Strange take off

[EG14_Marcast]

Not an issue of course, just a curiosity. In all planes when you lower the flaps on landing the nose rises. This is because the drag is increased by flaps. Some planes, especially german bombers, need some flap extension at take off. For the same reason explained before, when you raise flaps after take off your nose should go down: this happens in fact with the Bf110. In Ju88, as soon as the flaps are raised the nose jumps high so that you have to use stick and trim to correct and prevent pitching. Don’t you think it’s a strange behaviour, or is there something I don’t get?

[Pirabee]

Speaking from basic knowledge I believe when flaps are lowered they first increase the wing surface enough to generate immediate lift. It is this that the aircraft reacts to with that nose-up behavior but after it is trimmed the full effects of drag next step in.

[ATAG_Colander]

Besides drag, flaps change the position of the lift force vector on the wing.

[ATAG_Knuckles]

Full size aircraft all need trim changes after raising and lowering flaps, some more than others

If my memory is correct, high wing aircraft tend to pitch "down" when flaps are lowered, low wing aircraft tend to pitch "up"

[TWC_SLAG]

Full size aircraft all need trim changes after raising and lowering flaps, some more than others

If my memory is correct, high wing aircraft tend to pitch "down" when flaps are lowered, low wing aircraft tend to pitch "up"

Right, and just the opposite for raising the flaps. i.e high wing a/c pitch up

Some of that is because you have the nose trimmed up.

badfinger

[EG14_Marcast]

Right, and just the opposite for raising the flaps. i.e high wing a/c pitch up

Some of that is because you have the nose trimmed up.


The Ju88 is a low wing. And the strangest thing is that when you lower the flaps on landing the nose pitches up correctly, while on take off it pitches up when you raise them.

[92 Sqn. Philstyle (QJ-P)]

The Ju88 is a low wing. And the strangest thing is that when you lower the flaps on landing the nose pitches up correctly, while on take off it pitches up when you raise them.

Relative changes in attitude and airspeed also affect this.

On landing, your nose is down, the top of the wing is acting as a break. Dropping the flap slows you down, thus reducing the balance of the wing-break from the top surface to the lower surface. This will push the nose up.

One climb after take off, your nose is up, the underside of the wing is acting as a break. Raising the flap will remove some of the breaking from the underside, at the same time as increasing airspeed. This will mean more lift on the top side of the wing, thus pulling the nose up.

[Baffin]

The short answer is that this is normal and pilots have always had to "Just deal with it", using trim & controls. In more modern aircraft, designers have gone so far as to engineer hydraulic/mechanical "Flap/Stab Interconnects" that compensate automatically for this behavior. In the newest "Fly-by-wire" designs, this compensation is programmed into the flight computers.

Colander is most correct in explaining that the center of lift moves forward and aft as the flaps are applied, thus the plane goes somewhat out of trim when this happens. Shock waves have similar effects as Mach 1 is approached. While not understood at the time, this contributed to the inability of many WWII airplanes to recover from high speed dives as shock waves affected lift and control surfaces.

This explains why I frequently hit the ground vertically! It's not my fault, it's those darned engineers!