More stories of the development of the Standard and Super VC10 from Maurice Ungless.
Part 2: Tropical trials and equator crossings
By the time the first tropical trials started the "Beaver Tail" had been designed, constructed and fitted, although there was still no inner wing fence incorporated into the configuration. It was now time, after about a year since the 1st flight, for the tropical trials of the VC10 to commence. On 12th August 1963 Standard VC10 G-ARVB left Wisley en-route to Madrid Airport Spain and then onto Torrejon NATO Airbase nearby, for 4 weeks of tropical trials.
VC10 G-ARVB was the first and possibly only VC10 flight to land and take-off at Madrid Airport Spain, but certainly the first and only VC10 flight to land and take-off at Torrejon Nato Air base near Madrid Spain. Madrid, I believe, was only served by BEA, BOAC had no route network through any Spanish Airport as far as I know. The far side of Torrejon Airfield was a Nato Air Force Base and Spanish Fighter Squadron Base. For these tropical trials the VC10 was based on the Spanish Memorial operational base with hangers housing WW2 German Aircraft, Heinkels, Messerschmitts and Junkers.The reason for the Tropical Trials for any aircraft type is to gain information that had only previously been available from calculations in design and had to be proved as correct in actual operational circumstances, at a hot and high location, usually about 5000ft altitude, which Torrejon, Spain and Johannesburg, South Africa are. Most of these configurations had been already carried out during trials at home base Wisley or Boscombe Down with various aircraft before the tropical trials commenced. Tropical Trials were mostly, but not limited to, runway performance for Take-Off length of runs to VR at different weights and flap settings. Landing length of runs with different configurations: full flaps available, no flaps available as well as slats extended or retracted, also at different landing weights. Full thrust reversers available, none or a combination. Full air-brakes available, none or a combination. Full wheel brakes available or none. In fact every combination of the above failures of systems to correctly work. All this information would be collated for inclusion into the Flight Manual for reference by the pilots in normal circumstances and abnormal circumstances. Graphs for all conditions of aircraft weight, airport altitudes, pressures and temperatures throughout the perceived range of eventualities to be encountered during operational service. Also during these Tropical Trials information was collated as to the different aircraft systems operation and performance, such as air conditioning, cabin pressurisation, hydraulics, pneumatics, de-icing, fuel supplies and storage, undercarriage and brake performance, engine performance on take off and landing and extended running in ground conditions. All parameters for system analysis being recorded by fixed cameras on various instrument cabinets in the aircraft cabin, also being monitored by several flight test observers seated at each cabinet. The cameras were removed after each flight and the information recorded on film sent to the analysis laboratory.
The first group of runway trials were termed "accelerated stop test", (rejected or abandoned take-off). These tests were carried out at various take-off weights and V1 speeds and were recorded by ground based cameras at the side of the runway. As an aid for focusing these cameras the aircraft had a chequered square painted on the fuselage as a focus point. After each run the aircraft returned to the dispersal apron for a new set of brakes, and maybe tyres if considered applicable. To provide an insight into the work that had to be carried out between these runs, the following is an explanation of the procedures for carrying out this operation.
First job was to remove its protection panel and fit the undercarriage "bogie beam"/"truck" stirrup block. Then the "bogie beam"/"truck" stirrup jack was positioned to elevate one end of the "bogie beam"/"truck", with brakes selected "off". Jacking was effected until a working clearance between ground and tyre on the wheel assembly was obtained. Next job was to deflate the tyre to approximately 25 psi from about 130psi. Cooling fan guard and blade removed, axle nut split pin and locking bolt & nut removed, and the axle wheel retainer nut removed, along with a large keyed washer/spacer, then fitting the axle thread protector, then the wheel assembly was removed. The whole brake unit wasn't changed, only what was termed as the brake unit "heat pack". This consists of a full set of brake unit stators. These are the flat metal disc plates that have about 10 to 12 separate disc brake pads attached to the face of the disc plates. On about six or seven disc plate units in the middle of the pack, both sides have pads fitted. On the pressure plate only the operational side of the disc, the dynamic side, contains brake pads and the same goes for the thrust plate on its operational or dynamic side. The thrust plate is fitted adjacent to the brake unit hydraulic rams of which there are about seven or eight. The pressure plate, sometimes known as the back plate, is on the brake unit hub end and is attached by a ring of bolts, torque loaded and wire-locked. The stators are keyed to the brake unit hub by cut outs on the inner circumferential edge of the disc plates. Suitably shaped rails run from inboard to outboard on the outer circumference of the brake unit hub to engage these disc cut outs. After removal of the old used stators along with the rotors, which were re-used if not damaged, the brake compensators had to be reset. These units are cylindrical in shape, mounted on the brake unit inner body, spring loaded and consist of a stem that is connected to the inner thrust plate. The stem runs through a friction collet that is attached to the spring within the compensator which allows normal movement of the brake assembly when applied, but when the brake is released the spring will pull back the thrust plate to allow a working clearance between stators and rotors so there are no frictional loads between the two, allowing free movement for the wheel to rotate normally with brakes off. The stem passing through this friction collet allows the compensator to take up wear in the brake unit disc plates during service and provides a working clearance to the assembly with brakes released. Also present on the assembly was a wear indicator for engineers to gauge when to change "Heat Packs" or whole brake units during service. The compensators could either be removed from the brake assembly by removing a cir-clip, before resetting it, or the compensator could be reset in situ with the correct tool. The rotors are segmented into about eight or nine plates about half an inch thick and connected together at their ends by a type of dove tail joint, male on one to a female on the other, which allows a certain amount of flexibility. Each of these segmented rotors have a lobe on the outer circumferential edge which engages with an inboard to outboard rail on the inner circumference of the inner half of the wheel hub. Obviously brakes had to have cooled down before work could commence on changing parts. After assembly of all the parts a brake unit alignment tool was fitted over the axle and brake unit to align all the rotors with brakes selected "off". The unit was called a "Spider". After satisfactory alignment had been achieved of all the segments of the rotors, the "spider" and aligned rotors would be rotated a couple of times and the brakes applied, and "spider" removed. The wheel was then fitted, axle thread protector removed, keyed washer/spacer fitted, wheel retainer nut fitted and torque loaded, locking bolt, nut and split pin fitted, brake anti-skid checks carried out, cooling fan blade and guard refitted, and wheel finally rotated to ensure free rotation. Tyre re-inflated to 130 psi and jack lowered, stirrup block removed and "bogie beam"/"truck" guard refitted. Eight times each run. Did we need a drink after? YES.
After the whole series of accelerated stops previously taken place at different weights and V1 speeds over several days of tests, the ultimate braking test was carried out known as Max K.E. Stop (Maximum Kinetic Energy Stop) or High Energy Stop. This trial was carried out with the aircaft at maximum take-off weight and using maximum braking effort from the V1 decision speed. This resulted in the brakes becoming white hot, melting the fuseable plugs in the wheel hubs (which are there to prevent tyres exploding with higher pressure due to heat soak and temperature rise). The fuseable plug temperature rating had already been upgraded to a higher value of temperature before melting, to delay tyre deflation for the trial run. Before the trial run began the NATO commander for the base indicated to test pilot Bill Cairns that should the aircraft become immobile on the runway due to the test, the aircraft would be bulldozed off the runway. No pressure then!!! The logic was that the base was a first call nuclear alert base and in constant alert during the cold war of the sixties. After the run Captain Bill Cairns was just able to taxi the aircraft back to dispersal before the tyres entirely deflated. The tyres were deflating before the aircraft left the runway for the taxi-way. After Victor Bravo had been parked on dispersal apron and things had cooled off, particular problems with some wheels becoming welded to brake units became apparent. As a result of the max. K.E. Stop and the ultimate braking force used, the high temperature had caused the wheel hub and brake unit to be fused together. Due to this we were unable to remove some wheels from axles. To achieve wheel and brake unit removal the two sectional wheel hub had to be disassembled on the axle to remove the outer section of the wheel hub and tyre. The inner half section was then split by acetylene torch for removal, and access to brake unit flange retaining bolts. Due to this, later VC10 types had a modified brake unit retaining method applied, this being the internal axle brake unit retainer mechanism rather than the brake unit inner bolted flange.
The second group of runway trials at Torrejon were those of the VMU test which stood for Velocity for Minimum Unstick (minimum VR rotation speed) for various take-off weights. Before this test a wooden block was fitted to the rear belly of the fuselage and a ground proximity arm to the rear cone of the fuselage. This ground proximity arm provided the pilot with two indications of clearance between the wooden block and the runway on rotation at nine inches and three inches clearance. Two lights on the flight deck indicated this ground clearance to the pilot so that he could keep the VC10 in this nose-up attitude until the aircraft lifted off. This test was carried out several times at different take-off weights, but also later in tests at Johannesburg with the Standard VC10 G-ARVB in October 1963 and Super VC10 G-ASGB in January 1965 (see next page for a fuller description with photos).
That concluded the 1st Tropical Trials of the VC10 and we returned to Wisley on 14th September 1963.
A few weeks later we embarked on the second Tropical Trials, this time to Johannesburg South Africa. On 21st October G-ARVB departed Wisley en-route to Johannesburg via Cairo, Egypt for an overnight stay before proceeding the next day 22nd October 1963, (following the Nile for most of its length), en-route to Johannesburg South Africa. This flight was to be the 1st crossing of the equator by a VC10.
There were many firsts during this flight: 1st crossing of the Alps by a VC10, 1st flight beyond Europe for a VC10, 1st landing and take-off of a VC10 at Cairo Airport, Egypt. Also this flight was the 1st VC10 flight to follow the Nile and first and probably only direct flight to Johannesburg from Cairo. Most if not all flights had stops at Khartoum Sudan, Nairobi Kenya, and Salisbury Southern Rhodesia, (now Harare Zimbabwe), and routed from Rome Italy, instead of Cairo. During this flight Standard VC10 G-ARVB was the first VC10 to cross the Equator. All on board were presented with a certificate of the occasion, signed by captain Bill Cairns, dated 22nd October 1963 and crossing at longitude 32.25E. Also this flight would be the first VC10 to land and take-off at Jan Smuts Airport Johannesburg South Africa.
Sadly during this VC10 flight from Cairo to Johannesburg, BAC 1-11 G-ASHG, also flying on a test flight from Wisley, crashed on Salisbury Plain, Wiltshire during air tests, with the loss of all on board. On our landing at Johannesburg, captain Bill Cairns reported the event to us on arrival at our hotel. The atmosphere to say the least was subdued for the rest of the trials and apprehensive as the aircraft configurations were similar, rear engined, high tail plane. The VC10 trials were temporarely suspended until more information was received from London.
Once the trials continued we were able to carry out several tests, amongst which were those of the fuel jettison system and a duplication of runway trials of accelerated stops and Max KE stops as were carried out at Torrejon, Spain. Also another series of VMU tests, again duplicated tests, were carried out just like the ones which were done at Torrejon. However the ultimate accelerated stop of Max K.E. stop as described above during the tropical trials at Torrejon, turned out somewhat different at Johannesburg. The test consisted of the same criteria as Torrejon, but on this occasion at Johannesburg Jan Smuts Airport there was no available taxi-way to retreat too and as expected 'VB became stranded on the runway with eight deflating tyres. However we were expecting this and were ready with all equipment on a flat bed trailer to respond immediately. This included a fuel tanker for a quick de-fuelling, which normally took a bit of time from full tanks. As I had been involved in the construction of G-ARTA, with particular emphasis on the fuel system amongst other things, I was the fuel "Baron" during these trials. Before the trials I had made a suggestion to the fuel design engineer at Weybridge that perhaps we could utilise the engine fuel supply booster pumps to improve flow to the re-fuel/de-fuel gallery by utilising the jettison system without opening the master jettison valve. This would improve the de-fuel rate as normally a maximum of minus 11 psi suction is allowed, but if positive pressure from the booster pumps could be introduced it would probably near halve the de-fuel time. It worked and was adopted for all de-fuelling. (In later years at British Airways I adopted this procedure on Lockheed 1011 Tristars and Boeing 767s. OK as long as you don't open the Master Jettison Valve. Pulling the circuit breaker for this valve is the best protection from a "gusher".) Working between two lethal entities of deflating tyres, white hot brakes, and de-fuelling at the same time we managed to engage four stirrup blocks to all four ends of the two "bogie beams"/"truck" and engage four "bogie beam"/"truck" stirrup jacks before the wheel hubs contacted the runway. There are no photos of this as we were too busy as you can imagine, we had to clear the runway as soon as possible. It took about two hours to remove eight wheels and brake units, the brake units had to be allowed to cool from white hot to a manageable temperature before removal, then replace eight wheels with serviceable units, but no brake units, these were left off as time was of the essence. Towing the aircraft back to our dispersal area...SLOWLY. Another well earned drink was on the cards. Following this extreme Ultimate Max K.E. test , otherwise known as High Energy Stop test, and recovering the aircraft to our dispersal stand, the work started in replacing eight complete brake units. On this test, unlike the less taxing accelerated stop tests, the complete individual brake units had to be changed, not just the "heat packs". The brake units were either scrapped or returned to the workshop for analysis and maybe reworked if deemed acceptable to do so.
There were also periods of unsuitable ambient conditions for trials, which were not conclusive for recording aircraft performance. Reference wind speeds, wind direction, air temperatures, runway temperature, humidity, ambient pressure, visibility. This enabled the ground crew to do some sightseeing in the vicinity of Johannesburg.
That concluded the second Tropical Trials of the VC10 and we returned to Wisley sometime in November 1963 after about four weeks.
After returning to Wisley and as a result of the on-going investigation into the BAC 1-11 G-ASHG accident, a few months later all VC10s had a "Stick Push" system incorporated into the elevator mechanical control input run, below and forward of the flight deck. I was involved with others in the fitting and testing of this system. The system comprised of a mounting tray with a pneumatic ram and connection levers and rods fitted to the elevator control run. It wasnít physically fixed to the control run but when fired would impact a lever in the control run to input an elevator down signal to lower the aircraft's nose automatically. This was done so the pilot could over ride the input if neccassary, and also would not be stroking the pneumatic ram in normal operation of inputs to the elevator controls. The system was supplied by a compressed air bottle and air valve controlled by an electronic black box. This in turn was supplied with inputs from pitot and static probes, and fed with information from angle of attack probes on the side of the fuselage, the silver cones seen protruding from the fuselage in pairs both side with a series of holes in their circumference. These sensed the angle of attack of the aircraft and sent a signal to the electronic black box to signal the opening of the pneumatic valve when a critical stall angle of attack for any given air speed approached, this pneumatic pressure would then stroke the ram and push the elevator input system to elevator down, after the stick shaker was initiated, so pushing the nose of the aircraft down to recover from the stall before a deep stall was induced. The system was devised should the pilot not realize the close proximity of a stall in any given condition. Also around about this period a tail chute module was fitted to G-ARTA to enable stall recovery should the aircraft become involved in a deep stall condition. It was never deployed as far as I remember.
Sometime in early 1964 (exact date unknown, but before the C of A would have been awarded to the Standard VC10) before aircraft would be put into service with BOAC, I was again involved in a trial away from Wisley with other members of the ground crew. This was the nose wheel tyre chine trial. The nose wheel chine is the protrusion on the outer side wall of the nose tyre, a triangular shaped ring protrusion integral with the side wall of the tyre.
We flew to Rolls Royce's airfield at Hucknall for a two day trial, another first for the VC10, to land and take-off from that airfield.The aircraft registration used for this trial is unknown but I would assume it was G-ARVB. This trial was to confirm the design of the chine in practice. The reason for the chine is to deflect any standing water on the runway away from the engine intakes, on take-off mainly but also during landing. At Hucknall there was a facility built into the runway which consisted of an area of the runway about half way down the length of the runway, of about 200ft in length and full width of runway, that had been barriered to create a shallow pond of something like one to two inches in depth of standing water over that area. The walls of this shallow pond across the runway consisted of a flexible rubber wall, as the tyres passed over it the walls flattened and extended up again to retain the pond effect. This enabled the aircraft to accelerate through it at speed and the events were then recorded by fixed runway side cameras as well as cameras fixed to the wing and fuselage at pre-determined positions.
The next event in the VC10 development was the first flight of the Super VC10 G-ASGA on 7th May 1964.
Even after all the development associated with the drag criteria problem with the Standard VC10, it was found after a number of flight trials with G-ASGA that there still existed more drag than design criteria expectations. As a last resort to reduce drag and as a comparison all external projections such as radio aerials and drain masts were removed, except one radio aerial left for communication, but as it turned out this made no difference what so ever. Clutching at straws came to mind, but it had to be tried. The aerodynamisists then resorted to "area ruling" the airframe for peaks and troughs in cross sectional areas throughout the aircraft's length. It was found the area between the wing and nacelles had a particular trough in the graph. To combat this two blister fairings were manufactured in the shape of a "Sting Ray" fish in plan view and installed on each side of the fuselage over the two rear cabin doors, between the wing and engine nacelles. These protruded out from the fuselage to a maximum of approximately 8 inches, then faired into the fuselage aerodynamically at the edges. In total the area the panel covered was about 6ft by 4ft. After flight trials it was considered that the drag reduction was marginal and the benefit was not enough to incorporate as a modification.
During these early trials on the Super VC10 I was again deployed to Boscombe Down along with other members of the ground crew. This time the Super VC10 wing top surface was going to be pressure plotted in flight. This consisted of removing one cabin window panel in the centre section area of the cabin and substituting it with a dummy metal panel in the same shape as a normal cabin window pane, but with a group of small bore plastic hoses passing through it, approximately 12 to 15 in total, bonded together to form a mat of something like eight inches wide. This was bonded to the side of the fuselage on exit from the slave cabin window and bonded to the wing surface, over the inner wing fence and out to the wing tip. Each separate tube was then cut off at various wing span intervals until only one pipe section remained at the extremity. Each separate pipe was then connected to a pressure sensitive water gauge for in flight recording by camera in a cabinet in the aircraft cabin during flight. After this the excessive drag that had been unable to be rectified by various means, although reduced by some measure but not entirely to design criteria expectations, had to be excepted and no more developement was attempted.
However once the Super VC10 went into service with BOAC, it was found during service that by manipulating fuel usage between wing tanks and fin tank this greatly improved performance. Basically trimming the aircraft's in flight longitudinal attitude by fuel management, rather than conventional TPI adjustments. Much like Concordes fuel management for trim. (Note: on Concorde this was done to counter the aerodynamic change from subsonic to supersonic flight but recent long range Airbus aircraft have a similar feature where an active fuel management system 'trims' the aircraft to fly more economically - JH)
During this period of testing trials carried out at Wisley I was involved in a rescue of a BOAC VC10. On circa 11th or 12th August 1964, just over three months after Standard VC10s were introduced into service with BOAC, a Standard VC10 (Reg. unknown), landed at Kano Nigeria. During the landing run the nose wheel steering rotated by 90 degrees and remained there. The pilot was able to hold the aircraft on the runway and after shutdown the passengers were disembarked there on the runway. During the recovery phase by BOAC engineers it was found that the alternate steering selection valve had traces of corrosion within its hydraulic cavities and channels. They changed the alternate steering valve and carried out satisfactory functional tests of the steering system. The aircraft was to return to the UK by ferry flight. However the Captain decided, or maybe was instructed by BOAC Speedbird Control London, that on take-off this would be done with the nose undercarriage free fall lever pulled, which left the nose gear doors open for the take-off. The main gears were left to retract as normal. After an uneventful take-off and gear up selection the main gear retracted but as the free-fall for the nose gear was still selected to free fall, that remained extended. During the early stages of climb out it was decided to reset the free fall for the nose gear and retract it for the flight back to the UK. During this phase the nose leg retracted as the nose gear doors were attempting to close. With the undercarriage retract/extend lever already in the retract position, sequencing had been compromised by using the free fall lever. The result was that the retracting nose landing gear wheels came into contact with the closing nose gear doors and because of this the doors detached and were lost. The aircraft returned to Kano and BOAC requested two engineers from BAC to be provided.
Myself and a colleague were on the next available BOAC service flight out to Kano, arriving on the early morning of the 14th August 1964. On arrival we set about replacing the nose gear doors and mechanism and carrying out retraction functional tests. The Captain then carried out a high speed run down the runway to check steering and returned to finally refuel, collect the cabin crew, and we were off back to the UK on a ferry flight. From your web page information of first flights & delivery dates, I would hesitate to guess one of three aircraft was involved in this incident: G-ARVI / G-ARVJ / G-ARVK. These three would be the oldest of the seven aircraft introduced into service in that period and would think the more likely to have corrosion within a system. Pure conjecture but plausible.
About six months after the first flight of the first Super VC10 G-ASGA we again proceeded on the final Tropical Trials of the VC10 development to Johannesburg South Africa. Or so we thought !!!!.
Early on the 27th November 1964 we departed Wisley Airfield en-route for Johannesburg with a two day stop over at Khartoum Airport Sudan before proceeding onto Johannesburg South Africa for the last Tropical Trials of the VC10 to be completed before Christmas of that year. The reason for the two day stop over was for engine ground running tests over the intervening day of the 28th. After hot ambient engine ground running trials were carried out, the plan was to depart Khartoum on 29th November 1964 for Johannesburg. However prior to the VC10 departing for Johannesburg, a one hour demonstration flight for the Minister of Transport for Sudan and members of the Ministry was arranged. On landing after the demonstration the aircraft suffered a substantial brake failure, all four main wheel tyres on the port side burst on the landing run, along with two inner tyres on the starboard side. As we were waiting for the aircraft's return from the demonstration flight, the sound of boom..boom..boom...boom..boom...boom during the landing run, was to say the least, concerning.
There was extensive damage to all four wheels and brake units on the port side. Also during the landing run the port side undercarriage bogie beam had been severely damaged, the lower part of the casing was worn through from contact with the runway surface. A small fire developed around the undercarriage but was soon extinguished by the fire service. Subsequently it took six hours for us, the ground crew, to mobilise the aircraft for removal from the runway. We were unable to utilise the normal jacking proceedure for tyre or brake unit replacement, by means of the stirrup fitting and stirrup jack, due to the bogie beam contacting the runway surface. Fortunately, as the Standard VC10 was now in service with BOAC, they had main and tail jacks on site as well as a steady jack for the nose. After de-fueling, a complete height jacking procedure was carried out on the runway, thankfully there was no wind, we were then able to remove all wheels and brake units. We only had the original two undamaged Starboard main wheels and two spares carried onboard. These were utilised on a cross axle configuration basis. On attempting to lower the aircraft, after some rectification work to remove the aircraft from the runway, one of the main jacks, the Port side, failed to lower. To overcome this the stirrup fittings were again fittted to the Port side bogie beam at both ends, both stirrup jacks were manoeuvred into place and extended to take some weight and to gain some height with regard to the bogie beam. Then the port leg oleo was inflated to a pressure consistant with weight on wheels to then raise the aircraft off the main jack. The port main jack was removed along with the single nose steady jack and lowering was then recommenced by deflating the port undercarriage oleo and lowering the other jacks in unison. It worked, but then we had to tow the aircraft about a mile with no brakes.
Further Tropical Trials were abandoned and aircraft returned to Wisley for investigation of the brake failure on or around 6th December 1964.
Subsequent investigation found that during a short landing run attempt the Dunlop "Maxaret" anti-skid system could not properly function as the great volumes of fluid being displaced from the Maxaret units when put under extreme braking conditions could not return to the hydraulic reservior. In other words the return pipe was becoming "choked". It was found that the capacity of the common return pipe from the Maxaret units on the undercarriage oleo casing and beyond to the reservoirs was of insufficient size (bore) to allow a maximum flow under extreme braking conditions. Strangely this had not occured in any Standard VC10 brake trials. Although there had been isolated occasions at Wisley of Super VC10s with individual burst tyres during the landing run, this had been put down to one particular pilot, John Cochrane, who at the time was considered sometimes heavy on the brakes. As it turned out this was unfounded. As the Tropical Trials had to resume in the near future it was decided rather than modify the existing hydraulic return pipe back to the reservoir, some other course of action would be implimented. This temporary modification consisted of a hydraulic accumalator, installed at each Maxaret return pipe and "T" pieced into the hydraulic return pipe system. Each accumulator, there were eight in total, were strapped onto each brake reaction rod with two jubilee clips. Each hydraulic accumulator was around three inches in diameter and around eight inches in length, with an air pressure charge of around 60 psi. This allowed excessive fluid volumes to be absorbed into the accumulator under extreme braking conditions and worked throughout the remaining trials. Future Super VC10s were modified with a larger capacity return pipe.
This is the second part of Maurice's memories, to read the final installment about the Super VC10 trials at Johannesburg and other stories, click here.