Rapid Descent
Following is an extract from a TPs memoirs which may already be on an old thread. It's worth repeating for this thread.
In June, I flew a Mr Telford of the Melbourne University to 45,000+ feet to sample condensation nuclei. This was concerned with continuing weather research in that condensation nuclei are necessary for water droplet initiation to form clouds. We carried, in the crew compartment, a cylindrical device connected to outside air by specially fitted tubing. Telford would set up a tray containing a super saturated sugar solution and then introduce a measured sample of outside air. Then, after some cooling, the sugar solution would grow visible sugar crystals wherever a condensation nucleus had settled. Telford would then count these crystals as a determination of the number of nuclei contained within the measured sample of air. Years later, the U2s of the USAF continued this research. Perhaps weather forecasting and rain making will benefit from this type of research.
We used to fly at night, usually once each week. These were mostly training flights, unless we could do some of our flight testing at night. The routine also kept the base support active for night operations. So on 17 June 1958, I launched in Canberra A84-219, with Flt Lt David Smyth as Navigator, to fly a routine navigation training flight to Broken Hill and Adelaide. All went well until we were approaching Adelaide. I had the Canberra's marginally effective cabin heating on full hot and yet we were both becoming unusually cold. I put it down to a maladjusted air mixing valve and turned for home at high altitude over Adelaide. It did not occur to us that we were running low on oxygen.
The Canberra crew compartment was pressurised to 3 psi so we had a cabin altitude of around 25,000 ft. The P type mask I was wearing was fed from a regulator which only allowed breathing-in whilst there was an oxygen supply. But as the supply pressure reached a very low value, the mix of oxygen tailed off appreciably. So for some time we had both been deprived of a normal supply. Our performance and brain functions were consequently deteriorating to low levels. It was not until David Smyth said angrily,"I've had this oxygen mask. I can't breathe. I'm taking it off" that I became alarmed to the possibility of an oxygen problem.
During my pre-flight checks, I had observed that the panel lights which normally illuminated the oxygen pressure gauges had not been working and I had to use my torch to check the pressures. I again used my torch to view the two pressure gauges. I was shocked to see they were both showing empty. At the same time, my breathing through the mask also became impeded. I realised that I was on the verge of unconsciousness.
I immediately pulled the engines back to idle, put out the speed brakes and began to descend as rapidly as possible. My vision was now blurred and I had trouble reading the instruments. David Smyth was not talking anymore. I asked him a couple of times whether he could bail out if I gave the order. There was no response and I concluded correctly he must be unconscious.
I remembered the emergency oxygen bottle in the base of the ejection seat. A cable from this was attached to the floor of the cockpit so that on ejection its valve would be automatically turned on. This also provided for an emergency such as this. I reached under the seat feeling for a little wooden ball fitted to the cable and remembering the system as in the RAF Canberras I had been flying, I gave the ball a sharp pull. Nothing happened so I pulled harder and felt the ball move towards me as though it had operated the valve. But still no oxygen came into my mask.
The added activity and concerns were creating additional demands from my body for oxygen and any reserves to keep me conscious were rapidly disappearing. I desperately tried to assess whether I might still be conscious ten seconds hence, as I figured it would take me that long to try to get David to eject and then eject myself. Meanwhile, I was holding each breath I made of the thin air whilst using my chest muscles to increase my lung pressure to a maximum. This may have made the difference. I will never know. Using some valuable air I desperately transmitted a May Day call to Melbourne Control, saying I was doing an emergency descent through airways and may have to bail out. Melbourne responded and wanted to know details of the emergency and my position. All I managed to say was that I was close to Nhill.
I could only determine the aircraft speed by the extent of shock wave buffet shaking the wings. If I went too fast, I ran the risk of an uncontrollable nose down pitch. Altitude rapidly reduced and I felt my senses recovering a little. As soon as I assessed that conditions were improving I was able to give some more advice to Melbourne ATC. There was no conflicting traffic in the area. I levelled out at 8,000 ft and expected to recover rapidly as I had done when deprived of oxygen to unconsciousness in decompression chamber training. This time though the oxygen lack had been over a much longer time and contrary to belief, my recovery was also only gradual.
David Smyth recovered consciousness, wondering what had happened and how did he happen to have his seat harness undone. Evidently his last actions before becoming unconscious had been to try to get out of his seat. He would not have been able to eject successfully.
My head started to ache and my body was objecting to doing the simplest things. I descended towards Laverton, with Melbourne control giving me lots of encouragement and mustered my remaining efforts to put the aircraft on the runway. Taxying in to park was an extraordinary effort and I made my way home to our newly occupied house on the base with a headache which kept getting progressively worse. Collapsing into bed after some headache pills, I immediately fell asleep, waking up late next morning, still with the remains of a headache.
Later that day, I determined that the oxygen regulator in the bomb aimer's position in the nose of the Canberra had somehow been on its emergency setting, bleeding off our oxygen contents at a rapid rate. Also, the operation of the ejection seat emergency oxygen bottle required a push-down rather than a pull-up on the wooden knob on its cable. I had pulled up with enough force to break away the solder securing a brass sleeve within the wooden ball to the cable. The ball had then slid up the wire causing me to believe that the system had actuated. Soon after, all RAAF Canberras were modified, as had those in the RAF, so that the ball could be pulled for actuation. At the time, this modification had been almost ready for application by the RAAF as a follow on from the RAF.