Thank you all for your thoughts,
I have been sent some interesting stuff, it seams the Australian Navy and the Royal Air Force Sea King guys have done some work that suggests a caution when operating above 37.5 C, it suggests restrictions on ground idle time and also recomends extended recovery periods between flights.(up to 2 hours in some cases) It also defines an extreme danger period above 45 C ambient where all but non essential flights be avoided (I know which flights my boss thinks are essential - you guessed it!) Other research also shows that aclimitization is very important as is dehydration, physiological studies show it is difficult for a person sweating profusely to rehydrate during the period of sweating - so drink before and after the flight. Heat stress appears to effect different people in different ways, quite clearly some "cope" better than others. The research and anecdotal evidence does suggest a reduction in skills at higher temps and an increase in fatigue related to the lenth of time exposed (this more how it effects me personally, I don't feel particually stressed during the hot flight but am more knackered at the end of the day) I think that if there is a factor (that can be mitigated) that can adversley effect our performance (and therefore our obligations to passengers and crew) then as professionals we should at least consider it. It may be as simple as a water cooler in the crew rest area or a complex risk matrix that cancels flights above a certain temp, I thinks its probably somewhere in between, thanks again for the responses, I appreciate it,
Joe.