Corked nose wheel - the return

[Antoine]

Another crazy idea occurred to me while "working" on a better NLG.

From watching the video of a DA40 taking off shot from under the plane's belly, it seems to me that the reason why the nose wheel is corked is the airflow around it.

In order to twist it this way the airflow has to be exerting a force that is sucking the part in its corked position.
So maybe if we had a fence placed on top of the fairing ( maybe attached to the strut). we could direct this airflow to eliminate the lateral sucking component.

Now if we made the fence into a moveable flap, we could allow the corking effect or forbid it at will.

Did someone else notice that the corked nose wheel makes a nice trim setting for the climb ( no right rudder needed)?

What think you?

[Steve]

I recall that a few years ago, Lopresti was supposedly working on a new-design nose gear fairing to eliminate this problem (someone with access to the old Forum can search for this). It never progressed past the prototype stage, as far as I know...

Steve

[ricksigler]

I noticed the same thing. I'm thinking it might have to do with the way the air is coming off the prop and the position of the nose gear is just from seeking a parallel position to that airflow. If the nose gear doesn't twist after takeoff it might be because the joint is stiffer.

[SimonH]

Dumb question....what is 'corked' in this context? Normally I'm sending a bottle of wine back when I hear that word!

Cheers
Simon

[gfuller]

Twisted -turned

[Gnomad]

Thought I'd drop this video into the thread for reference...

http://m.youtube.com/watch?v=7dcXeTbP_3I

[Nirbm01]

Maybe a dumb question - but maybe it will be improved if the fairing is taken off?

[Antoine]

Amazing video Eric. This demonstrates the problem perfectly. Here is my analysis:
1. It is clearly the airflow that twists the NLG. It occurs about 20 sec after take off. Vy?
2. It twists to sit parallel to the airflow at low (climb) speed. A rough calculation shows that when flying at 75 KTAS, the radial speed f the airflow is about double the forward movement of the aircraft. This explains the odd angle to the general airflow.
3. It does not return to the "Normal" position in cruise. Part of it has to do with friction in the antishimmy and I calculated that the prop wash is still strongly influencing the local flow in cruise so that there is not enough force to recenter it.
This brings up an idea: what if we added a "tail" to the fairing that would be just big enough to recenter it in cruise? The tail would actually only force the nose wheel to sit exactly where it causes the least drag - parallel to the local flow.

[Antoine]

Maybe a dumb question - but maybe it will be improved if the fairing is taken off?

Not dumb at all - I think it would work, but of course we're losing even more by removing the fairing...

[rwtucker]

Great idea Antoine! I can't recall the make but I have seen NLG fairings with an aft vertical fin to keep the fairing aligned with the relative wind. They might have been aftermarket on old Cherokees.

To the best of my knowledge, my NLG has never been corked. I wonder what other factors are at play.