Seeing this story which is going around right now
I wonder if it is not enough runway, or something else like air conditioning limits?
What about limits for out GA planes, and turboprops like a PA46T, and light jets?
But why the limit? Is this related to engine limits? Because other than that, one could simply use more runway…
I assume avionics cooling. Hence note 3.
I believe the main part of the problem is that the performance charts don’t exist above a certain temperature. So anything above is “unknown” territory in terms of performance so the airplane will stay on the ground.
Yes, when there is no performance chart for a high OAT then interpolating is not allowed, they have to have a chart – at least that is what I have heard about the Airlines. Performance itself should not be a problem.
I will long remember taking off from DAAT Tamanrasset (4,500’) at a temperature of 40°C in an HS125. Eventually we just decided to rotate and go into ground effect, on the grounds that the acceleration had become so little as to be threatening :-(
It’s really interesting to find out the actual reasons for these limits, not just that they exist.
In physics i.e. the world around us, a lot of stuff is directly related to the absolute temperature (in degrees K) where zero K is -273C, ice melts at +273K, water boils at +373K. So the difference between say +20C and +40C is only 20/293 i.e. only 7% which is not a lot but to humans it feels huge. Chemical reaction speeds tend to be exponential versus K but there isn’t much in a plane which involves a chemical reaction at the ambient temperature 
I can see air conditioning systems might have very specific limits because the refrigerant may be unable to condense no matter how hard you compress it (and the compressor will have a very specific power limit anyway) and this will happen quite suddenly.
The other angle is discomfort. I recall departing from LEAX (near Malaga, Spain) in something over +35C and Malaga etc kept us below 1000ft for ages, and it was extremely uncomfortable for Justine. I was just about OK. This trip. The TB20 is like a greenhouse and needs no heating even at FL200 in sunshine and say -25C OAT. But the TB20 is nowhere as bad as some other types which have an all-clear roof.
That also leads to a need for a sun cover to avoid stuff getting damaged inside.
The last days we had temperatures of up to 36 degrees down here in Southern Germany, … very little flying. This was the time where my Air Condition paid off, otherwise it would have been un-flyable. I only hope it doesn’t break … (typical Air Condition repairs on a Cirrus are € 5000). It was so hot I didn’t even bother to clean the plane after flying but ran away to my air conditioned car …
At what temperature is ATC required to give temp as well as wind in the takeoff clearance? I recall it only once (Olbia Sardinia 42degC). Presumably required because of the performance limitations.
