supergimp,
You've addressed one of the major concerns that I encounter when developing Special Procedures for One Engine Inoperative operations.
Before proceeding any further, allow me to categorically state - "
Do NOT accelerate the aircraft until the Emergency turn is complete!!!"
The turns specified in Special OEI runway procedures ensure your lateral separation from obstacles, the speeds flown ensure your vertical separation from obstacles, but VERY IMPORTANTLY also determine the turn radii used to calculate the outer and inner edges of the lateral obstacle clearance splay. Thus, if you commence acceleration from V2 to your Final Takeoff Clean speed, the turn radius may well take you right outside the splay, and in conflict with obstacles not considered for the takeoff.
The greatest danger is with light weight Takeoffs when an early turn is required. Unlike an aircraft at it's limiting weight, you may well reach the acceleration altitude before or during a designated turn. If this occurs, my recommendation is to MAINTAIN the second segment speed (usually V2 to V2+10/15) until the turn is complete, even if this means delaying the acceleration until a greater than minimum acceleration altitude is reached.
One of "my" problem runways is Hobart (Australia) Runway 30. It's tight for obstacles. A right turn is required at the runway end, through more than 180° to ensure safe lateral separation from VERY high obstacles on the outer part of the splay. If the aircraft goes off at MTOW, it will still be at V2 upon completion of the turn, but a light weight aircraft will reach the nominated Minimum Acceleration Altitude during the turn. If the outer turn radius is based upon V2+10, the heavy aircraft has no problem, it is at V2+10 or less and on minimum turn radius. If a lighter aircraft accelerated to clean speed during the turn, terrain impact is
GUARANTEED.
My initial solution was to provide pilots with advice to delay acceleration until the turn was completed (as described above). Sounds simple enough, but then we had people who wanted to reduce thrust to maintain the speed, some who could not conceive of maintaining V2 to a higher than MAA until the turn was complete. My repetitive dream became one of being the star witness at a coroner's inquest.
The solution that I finally adopted was to assume, for the purposes of calculating the outer splay limits during the turn, that the aircraft was at clean speed all the way from screen height. It brought a whole new bunch of obstacles into play that weren't there before, with consequent performance and payload penalties due to the greater 2nd segment gradient required. The accountants groaned but I slept a whole lot better
So the bottom line is this, find out from your airline / Performance Engineering department / sub-contractor for performance analysis, just what speed and bank angle criteria do they employ for the calculation of outer and inner turn radii. (I include bank angle in this comment because some wanted to fly a 25° bank commanded by the Flight Director, and there goes the lateral protection for the inner part of the turn splay). If they use Final Takeoff speed for
ALL outer turn radii, then go ahead, accelerate as soon as you reach acceleration altitude. If they do not, then I say again - "
Do NOT accelerate the aircraft until the Emergency turn is complete!!!".
Fly safe, know how the performance information that you use was derived.
Regards,
Old Smokey