One damp and misty day towards the end of the course, I was in a lengthy queue of Jet Provosts waiting for my turn to take off on a dual instrument flying sortie. Because of the bad weather and a lack of radar cover, Air Traffic Control was imposing a minimum of 60 seconds between aircraft taking off.
"What are you thinking about?" asked Tony Ryle, suddenly.
"Nothing in particular, sir," I replied, thinking it was a bit of a daft question. Actually, I had been day-dreaming - and he probably knew it.
"While waiting for take-off clearance you should always be thinking of 'what-ifs?' Don't just sit there with your brain in neutral. Think about what you would do in the event of an emergency either during or immediately after take-off. What would you do today if our engine failed as soon as the wheels came off the ground, or just as we went into the low cloud?" It was a rhetorical question, but a lesson learned - and I never forgot it. In fact, I sometimes used that lesson years later when I was assessing Victor co-pilots on their captaincy potential.
On 1 February 1967, just two weeks before the end of my course at Leeming, I was programmed to fly a solo high level navigation exercise in Jet Provost Mk 4 XS218. The route I was given to fly was Leeming - Carlisle - Turnhouse (Edinburgh) - RAF Acklington (about 14 kms north-east of Morpeth and close to the Northumberland coast) - Leeming. I would be flying at heights between 27,000 and 29,000 feet which meant that I would have to obtain procedural clearance in flight to cross a very busy east-west civilian airway. One of the specific requirements of this solo navigation trip was for the student to practise procedural crossings of airways; presumably any student who fouled it up would be reported by the civilian ATC back to Leeming.
For the benefit of those of my readers who are not familiar with Flight Levels and Altimeter Standard Pressure settings, I'll refer to heights in feet throughout most of this anecdote. The climb out from take-off to the north-west was uneventful. Everything appeared to be working normally: engine, flight instruments, fuel consumption, oxygen flow meter and oxygen mask connections. As I mentioned earlier, the Jet Provost Mk 4 was unpressurised, so I needed to wear the oxygen mask on the 100% oxygen setting throughout the flight and make sure I didn't go above 29,000 feet.
All went well at first, but I was keeping an eye on an extensive bank of high level cloud that was getting closer - evidence of the warm front that the Met Officer had mentioned at the morning briefing. It was not a problem if I went into cloud because I had passed my Advance Instrument Flying Test several weeks earlier and so I was qualified to fly in IMC - instrument meteorological conditions. In any case it looked as though the base of the high level cloud would be above the height at which I was flying.
As I neared Carlisle, I spent some seconds checking my map and flight plan because I was approaching the airway and I needed to get ATC permission to cross it. Just as I was about to change my radio to the appropriate airways frequency, a controller at RAF Boulmer air defence radar station broke in to ask if I had contact with a civil aircraft in the airway crossing my path from left to right on a heading of 060 degrees at 31,000 feet. I looked out and was surprised to find that I was now flying in and out of the base of the cloud. I couldn't see the reported aircraft, so I told the controller that I had no visual contact because I was close to cloud. I was surprised that the controller did not acknowledge that call.
All of a sudden, some instinct warned me that everything was not well. I was uncomfortably hot and beginning to feel dizzy. I noted, to my great surprise, that I was now definitely inside the cloud. While I was wondering how that had happened, the Boulmer controller came up on the radio again, rather more urgently, and reported that the conflicting airliner was now passing directly in front of me, still at 31,000 feet, still heading 060 degrees. Once again I said that I had no contact but with a reported height separation of 2,000 feet I was not unduly alarmed. Again, Boulmer did not reply.
I then realised that I, too, was at 31,000 feet! Somehow, without knowing how, I had climbed to the height of the conflicting aircraft. At the same time, I saw on the compass that I had wandered off course by about 40 degrees - to roughly the same heading as the invisible civilian aircraft. I was now flying without permission in the civilian airway - a serious offence. More importantly, and much more worrying, I seemed to have interpreted ATC's information about the civilian airliner as an instruction for me to turn and climb. I must also have increased engine power to maintain airspeed in that climb although I had no recollection of having done so. Then, thanks to my sessions in decompression chambers, I realised that I was suffering from oxygen lack - hypoxia. I checked that my oxygen mask was still correctly fitted, that the hose was securely connected and that the rotating blinker on the oxygen regulator correctly blinked white and black alternately as I breathed in and out. Nevertheless, although the oxygen equipment seemed to be working properly, I needed to descend - and quickly.
Again, the controller came up on the radio, this time in a very urgent voice asking me for a radio check. The controller knew from my call sign, Romeo 32, that I was a solo student from Leeming. By then he would have seen on his screen that I had changed heading and from his height finder he would know that I had climbed above my authorised height. I then realised that I had not been pressing the transmit button on the control column. No wonder he had not heard me! The subsequent conversation went something like this, as best as I can remember it:
"Boulmer, this is Romeo 32 - sorry about that - I'm not feeling well. There's something wrong. I'm now at 31,000 feet in cloud and heading 060 degrees. Where's the other aircraft?"
"Don't worry about him, Romeo 32, he's well clear now. Have you checked your oxygen?"
"Affirmative - it looks OK - it's connected and flowing but I think I'm hypoxic."
"Can you safely descend on your present heading."
"OK Romeo 32, maintain your present heading and commence a slow descent - and call me every thousand feet."
In that manner I descended, gingerly at first but with increasing confidence, reporting my height every thousand feet as ordered. I came out of the high level frontal cloud at about 15,000 feet where visibility was almost unlimited with the east coast and the North Sea spread out before me. I was feeling much better.
The controller told me that instructions from my instructor at base were to proceed direct to RAF Acklington, the RAF's No 6 Flying Training School, and land there. With occasional steers from the radar controller I continued my gentle descent and soon I could recognise Acklington, although I had never been there before. In due course I joined the visual circuit and landed without further incident, feeling completely recovered. I was directed to park alongside a row of Jet Provosts. I shut down the engine, opened the canopy and an airman climbed up, as normal, to replace my ejection seat pin. I then got down from the aircraft to find a doctor was waiting to take me to Sick Quarters for a medical check.
As the doctor was checking me out, a telephone message came through from the Acklington Flight Line Controller to say that the ground crew had found a rare fault on the 'airmix' valve in the oxygen regulator in my aircraft. It meant that during the entire flight I had been supplied with only re-circulating cockpit air instead of the 100% oxygen that was required for the high level part of my flight. Thus, once I had climbed above about 15,000 feet, I had gradually become more and more hypoxic without realising it, especially as the blinker on the oxygen regular had continued to alternate between white and black as I breathed in and out. I had started to fly erratically and even failed to press the transmit button when I was initially trying to talk to the radar controller. Once I started descending towards Acklington under the guidance of the radar controller, I had quickly recovered without any ill effects whatsoever. That is how sinister hypoxia can be.
After filling in a Special Occurrence Report for the Station Flight Safety Officer at Acklington, I telephoned the controller at Boulmer to thank him for his assistance. It turned out that he was a former Jet Provost flying instructor now on a ground tour. He told me that as soon as he had realised something was wrong, he had ordered the civilian aircraft, an airliner en route from New York to somewhere in Scandinavia, to climb to 33,000 feet to avoid me.
When my aircraft had been refuelled and the oxygen regulator changed, I flew myself back to Leeming without incident. As it happens, my very next trip, on the following day, was my Final High Level Navigation test - which I passed with flying colours.