ERJ Flap Question

[tgrayson]

Originally Posted by BobDDuck

not in any procedure I've seen for the CRJ.

Bingo. That should be enough to cast suspicion on the concept. If flaps improved your climb rate, the airlines would likely be all over it.

The only way going slower would increase your ROC is if you were flying much faster than best ROC speed. And maybe you are, if you do some sort of cruise climb. So going slower may well improve your climb rate, but it has nothing to do with the flaps.

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.

(BTW, where I'm going with this is that one idea that I sneaking into the thinking of almost every pilot is this: 1) Airplanes climb because of excess lift, and 2) Flaps increase lift, hence increase climb rate. Both statements are false and potentially dangerous. In your scenario, flaps would have to decrease drag in order to increase climb rate.)

[Polar742]

Originally Posted by Doug Taylor

Flap overspeeds are a MASSIVE deal on the 757/767 fleet. In fact, you only extend flaps when you need them for lift, not drag.

On the -88/90 you will generally use flaps and slats for drag so descending at 280 and you need to get down, you'll call for 'slats extend'. On the 75/76, you generally only call for flaps as you decelerate through the maneuvering speeds.

Originally Posted by Doug Taylor

Do you know what works well is primacy. Nothing resets the situation like "positive rate?"/"gear up!" during windshear events or missed approach procedures.

Originally Posted by Doug Taylor

Pretty much depend on all that 'auto' crap not working. I've seen plenty of folks bork a landing because the autospoilers or autobrakes didn't work when expected.

Originally Posted by Doug Taylor

Pretty much like a Ron Popeil machine.

"Set it and forget it"

But sometimes they don't work so you need to have the SA to deploy them.

As usual, Mr. Taylor hits all the info you need to know.

As for the ERJ crew....well, we all make mistakes.

[BobDDuck]

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.