RV-6A nose gear with Anti-Splat device fails

[flightlogic]

Jeff, a wimp for sure... But not a whimp. I think that might be a British or Aussie term that goes with whilst. I am longing to put my 9A on some green grass. Can't find any here in Arizona! Darn.
Stuff breaks. Learned that in 40 years of flying aluminum around at high speed.
Got Allan to turn my little wheel on his lathe. A work of precision and enjoyable to watch! The special cutter he then used on my Chinese tire made it really round. We build, we fly, we fix we fuel. All in fun I hope.

[az_gila]

Originally Posted by rhill

Thank you Bob for posting this thread. There have been more than a few Anti-Splat accidents since there introduction. Trends are starting to emerge.IMHO,The brace alone is not enough.The sealed bearings and associated upgrades as well as the skid plate under the retaining nut are required.During construction and on inspection the fit of the leg&socket is another critical point of concern.The size of the nose wheel&tire as well as balance also play a roll.I can't help but to wonder if a hard wood dampener should be added to the mix.
Any Thoughts?
RHill

Just like the early -6A plans that showed a wooden dampener glassed and bonded on to the nose gear leg and was the only aerodynamic fairing involved.



IIRC this moved the breaking point to the top of the gear leg, and maybe corrosion issues occurred when foam was used instead of wood.

[rhill]

With the Anti-Splat brace clamp mounted center span underneath.I'm thinking two similar clamps holding a wood strip across the top to dampen the oscillations of the leg.

[rbibb]

I've read these threads with passing interest as I don't fly an A model. But the issue has got my curiosity up and am searching for an answer. One problem seems to be lack of hard data and an understandable amount of angst.

But it seems to me that if the nose gear is indeed "folding up" then there can only be on way for that to occur. Looking at the drawing above it would seem that in order to apply sufficient force in the "x" or horizontal direction to the gear leg to fold backwards the leg must be bent enough such that some part of the assembly holding the front wheel/tire must be impacting the surface. In other words "stubbing its toe".

This could be caused by flexibility of the gear rod being too great, locked up wheels, gopher hole, etc. The various solutions seem to attempt to address all three likely causes with varying degrees of success. With no intention of slighting anyone I tend to want to discount the notion that this would happen on a smooth roll out. Things happen so fast that the eyewitness probably can't distinguish between events that occurred prior to the fold up and the fold up itself.

Something has to be catching the front of that gear and then Isaac Newton takes over. Even at 20mph the force generated by a 1500lb vehicle hitting something is over 20,000 lbs if I did the math right.

But enough of that - how to fix? Would seem solution would require a design where the gear is constrained (or encouraged) to deflect more in the 'y' direction and less in the 'x' direction to prevent rotation of the front such that it catches on terra firma. There are much more qualified engineers than me on here and I'd appreciate if someone could point out flaws in my reasoning.

[FresnoR]

This is reminding me of the Zenith Ch601xl issues a few years back. The Zenith faithful speculated, argued and fought each other for years and the factory remained quiet rufusing to admit an issue. Eventually the NTSB and FAA got involved and all but forced AMD to supply a "fix" for the issue they still claim does not exist. I suppose the airplane being grounded in other countries didn't help either.

[Don]

Lots of speculation and few facts.

Anecdotally, it would seem the Anti-Splat mods are a significant improvement (and I've been skeptical). I can only recall one other failure with the ASA and as I recall it was a 9A in SC that landed on a muddy field. It was universally attributed to poor judgement, not technique nor a failure of the ASA.

Another bit of anecdotal evidence in my book is I don't know of any well-experienced and recognized RV pilots having problems on grass with A models. Doesn't Van fly out of a grass field? How many grass fields does Vlad have in his log book with the Van's gear and not all of them were manicured fields. My point is I think technique is important.

I'd be more than willing to collect data and report back once we know what we want to collect. I'd think the following data at a minimum: N-number, Model, if there's more than one front gear - ID which one, wheel bearing used: stock, Berringer, ASA mod, (are there more?), field condition (this is going to be a judgement), flip or collapse, and speed. Photos would be great to have and comments. I'll start a spreadsheet with what's listed here and will add more points as suggested. When I start getting data, I'll post it publicly and keep it updated.

My point is, lets get the data together that we can and see if it shows anything. Everything else is opinion and speculation...which have a place but data is king.

[rightrudder]

Great thread. When it comes time to get my currency training (most likely in a Cherokee), I'll really work on nose high/full stall landings, and keeping the nose up as long as possible. I plan only on flying only from paved strips, but I like the idea of the skid plate on the gear's pivot nut, just in case.

[rvbuilder2002]

To make this type of database of much use, one other important data point would need to be known.

We would need to know how many of the "A" models actively flying, have any or all of the listed mods installed.
Based on the total # of RV-6A's, 7A's, 8A's, and 9A's that have been completed, I think it would be very conservitave to estimate the total number of A models at 2500 (I am pretty sure it is a higher #).
We would need to know how many of those are flying with an entirely standard nose gear, and how many have (and which ones) modifications to make a meaningful comparison of the benefits of any/all of the modifications.

[az_gila]

Originally Posted by rvbuilder2002

To make this type of database of much use, one other important data point would need to be known.

We would need to know how many of the "A" models actively flying, have any or all of the listed mods installed.
Based on the total # of RV-6A's, 7A's, 8A's, and 9A's that have been completed, I think it would be very conservitave to estimate the total number of A models at 2500 (I am pretty sure it is a higher #).
We would need to know how many of those are flying with an entirely standard nose gear, and how many have (and which ones) modifications to make a meaningful comparison of the benefits of any/all of the modifications.

..and which year the "standard nose gear" belongs to.

I know of at least one that is still flying on the old style skinnier gear leg.

I've suggested an upgrade to him but to no avail.

[GrayHawk]

http://www.vansairforce.com/communit...ckstrap&page=4