D& X
D77, going back a bit, and you may get more answers on Tech Log, but here goes; taken from the Brize Norton `Aeroplane scheduled performance ` notes, which I believe were based on the VC-10, operated to `Perf `A`.
`D` represents the equivalent balanced field length, taking account of wind, slope ,etc.
`X` represents a correction to the respective deviation from the balanced field power failure speed ratio.
Values of `x` are ratios of V1 and Vr for a balanced field, but the value of 100 is equiv. to the balanced field length.
Thus `x` is 100 when `toda` and `emda` are equal in still air, no slope. thus a `toda` and an `emda` of 6000ft, `d` would be 6000, and `x` is 100.
Graphs are for `d` and `x` for toda and emda,,`d and x` for `tora ` and emda; `d` for `toda- all engines operating`; `tow ` for a given value of `d`; PFSR` for a given value of `x`; limitation on `pfsr( brake energy considerations).
If you want the notes , send me a pm. Syc