Mod. 80 had been introduced onto the assembly lines. This provided for the installation of either Martin-Baker 1F or 2F ejection seats into production aircraft. Although basically similar in design, the Mk.1F was a manual release seat, whereas the Mk.2F automatically released the pilot from the seat and opened his parachute. This would only happen at an altitude of 10,000ft or less, where a barostat would allow an automatic time cycle to start. This delayed separation from the seat for five seconds to allow the seat to slow down before the shock of parachute opening. This delay was later (under Mod. 205) decreased to three seconds to reduce the minimum height for safe ejection. Deliveries of the first Venom aircraft to be fitted with ejection seats began in early 1954.

A total of 375 Venom FB.1s and a further 18 Venom FB.50s (the export version sold to Italy and Iraq) were eventually built, with the last pair – WR308 and WR310 – being delivered in May 1955. A further 126 FB.1s were built under licence in Switzerland, together with 24 FB.1Rs for use in the reconnaissance role.

THE VENOM FB.4

One of the chief criticisms made by the A&AEE during the earlier tests carried out on the Venom was the loss of elevator and aileron control at high Mach numbers. The main problem was considered to be the aircraft’s flying controls. These were connected to the control surfaces by cable circuits that stretched as the speed of the aircraft increased and prevented the ailerons from achieving their full travel. Redesigning the trailing edge of the ailerons had helped to improve their effectiveness at high Mach numbers, while the fitting of spring tabs to the elevator and ailerons reduced the heavy stick forces; it was clear, however, that power-operated controls would also be needed.

In February 1952 a production Venom FB.1, WE260, was flown to Hurn where it was fitted with a new tail unit and power-operated ailerons of a larger chord. Hydraulically operated servodyne units were mounted on the rear spars of the main plane, the body of which was attached to the ailerons by an adjustable connecting rod. No aerodynamic loads were fed back to the control column so an adjustable spring strut unit was also incorporated in the system to give artificial ‘feel’ to the pilot while the ailerons were in ‘Power’. In the event of a hydraulic power failure, the system automatically changed over to ‘Manual’ control. Manual or powered aileron control could be selected in flight by means of a control valve on the pilot’s instrument panel close to the cockpit floor. If the hydraulic pump failed, resulting in a pressure drop, an additional audio warning sounded in the pilot’s earphones. The work to modify the aircraft was covered under Mod. 371.

Although the work on the system was briefly interrupted in April 1952 when the aircraft was flown to Boscombe Down for trials of the ‘stick shaker’ installation, it returned to Hatfield in June for further flight development work of the power controls. The following year it was flown back to the A&AEE for a preliminary assessment of the system, which concluded that the power-operated ailerons improved the high-altitude high Mach number characteristics of the aircraft by making the wing drop controllable, and that the rate of roll was also enhanced. It was also noted that the aileron spring tab ‘buzz’ and the associated wing-tip tank oscillations previously noted during the earlier trials of the Venom 1 had been eliminated.

With the number of modifications required for the standard airframe, the designation Venom FB.4 was selected for the improved version of the fighter. All design work was transferred to Christchurch, and in the autumn of 1953 a Venom FB.1, WE381, was taken from the production line at Chester and flown to Christchurch for conversion to the prototype FB.4. Although it retained the Ghost 103 engine, the tail unit was completely revised: to prevent excessive yaw and possible rudder locking at low speeds the height of the rudder was slightly increased and its shape altered to give a more flattened appearance. Additional rear ‘bullet’ fairings were also fitted at the fin/tailplane junction to improve handling by reducing elevator and rudder buffeting at high Mach numbers. The fins were removed from the wing-tip tanks, and additional 80-gallon streamlined fuel tanks could be mounted on pylons under the wings. Hydraulically operated flying controls were fitted as standard, as were Martin-Baker Mk.2F ejection seats. The prototype first flew on 29 December 1953 and was retained at Hurn for trials work until the following May, when it was flown to the A&AEE for the official handling trials. Although the preliminary trials found that the power controls did improve lateral control at high Mach numbers, they also revealed an excessive stick force at low altitude on this particular aircraft and it was returned to the company for further investigation.

The CS(A) decided to proceed with the new system, having already given its approval for work to begin on installing power-operated ailerons in the Venom FB.1, Venom NF.3 and the Sea Venom FAW.21 during the previous April:

Flight trials of the Venom FB.1 with power-operated ailerons at de Havilland’s by company and A&AEE pilots have proved so successful that we have agreed that they should be fitted as soon as possible. The system has not, however, proved entirely satisfactory but we understand that the firm proposes to introduce an elevator with a wider chord on the Venom 3 to take advantage of the increase in critical Mach number. It is also proposed to fit electrical trim tabs and new elevators and ailerons.

In October 1954 WE381 was transferred to Boscombe Down for the CA release trials and further handling tests with 80-gallon pylon drop-tanks, its place on the company’s trials and development programme at Hatfield being taken by another Venom FB.4, WR406. The A&AEE report was favourable towards the changes introduced in the FB.4, which resulted in an improvement in the handling qualities when compared to the earlier FB.1. The power-operated ailerons were seen to reduce the aileron forces and improve the rate of roll, while the high Mach number characteristics were now relatively mild and the severe wing drop experienced on the FB.1 was no longer present. Apart from certain criticisms made of the cockpit arrangement, the worst feature of the aircraft was considered to be the heavy elevator forces required to manoeuvre at low altitude. This criticism was particularly serious in view of the