Centaurus highlights very nicely the problems associated with decision making in the grey area of the early airborne phase of a takeoff in a light twin.
At the end of the day, unless the aircraft is reasonably light and at a lowish density height, then, until one is cleaned up and at a suitable height with respect to obstacles, and at a useful speed, there will always be a sweaty area associated with a significant risk in the event of a failure.
He poses a quite reasonable question which might be paraphrased to read "why the variety" ?
While Centaurus' view must be respected due to his vast experience (20,000 hours plus) both as a pilot and instructor, I see the main problem being one of trying to simplify the decision making process .. especially for comparatively inexperienced pilots.
Ideally one would like to transform this process to the programmed decision which applies generally for the FAR 25 cousin.
While this latter stategy is rarely achievable for a FAR 23 aircraft, some of the alternative approaches seek to reduce the period of time during which the pilot is faced with that sweaty problem of will it go or will it not ? The inexperienced pilot who perseveres with the continued takeoff in a clearly deteriorating situation sets him/herself up for an eventual Vmca departure.
I echo his concerns regarding ground effect acceleration. While I loved to watch a revered bearded elder do this in the Mustang out of Essendon from time to time, it is not a technique which is appropriate for the routine GA takeoff.
The concerns regarding blue line lift off are valid but I would propose that that situation still remains considerably simplified for the less experienced pilot when compared to a "normal" liftoff speed. It is an underlying principle that this technique is inappropriate for a short runway.
The question of overspeed and the potential for overrun is valid but can be addressed by comparatively simple calculations or a rescheduling of the AFM data.
The manufacturer generally will be constrained to schedule minimum speed data for all the normal commercial reasons. There is nothing sacrosanct about the normal takeoff speed and a higher speed can be scheduled if desired and appropriate for the Type's handling characteristics .. but perhaps not for the lovely Twin Commanche. Such overspeed scheduling was not uncommon in Australian charts produced to the old CAO 101.22 rules.
Perhaps Centaurus' concern is directed more to the endorsement training scenario. If this be the case, then I am totally in agreement with him. As the more generally applicable technique will remain the minimum speed takeoff, it is essential that the new twin pilot be very competent with the problems associated with such a takeoff. The other techniques canvassed in this thread ought only to be addressed in the endorsement situation as discussion items. After all, they are intended to be simplifying considerations, not basic technique.
As to which is the best approach ? How long is a piece of string ?
[ 07 January 2002: Message edited by: john_tullamarine ]</p>