Nose pitching with landing gear.

[louisv]

When taking off, the moment you raise the landing gear the nose suddenly pitches down...

 

I get it that the nose pitches down when lowering the gear, and then gradually as the gear comes out, and yaw as the wheels go in sequence.

 

But here the gear goes up and the nose pitches down, it should pitch up as the gear goes away and then not so suddenly as if the gear was in (out) in half a second.

 

It's not clear if there is yaw as the reaction seems too quick and inverted (gears going in).

 

Also when landing, the yaw from the torque reaction resulting from engine changes seems to be the same whether its a small power change or a big one. And that landing yaw is a killer.

 

Actually I'm not much better at landing even without engine changes, but still, the reaction seems overdone for small power changes.:smartass:

 

But I absolutely love it.:pilotfly:

 

And I just cannot wait for DCS 2.0 with the Rift...my god.:helpsmilie:

[Anatoli-Kagari9]

louisv,

 

I didn't notice that, but I have to test and will report back in this thread, anyway, I have a theory, because:

 

1) All DCS prop aircraft are very sensible ( wobble intensive ) after taking off or when at high AoA / low speeds;

 

2) I believe this could be justified by the same principle that explains why when inflight we use right rudder to stay coordinated, the aircraft starts pitching up..

 

Well, here it goes... Looking at a youtube I noticed that when the gear retracts, it's the starboard ( right ) side one that goes up first, so, there's asymmetric drag from the down standing left gear, making the nose veer to the left, and, by the same reason the aircraft pitches up when we apply right rudder, yawing right, it pitches down when veering left.

 

This has nothing to do with Gyroscopic effect, which in this case would rather account for a pitch up, just as it would for a pitch down when inflight we apply right rudder ( being a CW rotating prop we have in the K4 ) but rather and apparently, judging from some Yo-Yo answers, due to the P-factor, and how it is being modeled in DCS World prop aircraft.

 

I just don't know if this is realistic, but maybe others can help ? Yo-Yo ?

Edited January 20, 2015 by jcomm

[Yo-Yo]

When taking off, the moment you raise the landing gear the nose suddenly pitches down...

 

I get it that the nose pitches down when lowering the gear, and then gradually as the gear comes out, and yaw as the wheels go in sequence.

 

But here the gear goes up and the nose pitches down, it should pitch up as the gear goes away and then not so suddenly as if the gear was in (out) in half a second.

 

It's not clear if there is yaw as the reaction seems too quick and inverted (gears going in).

 

Also when landing, the yaw from the torque reaction resulting from engine changes seems to be the same whether its a small power change or a big one. And that landing yaw is a killer.

 

Actually I'm not much better at landing even without engine changes, but still, the reaction seems overdone for small power changes.:smartass:

 

But I absolutely love it.:pilotfly:

 

And I just cannot wait for DCS 2.0 with the Rift...my god.:helpsmilie:

 

The yaw reaction due to engine changes is one of the features of the 109 mentioned by several pilots in their notes including some contemporary operators.

The moment of the gears is right - try to retract and extend them at 280-310 kph. Then try to fly the plane with 10% of fuel retracting the gear at TO as you usually do it. See the difference. I Think, the reason is that the plane with full tank and rear tank becomes neutral or even unstable at full power. So, it's possible is your reaction to the nose up pitching moment... I do not know exactly because I never notice this effect.

Ok, and try to retract/exten the gears during gliding at the same speed you retract them on TO. By the way, unsymmetric retracting will cause yaw that produces pitch changes.

Edited January 20, 2015 by Yo-Yo

[Anatoli-Kagari9]

The yaw reaction due to engine changes is one of the features of the 109 mentioned by several pilots in their notes including some contemporary operator.

 

In the DCS K4 it is accompanied by a noticeable rolling moment too. I don't know if this is realistic, but I think it makes sense...

 

Regarding the pitch down when the gear retracts, couldn't it be due to p-factor, the same way p-factor accounts for the nose pitch up when we apply right rudder, since it retracts asymmetrically ( right gear 1st ) possibly creating a yawing moment to the left ? ( plz see my post above in this thread... )

Edited January 20, 2015 by jcomm

[Yo-Yo]

In the DCS K4 it is accompanied by a noticeable rolling moment too. I don't know if this is realistic, but I think it makes sense...

 

Regarding the pitch down when the gear retracts, couldn't it be due to p-factor, the same way p-factor accounts for the nose pitch up when we apply right rudder, since it retracts asymmetrically ( right gear 1st ) possibly creating a yawing moment to the left ? ( plz see my post above in this thread... )

 

Yes, I mean the same.

[Anatoli-Kagari9]

Yes, I mean the same.

 

Ok, so that's it most probably :-)

 

Talking to a friend who flies aerobatic aircraft, he also acknowledges the mostly unnoticed P-factor effects by many pilots who aren't even aware that it plays it's "magic" not only when taking off in taildraggers. Most aviation texts even say it's a negligible effect during other phases of flight, but it really isn't, and whenever the prop is loaded, it plays its effects.

 

Also spent some time reading a few comments from ww2 bf109 pilot notes, and it was interesting to read from one of them, don't recall the name now, that he used to advocate that takeoffs should be done with the three wheels on the ground until the aircraft lifts off by itself - "it wants to go up naturally", he wrote, and, I couldn't but compare this to exactly what happens with the K4 in DCS :-)

Edited January 20, 2015 by jcomm

[venancio.avf]

i think this "let the aircraft lifts off by itself" is due to the tiny free space between the prop and the ground so this way you would avoid hitting the prop on the ground