Originally Posted by
Jonty
I haven’t found anywhere in any of the manuals where the 10 mins TOGA limit is deemed more or less limiting than any of the other aircraft limitations. Nowhere does it say “to save your ass”...
What I am saying here is that the 10 min limit can be exceeded, but only in very limited circumstances where it is used to ensure the safety of the aircraft.
What I find very interesting is that everyone knows the 10 min limit, it says it in the book. What is that limit based on?
As a guy who has worked as an engineer in an engine workshop, and currently flying a B737...
1) The overspeed and overweight limitations and use are clearly explained in the FCTM. The books never say "to save your ass", that is my phrase. The books will always state the PIC is allowed to deviate in the interest of safety. However these situations are pretty clear and as said, the deviation should not be an excuse for lack of preparation.
2) your question on where the limit comes from. It comes from certification, it is related to airworthiness and maintenance plans and can be found in the AFM. If 20 years ago you would have asked me (the engineer) the question, my answer would be easy: the why is unimportant, it is a result of certification tests following a laid out plan that gives you a certainty it will work for 10', and continues to work for the remainder of the flight in MCT thrust situations. If you decide to deviate and bust limitations, you are entering a grey zone where engineers might not have valid test data, and basically nobody will certify your engine will continue to work as expected until you're back on the ground after a diversion.
So you might feel comfortable doing so based on your knowledge, the engineer will be very curious to look at your engine to answer some questions he didn't have the budget for in the testing phase.