Hi barit1,
With the first press of the TOGA switches, all Assumed / Flex thrust reductions are removed. With the second press, all de-rates are removed when on the ground. In flight, one press only is required for full TO thrust, or fire-walling the thrust levers. We have no cockpit indication of the setting required for Rated or Full thrust, and rely entirely on the engine computer to deliver the thrust asked for. The only posible manual setting, is Full TO at fire-wall, and this DEFINATELY does not apply to all aircraft, in many aircraft (or the B777 with EEC OFF) the fire-wall position would exceed full thrust.
As FEHoppy has pointed out, the maximum thrust reduction allowed from Rated thrust is 25%, and having lower thrust ratings is one way around the regulations for an even further reduction, e.g. for TO-2 (B777) Rated Thrust is 80% of Maximum, and 25% reduction amounts to a mere 60% of full thrust if maximum Flex/Assumed Temp reduction is made. Easy to see how advancing from 60% to 100% following engine failure could get you into J_T's 'smoking wreckage' scenario. In a wind shear recovery scenario (no engine failure) a huge thrust excess is available.
The other advantage of large De-Rates (e.g. 20% at TO-2) is that the Vmcg/Vmca is much lower, allowing much lower V1/Vr/V2 for contaminated or slippery runways. Engine failure at V1 on an icy runway is definately NOT the time to advance assymetric thrust, in fact our training recommendation is to leave the thrust 'as is' until airborne following engine failure, and then thrust may be advanced to the Takeoff rating if desired.
CAUTION - Thrust De-Rates are 'customer selectable', and the 8% reduction I've quoted for TO-1 and 20% for TO-2 are airline specific (our GE powered B777s have 10% and 20% De-rates).
It would be interesting to hear from mutt as to his policy for APR OFF Takeoffs on the Jungle Jet. Is there any recommendation to advance to APR after engine failure, and if so under which circumstances (definately not at V1)?
Regards,
Old Smokey