Take Off Charts
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Take Off Charts
Below is a chart for a Cessna 172. Wanted to ask the question as to what you personally would do if the temperature were in excess of that listed on the chart, in this case 40°C. For those in cold climes probably not something you would come up against, but nevertheless, your opinion please. We'll assume at a sea level pressure altitude.
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I kind of agree with TangoAlphad but if you HAD to make an attempt in such circumstances you could use the technique mentioned by Sparky Immeson in his book Mountain Flying.
Find the halfway point on the runway and mark it with something, or note some feature you will be able to see on the roll. On takeoff if you get 70% of flying speed by that point you will get off. If not abandon and stop in the remaining half. This assumes the second half of the runway is much the same as the first half and takes no account of obstacle clearance.
Find the halfway point on the runway and mark it with something, or note some feature you will be able to see on the roll. On takeoff if you get 70% of flying speed by that point you will get off. If not abandon and stop in the remaining half. This assumes the second half of the runway is much the same as the first half and takes no account of obstacle clearance.
If it was hotter than 40C I would be reasonably happy extrapolating on graph paper. I hope the temperature is not more than 50C!
BUT these tables tend to be on the optimistic side anyway. If there was any doubt I would wait for sunrise next morning when I hope conditions would be on scale.
BUT these tables tend to be on the optimistic side anyway. If there was any doubt I would wait for sunrise next morning when I hope conditions would be on scale.
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Interpolate, don't ever extrapolate. Extrapolation will normally void the insurance, leaving you in the wind to pay for any and all damages should you have an incident or accident.
Let's be clear too there is never, ever, a reason that you HAVE to go flying. If you're flying for pleasure, then have enough money to park it and go commercially. If you're flying commercially, have the fortitude to say "no" if you cannot back up your flight with actual, out of the book data.
Let's be clear too there is never, ever, a reason that you HAVE to go flying. If you're flying for pleasure, then have enough money to park it and go commercially. If you're flying commercially, have the fortitude to say "no" if you cannot back up your flight with actual, out of the book data.
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The chart ending at 40 deg's C is there for a reason; either flight testing was stopped, or the aircraft performance didn't warrant any further certification, either way be very careful if you decide to interpolate or extrapolate because if there is a reason for the insurance companies or CAA/FAA to get involved you won't have a leg to stand on.
As +TSRA says above "there is never, ever, a reason that you HAVE to go flying" especially for pleasure.
As +TSRA says above "there is never, ever, a reason that you HAVE to go flying" especially for pleasure.
Years ago, RSAF Riyadh (2,000' asl). C172 grading squadron, 40 degs. C plus, no flying! And we had 12,000' of runway.
Bill
Bill
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If you're prepared to sit in the cockpit performing all the necessary preflight/start up/post start up checks while it's > 40C outside, TBH you're mad enough not to care what the POH states! 
Guess there'll be no flying in central Australia this summer! Just work out the density altitude and do your sums and keep an eye on the eng and oil temps. Cessnas cope very well in the outback.
