Hypoxia
Tuesday 17 November 2015 - a day I will never forget.
8am Riversdale, raining, Southerly 10kts and gusty, overcast 1500' AGL. Weather reported clear in Canterbury and most likely to remain so. But how to get there, as Dansey's Pass would be socked in. However, the overcast appeared lighter far to the east, so headed out towards Balclutha, wearing the life jacket, and prepared for a seaward journey. Approaching Balclutha, found the sky clear to the East but a wall of solid cloud to the North, with clearly delimited tops, extending out to sea. My chart told me of Class C down to 9500' so I climbed towards it, intending to fly home on top, and preparing to make a request call at least ten minutes ahead of time.
I was making position calls every ten minutes and one of these was answered with a request to call on Control frequency, which I did, to be informed that I had broken Class D 3500' (which shared the same boundary as the Class C, on the VNC, and I had misperceived the double significance of that single line). I belatedly requested entry to Class D, and then to Class C, intention Controlled VFR on top destination Rangiora, to be told that it wasn't possible because of other traffic, but my suggestion of a seaward route proved acceptable, so I headed out to sea, then turned NE, and was cleared to 10,000'. ATC subsequently advised that the ceiling below had cleared to 4,000' but no holes opened up to make the descent possible.
The flight continued, uneventful, until it became clear that further north the tops were higher. ATC gave clearance to 11,000', and further north again to 12,000'. After more than a half hour above 10,000' I should have been concerned, but later it became clear to me that I was probably in the grip of hypoxia intoxication. The fingertip oximeter told the truth - the blood oxygen level was far too low, but I remember thinking "Oh, that reading is quite okay" - though of course it wasn't.
ATC then cleared me direct to Rangiora. When I was abeam Momona I heard them call an A320, preparing to descend to Momona, (and probably above Oamaru), clearing them to descend and warning them of a microlight ahead, that had by then climbed to 12,700'. When I heard that I called in and advised that the cloud tops had become higher, but also, about that time, I saw water below me through a large hole, and requested (and was granted!) a descent, which I did in figure-8 pattern, as my GP had earlier advised me, to avoid vertigo being caused by continued one-way turns without a clear horizon.
Below 9,000' I thanked ATC and continued without incident to an uneventful landing, in bright sunlight, at RT.
The aftermath: within a few days I had a (very minor) stroke (which at my age, then 77, is a known consequence of hypoxia), the effects of which soon largely dissipated. I was also treated to a free interview with the CAA, who, quite properly, viewed the incident as very serious indeed. They said that I was ill-equipped for such a flight, having neither oxygen, (which would have protected my health and clear thinking), nor an autopilot (which would have enabled an emergency descent through cloud in relative safety). Needless to say, Papa Lima Charlie is now equipped with both oxygen and autopilot. CAA also, very reasonably required me to take PPL Law before venturing into controlled air space again. I have yet to sit that exam, but staying in Class G is not a hardship.
Medical: after any stroke-type incident there is increased likelihood of another, and sensitivity to hypoxia is increased. So, my medical now only lasts one year; if I carry a passenger they must hold an IBIS rating (to save themselves if I collapse in flight); and I must use Oxygen above 5,000'.
I'm not an instructor, so it wouldn't be right to offer advice, but if you can take any lesson from this experience, please feel free to do so!
Papa Lima Charlie
Copyright © 2018 Peter Leon Collins
v2, 30/07/2019