Corked Nose Wheel

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Antoine
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Re: Corked Nose Wheel

Post by Antoine »

BRS wrote:
Thu Jun 13, 2019 5:33 pm

BTW - couldn't help notice your vent naca. If you tape off the bottom half you will have much less noise and more air.
Absolutely. And if you do it, do it right, not like me. All of sudden I heard a strange noise coming from the engine compartment and made an emergency landing. The tape had gone lose and was flipping in the wind...
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BRS
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Re: Corked Nose Wheel

Post by BRS »

Antoine wrote:
Thu Jun 13, 2019 11:00 pm
BRS wrote:
Thu Jun 13, 2019 5:33 pm

BTW - couldn't help notice your vent naca. If you tape off the bottom half you will have much less noise and more air.
Absolutely. And if you do it, do it right, not like me. All of sudden I heard a strange noise coming from the engine compartment and made an emergency landing. The tape had gone lose and was flipping in the wind...
Ha I've had the tape come loose a few times. I'm thinking of making some sort of plug. Scarry - but benign.


SORRY FOR THE THREAD DRIFT.
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Antoine
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Re: Corked Nose Wheel

Post by Antoine »

waynemcc999 wrote:
Thu Jun 13, 2019 6:36 pm
BRS wrote:
Thu Jun 13, 2019 5:33 pm
@Rich
BTW - couldn't help notice your vent naca. If you tape off the bottom half you will have much less noise and more air.
I concur with Brock that the air vent noise (esp the high frequency screech) is cut to less than half with the glider tape solution. Here's a quasi-scientific study I did:
https://docs.google.com/document/d/1TcM ... sp=sharing
Nice job Wayne. Thanks for sharing.
Knowing that our friends at Diamond do visit this forum I am just wondering why new DA40s still come with this defect and why they don't come up with a $ 200 certified mod for existing planes.
All it takes is one single buyer being put off by the noise on a hot day and they are losing big time.

I should stop ranting and apologize for the thread drift too.

After giving Rich's analysis a hard thought I think he has discovered another dimension of the problem.
The fact that the problem is fixed by aerodynamic means AND that it does NOT happen when the fairing is removed demonstrates that there is an aerodynamic aspect to it.
Either way, we've done more than our share and I think it is high time for London to wake up on this one too!
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Rich
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Re: Corked Nose Wheel

Post by Rich »

Antoine wrote:
Fri Jun 14, 2019 9:29 am
After giving Rich's analysis a hard thought I think he has discovered another dimension of the problem.
The fact that the problem is fixed by aerodynamic means AND that it does NOT happen when the fairing is removed demonstrates that there is an aerodynamic aspect to it.
Either way, we've done more than our share and I think it is high time for London to wake up on this one too!
I postulate the nosewheel still corks over with the fairing removed but the yaw problem may be less apparent because the bare nosewheel presents less resistance to the cross-airflow than the corked fairing. Has anyone done video of the behavior of the unfaired nosewheel?

In any case a solution like Bret's introduces an aerodynamic stabilizing element that also cuts down on drag to a significant degree. Once upon a time my plane had a best 75% cruise right at 137 Kn (i.e., book), but it sometimes would be lower for no (then) apparent reason. Addition of the Powerflow many years ago increased that to 142-143, but it also would often be lower. With bretfin installed and rudder trim adjusted to compensate, so far 147 at roughly 70% power - in conditions that the book says should yield 134. Note that in 17 years of flying I have never come close to this number in cruise. That suggests that this fin does more for the aerodynamics of the NW fairing than just eliminate/reduce the misalignment.

And yes, properly dealing with the problem (including the bureaucracy) would require Diamond to come up with a fix. Keep in mind it's likely to add airspeed to their newly manufactured aircraft. The complication is that Bret's fin doesn't fit all the nosewheel fairings Diamond has included over the years, so several different versions might be required. For just mounting hole location, perhaps a blank fin to be match-drilled?
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ZAV
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Re: Corked Nose Wheel

Post by ZAV »

I’m assuming I had my first encounter with the corked nose wheel. I’ve had my 2011 DA40 for 8 mo and this was the first time I have noticed it.

I departed with a mild left to right crosswind and small tailwind component. I had a terrible right yaw in cruise necessitating constant left rudder. I kept looking at the right wing/flap wondering if I had a flap problem. It was a short flight and everything on the plane looked normal after landing.

A corked nose wheel was the only thing I could come up with.

All of my training flights were in a DA40 without wheel pants. My plane has wheel pants so this was my first experience with this weird issue.
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BRS
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Re: Corked Nose Wheel

Post by BRS »

Instead of Diamond fixing the issues that our community has 'unofficially' solved - it's a good opportunity for someone to do a little STC and make a few dollars. I would think the break even point would come quite quickly considering the simplicity of the fin as well as the wide need for it.
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Re: Corked Nose Wheel

Post by Pilot55 »

I am working on that now, but you know how long a STC takes.
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Re: Corked Nose Wheel

Post by BRS »

Pilot55 wrote:
Sat Jun 15, 2019 3:53 pm
I am working on that now, but you know how long a STC takes.
Sure do - good grief. Though I doubt little fin held on by two screws will take seven years.
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Rich
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Re: Corked Nose Wheel

Post by Rich »

Pilot55 wrote:
Sat Jun 15, 2019 3:53 pm
I am working on that now, but you know how long a STC takes.
I don't know how this might play into a STC approval: Note the references Diamond makes in the AFM to the wheel fairings. First of all, flight with or without the wheel fairings is approved. Hence airflow changes around the wheels could reasonably be concluded to not affect airworthiness (spin recovery, e.g.). The only other mention is that removal of the wheel fairings reduces cruise speed by 5%.

Many STC's are created on the premise that they "do not harm" anything and typically don't have to prove value.

Here is the piece of AC43, Appendix A on the matter of owner maintenance regarding fairing work:

Making small simple repairs to fairings, nonstructural cover plates, cowlings, and small patches and reinforcements not changing the contour so as to interfere with proper air flow.

Clearly the fin is affecting air flow, but is it "interfering with proper airflow"? Let me know if I can help.
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Re: Corked Nose Wheel

Post by Kyle »

ZAV wrote:
Sat Jun 15, 2019 1:40 am
I’m assuming I had my first encounter with the corked nose wheel. I’ve had my 2011 DA40 for 8 mo and this was the first time I have noticed it.

I departed with a mild left to right crosswind and small tailwind component. I had a terrible right yaw in cruise necessitating constant left rudder. I kept looking at the right wing/flap wondering if I had a flap problem. It was a short flight and everything on the plane looked normal after landing.

A corked nose wheel was the only thing I could come up with.

All of my training flights were in a DA40 without wheel pants. My plane has wheel pants so this was my first experience with this weird issue.
Bryan,
FYI, this certainly sounds like the corked nose wheel issue to me. I've had the same intermittent issue several times and started documenting what the winds were on takeoff. Every time I had the issue, it was with some type of left crosswind. The crosswind was usually 5+ knots but it has happened on occasion with a lighter crosswind as well.
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