New Nose Wheel Fin

Any DA40 related topics

Moderators: Rick, Lance Murray

User avatar
firedwg1
2 Diamonds Member
2 Diamonds Member
FIRST NAME: josh
Aircraft: DA40
Registration: DA40XLS
Airport: KSNA

Posts: 16
Joined: Fri May 11, 2018 2:56 am
Been thanked: 5 times

Re: New Nose Wheel Fin

Post by firedwg1 »

Very informative, I’m going to consider the modification.
User avatar
Rick
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Rick
Aircraft: DA40
Registration: N171PS
Airport: KROA

Posts: 1481
Joined: Tue Jul 06, 2010 10:09 pm
Has thanked: 99 times
Been thanked: 252 times

Re: New Nose Wheel Fin

Post by Rick »

I have always felt like this problem is related to the fact that the nose gear is off-center, so not in the middle of the propeller slipstream, but I don't know how to prove it. If that's the case, then I imagine the Bret fin was designed to provide just enough steering or counterforce to keep the nose gear straight in the asymmetrical prop wash. That still doesn't explain why some flights are better than others, and I have never noticed any correlation between takeoff crosswind (or lack of) and the need for more or less right rudder in flight, either... so who knows... :scratch:
2007 DA40 XL - Roanoke, VA (KROA)
User avatar
Boatguy
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Russ
Aircraft: DA40NG
Registration: N454M
Airport: O69

Posts: 752
Joined: Mon Jan 22, 2018 4:48 am
Has thanked: 344 times
Been thanked: 483 times

Re: New Nose Wheel Fin

Post by Boatguy »

Rick wrote:
Mon Jan 18, 2021 7:31 pm
I have always felt like this problem is related to the fact that the nose gear is off-center, so not in the middle of the propeller slipstream, but I don't know how to prove it. If that's the case, then I imagine the Bret fin was designed to provide just enough steering or counterforce to keep the nose gear straight in the asymmetrical prop wash. That still doesn't explain why some flights are better than others, and I have never noticed any correlation between takeoff crosswind (or lack of) and the need for more or less right rudder in flight, either... so who knows... :scratch:
The offset nose wheel is probably a good guess. This is not a new problem so it's disappointing that Diamond has not bothered to either figure out the problem, or just add a fin themselves. Which raises a second issue.

I'm going in for my annual in two weeks. Has anyone gotten push back from their IA about the lack of an STC for the fin? I've considered taking it off before dropping off my plane.
User avatar
Rick
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Rick
Aircraft: DA40
Registration: N171PS
Airport: KROA

Posts: 1481
Joined: Tue Jul 06, 2010 10:09 pm
Has thanked: 99 times
Been thanked: 252 times

Re: New Nose Wheel Fin

Post by Rick »

Boatguy wrote:
Mon Jan 18, 2021 8:54 pm
I'm going in for my annual in two weeks. Has anyone gotten push back from their IA about the lack of an STC for the fin? I've considered taking it off before dropping off my plane.
I had my annual in December with the fin in place (but not yet painted), and my IA thought it was just fine. But if you have any doubt, it's easy enough to remove when you drop it off. In my case, I stayed with the plane and helped with the annual, so I was there to remove it if it became a problem... but it wasn't. Of course, your IA may feel differently about it.
2007 DA40 XL - Roanoke, VA (KROA)
User avatar
Rich
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Rich
Aircraft: DA40
Registration: N40XE
Airport: S39

Posts: 3238
Joined: Mon Aug 30, 2010 12:40 pm
Has thanked: 86 times
Been thanked: 616 times

Re: New Nose Wheel Fin

Post by Rich »

After I installed it my IA stated he didn't want to see it there during annual. But he's done other work on the plane that does not require dealing with the nose wheel fairing and doesn't even notice it there.

It's unclear whether the nose wheel and its fairing are in the prop wash. The MT has the smallest diameter and for sure the blade tips do not reach down that far on mine, even when the plane is sitting on the ground. But propeller blades also have a vortex coming off each (just like a wingtip vortex) in addition to producing a sort of helical air pattern coming rearward and are forced outward from the center to flow past the cowling. So there's lots of potential complexity to the airflow in this area.
2002 DA40: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
User avatar
perossichi
3 Diamonds Member
3 Diamonds Member
FIRST NAME: Peter
Aircraft: DA40
Registration: N925RH
Airport: KVNY

Posts: 155
Joined: Tue Sep 18, 2018 4:05 am
Has thanked: 30 times
Been thanked: 53 times

Re: New Nose Wheel Fin

Post by perossichi »

I make it a habit to remove all three fairings (and hence th fin) before annual. I clean and polish the fairings. This makes it easier to inspect brakes, wheels tires, repack wheel bearings, etc.

Technically the fin is a major alteration as it does affect the aerodynamic qualities of the airframe. So a real jerk could say the plane no longer conforms to the type certificate and there is no STC/form 337. The IA would have to be one of those safety police types. My IA just said to me. — don’t tell me about it.
2002. Powerflo, Hartzell composite two blade, 530W/430, 345 transponder.
User avatar
Boatguy
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Russ
Aircraft: DA40NG
Registration: N454M
Airport: O69

Posts: 752
Joined: Mon Jan 22, 2018 4:48 am
Has thanked: 344 times
Been thanked: 483 times

Re: New Nose Wheel Fin

Post by Boatguy »

Took my plane in for the annual today. The IA asked me about the fin because he had just heard about it. His primary interest was whether it worked or not and was surprised that I still had problems after he adjusted the spring on the nose wheel after the last annual. I assured him that I did and that the fin solved the problem. His comment was that Diamond should be putting the fin on the nose wheel!

He had no issue with the fin being there without an STC.
User avatar
Lance Murray
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Lance
Aircraft: DA40

Posts: 1077
Joined: Tue Jul 06, 2010 11:25 pm
Has thanked: 3 times
Been thanked: 78 times

Re: New Nose Wheel Fin

Post by Lance Murray »

I think that this is a pretty clear case of an unapproved part being sold and installed. While your IA may not take issue with it, the owner does share responsibility for the airworthiness of an aircraft. It may be small enough to fly under the radar or it may be a problem in a post-crash investigation that invalidates the airworthiness and causes the insurance to be void. Buyer beware. Certainly posting online about it gives a good case for the insurance company to void the insurance.
User avatar
Chris
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Chris
Aircraft: DA42NG
Registration: N449TS
Airport: KHIO

Posts: 675
Joined: Sat Jun 19, 2010 3:34 am
Has thanked: 464 times
Been thanked: 222 times

Re: New Nose Wheel Fin

Post by Chris »

I'd like to see somebody ask an A&P to install and sign off the fin as a minor alteration. Compared to some of the camera contraptions I've seen approved as such, the fin should have less of an effect on "weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness." I think the only one of those that could be argued would be "flight characteristics," and a draggy GoPro mounted 20' out on a wing would likely have more of a destabilizing impact than an "inoperative fin-style transponder antenna" mounted nearly on the centerline. It's pretty clear that there aren't any changes to operating procedures necessary with the fin installed. Rudder authority isn't changed and the nose wheel is still free-castering... just less likely to settle into an adverse angle. But yeah, it's probably wishful thinking.

I'd see about getting it approved myself, but I can't find a place to mount it on the DA42. :)
Chris
N449TS / DA42-NG / 42.AC049
KHIO
User avatar
Lance Murray
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Lance
Aircraft: DA40

Posts: 1077
Joined: Tue Jul 06, 2010 11:25 pm
Has thanked: 3 times
Been thanked: 78 times

Re: New Nose Wheel Fin

Post by Lance Murray »

I think by it's nature of being an aerodynamic change it won't qualify for minor.

I also expect to hear about an "unapproved parts notification" regarding this at some point.
Post Reply