The first ballistic interception trials were carried out in the winter of 1962/3 by the RAF Air Fighter Development Squadron, using a pair of English Electric Lightning F1As. The ‘target’ was an unsuspecting USAF Lockheed U2 from Upper Heyford, flying at its invulnerable altitude of 72000ft over the arctic on a surveillance mission. Image by Michael Turner.
Having entered service in the summer of 1960, the English Electric Lightning was the spearhead of the RAF’s fighter force and, despite early teething troubles with serviceability, had proved itself as a blisteringly fast and extremely agile state-of-the-art fighter by early 1962. One area in which the cutting-edge Lightning had not been tested operationally, though, was its ability to intercept targets at very high altitudes, mainly because targets capable of flying at heights above the Lightning’s operational ceiling of 56,000ft were simply not available.
This was to change with the arrival in the UK of a detachment of specially-modified Lockheed U-2As of the USAF’s 4080th Strategic Reconnaissance Wing (SRW) in August 1962. The three high-altitude aircraft – 56-6681, 56-6712 and 56-6953 – had been posted to serve with the 4028th Strategic Reconnaissance Squadron (SRS) at RAF Upper Heyford, Oxfordshire, as part of Operation Crowflight, a component of the USA’s High Altitude Sampling Program (HASP). Their task was to conduct particle-collection sorties which would yield information on the long-term behaviour and distribution in the stratosphere of fallout debris from atomic weapons tests, in this case those being undertaken by the Soviet Union at its nuclear test site at Novaya Zemlya in the Arctic Ocean.
The detachment arrived at Upper Heyford on August 19, 1962, and was warmly welcomed by the British press, which had been told that the bizarre-looking American aircraft would be undertaking “weather reconnaissance”. It was a surprisingly big story; even the famous Daily Express cartoonist Giles provided a caricature, in which the new arrivals were greeted by one of their countrymen at Upper Heyford with the words: “If you guys are only over here to study weather conditions you’re sure gonna need them suicide pills you carry!”
Operation Bongo Drum was the name given to the Upper Heyford detachment’s specific deployment, which would see them covering an area from 60-90°N, 30°E to 30°W, once a day for 90 days. They would head north early in the morning to follow one of a series of predetermined operational routes, all of which took them out towards the Arctic Circle and, having successfully collected the required scientific data, would return in the afternoon.
The Central Fighter Establishment (CFE) at West Raynham (relocated to Binbrook in October 1962) was keen to pit its most advanced aerial weapon system against the best of American technology, and leapt at this golden opportunity to investigate the Lightning’s very-high-altitude interception capabilities. A request was put to the USAF to permit its aircraft to be used as targets for interceptions and, having received a positive result, a series of trials was officially rubber-stamped by HQ Fighter Command in early September 1962.
The trial was to be conducted by the Air Fighting Development Squadron (AFDS) based at RAF Binbrook, the unit tasked with investigating how the Lightning, the first – and only – all-British supersonic aircraft, could be used in air combat. The trials were to be conducted at RAF Middleton St George near Darlington, Durham, because the interceptions would have to be made over an area of as few built-up areas as possible, so as to avoid the “sonic banging” of cities and towns.
As the AFDS had only Lightning F.1s on strength, it was decided to borrow a pair of F.1As from front-line squadrons, the upgraded variant having a far superior oxygen system, UHF radio and an improved four-position reheat control. The first two F.1As selected for the initial phase of the trials, to be held in October, were XM175 from No 56 Sqn and XM214 from No 111 Sqn, both based at RAF Wattisham. Initially the aircraft were to be flown exclusively by AFDS pilots, although provision was made for specially selected pilots from Nos 56 and 111 Sqns to participate in the second phase of trials in November.
The AFDS pilot chosen to undertake the majority of the first phase of the high-altitude tests was Flt Lt John Mitchell, who along with Sqn Ldr (later Air Marshal) John Nicholls, Commanding Officer of the AFDS (and formerly Fighter Command’s Liaison Officer for English Electric), was sent to Warton to develop flight profiles for the trials. Mitchell explains:
“We went to talk to the guys at English Electric – [test pilots] Jimmy Dell, Don Knight and an aerodynamicist – but it revealed very little because nobody had really investigated this sort of flight envelope.” Up to this point the Lightning had only been tested to 56,000ft at Mach 1·7; clearly a whole new technique would have to be developed. John continues: “We had to sit down and start at square one. We visited Upper Heyford, talked to the U-2 guys on the detachment, who told us their track and that was all. They said, `You’ve got the authority to do it, fill your boots, come and catch us if you can’. So we sat down with the Operating Data Manual, but it just didn’t cater for what we wanted to do. It was all trial and error.”
Looking after the borrowed Lightnings on the ground at Middleton St George was Fg Off Mike Mason, who had been posted to the AFDS in 1961. Mike recalls the strict regime the trials demanded: “The Lightnings had to be 100 per cent serviceable for every sortie and equipped with the Firestreak air-to-air missiles ready to fire in order to make the trial completely realistic. They had to take off around 0630hr every morning and [for the second phase of trials] again in the afternoon. We had to ensure that the returning aircraft were refuelled and repaired in time for the late afternoon slots, then again through the night for the next morning slots.
“The Lightning was very unreliable at the time. Faults were numerous and often involved removing the engines to gain access – a very laborious and time-consuming process. Back at AFDS HQ at Binbrook groundcrew were kept busy supplying spares and even cannibalising other Lightnings for them. We were putting up four flights a day with two aircraft for a week at a time – possibly the alltime record for intensive flying of the Lightning”.
Rules of engagement
With the AFDS pilots and CFE Project Officer Les Phipps working on effective flight profiles for interceptions up to 65,000ft and beyond, the rules of engagement for the top-secret trials were established and circulated on a need-to-know basis. The essential points were:
- if the fighter was not in visual contact with the target by five nautical miles the interception was to be broken off;
- the fighter had to approach no closer than 5,000ft astern of the target;
- the fighter had on no account to pass in front of the target.
The flying programme was to be broken into three distinct parts, the first being the interception of a target at 60,000ft, the second an interception at 65,000ft and the last would investigate interceptions above 65,000ft. The interceptions would be undertaken in two one-week-long phases, one in October and one in November. Before the interceptions were made, practice flights without a target would be flown over the sea, which would confirm the practicality of the theoretical flight profiles as well as establish ground distances covered by the fighter, thus giving the ground controllers useful information for the “live” interceptions.
The practice flights were usually flown singly, and while official records state that for live interceptions the Lightnings flew as a pair, John Mitchell recalls flying most of the interceptions alone, with the exception of a few when he was accompanied by Nicholls and the sorties made with the squadron pilots in November. He explains: “Very few of us had the pressure suits and the kit to be able to do it”. Although unconfirmed, it is possible that Flt Lt Roly Jackson also undertook some of the flying during the trials.
The all-important ground control of the Lightnings, vital to give the fighters an accurate steer towards the target, was to be handled by the radar station at RAF Buchan, near Peterhead in Aberdeenshire, with RAF Patrington in the East Riding of Yorkshire and RAF Boulmer at Alnwick in Northumberland acting as secondary stations for early warning, scramble and recovery.
Working the angles
As John Mitchell and his colleagues at AFDS were discovering, placing the Lightning at interception height with sufficient speed to enable it to close with the target before the fighter’s minimum practical control speed was reached presented something of a challenge. At high altitude the Lightning’s minimum practical control speed was around 190kt IAS (indicated air speed), which corresponded to a high Mach number (in excess of Mach 1), thus leaving only a small margin between arrival speed and break-off speed. Adding to the difficulties was the slow relative speed of the U-2 to the Lightning (110-120kt IAS/Mach 0·7), making a very high rate of closure inevitable.
After much deliberation a set of flight profiles was established, the most-used of which was for intercepts at 60,000ft, and which incorporated a cold power climb to 36,000ft followed by a maximum reheat acceleration to Mach 1·5. When this speed had been achieved a climb to 50,000ft was initiated, followed by a turn on to the target’s heading. On instruction from the ground controller the Lightning pilot would initiate a 10° “snap-up”, which would be held until 60,000ft was reached at a speed of around Mach 1·2. The fighter’s Firestreak would acquire the target and the Lightning would break away. That was the theory – now it was time to put it to the test.
The tests begin
With aircraft, pilots, groundcrew and ground controllers all in place, the trial, given the official codename Exercise Trumpet, officially started on September 29, 1962, but it would be a few weeks before the profiles and practice flights would commence. John Mitchell was sent to Manchester to be fitted for specialist high-altitude equipment manufactured by the two world-class flying clothing companies located in the city. Frankenstein provided a partial-pressure suit incorporating a specially-modified jerkin with pressurised sleeves and gloves and anti-g trousers and Baxter, Woodhouse & Taylor supplied the pressure helmet.
In the run-up to the first of the intercepts against a U-2, some 11 sorties were flown to test the flight profile developed for interceptions at 60,000ft, all of which yielded valuable information on times and distances for the acceleration, climb and snapup. Scramble times for the Lightnings could then be calculated, along with where the fighter was in relation to the U-2 at various points in the profile. At the same time the ground controllers had been watching the U-2 on its daily mission and had calculated that its average ground speed was 392kt and its average track 346° (true), enabling them to work out what they had to do to turn a theoretical flight profile into a successful interception.
By Monday, October 22, the practice flight profiles had all been completed and it was time to translate theory into reality. At 0726hr XM175 and XM214 were scrambled from Middleton St George for the first of the live intercepts. The official report describes the morning’s events:
“The fighters were airborne as planned slightly early and were flown from Middleton St George to Newcastle. This northerly track was continued until the target’s position could be accurately gauged. The fighters were then turned starboard on to a southerly heading and when target and fighters were positioned to produce the correct minus-6min position the fighters were turned westwards towards the target so that the target became 15° port, 47 nautical miles from the lead fighter as it rolled out of its starboard turn. This initial setting up procedure was satisfactory and was used on all other interceptions”. The report goes on to state that “all went according to plan except that the fighters were rather closer than five miles from the target after snap-up”. It was an excellent result.
The next sortie, on Wednesday, October 24, was less successful. There were radio problems between the fighters and the ground controllers, and the order to start the acceleration was received late – and had to be given to the Lightnings by the U-2, which was obviously far from ideal. The U-2 was also 15 miles east of its normal track. These two factors combined to give too short a distance for the Lightnings’ acceleration and climb. A hastily improvised Plan B was put in place, with the result that the fighters were forced to manouvre during the snap-up and broke off eight miles south-east of Edinburgh – causing the “mystery explosions” that made Edinburgh’s windows rattle and draw comment in the next morning’s Daily Mail. The trials were top secret and nothing was said – for the time being.
“The overtake was enormous . . .”
Live intercepts against U-2s continued over the next two days, with both trials yielding successful results. The flight profiles were adapted and perfected, with alternative routing points tried and tested. John Mitchell recalls a typical sortie:
“Sometimes we’d go south from Middleton St George in the morning, accelerate about over Norwich, or in the afternoon go north to Edinburgh. Ground control would take you to a point at 36,000ft, where you would accelerate to Mach 1·5 to start the climb to 50,000ft. When you got the cross-in at 50 miles, [you would make] a very gradual turn there, still accelerating but very gently, not very much climbing, then accelerate again to Mach 1·7 to get in astern at about 20 miles.
“So now you’ve got the Lightning at about 50,000ft, maybe 1,000-2,000ft above that depending on the day. What we didn’t know initially was that the U-2 was only 8,000-9,000ft above us. The energy at Mach 1·7 at 55,000ft could take you up to 80,000ft and the target was 20,000ft below that, so we were pulling up immediately behind, then he would come up on the radar scope; [that was] the first time I’d actually see him – the process had been ground-controlled up to then. He’d come down the radar screen bloody quickly and the overtake was enormous of course, a supersonic overtake.”
Thinking time was very short when approaching the target at 13 miles a minute and a “lock-on” for the Firestreak missile had to be acquired for the sortie to be deemed a success. John continues:
“It would all be over in less than a minute. The missile system worked fine, although I’m not sure how one of those things would have flown at 60,000ft. It acquired fine, though. We would have to break off at two miles [astern] or so. Having got your `splash’ you just wanted to get out of the way. There was a danger of `banging’ the U-2 with a shockwave. When passing it we were still going up in a vicious climbing vector. On occasions we would have a Mach 1·2 overtake speed and at that sort of height it wouldn’t have reacted that well. We had a good rate of climb and a good height attitude, so the change was a rolling manouvre to maintain altitude, but you couldn’t go over as you’re still supersonic, so you had to get subsonic before you could turn, otherwise you were going to bang the whole north of England.” The only option was to continue up – throttling back or using airbrakes was not an option as at that altitude the aircraft was getting towards the limits of its performance. “We would turn the reheat off to get out of the U-2’s way, with the stick hard back, still supersonic at about 190kt IAS, stuck there. Then the Lightning would just say `I’ve had enough’ – not a wing drop, not a slice, not a yaw, nothing. Absolutely beautiful.”
The second phase
With the first phase of live sorties completed with a successful fourth interception on October 26, there was a short break before the trials were resumed on November 11, this time including squadron pilots Fg Off Peter Ginger and Flt Lt Henryk Ploszek from Nos 111 and 56 Sqns respectively. The two new faces brought another pair of Lightnings, XM177 and XM191, to participate in the trials and were shown the ropes by Mitchell and Nicholls.
The first live sortie in the second phase of trials was completed on November 13 and was described as being one of the most successful of the 60,000ft interceptions. The 13th also marked the first of the 65,000ft interceptions against the U-2 on its inbound course in the afternoon. For these higher interceptions the profile differed by increasing the initial acceleration from Mach 1·5 to Mach 1·7 to get to 50,000ft and increasing the snap-up angle from 10° to 20°. This enabled the fighter to arrive at 65,000ft at Mach 1·25, which would equate to about 30sec of useful time before the Lightning’s minimum control speed was reached.
Scrambled at 1408hr from Middleton St George, the two Lightnings were set up in a good position for the first 65,000ft interception but once again radio problems intervened and, despite the fighters obtaining a good intercept position, a break was called 24min into the sortie.
November 15 saw the first trial sortie in which an interception was led by an operational squadron pilot, although whether it was Ginger or Ploszek is not reported. Both were equipped only with sleeveless pressure jerkins and were therefore confined to 60,000ft interceptions. On the same day, the last of the three 65,000ft interceptions of the inbound U-2 was made, the alternative flight profile proving to be a success. The final flight of Exercise Trumpet was a 60,000ft outbound interception made on November 16, the flight profiles having been thoroughly mastered by Ploszek and Ginger.
The official report states that eight profiles were also flown to investigate the possibility of intercepting targets above 65,000ft, the best results being obtained by an acceleration to Mach 1·7 at 36,000ft, a climb to 45,000ft followed by a 25° snap-up, which resulted in the Lightnings reaching 68,700ft. It was felt that this was unlikely to be bettered with the limiting of the Lightning to Mach 1·7 for the trials, although John Mitchell recalls initially being offered higher operational speeds: “They offered us Mach 2, but I didn’t want it”.
The official summary for the trials revealed that “it is apparent that this type of interception is within the capabilities of the control system provided that adequate planning by controllers – so that the interception profile is fully understood – is carried out before the interception is attempted”. In terms of radar and missile performance, the results of the trial were “extremely encouraging. Initial pick-up occurred at between 15-18 miles and the run culminated with missile acquisition between 2-3 miles at the same altitude as the target”.
The view from on high
The trials had been a great success for the AFDS team, which, through trial and error and a great deal of hard work, had proved the Lightning’s ability to intercept very high-flying targets should the need arise. But what had it been like from the target’s point of view?
Four USAF pilots flew the Bongo Drum flights. One, who would rather remain anonymous, gives an insight into the other side of the interceptions:
“I don’t recall being told anything except to expect the intercepts. We could see the contrails, but the Lightnings never approached very close to us. I remember seeing more than one contrail but I assumed they were individual intercept attempts. I know we turned on our IFF [identification friend or foe equipment] when we approached the UK on mission return. I do have a recollection of seeing a Lightning in the zoom [climb] at six o’clock and banking right at three o’clock at about my level – outbound – and fairly close”.
With the Cuban Missile Crisis rapidly warming up the Cold War 4,500 miles away, the services of the USAF’s U-2 units were urgently required back home, and orders were issued for their return Stateside. “We really had no way of knowing if the intercepts were considered successful or not”, the retired U-2 pilot recalls. “I ferried the last U-2 out of RAF Lakenheath when we shut down [Bongo Drum] – that was on November 19, 1962”.
With the trials over, the Air Ministry had to come clean about the “mystery explosions” heard in Edinburgh and its environs in October. This time the Daily Mail headline read “RAF CLEARS AIR OVER MYSTERY BANGS”. The report continued:
“A brief statement from the Air Ministry yesterday cleared up the mystery of loud bangs heard in the Borders recently. The Ministry said: `High-level interception practice by Fighter Command aircraft has been taking place during the past few weeks and this may have given rise to reports of sonic bangs’.