Originally Posted by
Drop The Dunlops
Aircraft B737-700, 20K powerplant
JAR Perf
hmm
Given that Boeing grandfathered a bunch of stuff on the later 737s, I wonder if their performance data is also grandfathered. Data on other than dry runways
used to be optional, rather than required for certification. In which case there will be no specific rules about scheduling V1 ...
To answer the original question:
Is is safe / correct to raise a V1(contam) to equal V1mcg, therefore leaving you above the speed that would guarantee a stop before the end of the ASDA?
It isn't as "safe" as your normal operations on dry, in that indeed, you are not guaranteed to be able to stop in the case of an engine failure between your V1stop and the V1 you're actually using. It would indeed be prudent to reduce the weight a bit to buy back that margin.
But, there's no hard line in the sand for much of certified performance - no matter how much we kid ourselves by quoting distances to the foot and scheduled speeds to the tenth of a knot! (I've seen both in worked examples in flight manuals, and it's frankly farcical). So in fact it is "safe" because we don't have to dig a bunch of airliners out of overrun areas every spring. By which I mean that operational experience indicates that
in practice the reduction in safety margins compared to the "dry" case is justified by the absence of an effect on accident rates.
Its exactly the same logic as for reduced wet screen heights, allowed use of all braking devices on wet runways, assumption of zero x-wind for Vmcg, and so on.