Originally Posted by
lomapaseo
Do a google search on MD80 reserve thrust (excluding all flight sim products).
This neat little feature doesn't need pilot input, it simply looks for differences between engines of 10% or so.
On most aircraft/engines with that feature - variously called things like "automatic power reserve", the official part 25 term is Automatic Takeoff Thrust Control System (ATTCS) and its regulated by § 25.904 - the thrust level even with the thrust increased by the system is still constrained by engine ratings.
Whereas, as mentioned, a manual "firewall" of the engines will generate thrust potentially far in excess of rated power - causing economic damage to the engines, but potentially saving the airframe. On a hot day, such as the accident, the engine rated thrust will be restricted by engine temperature considerations, and there will be considerable mechanical scope to increase fan and core speeds. As a complete WAG, there could be 20% or more thrust available, albeit for a limited time. Of course, in the OEI case it's generally NOT a smart move, because all your VMC numbers are also predicated on rated/ATTCS thrust levels.