CASA opinion: Aircraft must be grounded in temps over 40 degrees

[megan]

POH take-off charts typically provide pressure altitudes and temps however there is nothing to stop the pilot working out an equivalent density altitude and using that instead. It is just a convenience to help calculate, not a performance limitation.

Agreed, as a read of the FAA Pilots Handbook dealing with take off performance centres on density altitude, which is as it should be, since that is what determines aircraft performance. In entering the graph or table with pressure altitude and OAT what you are determining is that at that (unstated on the chart) density altitude the take off run will occupy XXX feet. Of course you can determine the density altitude easily enough should you so wish, it's just that it's not stated on the chart. Density altitude is the only altitude your aircraft understands, it doesn't understand pressure altitude, nor temperature, as stand alone parameters.

https://www.faa.gov/regulations_poli...t_handbook.pdf

Extract from a Cessna 207 manual - at gross, short field on a paved, dry, level runway, distance to clear 50 feet, where I've calculated the DA from the formula DA = 1.24 PA + 118.8 OAT − 1782 and extended it to 50°C.

PA/OATXXx0°CXXX10°CXXX20°CXXX30°CXXX40°CXXX50°C
0XXXXXX-1782XXX-594XXXx594XXX1782XXX2970XXX4158 DA
XXXXXXXx1770XXx1900XXx2040XXX2195XXX2355XXXXXXXfDistance
1000XXXX-542XXXX646XXx1834XXX3022XXX4210XXX5398 DA
XXXxXXXX1940XXx2085XXx2240XXX2410XXx2600XXXXXXXfDistance
2000XXXXX698XXx1886 XXx3074XXX4262XXx5450XXX6638 DA
XXXXXXXx2130XXf2295XXX2470XXX2665XXx2875XXXXXXXfDistance
3000XXXX1938XXx3126XXX4314XXX5502XXx6690XXX7878 DA
XXXXXXxX2345XXf2530XXX2730XXX2955XXx3195XXXXXXXfDistance
4000XXXx3178XXx4366XXX5554XXX6742XXx7930XXX9118 DA
XXXXxxXX2595XXx2805XXx3035XXX3290XXx3570XXXXXXXXDistance
5000XxXX4418XXX5606XXx6794XXX7982XXx9170XX10358 DA
XXXXXxxx2880XXX3125XXx3390XXX3685XXx4020XXXXXxXXDistance
6000xxXX5658XXX6846XXx8034XXX9222XX10410XX11598 DA
XXXXxxXx3215XXx3495XXx3810XXX4165XXX4575XXXXXXXDistance
7000XXxX6898XXx8086XXx9274XX10462XX11650XX12838 DA
XXXXXxXx3615XXx3945XXf4325XXx4760XXXXXXXXXXXXXfDistance
8000XxXX8138XXx9326XX10514Xx11702XX12890XX14078 DA
XXXXxxXx4095XXx4500XXx4970XXXXXXXXXXXXXXXXXXXfDistance

A Koch Chart will similarly predict adjustments, based on OAT and PA, to be made for both take off and climb data.

Their position is that the range of the parameters in the performance charts forms part of the limitations for the aircraft.

And if look at the C207 data I've posted that limit is take off at a DA of 10,514 feet.