RV nose gear accident study results

Here's some information with regards to the RV nose gear, that was just posted. Check out the information on the links.



http://www.ntsb.gov/ntsb/brief.asp?ev_id=20051006X01588&key=1

http://www.ntsb.gov/ntsb/query.asp

http://www.ntsb.gov/publictn/2006/RV_Study.pdf

http://www.ntsb.gov/publictn/2006/RV_Photos.pdf


NTSB Identification: ANC05LA123.
The docket is stored in the Docket Management System (DMS). Please contact Records Management Division
14 CFR Part 91: General Aviation
Accident occurred Friday, August 12, 2005 in Palmer, AK
Probable Cause Approval Date: 6/27/2007
Aircraft: Brabandt RV-9A, registration: N63EB
Injuries: 1 Minor.
The commercial certificated pilot was landing a tricycle gear-equipped kit-built experimental airplane on a private airstrip that had an uneven dirt/gravel surface. During the landing roll, the nose landing gear began producing scuff marks on the runway surface that became progressively deeper. The nose gear strut and fork eventually dug into the runway, and the nose landing gear strut was bent aft. The airplane nosed over, and received structural damage to the fuselage, left elevator, left wing, rudder, and vertical stabilizer. An exam of the runway revealed surface undulations in the area where the nose wheel fork assembly began to scuff the tops of the undulations, producing slight gouge marks that increased in depth and ended where the nose fork dug into the ground. There were no skidding signatures or evidence that the main landing wheel tires were locked before the airplane nosed over. An exam of the airplane revealed that the nose gear strut was bent aft and upward from its normal geometry. The nose fork assembly is comprised of a metal swiveling housing block, attached to the lower end of the threaded strut by a nut. The bottom edge of the threaded nose fork strut is about 4 inches from the ground. A teardrop-shaped fiberglass wheel pant enclosed the accident airplane's nose fork assembly and upper portion of the nose wheel and tire. The distance from the bottom of the wheel pant and ground is about 2 and 7/16 inches. Staff examined data for 18 recent accidents and one incident in which Vans Aircraft series RV-6A, RV-7A, RV-8A, or RV-9A airplanes have become inverted during landing. Several involved hard touchdowns, bounced landings (six), or landing in a slip. Several others involved off-field landings in rough terrain, hitting a ditch, or going down an embankment. Four of the accidents and one incident involved a touchdown and the start of a rollout on an unpaved runway, followed by the nose gear folding back. The airplanes would then slide for varying distances before nosing over. Staff also examined data for four additional incidents in which the nose gear collapsed during taxi but the airplane did not nose over. These nine accidents and incidents occurred on various unpaved surfaces including gravel, turf, soft turf, hard surface with "washboard" bumps, and slight depressions, and they all involved the nose gear strut and fork digging into the ground and the nose gear bending aft. The kit manufacturer posted a letter on their website stating that their review of NTSB accident reports pointed to pilot proficiency as the most significant factor. The letter said the company has produced a lighter weight leg/fork combination, with increased clearance between the nose strut axle.

The NTSB's Structures Study is available at the following address: http://www.ntsb.gov/publictn/2006/RV_Study.pdf . The NTSB's Photos and Data report that provides details on all of the RV nose-over accidents and incidents can be found at the following URL address: http://www.ntsb.gov/publictn/2006/RV_Photos.pdf.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The loss of nose gear strut/fork-to-ground clearance that led to the collapse of the nose gear strut and nose-over during the landing roll. Factors contributing to the accident were an uneven dirt/gravel surface runway.

In my mind, yes I know, here goes the debate again. BUT.... Just stop and look at is, yes *LOOK* at it.

a) the RV nose draggers have a very short distance between the main gear and the nose gear
b) where does the CG reside in relationship to that triangle?
c) the fork on the nose gear provides too much surface area that can be *caught* and *dug in*
d) go watch 8 out of 10 "A" models land and see how many of them "porpoise" on landing, even a little. Doesn't matter the surface.

Ok, with the above said. I suspect that the largest drivers towards probable cause is not the fork or the down strut, but more the short legs of the triangle and the CG as it relates to that triangle. That issue can really only be overcome by a) practice on specific landing surfaces; b) staying *off* soft landing surfaces; c) not building an "A" and then becoming proficient in a tail dragger

To each, it's a personal desicion and one where risks is either factored in or not.

BTW, the problem with the small triangle legs is not just an RV specific issue, even the Lancair FG's are short and I would never take one into grass or dirt.

6A Bashing - Time To Stop

I've heard just about all the bashing and trashing of Van's 6A nosegears that I can stand without getting my $1 worth in!

I landed out in a very small and rough cattle feed lot (no cows present at the time ). It was a very rough field with ruts hidden in the tall grass that bounced us off the ground more than once!

Hmmm...... when we came to a stop we were still upright!
Imagine that, my weak, poorly designed nosegear didn't collapse or bend and I'm flying with that same gear today, 600 hours later! Maybe it's because I kept the nosegear off the ground absolutely as long as possible. I NEVER, even on a paved runway, allow my nosegear to touch until it just won't stay up any longer.

You guys, if you're so freakin' paranoid about building and/or flying a 6A, 7A, 8A, or 9A without rekitting your plane on landing, you need to go buy a boat and take up fishing!

Enough is enough - give it a rest and find something else to bitch about.

There, I feel much better!

In the second to last paragraph of the study summary, note is made of the fact that the manufacturer redesigned the fork to provide an extra inch of ground clearance.

That's at least a 25% increase in clearance, not an insignificant amount. I wonder if all of the accident aircraft in the study had the old style fork-- I could not tell by looking at the photos if the forks were the original design or the updated design.

One other conclusion I would draw from this report is that low tire pressure might significantly reduce the ground/fork clearance. I'm not an RV flyer (yet) but what do most folks keep their A model nose tires inflated to? And what is the recommended pressure?

30-35 PSI in the nose wheel is what I run. The study does show that even the old style fork will work as designed, when treated properly. I'm keeping mine.

Thanks for sharing this, Craig.

Roberta

Nose tire presure

30 -35 psi

NOSE TIRE PRESSURE

GrayHawk said:

30 -35 psi

Click to expand...

45 psi here (most of the time)

I was out by our grass runway this morning sitting on my Kubota chatting with local residents as we were watching a helicopter who "borrowed" our field for an hour or so for student work. One subject that came up was RV flips. The guys remembered a landing last year when I could not clear the runway because the nose tire was flat. After reading the NTSB study, I am wondering why it did not flip, it should have. The grass was wet that day, maybe the fairing acted as a ski.

The NTSB study is interesting but a little too focuse on RV's - like maybe an exclusive on the machine for whatever reason. Flips happen in lots of airplanes for many reasons most of which are a part of an inherent risk of flying, sometimes managed better than other times. I do remember Charlie Hilliard being killed in a flip at SNF a few years ago and it was not in an RV.

The circumstances of these accidents can be avoided if recognized in time. That's what needs to be focused on. And for some that may involve a decision to go with a tail dragger - and all of its inherent risks.

nose wheels

Ok Here's my side of the story. I'm a low time pilot (300 hrs ) o time tail draggers, not current now. just put my $ down on a 7a kit. been to Vans shop many times this passed year trying to decide 7 or 7a.
Has Vans ever had a nose gear probelm on any of thier demo planes? I figure they fly alot more hrs than the normal RV.
thanks
Jeffrey
working on tail feathers
qb 7a on its way I hope
187kw reserved

soft field landings

As I was landing on my buddies grass strip this morning with all this debate was going through my mind. I was thinking, OK flair now, leave in a little power, hold it...hold it... rolling on mains only...hold it till you can't hold it any more. End result, text book soft field landing.

That is what you MUST be thinking EVERY TIME you land one of these things. I sure it's very similar in a tail dragger as far as keeping it straight on roll out.

With these -A's you can not get complacent on landings and fly them all the way to the chocks just like our tail wheel brethren.

THis type of debate is healthy as it keeps this monster from the Id fresh in our minds and more -A's upright.

I believe the true problem is people either having never learned, or have forgotten, that the nose gear is just that- a nose gear, for steering, and not for landing. Keep it on the mains until you no longer can keep the nose wheel from touching. A well designed nose, like the RV's, will hold up.

I just got my RV6a checkout yesterday. The aircraft belonged to the instructor. We did 21 landings, one at his home field, a turf runway. He has over 700 hours on the aircraft, much of it instruction. The nosewheel fairing was off for repair-- nonetheless that's a lot of landings. No problems so far. BTW, it was a 160hp FP.

All this talk of soft field technique disregards the ships that have come to grief taxiing or rolling out.

mrreddick said:

I've heard just about all the bashing and trashing of Van's 6A nosegears that I can stand without getting my $1 worth in!

I landed out in a very small and rough cattle feed lot (no cows present at the time ). It was a very rough field with ruts hidden in the tall grass that bounced us off the ground more than once!

Hmmm...... when we came to a stop we were still upright!
Imagine that, my weak, poorly designed nosegear didn't collapse or bend and I'm flying with that same gear today, 600 hours later! Maybe it's because I kept the nosegear off the ground absolutely as long as possible. I NEVER, even on a paved runway, allow my nosegear to touch until it just won't stay up any longer.

You guys, if you're so freakin' paranoid about building and/or flying a 6A, 7A, 8A, or 9A without rekitting your plane on landing, you need to go buy a boat and take up fishing!

Enough is enough - give it a rest and find something else to bitch about.

There, I feel much better!

Click to expand...

Great rant, Mike. Have you read the NTSB report and seen the pictures?
I can't remember when the NTSB has done a study of an experimental's landing gear! A board member must have flipped one!

http://www.ntsb.gov/publictn/2006/RV_Photos.pdf

Well if everyone is paranoid about buckling the nose gear, maybe they will keep the nose up on touchdown. This will probably prevent about 75% of these accidents. The other 25% well on grass, you takes your chances that Mr. Rabbit has not been digging under the path of your nose wheel- pilot skill does not enter into these ones. When hole depth exceeds fork to tire clearance, chances are good that something bad will happen.

I bet almost everyone has thought about these postings as they flare now. I always do but I'm thinking VAF posts as I ease the stick back even more now. I find the landing attitude on my 6A means you look out the corner for runway reference. If I can see the runway out the front, the nose is way too low.

If you can't train in an RV before flying yours, I strongly suggest a Grumman product with low fork breakout torque. It will give you the same sick feeling when you touch down flat and the gear starts a death shimmy!

I wonder how many other RV pilots with nose heavy C of Gs (Hartzell C/S 360, Subaru etc.) land with full flap and and misjudge the flare height due to poor elevator authority? My solution is to land clean or with half flaps. She flies much nicer. I did a nice one today in gusty conditions. It looked nasty at 10 feet.

David-aviator said:

45 psi here (most of the time)

Click to expand...

45 psi is about the highest I have seen for the nose wheel. Any shimmy problems? Would you keep it at 45 psi on uneven grass? I am guessing it would ride a bit rough on uneven surfaces at 45 psi??

Fin 9A

Yukon said:

Great rant, Mike. Have you read the NTSB report and seen the pictures?
I can't remember when the NTSB has done a study of an experimental's landing gear! A board member must have flipped one!

http://www.ntsb.gov/publictn/2006/RV_Photos.pdf

Click to expand...

John,

That could be the case, or 'paranoid voices and music'.......could it be that we are seeing the downside of all of this public whining, b.tching, and bashing all made possible by the magic of the net?!

Nah, my wife is probably right when she says I am too paranoid. Still, I hope all of this 'discussion', and playing blame games, over nose wheelers flipping hasn't awakened big brother and now our lives changed to protect ourselves from ......ourselves.

I am with Mike on this, enough already!

Fascinating reading.

The relevant NTSB report is fascinating and very informative reading. It includes the results of a detailed Finite Element Analysis (FEA) on a Van's nose gear. It also includes many previously unpublished photos of RVA nose gear incidents.

I strongly recommend that people who are too disinterested to read the report stop posting on this thread. It's time this topic moved beyond cheap and lazy one-liners. My argument is this: If you can't be bothered reading the report you're not SERIOUS about understanding the issues. So get off the line.

One of the points of interest in the report revolves around a finding that a tire grabbing the fairing due to insufficient tire clearance "is not a significant contributor to the fork's clockwise rotation, when viewed from the right side. Seizing the tire does increase the aft loading on the strut, but its affect was shown to be insignificant".

In other words the FEA suggests tire clearance has not been a significant factor in the failures investigated. This is interesting when you consider that, in responding to critisism of RVA nose failures, Vans have previously suggested that tire clearance was a significant factor.

Of course it was politically advantageous for Vans to say that...because builders were responsible for tire clearance. Meanwhile Vans quietly went about redesigning the nose wheel to improve on the inadequate ground clearance (the REAL root cause of the problem).

I personally would always opt for plenty of tire clearance on the basis that every little bit helps.....but I think the NTSB report puts things into perspective on this point.

Captain Avgas said:

Meanwhile Vans quietly went about redesigning the nose wheel to improve on the inadequate ground clearance (the REAL root cause of the problem).

I personally would always opt for plenty of tire clearance on the basis that every little bit helps.....but I think the NTSB report puts things into perspective on this point.

Click to expand...

IMO, the difference between 4 and 5 inches, isn't that big a deal. As far as I'm concerned, the new fork is just a matter of weight savings, because today's high tech engineering software says it can be done.

So................how many aircraft, has the new fork design saved? What's the real statistics on this?

Want adequate and "feel good, non paranoid" clearance? Then figure out how to throw an 8" wheel on there....

L.Adamson

jim said:

John,

That could be the case, or 'paranoid voices and music'.......could it be that we are seeing the downside of all of this public whining, b.tching, and bashing all made possible by the magic of the net?!

Nah, my wife is probably right when she says I am too paranoid. Still, I hope all of this 'discussion', and playing blame games, over nose wheelers flipping hasn't awakened big brother and now our lives changed to protect ourselves from ......ourselves.

I am with Mike on this, enough already!

Click to expand...

That's an interesting take, Jim! It's not the 18 accidents that got the NTSB's attention, it's the discussion here on the forum............ WOW!

READ the report !!!

L.Adamson said:

IMO, the difference between 4 and 5 inches, isn't that big a deal. As far as I'm concerned, the new fork is just a matter of weight savings, because today's high tech engineering software says it can be done.

So................how many aircraft, has the new fork design saved? What's the real statistics on this?

Want adequate and "feel good, non paranoid" clearance? Then figure out how to throw an 8" wheel on there....

L.Adamson

Click to expand...

In fact an increase of 1" may in fact be a VERY big deal.

The report states that in certain real world scenarios the clearance afforded by the MK1 RVA nosegear can be MUCH less than the 3.75" often quoted. For example the report claims that with a static weight on the nose gear of 440lbs (empty weight on the nosegear is approx 370 lbs) and a load factor of x1.5 times and a tire pressure of 20 psi (a pressure many who do not check their tires regularly will get down to) the actual clearance on the MK1 is actually closer to 1.5".

Under those circumstances an increase of 1" virtually doubles the available clearance.

It's early days yet but it could be significant that no RVA with the new MK2 nose gear with increased clearance has failed to date.

These reports from the FAA are finally bringing data into the discussion. Sad that it took the FAA to compile the data but maybe they have better access to it then the RV builders or Van.
I do not believe this is from the recent "whining" on this website from the Croft field incident. The FAA does not do anything in a couple of weeks. Also, obviously Van knew this was going on as he provided the nose gear info to them for the FEA. Therefore, I do not believe Van is sticking his head in the sand as I have heard people imply.

Captain Avgas said:

For example the report claims that with a static weight on the nose gear of 440lbs (empty weight on the nosegear is approx 370 lbs) and a load factor of x1.5 times and a tire pressure of 20 psi (a pressure many who do not check their tires regularly will get down to) the actual clearance on the MK1 is actually closer to 1.5".

Click to expand...

Remember this is a double failure already. One, you are letting the nose gear down too hard due to not holding back on the stick or excessive braking, and two, you are not maintaining proper tire pressure (is that not on your pre-flight check list?)

This being said the report does not mention that the higher tire pressure may contribute to the problem. Higher tire pressure (harder tires) will dig in to a soft field more than low tire pressure (increases tire foot print and therefore lower psi on the ground). This would require a floatation analysis and calculate CBR for each of the accidents. Therefore the extra clearance you get from the tire not deflecting with higher tire pressures may be lost in that the tire sinks into the ground a little bit more. I would not think high tire pressure is the best insurance on a soft field. Would work great for paved surfaces.

I wish the FAA would have included the published max TOGW of each of these planes. Not sure of where they get the 370 lbs on the nose gear. At max TOGW the highest loading I can get on my nose gear is 315 lbs. But then I limit my plane to the 1650 recommend by Van and not increased it to 1700 or 1800 as I have seen others do. Also Van's prototype had a empty weight 100 lb lighter than mine therefore his experience has a max weight on nose gear of just less than 300 lbs. That is a 20% decrease over the FAA analysis.

Correction

plehrke said:

At max TOGW the highest loading I can get on my nose gear is 315 lbs.

Click to expand...

I did a bit more analysis. Actually max static load on the nose gear occurs not at max TOGW, but at max fuel, min pilot weight, and no baggage. Then I get to about 340 lbs. I have a empty CG location of 70.3 in aft of the datuum. I have an 180 hp IO-360 with fixed pitch prop. The heavier your empty weight is and the futher foreward the empty cg is the more static loading will on the nose gear (obviouly).

rv6ejguy said:

Well if everyone is paranoid about buckling the nose gear, maybe they will keep the nose up on touchdown.......I wonder how many other RV pilots with nose heavy C of Gs (Hartzell C/S 360, Subaru etc.) land with full flap and and misjudge the flare height due to poor elevator authority? My solution is to land clean or with half flaps. She flies much nicer. I did a nice one today in gusty conditions. It looked nasty at 10 feet.

Click to expand...

Agree totally. I use 10 degrees or sometimes 20, but never 40, don't know why they go down so far except it makes it easier to step up on the wing.

Finley Atherton said:

45 psi is about the highest I have seen for the nose wheel. Any shimmy problems? Would you keep it at 45 psi on uneven grass? I am guessing it would ride a bit rough on uneven surfaces at 45 psi??

Fin 9A

Click to expand...

I do all the tires to 45, have since day one. They ride up higher, last longer, and are less likely to go flat. The nose tire got a bit low last year over winter and it did go flat one day for no good reason. Tube simply split on take off or landing. New tube fixed it, same tire still in use. The mains (Air Hawks) were just changed out after 4 years and more than 500 landings, they still had thread.

45 psi works for me but if you-all don't like it, don't do it.

Nose wheel will shimmy if the spring is too loose. Just tighten it up a bit and shimmy goes away.

Phillip,

It was not the FAA, but the NTSB that did this study. Two very different governmental agencies. Quite adversarial agencies too.
Read the article again. The weight on the nosegear increases radically during deceleration, both due to braking and nose strut contact with the runway, much beyond the static weight of the aircraft.

Dynamic forces at work ?

Most of the "A" fraternity live by the "hold the stick back" when on the ground rule but I wonder if there is something else at work here.

I recently had the unpleasant experience of watching a very experienced Ag pilot destroy my (9A) front wheel pant and come within a fraction of a prop strike as he approached the hangar at a modest taxi. I was standing on the apron about 20 yards in front and later measured the slight depression which caused the incident as about 4' across and 3" deep with a gradual entry and exit.

The nose wheel fork nut broke through the fairing and gouged an 8" long furrow in the reasonably firm soil at the exit to the depression and a further smaller furrow 6 to 8' further on. The wheel pant brackets were both fractured.

The aircraft appeared to stumble multiple times and looked to be experiencing some horrible sort of resonance in the gear leg.

I have purchased the new gear leg and fork and will also strengthen and raise the bottom of the wheel pant as discussed elsewhere but wonder if this gear leg behaviour can be explained by analysis of the forces at work on the leg and more importantly on the few inches above the fork.

When you look at a new leg (and I think the old one too) the narrowest cross-section appears to be about 12" above the fork. Bending down at this point (from a rearward force ?) would need to be really severe to lower the fork retaining nut sufficiently to contact the ground. For this sort of contact to occur the bending probably needs to take place very close to the fork so the short radius can lift the wheel sufficiently to allow the nut to strike.

Maybe the root cause of these incidents is a situation where the net force on the gear leg is aligned exactly up the shaft leaving the short radius above the fork as the only possibility for movement. Perhaps there is room for some redesign to retain suppleness over the whole leg and to reduce the forces at work in the region of the fork ? Perhaps the new fork already does this by increasing the offset of the wheel axis to the gear leg plane ?

Rupert Clarke
90 hrs RV-9A flying off farm strips.
Australia

Wonder

I wonder how many of the flip overs were constant speed?

Maybe the fixed pitch ones are faster on touch down which would cause a stronger dig in.

Maybe the small extra weight of the CS makes it dig in.

It would be nice to have more stats.

Regards,
Mike Stephenson

The extra weight of heavy engines and props don't help the leg deflection and tip over problem for sure. How many O-320 A models with wooden props have flipped? Just curious.

Yukon said:

Phillip,

It was not the FAA, but the NTSB that did this study. Two very different governmental agencies. Quite adversarial agencies too.
Read the article again. The weight on the nosegear increases radically during deceleration, both due to braking and nose strut contact with the runway, much beyond the static weight of the aircraft.

Click to expand...

I meant the NTSB. Thanks for the correction.

The report states "The weight on the nose gear at empty weight is about 370 pounds." The factor of 2X load (740 lbs) is for braking, nose gear touching down, and dynamic effects,. If executing a proper soft field landing the nose gear should just settle down (barely above static load) and there should be no (or minimal) braking. That leaves all 2X for the bumps in the field. If you brinng the nose down hard or use heavy braking you have no margin for the bumps (or rabbits).

Anyone know what sort of QC the legs go through- specifically if heat treatment is properly done. Not trying to open a can of worms here, just asking. It seems as though we hear from quite a number of people with many years of relatively rough field landings and no problems yet have seen a few with reasonable landings and rollouts on asphalt who had the gear fold.

photoadjuster said:

It would be nice to have more stats.

Click to expand...

I agree - there are a lot of questions unanswered that could be causal....I'd like to know what the "time in type" was for each accident. That could help us understand the relationship of pilot action to the accidents. We have heard in many threads from folks that have never had problems with their "A's"...it might be that they have survived the potential pitfalls through experience.

Paul

Oh, come on now. Not one of those accidents according to the NTSB was from normal use. They were, extreme use. I have a tail wheel kitfox4, I landed on a strip that was a real pile. I wouldn't think of landing any RV there, tail or front wheel. I brought that fox in and stalled it right about a foot off, thump rolled about 200ft. if that. rougher than ... Anyway, this boy is building an A, why, I think it will be fun to run that baby down the runway with the nose off the ground and show those front wheel boys and girls how to land. Most I see land on the nose or at least flat, and I just want one, no real reason other than I THINK THEY LOOK BETTER. So there.

a couple things-- my 7a with a IO-360 parallel valve and WW composite prop weights 227# on the nose gear and I lost 40# of luggage area use due to the light front end.

I practiced 10-17 landings at a time at one time.

I still notice regardless of flap settings, with nose up and plenty airspeed-- the nose drops and goes down and bounces off the pavement--maybe once or twice during certain roll outs.
(and I think; if i was off pavement and caught a divet just right....)

Not a thing I can do; the stick's All the way back. I look down and see 45 kts. sometimes 54 kts. and it still happens. It's either me and I've been caught off guard or something else. Could be down hill humps on runways like the first 100ft of Flabob and Riverside Muni also.

Yesterday I passed on landing out at Lake Elsinore dirt strip to pick up a friend who needed a ride due to the remote possibility of a nose gear problem. Too bad we aren't the limiting factor and the plane is. (in some people's eyes.)

FWIW

late /mkII nose o.k.???

Bob has posted: the new series gear has not failed- where is the data to support this? Did I miss it?
I just got my 8a out of the paint shop, I usually land with half flaps. I concur that the nose will bounce down with full flaps after a nomal landing-happened yesterday-forgot and went to full flaps . I have never had a passenger in my plane. I am sure loading will change this.
I am happy to see you guys working on a solution--first step find the problem!! I will wait before going to grass/dirt airports. I will not move my plane without full back stick only lessening pressure to delay premature take off.
I wish those who are not interested in the 'fix' would not post 'shoulda bought a taildragger' post. I am concerned with a solution! I don't think this is all pilot error!!
O.K. just my .02 please no flames needed!! ED

whirlpool said:

I wish those who are not interested in the 'fix' would not post 'shoulda bought a taildragger' post. I am concerned with a solution! I don't think this is all pilot error!!

Click to expand...

I agree. I also read many -A drivers posting that they've never had a problem. Kudos to all of you, and either you exhibit excellent piloting skill each landing or have fantastic luck if not. I imagine that some of the pilots who have dug-in and/or flipped their -A might have been on the same "no problems here" soap box prior to their incidents.

Many factors led me to choose the -A model as the one I'm going to build, even in the face of the nose gear design debate. Regardless of whether or not the majority of dig-in / flip-over problems are pilot error, I would hope that as a group we would work together and continue to discuss engineering solutions that would provide a greater margin of safety for -A drivers. I for one would welcome the option to have several different choices for nose gear solutions beyond the stock design.

BrickPilot said:

I agree. I also read many -A drivers posting that they've never had a problem. Kudos to all of you, and either you exhibit excellent piloting skill each landing or have fantastic luck if not. I imagine that some of the pilots who have dug-in and/or flipped their -A might have been on the same "no problems here" soap box prior to their incidents.

Many factors led me to choose the -A model as the one I'm going to build, even in the face of the nose gear design debate. Regardless of whether or not the majority of dig-in / flip-over problems are pilot error, I would hope that as a group we would work together and continue to discuss engineering solutions that would provide a greater margin of safety for -A drivers. I for one would welcome the option to have several different choices for nose gear solutions beyond the stock design.

Click to expand...

Jeffrey,

Could luck in your endeavor of building your noseroller! It's a very safe plane and will give you many years of enjoyment. Land it like you should and you won't have any problems. The "great debate" may be causing you a lot of concern but it's not over there, wait until you read the other "great debates" about which prop or which GPS or autopilot you SHOULD be using because all the other stuff is just inferior or unreliable.

My point, Jeffrey, is some of this stuff has to just roll off of your shoulders into oblivion. So many experts and a lot of them aren't even flying RV's, yet.

Don't get paranoid about flying your project due to some of the ramblings going on in these debates.

If you're concerned about your "A" model gear, ask Paul Rosales how many hours he has and where he's been in his 6A. 'Nuff said!

mrreddick said:

Jeffrey,

Could luck in your endeavor of building your noseroller! It's a very safe plane and will give you many years of enjoyment. Land it like you should and you won't have any problems. The "great debate" may be causing you a lot of concern but it's not over there, wait until you read the other "great debates" about which prop or which GPS or autopilot you SHOULD be using because all the other stuff is just inferior or unreliable.

My point, Jeffrey, is some of this stuff has to just roll off of your shoulders into oblivion. So many experts and a lot of them aren't even flying RV's, yet.

Don't get paranoid about flying your project due to some of the ramblings going on in these debates.

If you're concerned about your "A" model gear, ask Paul Rosales how many hours he has and where he's been in his 6A. 'Nuff said!

Click to expand...

Hey Mike,

Remember when the tails kept falling off V-tail Bonanzas? Beechcraft blamed the dead pilots right up to the day they installed a $100 reinforcement cuff on the leading edge of the stabilizer...........and it never happened again.

18 busted planes is way too many, even if you and Paul Rosales have not had problems. Poking fun at those who care enough to contribute suggestions will not get this problem fixed.

Taking a cautious stance

I have about 360 hrs on my -7A now and have taken it to various grass strips and paved runways with no problems so far. I ALWAYS taxi and take off with the stick held full aft, relaxing pressure as the nose comes up to let the plane "fly off" the runway. I ALWAYS land nosewheel off and hold it off by increasing back pressure until airspeed bleeds off, then set it down gently, not letting it just "fall" when it runs out of airspeed. I gauge this by paying attention to when the stick is almost full aft, I begin lowering the nose. If you let it go full aft and hold it, the speed will bleed off and the nosewheel will slam down on the runway.

That said, after reading the NTSB reports, and as much as I hate to do it, I am making the decision to steer clear of grass strips from now on, unless absolutely necessary. I really enjoy going to grass strips and think that is part of the fun of having an RV. But the thing that scares me the most is not the landing on grass strips, it's the reports of the 4" deep X 10" radius divot that can take out the nose gear from a slow taxi.

I just couldn't bear losing my RV like that and would feel like an idiot if it happened and I had been forewarned. I have the original nose gear design.

Like I said, no problems at all so far, but I am now convinced it can happen while simply taxiing. I think having the front nose pant on helps significantly as it gives something to "bounce" off of instead of the big square nose fork.

Love my RV!

True Issue

I am a soon to be builder and would like to add my .02. I like the debate on the issue as it make everyone think. Some like to bash the A's some like to bash Van's. Personally I think the answer is in the middle. Obviously the gear has been redesigned by Van's to some extent, whether he thought it was required or he knew the heat might be on from the FAA/NTSB (FAA can use NTSB recommendation for policy changes) remains to be answered. If he provided the data to the NTSB then he must have know the issue was being elevated. That is not my point with this post.

My point is the gear design seems good for normal use with proper technique. The issue is how do you mitigate the potential accident due to non-normal use and bad technique. It is an invalid argument to say that you will be safe with good technique alone since everyone has a bad day. Everyone has a different skill set and the design needs to accommodate the skill level and just plain bad day many pilots have sometimes, it may not be skill alone it could be an unknown gofer hole.

Given that then, to me the need for a design modification that may stop the dig in when the various factors align and the nose strut clearance reaches the critical level. The Fork nut appears to have sharp edges, perhaps a metal shield would help the gear slide out of the turf dip in the runway without digging in to the point if flips over.

My concern with this problem is not the normal landings but the emergency landing on and unimproved surface. The potential to flip over is high in this situation and you just don't jump out of an RV after it lands on its back. On that line, would it be possible to develop a no flip safety bar that as the nose gear collapses back it pulls another bar out with skip plate that would help prevent the flip. My vision is a metal bar attached to the nose gear leg that would be out of sight under the cowl (not sure there is room). It would be attached at a point up the gear leg such that as the collapse happens the bar with footed skip tears from the cowl. Just a brainstorm, I am not an engineer but there are many smart builders that are and I think as a community we could come up with a cost effective design to make the A's safer in the off airport landing scenario.

How is the condition inspection on the nose gear strut performed? It seem that it could deform slightly from a few rough landings which would weaken the strut, but without something to compare it with, the deformation might be slight enough to be unnoticed. Do any of you take an shape measurements when new to compare to down the road. Perhaps a template of the strut shape.

I would like to hear of other ideas for designs, or what others have tried. The tire pressure is and obvious one, how easy is it to check the pressure with the wheel pant on the aircraft? If you assume there may be some circumstance that the wheel would drop into a hole how would you design a feature to mitigate this, reinforced fairing that would hold some weight and help the wheel slide out of the hole instead of digging into the hole? Just some things going through my head on this issue, I will start my build this fall but plan to build the 8A.

Cheers
Nemo

Yukon said:

Hey Mike,

18 busted planes is way too many, even if you and Paul Rosales have not had problems.

Click to expand...

Not to mention the many RV "A's" that I've been around for the last 12 years in just my small part of the world................that have had no nosewheel problems.

But, like I said before, the only two RV's around here that flipped in the last few years around here, were those "taildragger jobs"!

And, if there has been two, just around here, then how many flipping TD models across the USA & world wide????

L.Adamson

The issue is not just at touchdown

I have read all of the posts on this and the other threads concerning the nose gear issues. I think there is much too much discussion about pilot technique on landing flair and roll out. Although there have been some spectacular examples of nose gear failure in these situations I think too much attention is being placed on these "landing" accidents.

The point that many seem to be missing is that these nose gear are failing at taxi as often, if not more so, than at landing touchdown or roll out. All of the talk about holding the nose off at landing and such are not going to help in a situation where a nose gear digs into a grass taxi way when moving slowly at just a few mph.

If the gear cannot withstand turning the plane around on a turf taxi way then I think there is something that needs to be addressed with the engineering of the gear. This should not be an issue of Pilot Technique if there is a failure in the gear when performing a 180 on grass during taxi. Surly something else besides pilot technique has to be affecting this gear if it fails in this environment.

L.Adamson said:

Not to mention the many RV "A's" that I've been around for the last 12 years in just my small part of the world................that have had no nosewheel problems.

But, like I said before, the only two RV's around here that flipped in the last few years around here, were those "taildragger jobs"!

And, if there has been two, just around here, then how many flipping TD models across the USA & world wide????

L.Adamson

Click to expand...

Fixes aren't generated by the flying aircraft, it's the busted ones that lead to
product improvement. With 10's of thousands of Bonanzas flying, only 247
lost their tails in 30 plus years. Aren't we glad that Beech didn't use your logic.

That settles it. Neither the TD or NG are any good. I'm putting my 7A on amphibious floats.

Roberta

RVbySDI said:

The point that many seem to be missing is that these nose gear are failing at taxi as often, if not more so, than at landing touchdown or roll out. All of the talk about holding the nose off at landing and such are not going to help in a situation where a nose gear digs into a grass taxi way when moving slowly at just a few mph.

Click to expand...

Sometimes the sequence of an accident destroys the evidence on an initiating event (folding of the gear, for this discussion, not how we got to that point). The four taxi incidents give some clear data that the strut and fork are digging in and 3 of the 4 indicate that the hole was deeper than the fork could accomodate or the dynamics of the washboarding was a factor. If you taxi into a 3-4 inch hole, you may have problems. I suspect that there are a number of those taxi events that go unreported, much higher than four. The incident data seems consistent with the data from all the nose-over accidents, thus good, clean data from the incidents.

There seem to be four or five nose-overs that were not explained by pilot or witness statements or the evidence, such as bouncing, hitting hard, off the runway into a ditch, etc. Those four or five are of concern, but there is not sufficient data to know for sure how they got to the point of the strut digging in. However, there is a lot of information for you to make your own decisions about how to mitigate the risk.

John C said:

I would not worry too much about the taxi events.

Click to expand...

I'll give you $100 cash any time you want to taxi your 9A over the very small hole that got me while I video tape it! This is a standing offer for any "A" driver that thinks this is only a landing technique issue.

I agree Bryan

I removed the sentence. I did use up the 4 inch clearance by taxiing from grass to asphalt. I cracked my wheel pant much like yours. I had walked the area several times and the transition looked smooth. After the gear banged, I went back and looked. The asphalt stuck up a little and there was a tire depression (not from my airplane) in the soil right at the edge of the asphalt. Guess where I crossed. The nicely clipped grass masked the tire depression. The net depth (ridge of asphalt and tire depression) did not look like much but when I rolled the nose gear into the depression, the wheel pant scratches nicely matched the paint smears on the asphalt and granular surface. Static, the pant was almost touching. My tire pressure was 26 psi and I think that let the fork displace further downward. I've used 35 ever since.

1500+ landings on grass in my RV-6A. I have always taken off with the stick all the way back and the nose gets real light immediately when I throw the power in. The nose is off the ground in a very short distance on takeoff. On landing the stick is back and once my mains bark I ease in a touch of power (depending on conditions) and keep the nosegear up until I choose to set it down. I don't see a big problem with the nose gear and I believe the "A" is a great grass strip airplane. I usually always use a soft field landing technique on a grass strip. I run 45 psi on all tires as it rolls noticably smoother with less power than a lower psi on grass. Am I concerned about my nose gear...NO. I have enough grass strip landings to figure that if somethat happens now it probably is because the grass strip landing has become too much second nature. I will join Roberta at the mirror to view the problem.

L.Adamson said:

Not to mention the many RV "A's" that I've been around for the last 12 years in just my small part of the world................that have had no nosewheel problems.

But, like I said before, the only two RV's around here that flipped in the last few years around here, were those "taildragger jobs"!

And, if there has been two, just around here, then how many flipping TD models across the USA & world wide????

L.Adamson

Click to expand...

My rough calculations are that RVA nose gear collapses occur approximately one in every 7000 flight hours. Therefore if you have several friends who fly RVs and none of them have experienced a collapse it should not be surprising. Nor is it meaningful one way or the other.

These sort of anecdotal remarks are basically worthless (and a bit lazy). I recommend posters actually take some time to read the report so that they can make a REAL contribution to the discussion.

Ok, I've just read the report and can't say that I found anything too surprising. Basically I learned not to bring the nose down hard, bounce, let my tires run too low, or taxi into a hole. The only thing that I didn't see coming was the bit about the collapsed gear storing energy and sort of tossing the plane upside down like a big ol' mousetrap.

I think there is way too much emotional attachment between planes and their owners for an A-type to publicly say the nose gear is a wee bit on the delicate side, but it is. That being said, it's pretty hard to imagine a plane as light as these to have much more. Regarding the gopher hole type accident, can we really expect to drive a thousand pound vehicle's front wheel up to it's axel into a hole at 15 mph and not expect something to let go?

Overall, the report had no smoking gun that I could find. Keep your nose off, know the condition of the grass if you go there, and taxi like they taught you (walking speed).

Captain Avgas said:

These sort of anecdotal remarks are basically worthless (and a bit lazy). I recommend posters actually take some time to read the report so that they can make a REAL contribution to the discussion.

Regards
Bob Barrow
RV7A Finishing

Click to expand...

After weeks of reading your remarks, I'm honestly surprised, that instead of "RV7A Finishing".....................that it's not "RV7A soon to be converted to a 7"!

How one can come up with statistics of one flip per every 7000 hrs., is also beyond my comprehension. IMO, It's just a statement to fan the flames at this stage of rising paranoia.

Who's been out counting all the flight hours of "A" models across the world?

And yes, I read the complete report. Beginning to end...

L.Adamson RV6A