galaxy flyer:
Yes, V “go” must take Vmcg[1] into account. On 4-engine airplanes configured like the B707, that’s quite limiting to the range of V1s when you are light. But on those (rare) beasts like the VC10, Comet/Nimrod (and maybe Concorde/B1), with less asymmetry, Vmcg can be quite low.
Must admit I’d forgotten the difficulty of obtaining a range of V1s with present-day instant tables or computer programmes. Good idea of yours to use the RTOW case to find the top figure, but wouldn’t know how to find the bottom one. On the VC10, we used to do it all from basic principles, taking about 10 minutes (including a Flex calculation).
Surprised to hear of 50% braking in some single-failure circumstances on your present type.
Pace and Diesel8:
Yes, a double engine failure before VR sounds unlikely on a 3 or 4-eng aeroplane, so why did we consider it unofficially on the VC10? Because the engines are behind the landing gear and mounted in pairs, like the Comet/Nimrod, Jetstar and Concorde (not to mention the B1 and B52). As far as conventional aeroplanes are concerned, there was the El Al B747F that was unlucky enough to throw a blade from one engine into the other over Amsterdam.
By the way, the VC10 can get airborne on 2 quite nicely even at medium-to-high weights, particularly at sea-level. [After all, it’s only like a twin losing one, although the performance regs don’t have to cater for it.] Not so the under-powered Seven-oh. And I seem to remember the 707-320 with JT3D-3Bs had a Vmca[2] of 147kts, so it could not manage it even at low weights, if the failures were on the same side.
ssg:
I know that you are, to some extent, playing Devil’s advocate. But in relation to Flex, don’t forget that TOGA is still available as a bonus (though not assumed in the calculation). De-Rate, of course, is another matter.
Having “taken the shilling”, I advocate sticking to SOPs to the letter; but not all scenarios can have an SOP. The trick that we all hope we will never have to perform is that of recognising that there is no applicable SOP, no time for “DODAR”, and still making a good decision.