Originally Posted by
Tomaski
And yet I have actually seen this difference in the Engine Out Acceleration Altitude (EOAA) happen when comparing the takeoff data for full length vs intersection during preflight, so something changed. The explanation I gave is the one given to me by our training department.
So, theorising what might have occurred (please understand - This is just one of many possibilities!). Say you have two obstacles to be cleared, one close in, one further away.
For the intersection departure, the thrust requirement is a large one to clear the close in obstacle. As you have a large amount of thrust on, the OE climb angle is steeper and acceleration segment is shorter and you climb away without the second obstacle having any effect.
But for the full length departure, the thrust requirement to clear the first obstacle isn't too great so the performance app reduces the thrust to just clear the first obstacle be the required margin. But because the subsequent climb out and acceleration are that much longer the second obstacle comes into play, requiring the performance app to raise the EOAA to avoid this...
But say you take off from the full length with intersection data - Because you'll have the higher thrust selected, you'll not only avoid the second obstacle by miles, you'll also avoid the first by a greater margin...