I suppose what I'm after is the more static speed case really. I realise that if you are able to allow the speed to increase, and particularly if you use speedbrake also, then extremely high rates of descent are possible. But, they are reasonably short lived. (I accept that from FL390 a rapid descent can be maintained for quite a while until MMO becomes VMO)
So what about after you've reached 340 Knots with the speedbrake out? What would you expect the descent rate to settle at in that case and more improtantly, how much different from 340 Knots
without speedbrake would it be??
I'm trying to get some idea of how many track miles would be too few if you're suddenly given a short cut for an approach for example. The aircraft at an average rate, descends at 250 Knots fairly close to a 3 degree path. How much does that increase with speedbrake? If you're descending at 250 Knots a steady 1,400 FPM and then with speedbrake you get 2,000 FPM then super! You've just taken one third off your required track miles. You've gone from 3 degrees to 4 1/2. From FL100, where you needed say 35 miles originally, now you only need 25.
That's kinda what I'm looking for. For average conditions, will the speedbrake add half your original RoD? A third? A quarter? Double it??
Hmmmm.........
