How much lift is produced by flaps?

[Byrna]

Hello Everyone,

I use Microsoft Flight Simulator 2004 and fly commercial jets like The A320, 737NG, 742, 744 etc...

I have a feeling that, like everything else in FS2004, the amount of sudden lift we get when lowering flaps during the final approach is probably too much - i.e. the aircraft is too sensitive to flaps being lowered.

But I wanted to ask any real-life pilots out there if this is indeed the case. For example, for an A320-200 series, let's say you're descending at 800fpm and then lower flaps to 1 (assume speed of about 180KIAS), does your descent rate suddenly change to say 200fpm unless you compensate right away with the ailerons/trim? or does it change more gradually to, say 600fpm? In FS2004, the plane's descent rate changes by a large amount. How does it change in real-life?

This question is also for any other commercial jet you may be flying, not just for the A320.

Any feedback would be much appreciated.


John

[Intruder]

In many airplanes there is a temporary "ballooning" effect as the flaps are lowered. However, there will be a net increase in drag after the airplane is stabilized, and there will be a greater rate of dexcent at the same airspeed when more flaps are extended.

[catchup]

Theoretically extending the flaps should have no influence on sinkrate during approach on A320 (and so on).

That's cause a "load factor" is commanded by the stick. But like I said "theoretically." ;)

regards

[Byrna]

Hello catchup,

I don't understand what you mean by this "load factor" commanded by the stick. Are you implying this won't happen with aircraft which have a yoke instead of a stick like the 737 series?

John

[ifleeplanes]

Flaps have two main purposes, to increase lift and to increase drag. Jet transport aircraft have high speed wings (since this is the enviroment they spend most of their time in) and in order for them to fly slowly enough to land/takeoff on a reasonably short runway they have to produce more lift. Thus if you extend flap you produce more lift and thus baloon. You compensate by reducing the AoA, if you anticipate this you can compensate and after a while you will do it automaticaly and by the correct amount. On the B737 Stages 1-25 compartively produce more lift than they produce drag. Flap 30 and 40 produce more drag than they increase lift.

[catchup]

Hello byrna,

on A320 controlling the vertical profil with the stick is desiegned that way, that a load factor (g-command) is commanded.

e.g. flying level means 1.0 g. Descending means < 1.0 g, climbing means > 1,0 g.


http://www.apollosoftware.com/products/FlyByWire/FlyByWire_english.pdf

Much better explained than I can ;)

regards