I have a certain jet airliner I was tooling around in today and while holding at typical landing weight, at 3000' MSL and at IAS 180, my pitch was 7 deg. So to lower the pitch, I threw out slats and.....pitch rose to 10 degrees! After throwing out the first notch of flaps, pitch reduced to 9 degs, then with the next notch to 8 degs. But I had to throw out 5 notches to get down to 2 degs pitch which seemed incredible to me.I had figured without thinking even beforehand that slats and flaps would surely lower my pitch while holding, so this was a nasty surprise.What IS supposed to happen in such circumstances?JS

The slower you are the higher the angle of attack will be. First, on the NG you want to be at least flaps 15 gear down @ 180 knots. You want at least flaps 1 @ 210 and can even use 5. Flaps 5 is not flaps five positions, it's flaps in 3 positions and you NEVER use flaps 2. Don't know why they just don't. The thing to remember is to be properly configured on approach and you will have the correct pitch angle.. Best Wishes,[h4]Randy J. Smith[/h4]http://www.rawbw.com/~bdoolin/shinault/Animation1.gifCaution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |

Thanks for this reply, but I was asking essentially if there is something wrong with an a/c that pitches UP when you lower the flaps. I deliberately set myself up to fly low and slow and in the wrong attitude in order to test the flaps (not of the NG either!) and I was surprised to find how the a/c pitched UP (instead of what I thought would be down or more toward the horizon at least) in this exercise. I think that in every jet I've flown in FS, the a/c pitches downward if you throw out flaps during level flight as I was doing. JS

I first noticed this effect when learning to fly a Cherokee. If you lower flaps without touching the yoke the aircraft will initially pitch up. As speed decays the aircraft will pitch down again.My guess is that on lowering flaps you increase wing camber and this probably moves the Centre of Pressure forward with a resultant pitch up (someone correct me if I am wrong here). Then, as speed decays, the aircraft will naturally pitch down again.Of course in real life pilots don't put down flap with their hands off the yoke. In the Cherokee you need to push forward moderately on the yoke as flaps go down (and on an Aztec you have to push fairly hard!) but this is only momentarily because as the speed then decays the stick pressure actually reverses.Having not flown big tin jobs I can't speak for them but I guess the same aerodynamic laws apply. boneshttp://fsaviation.nethttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

So, are you saying that after the initial ballooning due to flaps extension settles, the a/c pitch goes DOWN naturally?JS

Who can say unless you state which type of aircraft you are talking about? Certainly not all rl aircraft react the same with flap deeployemnt. It's true most GA aircraft in flight sim pitch with flap extenstion then settle down a bit but how it is in reality is only for rl pilots of each aircraft type to comment on.Best Wishes,[h4]Randy J. Smith[/h4]http://www.rawbw.com/~bdoolin/shinault/Animation1.gifCaution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |

I have avoided these "flap" discussions over the years because they quite often become unfriendly. I'm not interested in this one either, but I will offer up just some of the variables of the subject:Coefficient of LiftCoefficient of Drag-- including Profile, Induced, and ParasiteCoefficient of Moment, PitchVelocityReynolds Number-- just to include kinematic viscosity into the mix.Aspect RatioWing LoadingCenter of GravityCenter of PressureMoment, PitchMean CamberDesign of Flap--- Fowler, Split, Simple... you name it.Again note, these are just a few of the variables. Finally, a rather important variable in all this has little to do with aerodynamics... it is the matter of airspace qualifications. Factors such as desired airspeed, rate of decent, and others dependent upon any given approach will play a very important role in what happens when flaps (and other drag and/or lift inducing devices) are deployed.The only really hard and fast rule about the deployment of such devices is that it is a very dynamic thing. I point this out because it's important to not make the mistake of asserting what SHOULD happen when flaps are hung out into the airsteam. Cheers,Greg, BSAE Cal-Poly 1974

Greg:OK, OK, I get your point.This is sorta like the pitch-or-power? discussion on climb vs. descend, isn't it ?!Anyway, thanks for jumping in and muddying the water further (!)JS

Hi,Just though I would chip in with a generic answer that assummes - very important this - that all changes of configuration are from a trimmed straight and level attitude. As the previous poster says, any discussion outside of this will not achieve anything :)Any type of flap increases wing camber and angle of attack. Some like fowler flaps increase wing area too. All results in an instant increase the lift coefficient (CL) and angle of attack.The secondary effects are that the centre of pressure (centre of lift) move back along the wings. Normally the centre of gravity is a little ahead of the centre of pressue to promote static and dynamic stability by inducing a gentle and natural nose down tendancy. As the centre of pressure moves further back with flap extension it will lever the nose of the a/c down more. However, an increase in angle of attack will tend to move the centre of pressure forward resulting in a nose up condition (from a previously trimmed straight and level condition). It is entirely possible on some aircraft that the INITIAL application of flap will cause a nose pitch up due to the sudden increase in angle of attack as well as a climb, but as speed decays to maintain straight and level againt the a/c would settle into a lower nose down attitude than it would otherwise settle into if it were flapless. The generic text book says that flaps cause a nose pitch down. On my AA5 as with any other a/c I have flown the a/c will intitially just climb (baloon) without any pitch change if left to its own devices.HOWEVER! Swept wings cause all sorts of strange effects. If and only if you are approaching the stall in a swept wing aeroplane, you may experience a pronounced nose up tendancy as the tip of the wing starts to stall. Sewpt wings tend to stall at the tip first thus concentrating the lift on the inboard section of the wing thus moving the effective centre of pressure forward, twisting the nose up. In addition the downwash of the air in such a situation from the inboard section of the wing on some aircraft may push down on the tailplane causing a further pitch up - this is called the "ramshorn effect". Some a/c have been fitted with T tails to help get around this, but in those cases the air to the tail could be blanked and all elevator authority may be lost thus resulting in a "deep stall" - a loss of lift and nose up...very scary I should imagine. The usuall method of getting out of this is....you guess it...full flap to get the centre of pressure rearward again, sometimes with the gear deployed to cause drag below the normal drag line helping pitch the a/c down too so that elevator authority can be reestablished.Hope that helps, gives you some food for thought and some things to consider :)Kef.

Referring to the excellent response by Kefuudle in this thread, I would add that you have to consider the sum of all the terms that make up the equation for the total pitching moment of the aircraft, with the emphasis on the word "total".In this context the overall pitching moment depends on :1) the difference between the position of the aerodynamic center of the wing (about 1/4 chord aft of wing leading edge in subsonic flight and about 1/2 chord aft in supersonic flight) and the position of the center of gravity.2) the pitching moment of the aerodynamic center (which is not zero even though its variation with angle of attack is zero).3) the lift, which depends on the angle of attack.4) the changes in lift and pitching moment due to a particular flap type and configuration.So, we really have to look at the forces and moments at play for the entire aircraft, head to toe, to answer the question, not just the flaps or the wing.The really interesting part comes when we impose the two restrictions to to the total pitching moment above in order to find out what may interest us most: is the aircraft statically stable or not in flight? But that's another topic.On the practical side, having a lot of flight time in the real Twin Cessna series aircrafts and other I will answer the question of the flaps with a definite:" it depends".The Cessna 310 model on one hand and the Cessna 421A or 421B model on the other, both have the same NACA airfoil and the same type of "split flaps" that extend underneath the wing, the kind that is invisible from the cockpit. Well, flap extension in the C310 causes an abrupt and very large pitch up moment of the aircraft while it is barely noticeable in the C421. Draw your own conclusions! It does depend on the rest of the aircraft.Other pilots out there can probably report a pitch down moment due to flaps with other GA aircrafts. By the way, an excellent source of fundamental documents for this kind of topic is the M.I.T. web site in the "Openware" section of the Aeronautical Department. Some of it is not for the faints in math, but it is well worth the effort.Charles