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The Tanker Conversions

Although designed as a civil airliner the VC10 has proven to be an excellent platform for Air to Air Refuelling (AAR), and in this role has served the Royal Air Force (RAF) for almost twenty years. The VC10 was never designed as a tanker and it took quite a bit of work to convert the different airframes for their new role. Three conversion programs took place, creating four different types.

The K2 and K3 conversions


Ex-Gulf Air and EAA VC10s during the early stages of dismantling.
Photo copyright BAE SYSTEMS

In 1978 the RAF announced that instead of converting yet another bomber, which they didn't have anyway (after the Valiant, Victor and Vulcan conversions no more large bombers have been built), it would form a squadron of nine dedicated tanker aircraft. These tankers were sorely needed to support the forthcoming Tornado F.2 fleet in its air defense role. After a successful feasibility study it was decided that the tanker fleet would be created by converting ex-civil VC10s. By that time BAe was able to supply several VC10s 'off the shelf' as it had recently repossessed the four remaining EAA Supers from the bankruptcy of the airline, and Gulf Air had also terminated its VC10 operations. Successful negotiations saw these nine aircraft sold to the RAF, and a contract was awarded to British Aerospace Filton for the huge task of converting the airframes.

The RAF's 'wish list' was extensive: three refuelling points, extra fuel tanks, commonality with the existing C Mk 1 fleet, self supporting capabilities and a small passenger capability to top things off, and this from two completely different types: ex-BOAC / Gulf Air Type 1101s (becoming K2s) and EAA Type 1154s (becoming K3s). The work was carried out in the huge 'Brabazon hangar' at Filton, and to start with, the airframes were completely stripped to the bare structural members. Aircraft awaiting treatment were protected by 'Driclad' bags with internal dehumidification which allowed movement of the aircraft if needed. Up to six airframes would be inside the hangar for the structural modifications necessary.


  • The underwing refuelling pod seen on K3 ZA148
    Photo J. van Hest
    Five cylindrical fuel cells were mounted inside the fuselage holding 3,500 imp gallon. The K3s had the advantage of the cargo door which was used to get the fuel cells into the fuselage before being sealed shut, but on the K2s a section of the top fuselage skin was removed to get the cells inside.
  • The rear cargo hold area was converted to hold the fuselage hose drum unit (HDU). The area had to be strengthened for this, and new pressure bulkheads were mounted fore and aft of the HDU with a pressure floor above and strengthened sidewalls.
  • New structural members were mounted between the front and rear spar in the outer wings to support the fixed pylons that were to hold the underwing refuelling pods.
  • Rolls Royce Conway Mk 550 engines were fitted to the K2s, creating similarity with the K3s and C Mk1s. Thrust reversers are fitted to the outboard engines only.
  • The extreme end of the fuselage was modified to fit a Turbomeca 'Artouste' APU which would provide electrical power and bleed air for engine starting.
  • The fuel system was modified with extra pumps and fuel lines to connect the HDUs and the new fuel cells.
  • A refuelling probe was installed on the nose to enable the tanker aircraft itself to be refueled.
  • A CCTV camera was installed under the fuselage to monitor refuelling operations.
  • Lights illuminating the refuelling points were fitted to the fuselage and wing trailing edge.
  • The left front entrance door was converted to enable crew members to exit the aircraft by parachute in case of emergency. Because of this the right front service door would from now on be the main entrance door. The escape chute was extensively tested, but later on in the service life of the tankers a decision was made to block off the system as there was no need for it.

Photos of the conversion process

1. Two VC10s in the Brabazon Hangar at Filton at the start of the conversion.
2. ZA141 slowly turning into a VC10 K2 tanker, with another airframe covered in a Driclad bag behind it.
3. ZA141 now looking more complete.

Photos copyright Airbus UK

1. ZA141, same location as the previous photo but this one in black and white.
2. Engine runs on ZA141 with the fire services looking on.
3. ZA141 in the hangar nearing completion of the conversion process.

Photos copyright Airbus UK

1. An unknown tanker, looking ready for delivery.
2. This could be ZA144 looking at the camouflage colours on the rudders. These were delivered painted after refurbishment but in the meantime the decision had been made to finish the aircraft in the hemp scheme.

Photos copyright Airbus UK

First flight and testing

The BAe newsletter announcing ZA141's first flight

The first K2 conversion (ZA141) made its first flight in its new guise on 22 June 1982 and flew most of the proving flights for the new tankers. It was finished in a grey and green camouflage scheme that was not adopted for the VC10 tanker fleet, all the other aircraft being finished in an all over hemp colour. ZA141 did enter service as the only camouflaged VC10 tanker, sometimes being referred to as 'The Lizard' because of its colouring. This was coined when the need arose to specify the 'aircraft color' on a US flight plan, lizard being their term for camouflage. It was later repainted to match the other VC10 tankers.

The test crews spoke fondly of the VC10 conversions. Each one was a bit different, and "each one has its own little character, they all have their little quirks." These quirks can sometimes lead to problems, as proven by ZA141 while undergoing resonance testing at altitude. The aircraft failed to correct itself after a manoeuvre and, to gain the speed necessary to carry out the test, the aircraft was in a steep dive. Due to the fact that is was a Standard VC10 it had a dry fin and, unknown to the crew, there was a slight crack in an inspection plate. During such manoeuvres the whole tail section bends slightly from side to side and the increased stress on the tail frame caused a strut to snap and pierce through the skin. Had the crew not reacted swiftly, the continued stress would have caused the two remaining struts to snap which would have led to the loss of the tail. The aircraft landed safely and was re-fitted with the tail of an ex-BUA VC10, G-ATDJ. The RAF had bought G-ATDJ and it was given the serial number XX914. It had recently been withdrawn from use as a test-bed at the Royal Aircraft Establishment at Bedford.

ZA142 seen on the day of its last operational flight

Photo Crown Copyright/Darren Hall, MOD UK

It took several years for all the aircraft to slowly advance through the Brabazon hangar towards their new life as VC10 tankers but in May 1987 the last K3 of the program was delivered to 101 squadron. With this delivery the full complement of nine was finally operational, and with a new lease of life the VC10s were soon flying long hours again, only this time with a military crew, and a lot less passengers.

The BOAC/Gulf Air airframes were the oldest VC10s around and were also the first to be withdrawn again. In March 2001 ZA142 made the last flight of an operational K2 and was soon flown to St. Athan and scrapped. Since then, only the nose section of ZA144 is still around for training purposes, see here:

Surviving Bits & Pieces

The ex-British Airways Supers

In early 1981 the last of the British Airways VC10's had been retired, Fourteen of these aircraft were bought by the RAF, along with a supply of parts and engines. When the Victor K2 tanker fleet would be nearing the end of its fatigue life, the RAF would be facing a shortage in tankers again. As the K2 and K3 conversions were still being carried out, there was no need to start converting the Supers immediately, in the meantime they were stored at RAF Abingdon and Brize Norton. The airplanes were either wrapped in 'Driclad' bags, or when these were torn to shreds by the prevailing winds, covered in a sticky sealant preservative that caused layers of grime to stick to the airplanes.

ZD235, ex G-ASGG, landing at Filton after the 20 minute ferry flight

Photo J. Maynard

In 1985 the RAF slowly started scrapping the aircraft with the highest number of airframe hours. Another four years later the Ministry of Defence invited tenders for the conversion of five of the Super VC10s to K4s and conversion of the 10 squadron VC10 C Mk 1s to C Mk 1 Ks. Eventually BAe was awarded the contract in early 1990, with FR Aviation at Hurn as a subcontractor for the C Mk 1 conversions. Upon inspection by the BAe Woodford division it was found that the long years in storage had caused severe corrosion problems and the MOD realised that major structural work was needed to ensure a future career for the airframes. The major corrosion problems were centered on the wing torque box, and the next step was figuring out whether this could be rectified in situ, so that the airframes could be ferried prior to the conversion work. After a trial repair on G-ARVJ, which by this time was lying on the RAF Brize Norton scrap dump without wings, the conclusion was reached that through careful stress jacking of the fuselage the repair to the centre section torque box was feasible and could be done economically. Readying the airframes for the ferry to Filton involved a lot more then just the torque box repairs. Lorry loads of spares started arriving at RAF Abingdon and many components were exchanged to make the first aircraft, ZD242, at least fleetingly airworthy. The hardest task during the preparations was stripping off the grime and preservative that had accumulated on the airframe. The actual ferry flight on 27 July 1990 was pretty uneventful, with the gear locked down, slats and flaps hand-wound out and locked and the tailplane set to a fixed setting for 210 knots at 6000 feet, nothing could go wrong. And nothing did, after two extra circuits of the airfield the aircraft made a perfect landing.

ZD230 emerging in a new coat of primer paint
Photo J. Maynard

Within several weeks, the five aircraft selected for conversion had arrived at Filton, and work had started in earnest. The process by which these airliners would give up their civil identity and emerge as a purposeful piece of military hardware would mainly go along the lines of the earlier K2/K3 conversions, but there were large differences between the programs. The K2s and K3s had still been airworthy aircraft, even though some of them had been stored briefly. The K4s however, even though the ferry flights belied the idea, were not. Having stood idle for years, many modifications that had been incorporated in the other VC10s in RAF service would have to be incorporated in the conversion program to get the modification standards up to spec. Also, the ferry flights had been made on a minimum of serviceable equipment, now all the systems had to be restored to fully working order, and not only that, they would be serving with the RAF for many years to come. In effect the aircraft were completely stripped to the bare airframes, and in some places beyond that, and completely rebuilt again. When the first airframe emerged from the hangar in its new colours the RAF took on an aircraft with a new lease of life.


Two ex-BA Super VC10s during the conversion process into a VC10 K4 Tanker

An overview of the 'production line' in the Brabazon Hangar at Filton

Photos copyright Airbus UK


A VC10 K4 pictured at Avalon, Australia
Photo David Pryde via www.airliners.net

There were some changes compared to the earlier conversions though. The most striking one was the decision not to incorporate the extra fuselage tanks. To install these, a hole would have to be cut in the fuselage similar to the K2 conversion, and with the high airframe hours on these airframes the RAF did not want to weaken the structure of the airframe. The K4s do have the fin tank which holds 1,750 gallons, but even without the extra 3,500 gallons that the fuselage tanks would have added, the K4 is a very capable refuelling platform. As the latest additions to 101 squadron the K4s sport the latest equipment available on the flight deck, and therefore the crews prefer them to the earlier models. Especially the extra radios that were installed in the K4s but not in the earlier conversions are very much appreciated during a busy sortie.

So what happened to the other ex-BOAC Super VC10's that were bought by the RAF but were never converted into tankers? Mainly they were robbed of all spare parts and the remains were scrapped. One or two airframes were used for fatigue testing and were broken down for this purpose, and others ended up on the fire dump. G-ASGE was one of these aircraft, and the airframe of what was once a proud BOAC airliner is shown below with a HP Hastings nose section in place of the original nose.


G-ASGE with added Handley-Page Hastings nose on the fire dump at Catterick
Photo from the Oldprops website

As this image shows G-ASGD (ZD232) had already been stripped of many useful parts in 1987
Photo M. Burrell

Also G-ASGD seen in 1991 during dismantling, seeing this makes me wonder what sort of stuff is covering her in the other photo
Photo F. Goodman via www.Airliners.net

The C Mk 1 K

The C Mk 1 was the first VC10 type in service with the RAF but was the last type to be equipped with an AAR capability. The conversion program for the remaining 13 RAF airframes was part of the contract for the K4s and was initiated in the early nineties. The contract was awarded to FR Aviation at Bournemouth, under subcontract to British Aerospace. Of the three programs this was the least extensive conversion, as only two wing refuelling points were added to the airframe.

XV109 after its conversion to a tanker / transport

Photo Peter R. Foster

At the time of the conversions the C Mk 1s were actively flying with 10 sq and therefore all the airframes had already been modified up to the latest standard, and the major changes needed to fit the two underwing refuelling pods were restricted to the outer wing sections. These were strengthened to accept the weight of the underwing pods and extra fuel lines were installed to connect these to the refuel/defuel gallery. Four new pumps were added to the main tanks to feed the fuel outwards to the refuelling pods. Monitoring the refuelling operation is the task of the flight engineer, and his cockpit station is modified for this purpose.

The first conversion (XV101) flew in June 1992 and the last (XR808) was delivered in October 1996. The aircraft have retained their full transport capabilities, and the new refuelling capabilities were only to be used when other assets are unavailable. Because of this not all the 10 sq crews were to be trained to fly AAR missions.  

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