No .. this is typical of the problems between the artificial world of certification and flight test and the real world of aeroplane driving ....
The value declared in the AFM for Vmcg will be appropriate for a set of conditions, including nil wind (US certification). But the story is a little more complex than that ...
Consider certification and flight testing, generally. If we were to run a test program or a certification exercise in the absence of defined "standards" or "assumptions", then we would need to pad out the work report(s) with a whole bunch of information so that the reader would know what the conditions, assumptions, and so on which went into the work were. Making comparisons of different tests etc. would be a nightmare workload. Such a system would last all of about 5 minutes ....
So, we refer performance data to (nominated) "standard" conditions (which represent some sort of average atmosphere) and use defined conditions for tests such as Vmc and Vmcg.
The problem arises in that the values so obtained relate only to the presumed and defined conditions. So, the AFM Vmc/Vmcg figures are reasonably conservative but not necessarily always conservative, when measured against normal operations.
It is quite "legal" to takeoff at Vmcg-limited minV1 in maximum crosswind, from a low elevation aerodrome, with maximum aft CG and rated thrust ... just don't lose the upwind engine approaching V1 and expect to be able to continue the takeoff without some handling problems and wide eyed looks of amazement ... I can well recall when I started to use this sort of exercise for familiarisation in endorsement training programs ... provided that the particular simulator has a half decent program for this area of the envelope it opened more than a few eyes to the potential for high pulse rates if a pilot doesn't keep his/her wits about him/her. On simulators which don't it often is a total waste of time.
It comes down to a need for the commander to have an appreciation of the limitations inherent in certification matters as they might affect line operations.
So far as "critical engine" is concerned, think in terms of which engine (having failed) is going to give you the greater problems ... this is the critical engine. However, for certification, the conditions under which this and any certification parameter is determined are constrained ... although there is nothing to stop an OEM from making more extensive investigations (except the fact that it might cost a lot of extra dollars).
Last edited by john_tullamarine; 20th April 2004 at 06:52.