I've seen quite a few posts lately....many a bit too hot under the collar, about whether an "average" GA aircraft (such as the Warrier or Cessna 172 etc) displays a nose up or nose down attitude on deployment of flaps. For a developer this is a nightmare, because everyone's right and wrong at the same time!My understanding of flap deployment in the vast majority of GA aircraft is that 99% of flaps produce greater lift but of course also drag. The INITIAL response in pitch can vary depending on speed, loading and C of G at the time of deployment. The initial reaction is not the same as the EVENTUAL reaction. For instance, A Piper Warrier with 2 heavy passengers in the back seats might well pitch up alarmingly on deployment of flaps at greater than normal speeds, but after airspeed has reduced (inevitably, assuming no pilot input other than flaps)the nose might well drop due to the reduction in airspeed and therefore lift.On the other hand in a light aircraft with a forward C of G due to two heavy pilots in the front seats and no-one in the back, and flap deployment at comparitively low speeds, might produce a brief nose down (but this is more rare). But eventually almost all aircraft are going to produce more lift with flap, which implies a tendency for the nose to rise. But then again if the pilot does not anticipate this with a slight forward pressure, the nose up can be followed quite quickly by a nose down as the speed bleeds off and overall lift is reduced.I'm not trying to sit on the fence here....merely pointing out that aerodynamics of flap deployment is not a simple matter and that all flying is a matter of fluidity and constantly changing response.That has never been more demonstrated than in my current work which involves a well-known GA aircraft, test pilots of which have all disagreed amongst themselves as to whether the nose rises or falls after flaps!In situations like this, no-one has the monopoly of wisdom and one trusts in instincts and logic about how flaps change the dynamic of a given aircraft at a given speed, weight, balance and altitude.In short there are no definitive rules and unless a particular aircraft is RENOWNED for a definite attitude due to individual peculiarities, I would always err on the side of slight pitch up on deployment followed by an eventual opposite reaction once the speed has decayed, all other things being equal!Kind Regards,Rob Young - www.realairsimulations.com

Thanks Rob for the interesting and detailed info. Food for thought! Robert J

http://forums.avsim.net/dcboard.php?az=sho...ing_type=searchGreg

Depends on the aircraft type and other factors.Most high wing aircraft pitch up initially after adding flaps due to downward moving air (which is increased or redirected when flaps are added) trailing off the wing and hitting the horizontal stabilizer. Low wing aircraft can experience a change in pitch depending on the aircraft and even the current CG (since it relates to the change in the center of pressure or lift)

In the Piper Cherokee aircraft we fly at the Spokane UND satellite (Cadets, Warrior IIIs, Arrows), they all seem to have no pitch change tendancie. However, there's a sudden upward balloning as the AoA has just changed with the flaps requiring you to pitch nose down to get the AoA back where it was and arrest the ascent. This might be percieved by some as a pitch up tendancy (after all, you had to pitch down, leading those that don't understand AoA and flaps to think that they've pitched up)----------------------------------------------------------------John S. MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private 130+ hrs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach