Originally Posted by
BraceBrace
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.
Thats not where the limit comes from though is it? The regulatory requirement is to be able to operate the engine at TOGA thrust setting for 5 mins, 10 mins OEI without exceeding engine limits. That actual limit the engine feels is EGT (amongst others, but this is one of the most critical) for the CFM it’s between 940 and 975 depending on type. Max continuous limit is 905 to 940. Given that EGT falls 3.5 degrees for every one degree of OAT you could argue in northern Finland in winter your not likely to ever see 900, never mind 940. So it could be that you’re nowhere near the EGT limit, even with TOGA selected. And if that is the case, why would you deselect it if you needed it to maintain the safety of the aircraft?
I’ve seen it done, time and again, where people react to the book limit without looking at what’s actually required to maintain safety.
Now going back to the original question. Airbus states that for OEI go around. “When following a published missed approach procedure, the EO ACC ALT should be the lower of the missed approach altitude or the MSA”.
So the thrust leavers should go to MCT at the end of the acceleration, which should be at MSA or the missed approach altitude.
FCTM/Procedures/Abnormal and Emergency Procedures/ENG/One Engine Inoperative - Go Around.
If you can’t achieve the gradient then do the EFP. And I would include the TOGA limit here. If you needed 12 mins of TOGA to complete the standard missed approach, do the EFP instead. Now if you were to lose the engine on the go around, and you can’t do the EFP, all bets are off. And if you need 12 mins of TOGA, use it.