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Take Off Charts

Old 9th Aug 2017, 07:01
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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 40C. 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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megan is offline  
Old 9th Aug 2017, 07:41
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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.
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Old 9th Aug 2017, 09:11
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.. by what means does the cited text come up with the figure quoted ? I presume he is following the Hartman method ? .. just for interest ..
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Old 9th Aug 2017, 09:39
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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.
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Old 9th Aug 2017, 12:06
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I'm with RT - sketch it out on a bit of graphpaper, extrapolate the curve, add the standard public transport safety factor to be safe.

G
Genghis the Engineer is offline  
Old 9th Aug 2017, 17:29
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40 deg C..?


That's Mirror Shades, Tee Shirt and Baggy Shorts, whilst sitting on a beach.
or..
Climb to FL100 asap.
.
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Old 9th Aug 2017, 17:38
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If the OAT is >30 deg C (never mind 40 deg C) and there's no air conditioning I don't go flying.

Also is there anything in limitations about max temperature for operation?
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Old 9th Aug 2017, 20:07
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Originally Posted by scifi View Post
Climb to FL100 asap.
Last week we were getting gondelbhans up to around FL100 just to keep cool.
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Old 9th Aug 2017, 20:26
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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.
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Old 9th Aug 2017, 20:32
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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.
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Old 9th Aug 2017, 21:10
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Years ago, RSAF Riyadh (2,000' asl). C172 grading squadron, 40 degs. C plus, no flying! And we had 12,000' of runway.

Bill
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Old 10th Aug 2017, 08:10
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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!
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Old 10th Aug 2017, 08:40
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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.
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Old 10th Aug 2017, 18:26
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Better Take Off Charts than Take Off Pants!

(sory, couldn't resist any longer)
Jan Olieslagers is offline  

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