Quote:
Originally Posted by tgrayson  The question is, do you HAVE to add flaps to fly 20 knots slower, or is it that this is the only configuration in your performance charts? At jet climb speeds, you are likely far above your stall speed and so the flaps would do nothing for you, other than adding drag. |
I don't know about ERJ speeds, but for CRJ speeds, yes, you need to first indent of flaps to go 20 knots slower. I don't have a speed card book in front of me, so these numbers probably aren't accurate, but at max landing weight in the -200 (47,000lbs) our clean min ref speed is about 170 knots. Ref is figured on a whole bunch of stuff including 1.27 Vso. Our manual (which is based on aircraft certification data) requires that until stabilized on an approach (read: steady state flight) we must be at least at Ref+10.
So at max landing weight we can go no slower then 180 knots without going to flaps out. Our ref speed for flaps 8 at 47,000 is around 158 (I think), so just by putting out that 8 degrees of flaps we can go from 180 knots down to 168 knots.
The question of course is, do those 12 extra knots of airspeed that we can burn off in a climb amount to a bigger change in the climb efficiency curve then the added drag of 8 degrees of flaps. I'm thinking probably not, as, as you said, if climbing with flaps increased the ROC then airlines would be using them.