737NG-Engine Failure during a Double Derate take off

[PEI_3721]

soundlover, et al, the risk assessment is not quite as is suggested.
First the thread title might be misleading; consider a takeoff with engines rated at a value less than maximum, but where this is the new max thrust. Then a reduced thrust takeoff would be allowed under existing rules.
These ensure that in the event of engine failure the minimum speeds do not jeopardise the flight handling safety margin, or the climb performance detracts from the obstacle clearance safety margin. Thus like-for-like, a ‘double derate’ takeoff provides equivalent safety.
It is only when additive and rare circumstances are considered that many aspects of this debate apply, but even then, the safety of any operation requires other considerations, e.g. consider the wind shear risk before takeoff.

Whilst all of the non-additive situations provide a safety margin, the value of the margin or the rate at which the limit could be approached are not identical; in this instance low weight / speed being more demanding.
Thus whatever reasoning there might be for applying more power in rare circumstances, the risk assessment should consider the aspects above, particularly where the bottom line of doing nothing is no more hazardous than for any take-off with or without the ‘additive’ situations, but alternatively acting hastily, or with surprise, or misjudgement of the situation, then the actions could seriously reduce the safety margins and the the ability to maintain control.
Safety is the art of knowing where the ‘edge’ is and maintaining a sufficient margin for any error – yours or others.

Engine Malfunction Recognition and Response.

http://www.faa.gov/documentLibrary/m...ar/AC25-13.pdf

http://www.theairlinepilots.com/foru...atedthrust.pdf