The results were very illuminating. The ground heart rate, say 65 for a healthy individual, would be 100-110 at FL120. There was a huge individual variation too. I was pleased that I was the least affected of the group (about 85/min) but I still get very tired flying without oxygen at say FL100. I have flown with an instructor who could not read the altimeter at FL120.
So does that mean that when flying we are all doing cardio-vascular exercise? More fun than running…..
I have only used the boots once every 20-30 flights …
It very much depends on the aircraft. There are aeroplanes that pick up almost no ice, eg. the Cessna 421, where I have uses the boots less than five times in over 1000 hours. But others like the Seneca seem to attract every supercooled drop of water inside a radius of a mile and you find yourself operating the boots in almost every cloud…
However, in the 421 your TAS might have been 200-220kt, whereas in the Seneca only 150-160, which is a huge difference in the aerodynamic heating which is logarithmically related to TAS.
Coupled with that, in IMC one needs to be a little careful about flying faster than Va. If it isn’t actually rough, there is a chance that suddenly it might be.
So does that mean that when flying we are all doing cardio-vascular exercise? More fun than running…..
Very funny 
I am not sure / don’t remember whether the breathing speeds up also. Also there is a view that the heart itself doesn’t need more exercise (it already gets it all the time) and it is other parts of the body that benefit from normal exercise.
However, in the 421 your TAS might have been 200-220kt, whereas in the Seneca only 150-160, which is a huge difference in the aerodynamic heating which is logarithmically related to TAS.
But you see the most ice during climb and descent where a C421 (good climb speed is 130KIAS) and a Seneca (maybe 120KIAS) are not much different. And during cruise (values from real life, not sales brochure: C421 – 200KTAS, Seneca V – 180KTAS) the 421 will usually fly higher at lower ambient temperatures, thereby compensating the ram air temperature rise.
I am not sure / don’t remember whether the breathing speeds up also
I’m not a doctor, but I believe breathing rate is mostly determined by the need to flush CO2 from the blood.
(As CO2 is metabolised, it ends up in the blood, and the resulting mild acidity increase is detected).
So unless you are shivering or nervous you should be breathing at the same rate sitting in an aeroplane as sitting on the ground.
This is why scuba divers waste most of the oxygen in the high pressure air that they breathe, and conversely, sedentary pilots at altitude get less than they need.
Climbers or skiers at altitude are less likely to be affected while they are exerting themselves, as they are making more CO2 than usual, which has to be breathed out, with the useful side effect that more oxygen is breathed in. So performing OK at FL120 while skiing may not be a good prediction of how you will feel while flying that high.
Going back to the earlier part of this thread…..using the UK Met Office wx…..they often say “30% chance of CB”. For years I took this to mean a 70% chance of not meeting a CB. In June 2011 I flew to Calais on a “Yankee” flight plan, which gives me the option of an ILS into Calais. Crossing the channel at FL60 kept us out of cloud. Coming back, I climbed back up to FL60 and it was obvious I would soon be in IMC. The cloud looked dark but “feathery” and once inside it was very smooth. I decided to stay at this level because once I was 10nm north of DVR vor I would have to descend to remain below CAS. This is where the “70% chance of not entering a CB” went completely wrong. I started to pick up loads of static on the radios plus other weird noises in the headsets. Then my co-pilot said “Lightning!”. I looked up to see more strikes all around us. I asked Manston for a descent and traffic service. During the descent we had hail followed by heavy rain. It was a short time, maybe 5 minutes, but it seemed longer. Now when I see “30% chance of a CB” I take this as a serious warning not to enter IMC.
The problem is that the forecaster is permitted only PROB30 or PROB40.
So, in the UK anyway, PROB30 is a shorthand for “I don’t think it will happen but it might and I need to cover my xxxx” and PROB40 is a shorthand for “I think it will probably happen”.
Also, any trough on the MSLP chart
translates to a PROB30 TEMPO TSRA (or similar) so there could be a CB forming, especially later in the day.
PROB30 in a TAF can mean two vastly different things, the extremes of which are
1) Scattered stuff. 100% chance of CB but scattered enough not hit the airfield with more than 30% likelihood
2) Unlikely stuff. 30% chance of a front or air-mass taking off big time, and when it happens it will hit the airfield with certainty.
The former is the one where you need eyeballs or radar to avoid tactically, and the likelihood of arriving in one piece is very high.
The latter is where you need enough warning to turn around, and the likelihood to arrive is only 70% [higher if you survive the CB encounter…]
Quite a difference… I like (1), and hate (2).
Yesterday I was on my way from EDAZ (Schönhagen) back to EDFC (Aschaffenburg) at FL70. OAT was between 1C and 3C. I was initially asked to climb to FL80 but opted for FL70 as FL80 would have put me right inside the base of the clouds and there was some heavy precipitation further ahead. So I asked to stay south of it and decided to stay in positive temperatures as well. For about 5 minutes I was going through a section of rain that on the ADL was depicted in yellow. It was loud but there was no turbulence.
Much closer to Frankfurt I got “Advice when ready to climb” and I responded that I want to stay at FL70. Minutes before that I was given vectors for separation from military traffic. ATC was fine with me at FL70.
Had I accepted to climb I would probably have had to climb through the thin looking layer and then be at -2C or less at FL110. As I was about 50NM from my destination, I didn’t think that climb would have done any good to me.
Nobody complained and I continued on for some nice sunset view.
Yesterday I was on my way from EDAZ (Schönhagen) back to EDFC (Aschaffenburg) at FL70
At the same time I was heading in the opposite direction Kassel EDVK to Schoenhagen EDAZ. I did try my chance climbing on top. Above the freezing level I did pick very light ice so I switched from a cruise climb to a short full power climb. I became VMC at about FL150 and cruised at FL170 in the sun.
On the decent I picked up some light ice:
As Stephan shows this flight could have been done without a turbo but while he was going through the rain shower I was enjoying the bright sunshine above it wink:
