Insomniac
I hear what you're saying, but the bit I had a problem with is as follows:
(The numbers are not accurate, I'm just using them to show what I mean)
If we use Improved Climb (Airport Analyses) tables with a given weight of lets say 55.8t under the 0 wind column, it gives us speeds of v1:150 vr:154 v2:159
Now, although you are more temperature limited for a given weight under the 10kt tailwind column (although not prohibitively in most cases) the speeds for 55.8t are v1:144 vr:150 v2:159
As I said, these are not actual figures, just an example.
So the question is, for a
given weight if lower V-speeds (V1 and Vr) are acceptable with a tailwind, then why would those speeds not have been used in the 0 wind column to start with?
The V1 is not a problem - I got that. But why Vr?
I am starting to see though that it has probably got a lot to do with engine out performance and achieving screen heights, which with a tailwind, might not be so easy if you spend longer on the tarmac with one engine inop. And the reason for not putting those same speeds in the 0 wind column seems to be that the 0 wind speeds are worked out for optimum performance whereas the 10kt tailwind speeds are calculated for minimum required performance. (Did I get that right? Or even close?) It should be borne in mind that the figures I am talking about come from the Airport Analyses, and the resultant speeds really depend on the criteria that they have used for calculation and the factors they use for different wind conditions.
I'm sorry if I haven't explained it very well, but it's the best I can do at this time of night!
I do, of course, appreciate any other help you can give me.