VMCG Testing
Gents,
I work for an outfit that has operated the A330-300 for many years. Just recently we have changed our performance planning system from AI Octopus to an LPC (computer). The result is that we will be using very much lower speeds almost all the time. The change is in the order of 10-15 knots (from typically 137, 137, 140 to something like 126, 128, 135).
I know from watching other Prune threads that VMCG 'grows' with a crosswind and I am concerned that we are now operating all the time much closer to our limits than before. Indeed our Boeing 747 manuals talk about this very problem.
Vmcg for the -300 is 122 knots but our sim is based on a -200 and has a Vmcg of 112 knots. I think therefore that we are 'flattering' ourselves into believing this is a satisfactory situation! A contributing factor here is that we are required to do the V1 cut in 150M viz for LVP certification and many crews are right on the runway edge when rotating. Doing it in CAVOK makes it much more controlled.
I have access to the sim and have tried to do engine failures at these limiting speeds (and even 10 knots lower) but the results are inconclusive.
So how do you go about establishing Vmcg during flight test and am I barking up the wrong tree with a problem that is more evident on quads than twins? Is there a time factor built into the certification that I'm missing? Other threads mentioned 5 seconds but this seems too long to me! How much would the CoG (being at the mid point) shift the actual Vmcg vs fully aft?
Humble apologies for the long post and looking forward to being enlightened!
Last edited by idg; 19th June 2007 at 22:38.