Tailplane negative lift

[Spaceman_Spiff]

One thing that has been bugging me for quite some time, is that I can't mount a tail plane with negative lift; when attaching a tail plane, the lift vector gets moved further aft. On real aircraft, tail planes have negative lift to counteract the CoG being in front of the lift vector.

Usually I end up making aircraft with canards instead which do have positive lift.

Is there any way that I don't know of to make negative lift tail planes? With the new aircraft parts in 1.0.5 I tried making some realistic aircraft, but they ended up with the CoG so far in front of the lift vector that they hardly had any positive pitch range in flight. I suppose KSP somehow takes into account the negative lift of the tail plane while flying, just not when building in the SPH. Otherwise the aircraft would be highly unstable in flight.

Edited November 10, 2015 by Spaceman_Spiff

[Boris-Barboris]

CoL indicator in SPH is true when your control surfaces are at 0 action (neutral). Real aircraft tail planes don't provide negative lift in neutral state either. When you pitch up, on the other hand, they do, both in KSP and RL.

[Spaceman_Spiff]

Real aircraft tail planes don't provide negative lift in neutral state either. When you pitch up, on the other hand, they do, both in KSP and RL.

That's because in level flight the tail plane is not at 0 degrees angle of attack (in most normal aircraft, I know there are exceptions). Only when pitching down.

This still doesn't change the problem that the tail plane creates positive lift, when it shouldn't except for special designs.

[Red Iron Crown]

Angle the tailplanes' leading edges downward. I'm not sure if it affects the CoL marker like you might want but it has the right effect in flight.

[Boris-Barboris]

Draw a sketch in paint of the situation you don't like, I have a feeling you're missing something.

[Spaceman_Spiff]

Angle the tailplanes' leading edges downward. I'm not sure if it affects the CoL marker like you might want but it has the right effect in flight.

I just tried this, and it works, thanks! It only has to be angled very little downwards, pressing the c-key so it doesn't snap. If I angle it too much downwards, the lift vector moves backwards again somehow.

[Val]

I just tried this, and it works, thanks! It only has to be angled very little downwards, pressing the c-key so it doesn't snap. If I angle it too much downwards, the lift vector moves backwards again somehow.

In KSP it better to angle the main wing up, rather than angle the tailplane down, because wings in KSP don't provide lift unless they have Angle-of-Attack.

If you don't angle your main wings up, then your craft is forced to fly a little nose-up all the time, for the wings to produce lift. That's bad for drag, especially if your trying to go super-sonic.

My suggestion is to angle the main wing up, up to 5° (one snap) and angle the tailplane a little less up or not at all.

[DancesWithSquirrels]

Normal airplanes have negative lift on the tailplane - in large part because the airfoils used for the wings have a pitching moment attempting to drop the nose. STOL aircraft can have very large negative lift to get the nose up at slow speeds: here's a pic from the Zenith 701 STOL page:

The negative lift on the tail is also a serious safety feature. In case of an approaching stall, the tail is usually set to stall first - and without the negative lift on the tail the nose drops, reducing the angle of attack and getting you out of the stall.