What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

RV-9A front gear folds

Hmmm

I for one think it is all in the design. I will bet you could drive across the same bump at the edge of the runway in your average Cessna or Piper without causing a bit of trouble. The thing just appears to be way to light in the material used or has been suggested the hardness. The problem has been happening with too much frequency. These aircraft are short field performers, kinda sux you have to be so careful about grass, rough surfaces, etc. Needs FIXING! I am game for whatever assistance I can be.

One question since I have never seen one of the gears off, is it solid or tubular?
 
Similiar Incident

The ledge in the runway is very similar to an earlier nose gear failure, see the thread below:

http://www.vansairforce.com/community/showthread.php?t=21393&highlight=nose+gear+taxi

Coming onto the apron area, there is a very slight unevenness to the
surface. The aircraft started to pitch up and down, and then the
grinding noise started. Chunks of mud started coming into the air
with the pitch up movement.
Click to expand...

This incident did not result in a flipped airplane, but a bent under nose gear, similar to the failure we're discussing here.

Kent, I agree that the design of the RV-A nose gear is not optimal and would benefit from a redesign. I'm just advocating that in order to improve upon the current design to eliminate the failures we have seen you must first understand what is causing those failures. I have been involved in many failure analyses in my professional life and I can tell you from experience the root cause of the failure has never been what was theorized before we began the investigation.

GrawHawk's list is a good start in compiling all the information needed to begin a failure analysis.
 
Don Jones said:
One question since I have never seen one of the gears off, is it solid or tubular?
Click to expand...


The gear is solid. It is made of 6150 and the hardness should come out to 42-44 Rockwell C.

That is all from memory though, so maybe a call to someone that knows for sure is in order. Well, except for the solid part. That is easy to see if it is off the plane.

Also, as I recall, the firm that does that actual heat treating is a VERY LARGE company that also does work for certified companies like Boeing.
 
Last edited:
yup

Don Jones said:
I for one think it is all in the design. I will bet you could drive across the same bump at the edge of the runway in your average Cessna or Piper without causing a bit of trouble. The thing just appears to be way to light in the material used or has been suggested the hardness. The problem has been happening with too much frequency. These aircraft are short field performers, kinda sux you have to be so careful about grass, rough surfaces, etc. Needs FIXING! I am game for whatever assistance I can be.

One question since I have never seen one of the gears off, is it solid or tubular?
Click to expand...

I have to agree with Don on this one. I believe the 7 & 9 A model gear is simply not up to the task.

When I decided on building a RV I was sold on the idea of "total performance". Even though I didn't need it, the idea of being able to land on a short grass strip sounded great. Then all the A-model nose gear problems started showing up. I decided to stick with the A model since I probably will never land on grass anyways. Now I'm learning of a gear failure on a paved runway? Say WHAT? An airplane LANDING gear should be able to handle a friggin bump on an open runway. Short of the "lip" being the size of a curb or a pothole as big as a bucket a proper gear should handle the occasional bump! A pilot has enough to worry about already he shouldn't have to handle his gear with kid gloves! When was the last time you heard of a spam can collapsing a gear on a lip on the runway?

I was watching a show about helicopters on Discovery channel the other night. They showed video of test footage that shocked me. A blackhawk was in a rapid tail low decent for what I thought for sure was a crash. I figured at the very least the tail wheel was toast and more likely the whole tail section would break off on impact. Boy was I wrong. The gear absorbed the impact springing the tail of the copter up into a nice level landing. I thought HOLY COW! Now I know our gear is not designed for that but it should at the very least save our bacon from a bad situation. Not toss us over on our face like a pole vault!

Van's canned response of "none of our gear have collapsed in 4000 hours" is terrible. I think they need to go back to the drawing board on this one.

Step off soap box..
 
LETS DO IT!!!

Thats terrible vans would say that!!! The nose gear is not up to the task, period. Vans can say all day long there planes have never folded. But ours have, over and over again. No matter what side your on I think we all would have to agree that vans did not put enough of a real life fudge factor into there creation. I know all my landings arn't perfect and I don't want to have to worry about flipping my new plane and hurting myself or my passenger in the likely event I have a not so suave moment. Lets find the cause and see if we can't get vans to correct it.
 
Last edited:
Wild theories

Most everyone posting here wants the nose gear issue to be an engineering problem, not an operator issue. This is fairly normal human behavior, something I call the Bart Simpson reaction, "I didn't do it, nobody saw me, nobody can prove a thing." My best guess is that the truth is somewhere in the middle. My nearly worthless, non-scientific, answer to the nose gear failures works like this. Van's designed a nose gear that fit their design philosophy, simple, light, and relatively inexpensive. Flown properly they have worked flawlessly for a majority of the operators, including Van's own fleet. Having watched the few available videos of the failures I see a common thread. The gear doesn't fail on the initial impact with the gopher hole, bump or whatever. There is mention of oscillation before the final failure in many cases. My theory is this; if you really whack the gear by landing flat, hitting a bump, hitting a hole, or a pavement lip, the gear is going to load, then unload. It is, after all, just a big spring. A big spring with no dampening. The steel spring suspension on your car has shock absorbers (a poor term, they are really dampers) to control the rebound of the spring. Same with oleo struts on aircraft, the valving in the strut keeps the energy from reversing direction quickly and launching you back into the air. My thought is that when you mix the undamped spring with a dose of PIO (pilot induced oscillation) the ugliness starts. The scenario looks like this. You land a little "hot" and force it onto the runway in a flat attitude, or hit the bump, or gopher hole. On contact with the runway the nosegear compresses more than usual, then rebounds, popping the nose into the air. The reaction is to release any back pressure you were holding and the nose goes back down loading the gear even more. In an extreme case, after a couple of cycles the gear collapses.

John Clark ATP CFI
FAA FAAST Team Member
RV8 N18U "Sunshine"
KSBA
 
I don't buy all of that

John Clark said:
Most everyone posting here wants the nose gear issue to be an engineering problem, not an operator issue. This is fairly normal human behavior, something I call the Bart Simpson reaction, "I didn't do it, nobody saw me, nobody can prove a thing." My best guess is that the truth is somewhere in the middle. My nearly worthless, non-scientific, answer to the nose gear failures works like this. Van's designed a nose gear that fit their design philosophy, simple, light, and relatively inexpensive. Flown properly they have worked flawlessly for a majority of the operators, including Van's own fleet. Having watched the few available videos of the failures I see a common thread. The gear doesn't fail on the initial impact with the gopher hole, bump or whatever. There is mention of oscillation before the final failure in many cases. My theory is this; if you really whack the gear by landing flat, hitting a bump, hitting a hole, or a pavement lip, the gear is going to load, then unload. It is, after all, just a big spring. A big spring with no dampening. The steel spring suspension on your car has shock absorbers (a poor term, they are really dampers) to control the rebound of the spring. Same with oleo struts on aircraft, the valving in the strut keeps the energy from reversing direction quickly and launching you back into the air. My thought is that when you mix the undamped spring with a dose of PIO (pilot induced oscillation) the ugliness starts. The scenario looks like this. You land a little "hot" and force it onto the runway in a flat attitude, or hit the bump, or gopher hole. On contact with the runway the nosegear compresses more than usual, then rebounds, popping the nose into the air. The reaction is to release any back pressure you were holding and the nose goes back down loading the gear even more. In an extreme case, after a couple of cycles the gear collapses.

John Clark ATP CFI
FAA FAAST Team Member
RV8 N18U "Sunshine"
KSBA
Click to expand...

John, while I agree some have been pilot induced, an airplane at taxi speed should be able to take a lot more abuse than has been demonstrated by the nose gear failure being discussed here. Like has already been noted, there has to be some safety margin in the thing, after all NO pilot is perfect 100% of the time and the airplane should be able to stand the less than perfect technique or the un-seen pothole in the grass runway.
 
Vans Fleet

Maybe Vans demo Aircraft have not suffered a gear failure, but their Demo pilots have experienced this in their own personal aircraft (RV6A). I know this because a friend of mine was purchasing an RV from a Vans Employee and the sale fell through when it was disclosed the nosegear had failed and a propeller strike had occurred. The engine had not been inspected after the incident so we went looking elsewhere.
 
John Clark said:
Most everyone posting here wants the nose gear issue to be an engineering problem, not an operator issue.

xxx snip xxx

John Clark ATP CFI
FAA FAAST Team Member
RV8 N18U "Sunshine"
KSBA
Click to expand...

The reason you don't see pilot error in my suggested list, is that one is much more difficult to measure and repair. The idea is not to fix any problem for all pilots but to improve the safety margin. Most pilots will assume they are better than the next pilot. Illogical things like egos come into play. I feel this exercise will be one of accrurate failure analysis considering all mechanical factors with the goal of improving the safety margin.

Even after all is done, if someone lands on the nose gear, be ready to accept a wrinkled firewall or worse.
 
The point is, no spacer is required. the fact that the seal is between the puck and bearing makes little difference. It is doubtful that the "little 3/8 bolt" flexes when it hits a load. if it were flexing it would likely enlongate the hole in the alumuminum fork and exhibit a smoke trail. lack of the aforementioned preload could allow the pucks to turn and also the bolt, thus wearing the fork and bolt. i suppose thats why some stake the pucks. if you want a free spinning wheel with no preload than that may be the best option.
either way good luck and good night.
 
Check out this nose gear

A while back Pilot Getaways did this report on a plane called an Expedition
350. The nosegear leg looks very much like the one on the "A" model RV's, but there is a difference at the top of the leg. It seems like this company is on to something here. Check out page 4, picture 3. I don't know if this would help to keep the gear from tucking under, but this looks like a pretty beefy setup.
 
Last edited:
Mr. Clark, sir, I believe you have hit the nail on the head.
And, Mr. Hegy, what exactly is a "less than perfect landing"? And how much is the "safety margin"?
What we don't need is a congressional subcommittee to establish rules as to how much of this and how much of that. It is an experiment, after all.
Mark


John Clark said:
Most everyone posting here wants the nose gear issue to be an engineering problem, not an operator issue. This is fairly normal human behavior, something I call the Bart Simpson reaction, "I didn't do it, nobody saw me, nobody can prove a thing." My best guess is that the truth is somewhere in the middle. My nearly worthless, non-scientific, answer to the nose gear failures works like this. Van's designed a nose gear that fit their design philosophy, simple, light, and relatively inexpensive. Flown properly they have worked flawlessly for a majority of the operators, including Van's own fleet. Having watched the few available videos of the failures I see a common thread. The gear doesn't fail on the initial impact with the gopher hole, bump or whatever. There is mention of oscillation before the final failure in many cases. My theory is this; if you really whack the gear by landing flat, hitting a bump, hitting a hole, or a pavement lip, the gear is going to load, then unload. It is, after all, just a big spring. A big spring with no dampening. The steel spring suspension on your car has shock absorbers (a poor term, they are really dampers) to control the rebound of the spring. Same with oleo struts on aircraft, the valving in the strut keeps the energy from reversing direction quickly and launching you back into the air. My thought is that when you mix the undamped spring with a dose of PIO (pilot induced oscillation) the ugliness starts. The scenario looks like this. You land a little "hot" and force it onto the runway in a flat attitude, or hit the bump, or gopher hole. On contact with the runway the nosegear compresses more than usual, then rebounds, popping the nose into the air. The reaction is to release any back pressure you were holding and the nose goes back down loading the gear even more. In an extreme case, after a couple of cycles the gear collapses.

John Clark ATP CFI
FAA FAAST Team Member
RV8 N18U "Sunshine"
KSBA
Click to expand...
 
cytoxin said:
Tapper roller bearings have been used in this manner for longer than most of us have been around. All rear wheel drive cars are set up exactly this way and see service of 100,000 miles or more.
Click to expand...

There are two things that are significantly different between the Van's nose wheel and all those millions of cars.

1. One side of the bearing must be kept from rotating. The current A fork allows both sides of the bearing to rotate together. Installing a pin or bolt between the fork and spacer may be better than nothing, but it's a poor fix that doesn't address other problems.

2. The two halves of the bearing much be held rigid relative to each other. There is very little tension on a long 3/8" bolt and the bolt only has to flex a small amount to cause the bearing to bind and the spacer to spin. Once the spacer spins the preload on the bearings change.

By installing a spacer between the halves you can torque the other two spacers down enough so that the friction of the bearing and the seals can't overcome the friction between the fork and spacer.

The Van's nose wheel is much more like a motorcycle wheel than a car wheel.

Here's a good photo of a motorcycle wheel bearing assembly showing the internal spacers. The band in the photo is the part of the assembly that is changed out to adjust bearing preload.

http://w6rec.com/duane/bmw/wheel_bearing/stack.JPG
 
Last edited:
kentb said:
Do you have drawings for you spacers? Or have more that I could buy?

Kent
Click to expand...

Sorry no drawings, in fact I doubt any two sets of spacers are the same.


As a side note, by advocating making a change to the nose wheel bearings, I'm not trying to bash Vans. I just think it's a poor choice of designs and in the experimental spirit I decided to change the design to a much better, but possibly easy to screw up design. If you didn't know how to tension a bearing and all the plans said was to cut the internal spacer down so the bearings where tensions properly, you may not know what to do.
 
I agree, sort of

John Clark said:
Most everyone posting here wants the nose gear issue to be an engineering problem, not an operator issue......My best guess is that the truth is somewhere in the middle. ........
John Clark ATP CFI
FAA FAAST Team Member
RV8 N18U "Sunshine"
KSBA
Click to expand...

It happens enough, compared to their airplanes, that it must be an engineering weakness. On the other hand, it doesn't happen to everyone so it is obviously related to pilot technique.

The burning question in my mind is whether or not some of the "less than perfect" landings I've made in other airplanes would collapse the nose gear of my 9A???????????
 
Having followed the accident preliminaries for many years, I have noticed many aircraft accidents involving the collapse of the nose gear. The RVs are not alone in this malady. Granted, the RV nose gear is not the most sturdy of gear. It was never designed to withstand the abuses subjected to many planes used as trainers. RVs are not trainers, they are high performance aircraft, and are not as forgiving as the planes we trained in.

Deviating from what Van's intended for their airplanes, regarding weights, balances, and engine size is putting unknown forces and stresses on the airframe and possibly altering flight characteristics. This can also add to the probabilty of an accident.

I think all the factors leading to accidents need to be considered and not just point to one area. Fight experience, design modification and alteration, runway conditions, and weight and balance all have to be considered, too.

There are many RVAs flying now. Way many more than any other kit plane. We see so many RV nose gear incidents purely because of the disproportionate amount of them operating. There are nose gear incidents involving every type out there.

How many Long Easy drivers are willing to replace their nose gear?

Roberta
 
redbeardmark said:
Mr. Clark, sir, I believe you have hit the nail on the head.
And, Mr. Hegy, what exactly is a "less than perfect landing"? And how much is the "safety margin"?
What we don't need is a congressional subcommittee to establish rules as to how much of this and how much of that. It is an experiment, after all.
Mark
Click to expand...

Oh boy here we go... I don't want to start an ugly forum war here. I served my country and thought I earned my rights (freedom of expression and speech)But since one persons opinion automatically makes rules concerning safety and puts him on his own ONE PERSON CONGRESSIONAL SUBCOMMITTEE (I'm getting that on a t-shirt) I will answer the questions presented to the committee.

1. A less than perfect landing shall be defined as a landing that is not so lined up, not so pitch up, speed not so good i.e. not the proper attitude, heading or speed etc.

2. Safety margin shall be defined as there has been found to be proper eng. design to allow Joe Shmo/Jane Shmo to make many "less than perfect landings" (see step 1.0) without cause for concern for his/her own personal, passengers, rabbits, aircrafts or other properties well being.

3. Experiment IS defined as
1 a: test, trial <make another experiment of his suspicion — Shakespeare> b: a tentative procedure or policy c: an operation or procedure carried out under controlled conditions in order to discover an UNKNOWN EFFECT or law, to test or establish a hypothesis, or to illustrate a known law
2obsolete : experience 3: the process of testing: experimentation

4. Insanity IS defined as doing the same thing over and over and expecting different results.

The congressional committee shall now go to work on a Saturday to address issues of corrosion with the engineering committee... Sheeeeesh!!!
 
Steve Brown said:
It happens enough, compared to their airplanes, that it must be an engineering weakness. On the other hand, it doesn't happen to everyone so it is obviously related to pilot technique.
Click to expand...
Not obvious to me. Could be it doesn't happen to everyone because of occasional bad nose gears. Or building technique (improper installation). Or--and I believe this most likely--plain bad luck.
The burning question in my mind is whether or not some of the "less than perfect" landings I've made in other airplanes would collapse the nose gear of my 9A???????????
Click to expand...
Right, and this is what has me and other -XA <future> drivers concerned and upset. That, plus Van's attitude, which in spite of the change they made to the nose gear is still that it's pilot technique. Nuts!
 
Bryan Wood said:
A while back Pilot Getaways did this report on a plane called an Expedition
350. The nosegear leg looks very much like the one on the "A" model RV's, but there is a difference at the top of the leg. It seems like this company is on to something here. Check out page 4, picture 3. I don't know if this would help to keep the gear from tucking under, but this looks like a pretty beefy setup.
Click to expand...

That is an interesting setup from the perspective of dampening (maybe this would help prevent the fore-aft oscillations?), but the fact is if the fork or wheel pant catch on something and there is sufficient momentum behind the aircraft he nosegear will fail...I don't care if it's on an RV or a C-172.

I think the answer to the perceived problem is clearance.

Unfortunately in this case we can't even determine *if* clearance was the problem because we don't know what the height of the bump in the runway was. Please, somebody measure that thing after the class D shuts down so we can know the facts and people can quit guessing at a fix for a problem we can't even factually describe.
 
My .02

Would this keep me from flying an "A-model" today?... No

Do we need to investigate further?...Yes

There are quite a few factors that could have caused this. Could a defect in the heat treating process cause this? Sure. Is it the only possible cause? I don't think so.

The design causes reductions in ground clearance with increased vertical loads. Gil has calculated the loads due to the W&B, but there are also loads due to the rough runway surface, and braking that was being applied. Braking would contribute a relatively constant force while the runway condition could setup an oscillation which would grow in magnitude due to the undamped nature of the design. Tire pressure likely played a contributing role. The edge of the intersecting runway was the straw that broke the camel's back.

In addition to the nose gear material analysis, we need to see what the transition from one runway to the other looks like, and we need data on the condition of the "old runway".

It is interesting to note that we haven't see the "pole vault effect" on a paved runway. Is that because of the nature of the runway surface? Or, in this case, is it due to the heat treatment of the nose gear?

So is it a design issue, or pilot error? People like to put their finger on one cause; I don't think it's that simple. The design coupled with pilot technique, runway condition, and aircraft maintenance all play a contributing role.

I have no doubt that the RV-10 design is much less susceptible to these factors. Is it worth the extra weight? I guess that depends on your mission.

Paige
RV-8A
 
There are some trainers....

robertahegy said:
....... RVs are not trainers, they are high performance aircraft, and are not as forgiving as the planes we trained in.
.......
Roberta
Click to expand...

Roberta.... there is a fleet of slightly modified RV-6As that were built specifically as trainers for the Nigerian Air Force.

http://www.vansaircraft.com/public/nigerian.htm

Does anyone have any data on how these Primary Trainers are holding up?

Are they buying many replacement gear legs?

Any VAF readers in that area? The data from this group of 60 aircraft would be very interesting.

gil A
 
Last edited:
BUILT BEFORE THE CHANGE....

az_gila said:
Roberta.... there is a fleet of slightly modified RV-6As that were built specifically as trainers for the Nigerian Air Force.

http://www.vansaircraft.com/public/nigerian.htm

Does anyone have any data on how these Primary Trainers are holding up?

Are they buying many replacement gear legs?

Any VAF readers in that area? The data from this group of 60 aircraft would be very interesting.

gil A
Click to expand...

Gil, Most of these aircraft were built before 1999, and used the original gear leg that was designed to flex near the socket. When Van had a few fail, they changed the taper location to just behind the wheel. So now when the wheel encounters a resistance to roll forward.... a chuck hole.... binding bearings or the faring draging on the wheel, it will cause the wheel to tuck under, and if it goes far enough, the nut will hit the ground and under the gear will go.

So the question is..... when they did the fix in 2000, DID IT ADD TO THE PROBLEM? And they have also changed the way the wheel is installed and the bearings are held.
 
Old gear legs.

gasman said:
Gil, Most of these aircraft were built before 1999, and used the original gear leg that was designed to flex near the socket. When Van had a few fail, they changed the taper location to just behind the wheel. So now when the wheel encounters a resistance to roll forward.... a chuck hole.... binding bearings or the faring draging on the wheel, it will cause the wheel to tuck under, and if it goes far enough, the nut will hit the ground and under the gear will go.

So the question is..... when they did the fix in 2000, DID IT ADD TO THE PROBLEM? And they have also changed the way the wheel is installed and the bearings are held.
Click to expand...

So I should use my original nose gear leg (c. 1996)?

Sounds like it might be a better deal with the oak stiffener added....:)

I could still have it modified for the new, angled yoke.

gil A
 
az_gila said:
So I should use my original nose gear leg (c. 1996)?

Sounds like it might be a better deal with the oak stiffener added....:)

I could still have it modified for the new, angled yoke.
Click to expand...

I remember the Van's "testing" video of a four foot diameter (or so) offset cam wheel that would revolve and slam against the nose wheel/leg.

The early legs failed rather easily. The revised leg didn't. Based on that, I wouldn't go back. But I'm keeping my original '96 fork setup.

L.Adamson --- RV6A
 
Gil,
I added the wood stiffener to the data list.

Roberta,
Correct pilot technique is extremely important but I still feel it should be addressed separately. No one is perfect all the time and if they believe they are, well that in itself, is an imperfection. I just felt the idea here is to look at all the design, engineering & mechanical factors towards the goal of improving the margin for those times when the pilot is not so perfect.

----
GENERAL:
Model: 6A,7A,8A,9A
Engine:
Prop:
Airport & Runway:
Operational Phase: landing, taxi, etc
Pre-fold event: Selectable answers: Normal rollout, PIO/galloping, nose gear first touchdown, shimmy/vibration noted on rollout, etc
Ground/air Speed:
Weather Conditions:

WEIGHT & BALANCE (at time of incident):
Nose:
Left:
Right:
Location on the Van's W&B charts:

NOSE GEAR:
Leg: (believe there have been 3 versions)
Wood (oak) stiffener:
Leg Metalurgy Testing:
Yoke: (believe there have been 2 versions)
Bearings: (believe there have been 2 versions)
Biscuits staked:
Tire pressures:
Bearing Preload:
Pull out:
Pants Installed:
If installed, ground clearance, tire clearance:

GROUND SURFACE:
Material: sod, gravel, dirt, asphault, etc
Hardness:
Smoothness:
Topology at start of or just before the catch or skid: Dead rabbit, pot hole, ledge, etc.
 
Last edited:
Database & Grove conversation

I'd add some form of standard pilot reporting as well to the list, after developing some broad descriptions to select from. Category: Pre-fold event: Selectable answers: Normal rollout, PIO/galloping, nose gear first touchdown, shimmy/vibration noted on rollout, etc, as best we've collectively able to bucket them - such that each reported event only really fits into one description.

I had an interesting conversation with Robbie Grove last week, and he talked at length about excessive bearing preload and seal drag being bad things relating to this issue. He convinced me to take a very critical look at the seal drag, and I know firsthand about bearing preload. I failed to ask what he was doing on his airplane. I many play with the parts sometime to week.

Rick 90432 fuse
 
Last edited:
Organization and progress report

rjcthree said:
I'd add some form of standard pilot reporting as well to the list, after developing some broad descriptions to select from. Category: Pre-fold event: Selectable answers: Normal rollout, PIO/galloping, nose gear first touchdown, shimmy/vibration noted on rollout, etc, as best we've collectively able to bucket them - such that each reported event only really fits into one description.

I had an interesting conversation with Robbie Grove last week, and he talked at length about excessive bearing preload and seal drag being bad things relating to this issue. He convinced me to take a very critical look at the seal drag, and I know firsthand about bearing preload. I failed to ask what he was doing on his airplane. I many play with the parts sometime to week.

Rick 90432 fuse
Click to expand...

Alex Peterson is interested in this aspect of the issue also and has sent me a private email expressing his theories. Alex has already produced many posts on Doug's website. My suggestion is that those folks interested in each aspect begin to communicate and work together to solve this problem or at least make sure it is completely identified. A delineation that seems to make sense is FORK & BEARINGS, GEAR LEG and STIFFENING METHODS, & PILOTAGE (let's learn from the best). This is an expensive mishap which could have been deadly for me and my bride. If there is more to learn about avoiding it, I'm all for it.

My wife and daughter may scream but I'm using this Father's Day to remove the engine from the mount so it can be inspected by Weds and returned to service.

Another writer told me that AIR POWER is the best place to buy bearings and gaskets.

Harmon Lange (makes the front gear) called yesterday and told me how to identify the vintage of the front gear. He said that he uses an electric pencil to write the date (mm yy or m y) on the top of the nose gear. I cannot get my nose gear out of the engine mount yet but in a few more hours we should be there. Before scraping off the powder coat and destroying the writing, examine it carefully (says Harmon). We used a felt tip pen to make the numbers visible and identify Jim's gear.

WHY DIDN'T THE PLANE ROLLOVER? I think I know the answer. The top engine mounting bolt on the pilot's side is bent. Apparently, the prop stopped at the lower rite, held the plane upright, and the force bent the bolt on the opposite side, pilot's side.

Another friend gave me his engine mount so we can compare mounts when mine is off. If it's not bent, if the bolt suffered the damage, I may save a $1000 on a new mount.

I'll know in a few hours.

Barry
Tucson
 
other A's on sod or grass runways

I have been following the posts since the unfortunate/fortunate incident(depending on how you look at it) and thought I would let all know that at least two 9A's that I am aware of, mine and Roger H's. have been operating off a sod runway for several years with no problems, so far. This runway has undulations, and can be a bit rough. His has the new fork, mine is on the shop table about to get installed. My tire pressures are 45, I land with full flaps, hold the nose off as long as possibe, and we both have 360's, mine with a CS prop. I believe that there are many, many other A's all of which have accumulated thousands of landings on non hard surface runways, and have taxied for thousands of miles on similar surfaces with no problems. If this is a problem that applies to all A nose gears is there some reason it is not more wide spread in the case of A's being used in this manner? I am confident that not all of us who operate on sod or grass runways execute perfect technique each time.
 
Surface effects

questair said:
I have been following the posts since the unfortunate/fortunate incident(depending on how you look at it) and thought I would let all know that at least two 9A's that I am aware of, mine and Roger H's. have been operating off a sod runway for several years with no problems, so far. This runway has undulations, and can be a bit rough. His has the new fork, mine is on the shop table about to get installed. My tire pressures are 45, I land with full flaps, hold the nose off as long as possibe, and we both have 360's, mine with a CS prop. I believe that there are many, many other A's all of which have accumulated thousands of landings on non hard surface runways, and have taxied for thousands of miles on similar surfaces with no problems. If this is a problem that applies to all A nose gears is there some reason it is not more wide spread in the case of A's being used in this manner? I am confident that not all of us who operate on sod or grass runways execute perfect technique each time.
Click to expand...

I just posted this on another thread, but I think it is relevent here too...

I just had a chance to closely look at the San Diego nose strut (only light tapping was needed to remove it from the mount) and one very interesting thing became obivious.

The nut and lower forward portion of the yoke were totally undamaged! Not even scratched.

There must have been enough fore and aft oscillation (hit resonance?) that the edge of the lip hit at a bad point in the travel and the nose gear contacted on the lower bend.... and then the gear folded under.

The nose tire showed no scuffing, cuts or any other marks.

The grass effect (potholes, etc.) of the nut hitting the ground may be different from the hard surface effect which may be more related to fore and aft resonance - which cannot be felt by the pilot, but can be observed by outside spectators. This effect may be related to axle/bearing drag.

There may be two different effects in play....

gil A
 
The only way I could see that the nut/lower yoke would not be damaged is if the impact with the runway lip bent the leg and threw the nose into the air at the same time and when the nose came back down it was the bent strut that contacted first?? I have been thinking about the geometry of the new fork, but I need an expert to set me right. The top of the yoke on the new and old forks are at the same position on the strut. The new fork puts the bottom of the yoke 1" higher on the vertical part of the strut than the old fork. Would this change the effective leverage of the fork/wheel on the strut such that the bending forces are transmitted further up the strut than at the bend.:confused:

Fin
9A (on a short, undulating grass strip with no problems so far)
 
Last edited:
Vans ignorance?

Barry, I am sorry this happened and I am glad that you and your wife are OK.

I am building an "A"-model to and wish I had done some investigating before I made up my mind. I have not had any experience in any other planes than C152's and C-172's, so I did not even consider a tail dragger, because try-gear is what I new and it worked fine. In my days as a student pilot and now still, I bounced, landed nose wheel fist, landed on rough grass (because I did not know the field), flaired about 10 feet to high (ouch), taxied on very rough taxiways, and so on, and so on!!!!.

Now that I know that any of the above (not even all at the same time but just one!) will cause a serious accident or even flip the plane, I would not have started building at all, or would have considered a tail dragger.

A lot of other posts from the so called "experienced" pilots blame it all to bad pilot technique. OK, fine, so I am a bad pilot, but the Cessna's held up fine so far. The advice I hear for the A-models is: "keep the stick aft" (I never did that in a 152 or 172!), do not use the front gear for landing (every so many of my landings is a bad one and may be touching nose wheel first, do not land on rough grass (do you go to the destination by car first, to check out the grass, or do you fly there ?). Etc. Etc.

OK, I understand the RV is a different type of plane than a C152, but it should at least be able to taxi without being wrecked, right? Every vehicle, machinery, equipment, etc, should have some safety margin. experimental or not!

What I do not understand is that a lot of builders are trying to find out what the reasons for these accidents are, but Vans does not seem to care. Obviously Vans pays a highly trained, professional, pilot to fly their plane, who can not afford to have a "bad landing day" and that is why they have flown 4.000 hours without a problem (that we know of!). How is it possible that Vans ignores so many of these accidents, that happened to their builders who will treat their planes as if it were their own children ?

I am to far into the build to change to a tail dragger now, so I am going to think about what I can change to the nose gear to make it safer ("bad pilot"-proof?).

I know from earlier posts that any "Vans criticism" is reason for the post to be removed from the forum, but I hope this time safety will be more important and the discussions may hopefully help to solve this problem.

As long as Vans is not doing anything, I request, no, I insist! that anybody who has any idea on how to improve the front gear of the A-models, will post it on this forum, for all other A-model builders to learn from it.

Regards, Tonny.
 
Last edited by a moderator:
Pilottonny said:
I know from earlier posts that any "Vans criticism" is reason for the post to be removed from the forum, but I hope this time safety will be more important and the discussions may hopefully help to solve this problem.
.
Click to expand...

Ronny,

I am sorry that you think so poorly of the judgment of the Moderator crowd here. AS you can see, your post that is "critical" pf Van's has not been removed, so you're wrong on that count. Safety is extremely important to me and anyone else that considers themselves a professional pilot, and we won't compromise on it.

The nose wheel issue with the "A" models is both troubling and puzzling to me, as it is to just about everyone. I am a pretty neutral observer on it, as I don't fly an "A", but I do fly one of those tail draggers that a lot of "A" model pilots avoid because they are worried about ground loops, etc. I simply accept that there are limitations and performance expectations that have to be observed. (A month or so back, faced with landing Louise's -6 on our very narrow airpark runway without any recent -6 landings, I elected to go elsewhere, switch seats, and let her do it. It was safer, and te right thing to do.)

I don't think that it is fair to say that Van's is doing nothing. Within the past year, they have done a re-design and recommended that it be followed by all builders. Just because you don't see them posting here or elsewhere doesn't mean that they aren't doing anything. It might mean that they are as puzzled as everyone else is, and choose to engage in engineering rather than speculation.

I am very sorry to hear about what happened to Barry, and bothered by the fact we can't figure it out. The only "answer" at this point would be to ground all the "A" models until the problem is resolved - or continue to let folks know that there is an unresolved issue that they must accept if they wish to fly. Hundreds and hundreds do so every day.

Paul
 
Pilottonny said:
A lot of other posts from the so called "experienced" pilots blame it all to bad pilot technique. OK, fine, so I am a bad pilot, but the Cessna's held up fine so far. The advice I hear for the A-models is: "keep the stick aft" (I never did that in a 152 or 172!), do not use the front gear for landing (every so many of my landings is a bad one and may be touching nose wheel first, do not land on rough grass (do you go to the destination by car first, to check out the grass, or do you fly there ?). Etc. Etc.
Click to expand...

I did six landings in a 9A yesterday. And I didn't worry about it at all. The two 6A's close to my hangar have over 2000 hrs. between them, and their (non test pilot) owners haven't been worrying either.

As to those Cessna's. Their design, is not to land on the nose wheel. Many Cessna firewalls have buckled because of it. You should land them on the two mains, just like an RV.

However, as I've mentioned previously, I do know of three taildraggers.................locally, that flipped! I'm not saying the "A" design couldn't use some improvement, but I think this forum (as well as a few others) tends to throw the problem out of proportion; because there are just too many non-worrying "A" owners who don't frequent internet forums. Since I've been around RV's for 15 years, I just know of too many planes that have accumlated many thousands of hours between them without flip damage. What we see here, is a condensed form of the problem, with only a small slice of actual RV owners participating. It often tends to make the problem look far worse than it actually is.

L.Adamson --- RV6A
 
As a 9A owner, just weighing in. First, I am no expert on the engineering or on piloting, but I think that covers a bunch of us.

These are facts: I have several hundred 9A landings and haven't flipped. I have never had a shimmy or other "strange" happening. I did the nose gear mod, so I have flown both forks. I have the old style bearings with the spacer (my nose gear came from an early 6A) and absolutely will not switch to the through-bolt axle!! My preload is lighter than what some might prefer; I want a freely turning nose wheel. I carry 40 psi in the nose wheel. I haven't dropped my nose gear earlier than I wanted in a LONG time, now that I am comfortable with landings. I seriously doubt anyone can bend a nose gear that is being held off the ground. I have never been on grass with it, although I believe my skill level will allow it without lowering the nose prematurely.

These things I believe (but may be wrong): The earlier spacer type axle is better. I modified it to accept spacers that I made on a lathe to give me the preload I want. This is instead of the old washer route that I consider less than accurate. I can adjust in .001" increments. I consider the nose gear bearings to be some of the most critical parts on the aircraft. I believe the whole nose gear need improvement, but can absolutely be safely flown. Conjecture, but I would guess that we see more flips on 9A's than other A models because 9A builders may have somewhat less experience than those who build aerobatic ones (and tail draggers, for that matter.) Also, our lower landing speed may actually be a hindrance, although I haven't flown a 7A to see how it lowers it's nose. I have flown a 7 (took transition training it one.) I would like to see data on experience versus model chosen. I would also like to see honest data (tire pressures, stick back or not, ground speed, size of ledge, etc) on more of these accidents. Personally, I don't CARE if my gear is as strong as that of an F-15, as long as it will hold up. I would like a little more margin for those times when I will need it, either by marginal piloting, or poorer conditions. And I don't care who comes up with the idea. Van's has a great product, but all products can be improved.

Bob Kelly
 
I found this interesting

I found it interesting that the yellow prototype of the RV12 has (or had) a strut type nosewheel. I notice the red one has the traditional strut. Seems Van's has been experimenting with different options.

http://weflyforfun.com/rv12.jpg
 
I've landed on the nosewheel on a cessna before without any damage. I've also landed on the mains a cracked a brace once. Either one of those instances would have totalled a nosewheel RV... That said, they aren't Cessnas either.
 
There are no planes designed to be landed on the nose wheel

Just ask any A&P that have worked on Cessna (trainer) airplane about buckled firewall repairs.
The proper way to land an airplane is on the mains. That is why the call them "mains". They are what you should mainly use for landing. The nose wheel come to the runway last.

The Cessna can handle new pilot errors better then the RV, but if you wanted an airplane that lands like a Cessna then you will have to have one that flies like one as well.

I would like a stronger, more forgiving nose gear, but I am not willing to give up my RV performance.

Kent
 
Landing gear specs?

Paul, I am sorry if I offended you because I assumed that my post may be deleted, but I had one "modified' before, that is why.

OK, Vans may be doing something about the A-front-gear-problem, behind the screens, but we, (A-builders) do not know anything about this!

As I stated, the gear should be able to cope with some "stupid pilot"-errors. I do believe there are regulations for what the landing gear should be able to cope with, like a drop-test?, max. braking force?, etc.? I just do not know exactly what they are. Maybe there is some knowledgeable people out there that know this?

Looking at the accidents that happened the last year or so, I just do not have confidence in the (front)-landing gear as it is now.

Regards, Tonny
 
I think if people are concerned about the bearing set up, than you should contact Grove and order up the wheel and bearings that they have to offer. Has a spacer for preload on the bearings and they stake the spacers to the fork. This is the setup that I'm using, haven't tried it yet, airplane ain't done, but from what I have, I know it's going to work just fine. Also take the wheel to a motorcycle shop and have it balanced.
 
Pilottonny said:
I do believe there are regulations for what the landing gear should be able to cope with, like a drop-test?, max. braking force?, etc.? I just do not know exactly what they are. Maybe there is some knowledgeable people out there that know this?
Click to expand...
Tonny,

They do have regulations for this but they apply to Cessnas, Pipers, etc.

That is why these are called "Experimentals".
 
I just talked to Grove.

allbee said:
I think if people are concerned about the bearing set up, than you should contact Grove and order up the wheel and bearings that they have to offer. Has a spacer for preload on the bearings and they stake the spacers to the fork. This is the setup that I'm using, haven't tried it yet, airplane ain't done, but from what I have, I know it's going to work just fine. Also take the wheel to a motorcycle shop and have it balanced.
Click to expand...

The part front wheel replacement would be:

59-1ARV (aluminum) $269.00
59-1MRV (magnesium) $299.00

Switching over sounds not to hard.

I might give this a try.

Kent

Grove 1-619-562-1268
 
allbee said:
I think if people are concerned about the bearing set up, than you should contact Grove and order up the wheel and bearings that they have to offer. Has a spacer for preload on the bearings and they stake the spacers to the fork. This is the setup that I'm using, haven't tried it yet, airplane ain't done, but from what I have, I know it's going to work just fine. Also take the wheel to a motorcycle shop and have it balanced.
Click to expand...

Interesting! So is this essentially a drop in replacement for the Van's wheel but with spacers for preload?
 
You must log in or register to reply here.
Back
Top