Hot and high??

[Lump Jockey]

What's the elevance/significance for hot and high testing? How does the temp and altitude of an airfield actually affect teh a/c's performance. TIA.
LJ.

sorry, that should read "relevance"....had a bit of trouble editing that one!!:O

[Sheep Guts]

Well speaking on turbo Props in respect to KING AIRS. At higher altitudes and hotter temps, the engines reach their ITT limitations much earlier, which in effect governs the amount of available Torque or Power for takeoff, which inturn affects Take off Distance Required. This also if your high enough in extreme circumstances, it affects the SINGLE ENGINE climb performance and may cause the need to totaly revise drills for single engine recovery at very high aerodromes ie 8000ft and above, ie. Close both power levers and ditch or use available power and negative performance to ditch.

I assume that Jets are affected in a similair way.


Regards
Sheep

[Keith.Williams.]

The effects of altitude and temperature on thrust, drag, power available and power required have recently been debated in the Tech log forum. The title of the string is sonething like "Cold weather climb performance fact or fiction"?

The basic problem is that increasing altitude or increasing temperature decrease thrust and power available while increasing power required. The overall effect is that best climb gradient and best ROC decrease as altitude or temperature increase. This process continues up to the absolute ceiling where best gradient and best ROC are both zero.

In a normal atmosphere the effect of increasing altitude is partly offest by the reduction in temperature. But in some areas you get the worst of both worlds, high ambient temperatures at high elevation airfields. Under these circumstances the mass at whcih you can take-off will be severely degraded.