Think of this one as you would a Anti-Ice ON penalty, or as A Comfy Chair has put it.
In similar style to A Comfy Chair's input, imagine an aircraft with an RTOW limot of 100,000 Kg. Along comes an MEL (or Anti-Ice ON) reducing your RTOW by 10,000 Kg. Now, the new maximum weight for operation is 90,000 Kg, and the aircraft will perform at 90,000Kg as it would in normal circumstances at 100,000 Kg. So far so good, this is for a Full thrust operation.
What now if the ACTUAL weight of the aircraft is 75,000 Kg? After applying the MEL (or Anti-Ice) correction of 10,000 Kg, the weight for performance calculation is 85,000 Kg, some 5,000 Kg less than the prevailing adjusted limit. We are less than the limit by 5000 Kg, and may use Assumed (Flex) Temperature thrust reduction.
From the performance perspective, that's perfectly legal, safe, and within accepted conventional procedures.
There is a kicker to this. Many operators sensibly dictate that for non-normal operations thrust reduction is not to be used (even though it could be). This is a matter of policy erring on the conservative side. If the operator does do things this way, there will probably not be any instruction for other than full thrust takeoff. Gards, does your operator in these circumstances specify that Full Thrust MUST be used, or say nothing at all? Interested to know.
Regards,
Old Smokey
Last edited by Old Smokey; 29th Jan 2009 at 09:08.