RV tip over (flip upside down)

I'm sure that I'm just one of many monitoring this thread, but I have to chime in and say that too many of the suggested "fixes" are what I would call the long way home.

Get back to basics and note that there seems to be mainly two reasons why a nose gear will dig in and pole vault. And they are that 1. The fairing has too little clearance to the tire and the tire binds on the fairing, and 2. The nut is too low to the ground and digs in.

It seems to me that two VERY simple changes would have averted 95% (my arbitrary number ) of these kinds of accidents, and that is to further angle the fork so that it is almost at a 45? rearward angle so that the nut is above the centerline of the wheel, and then to allow more like a third of the wheel to protrude below the fairing rather than the small distance it does now.

While that may affect cruise speed a smidgeon, it would take away the two most obvious reasons given for nose gear accidents on soft ground.

Admittedly I am not a structural or metallurgical engineer, but my common sense experience tells me that these engineered changes wouldn't give any unknown dangerous side effects.

So carry on as we take this thread to the 500 message mark

fodrv7 said:

The only satisfactory fix is to redesign the Engine/Nosewheel mount to move the Nosegear/airframe attach point forward, such that the spring strut is ahead of the nose wheel and slope backwards.
The current design with the strut angled forward means that the further the nosewheel bends back the more it moves DOWNWARDS and the more load it places on the strut, and so it bends still more and more load is placed on the strut,etc. etc. etc.
Which explains why the bending is so large at even low speeds.

Click to expand...

Adding this, to a few other proposed design changes....

We now want to add the weight of a forward structure to support the nose leg, which of course will require some additional weight towards the tail to offset this. Some pilots will now have to diet more often, just to be skinnier for a lower useful load; or perhaps "heavier", and just re-design the seats to sit farther back, but install smaller fuel tanks to keep gross weight within bounds.

We want to expose more wheel area, perhaps like a sliding canopy "Tiger", which of course is a lot slower than an RV in the 130 knot range at 180HP.

And then all this time, we blame it on the nose gear, in which the problem starts, when the catching wheel pant siezes the wheel from turning, putting extreme loads on the gear leg; but pretending as though this won't happen to either main on a taildragger, perhaps flipping it over....................which of course, it has!

In the end, let's put the wings on top, remove the wheel pants, install larger diameter tires, redesign the flaps for STOL performance, and call it an Aviat Husky or something!

L.Adamson ---- RV6A, but prefers the Husky for the outback bush country

edit: repair incorrect letter keys for two words, not that I'm perfect with spelling, anyway....

New angled yoke/leg

Would someone with the new angled leg/yoke combination post a photo?

fodrv7 said:

The only satisfactory fix is to redesign the Engine/Nosewheel mount to move the Nosegear/airframe attach point forward, such that the spring strut is ahead of the nose wheel and slope backwards.
The current design with the strut angled forward means that the further the nosewheel bends back the more it moves DOWNWARDS and the more load it places on the strut, and so it bends still more and more load is placed on the strut,etc. etc. etc.
Which explains why the bending is so large at even low speeds.
If you aren't convinced, go out to your favorite grass strip and trying pushing a stick down the runway angled as per the current design. Then try dragging it behind you with the equivalent angle. If it strikes a rut it will lift and relieve the load.
Pete

Click to expand...

Pete: You are absolutely right: the only fix is to redesign the nose gear. I've talked to Van's, and they are not inclined to do it.

Since they have all of the engineering data, any field redesign would be difficult. Several of the proposed 'fixes' have knock-on effects that may make the problem worse or cause other problems (porpoising for example).

Van's has already redesigned the fork axle to move it up about 1". This is a help, but does not prevent the nose fairing from digging in and impacting the tire.

My suggestion addresses both the nose fairing collapse and protecting the axle nut, but I really don't know what it will do in the field. My inclination is that it cannot hurt, and will probably help.

As for some of the gratuitous comments from others (build a tail dragger, build a Murphy), these are not helpful. Sharing technical ideas may lead to an improved safety margin, which is what we are after. If someone wants to start a thread on how to avoid ground loops in tail draggers, I'd be happy to chime in with "nose gears rock!". No design is perfect, and all designs can be improved.

Keep the ideas coming.

Vern Little

Howzabout easliy removed nose wheel pants? Left and right halves. Remove the damn thing before landing at Johnson Creek. Maybe a breakaway patch in front of the tire? Note also Cessna encourages removal of their 152,172, 182, etc pants for winter operations. Our planes are placarded EXPERIMENTAL for a reason. Like the sign on the hangar wall says, "CAUTION, men playing with power tools"

Steve
-9A fuse

use search button!

Hello all

It is not the first time that here is a discussion about the nosegear, use the search button and you will find what you are looking for.

Here is a link to one of this thread with pictures of the old/new fork and gearleg new/old fork

Dominik

DGlaeser said:

In the end, the loads on the tube are the same (it has to react the forces on the spring). The trailing link (if it exteded down as much as possible) would help to keep the tube itself from digging in, but it also adds a lot of weight (you need a shock absorber with that spring).

Upward loading (vertical through the nosewheel) doesn't seem to be an issue. The loads that seem to be causing the problem are when the tube is bent down/back (nosewheel gets caught in a pothole) and possibly to the side at the same time. Then that long tube becomes a pretzel.

The correct structural solution is to bring the attach point forward, so the tube is shorter (keeping the nosewheel in the same location). If that pesky engine weren't in the way it would be easy to do

Dennis Glaeser
7A Wings (main structures done, working on ailerons and flaps)

Click to expand...

David,
your design would solve the problem if the strut from the Engine Mount to the your trailing link system was rigid. Then the wheel could flex up with out moving back. If the Nosewheel fairing was fixed the the rigid strut (Not the axle.)it would not rotate down to the ground or back onto the wheel.
Pete.

Reinventing the wheel.

This has been a very valuable thread. It has allowed all of those builders with nose gear concerns (and there are many) to have a say or read the comments of others. And it has generally been a polite thread which I also find most encouraging.

At a recent Experimental airshow I was driven to start examining all the different nose gear designs. Even among the light sport aircraft there were quite a lot of very advanced designs. For instance all the Tecnams have a sophisticated looking trailing link design. I'm not aware that the Tecnams have had any undue problems with nose gear failures or tip-overs, and Tecnams are very frequently used as ab-initio trainers. The thing just looks like real landing gear. But it would undoubtedly cost a few knots.

However I doubt that Vans is about to make any major structural changes to the RV7A nose design in the short term so it is now up to us to discuss ways to increase the safety margin within the framework of the currently supplied kit items.

I have concluded that the only sensible thing that I can do that will:
a) Actually improve the safety margin, and
b) Not make things worse from a structural point of view and
c) Not cost me 20 knots of speed
Is to use the new angled forks and redesign the fairing to provide significantly more ground to fairing clearance. In addition I will be ensuring very generous fairing to tyre clearance.
I would imagine that increasing the ground clearance of the fairing from 2 to 3 inches would make a lot of difference to the propensity for the fairing to bottom out.

In fact as I looked around the recent airshow it was interesting to note that for similar size nose wheels the RV fairing had the most minimal ground clearance of any aircraft on display. Most other designs were showing considerably more tyre. The difference in aesthetics is minimal.

I totally agree that using the new style fork plus trimming an inch off the bottom of the nose fairing and increasing side clearance to the tire is probably the simplest and cheapest way to increase soft field safety margins a LOT.
I can't imagine that anyone would argue, knowing what we now know, that doing those three things wouldn't add a large safety margin.

It would be great if a FLYING RV7A owner also agreed and actually did so, and then could accurately report any difference in cruise speeds from before (old fork, pre-trimmed fairing) to after.

How I'm fixing mine

Bob, I completely agree with you on taking precautions with this. I was getting the information to send my nose gear to Harmon on Monday so he can evaluate if it is bent and/or needs replacing or straightening. If it is not bent he will cut it, rethread it and send it back. Along with that the new fork from Van's which is only $154 and an attempt to raise the fairing higher.

A couple of posts back Steve suggested removing the wheel pant before going into Johnson Creek. From what I experienced this might be a mistake because the wheel pant in my case did more good than harm by being on the plane. With out a doubt it acted as a skid and helped to save the gear. There are a couple of ideas bumping around in my head on how to make the nose fairing adjustable so that it can be lower for everyday use, but just loosening the bolts will allow it to slide up. Basically slotting the mounts on the fairing itself and not using the axle as a mounting point. This would make it easily adjustable even during a preflight in a minute or so if the destination is un improved. The front of the fork is basically already set up by being drilled and tapped, so just the rear mount would need to be set up differently.

On another note I was e-mailed recently and told of somebody who had bent their nose gear during taxi on a paved taxi way after hitting a small rock. According to the person the rock was very small and the pilot didn't see it, but his nose gear bent under some and didn't flex back to the way it looked prior to the incident. Since this is not my story to tell, if you are monitoring this thread and do not mind coming forward please share the details with the rest of us.


Regards,
Bryan

New model Photo 9A



New as of 8/8/05
Frank K
9a

nose leg design

Anyone else notice what the -12 nose gear looks like in the drawing in the -12 forum thread?????

Wonder why the change???????

Mike

nose gear

Another good idea. I'm not convinced that the fork axle nut is the primary cause of nose wheel dig-ins, but it sure can't hurt.

I still think that it's the chain reaction of nose fairing collapse--digs in to tire--tire stops suddenly--weight transfers to fork--fork 'rolls over'--axle nut digs in--bad things happen.

Raising the axle sure will help, but stopping the fairing from collapsing is the first link in the chain.

The discussion on a new fairing is interesting. I can envisage a nose fairing that has quite a different shape in order to prevent a collapse.

I still think that some sort of skid plate may be in order... it will prevent the collapse of the fairing.

Vern Little

Check out this strip.

I don't think I'd be landing an RVA (or any RV for that matter) on this strip in the mountains of New Guinea. It's at high altitude as well. Note the trusty old Cessna departing (nosewheel too). Forget about the spam can tag...those machines demand respect.

[/URL][/IMG]

You don't think you could get a tailwheel RV into there?

RV12 nose gear update

I recently sent an email to Ken Kreuger at Vans re the new nose gear on the RV12 prototype. Here is a copy of that email and Ken's verbatim response:

On 17 Nov 05, at 22:12, Bob Barrow wrote:
> I notice on the Vans write-up on the RV12 on your website that it seems to
> feature an oleo strut for the nose gear. This is a departure from previous
> models. Can you advise why this is so.

Hi Bob,
There are a number of desires that drove us to the type of nosewheel we
are planning for the RV-12.

First-up, while an oleo strut would be really neat, the nosewheel uses
two springs in series...not compressed air and oil.

We are going to use a single brake master cylinder mounted near the
center of the instrument panel. One of the missions of the RV-12 is
training and in that mode, the single master cylinder allows either pilot
to actuate the brakes without resorting to the cost/weight/packaging
issues that we would have with a full dual toe brake set-up. This choice,
however, requires a steerable nose wheel. We believe that the simplest
steerable nose wheel is what we have currently shown.

As with almost all the features of the RV-12, reality may intervene and
expose the shortcomings of our "proof-of-concept" aircraft.

I hope this helps! Thanks for your interest in the RV-12.

Ken Krueger, Engineer
Van's Aircraft

Way back when I was building my 6A I was concerned about the big nut sticking down in front of the nose wheel. I built up several extra layers of heavy fiberglass cloth on the bottom front of the fairing. The intention was to provide a bit of a ski to keep the nut from ever diggin in.

Well, many years later and while less than 5 hours into my fly-off period I porpoised it (yes, it was pilot error). The nose "bonked" but the landing was completed without incident. Back at the hangar I gave it a good look and saw that the nosewheel had tucked under a bit until the front of the wheelpant hit the pavement. I had ground a flat spot in my reinforced area right where the nut is. I am certain that if I had not built in the ski, the nut would have dug in and collapsed the gear or flipped the plane.

Skid plat

Pilot Dane said:

Way back when I was building my 6A I was concerned about the big nut sticking down in front of the nose wheel. I built up several extra layers of heavy fiberglass cloth on the bottom front of the fairing. The intention was to provide a bit of a ski to keep the nut from ever diggin in.

Well, many years later and while less than 5 hours into my fly-off period I porpoised it (yes, it was pilot error). The nose "bonked" but the landing was completed without incident. Back at the hangar I gave it a good look and saw that the nosewheel had tucked under a bit until the front of the wheelpant hit the pavement. I had ground a flat spot in my reinforced area right where the nut is. I am certain that if I had not built in the ski, the nut would have dug in and collapsed the gear or flipped the plane.

Click to expand...

This is terrific information, thanks! I've been investigating a similar skid plate design for my -9A and your anecdote is important. You can see it by browsing through past posts on this list.

Vern Little -9A

When you feel it sink add power not AOA

Somewhere in theis thread I saw a technique for handling sink close in described as pull back on the stick. You shouldn't let it get that far but when it happens and you are already in landing configuration try regaining control by feeding in a little power to arrest the desent (no for God's sake don't shove the throttle in in panic). Try to roll the mains on with the plane trimmed for slow speed flight using power as one of the controls available to you - don't come in with no pitch trim adjustment and hold the nose off with muscle and expect to get consistent transition results from flight to low speed taxi - nobody is that good.

Bob Axsom

Excellent advice, Bob. Probably the biggest reason pilots have trouble with the proper speed, attitude, sink rate, and ultimately keeping the nose light and keeping it off the ground during landings, is failure to properly trim the aircraft. Trim needs to be adjusted to balance the plane during those steps in the landing process. Without those incremental trim adjustments, the force needed to hold the nose wheel off the ground is way more than I can deal with. And the addition of just that smidgeon of power, if and when needed, settles the plane in without trying to yank the stick back, ballooning in ground effect, and stalling the plane in.

The best practice for good landings is go out and do some slow flight with full flaps and fly around at about 70 mph. Get that plane trimmed up and fly around at any given altitude and hold it there while maintaining your speed at 70 mph. Then, in the pattern, use those learned skills and control the descent with power. The best landings start on the downwind leg.

I try to get my speed down to about 140-150 as I approach the downwind leg, easing off the power and trimming for level flight. I hold pattern altitude all through the downwind and get to flap speed by the time I'm abreast my touchdown point. By then I have reduced rpm to below 2000 and pushed the prop control in all the way, then reset the throttle to hold about 1800 rpm. I ease in the first flap setting (20 deg ) when abreast the runway threshold and add trim to maintain level flight. I start my descent after I have turned base and then add the rest of the flaps to 40 deg., again retrimming the plane to level attitude. I maintain 80 mph as I descend on final, watching my glide slope as I was taught to do ( pick your touch down spot and keep it in your view). Adding power if my speed decays or my touch down spot rises or decreasing power if my spot falls too low, always trimming accordingly. Keep that stick light. I pull out the power on very short final and ease back the stick to set the mains on the ground. With the plane properly trimmed, stick forces necessary to keep the nosewheel off the ground are easy. Easing the plane down with the speed controlled helps you reach that touchdown zone at a speed that will help prevent the plane from balooning into an uncontrollable attitude resulting in a bad landing or accident. Holding the wheel off the ground gives you dynamic braking allowing you to stay off the brakes. Getting on the brakes too soon forces the nose wheel down too soon. Planning and finesse are KEY!!! Always be ahead of the plane and don't strong arm it.

These are marvelously designed airplanes that fly an incredible envelope of speed, both fast and slow. Learning both ends of the speed envelope will ensure a most pleasurable flight.

Hope this helps. It's what kept me out of trouble. I fly from a 1700 ft rolling grass runway. Controlling my speed and descent makes this runway a piece of cake. I am a firm believer in C/S props for best controlling speed on approaches.

Roberta
N2447A 0-360 A1A with Hartzell BA prop

robertahegy said:

I try to get my speed down to about 140-150 as I approach the downwind leg, easing off the power and trimming for level flight. I hold pattern altitude all through the downwind and get to flap speed by the time I'm abreast my touchdown point. By then I have reduced rpm to below 2000 and pushed the prop control in all the way, then reset the throttle to hold about 1800 rpm. I ease in the first flap setting (20 deg ) when abreast the runway threshold and add trim to maintain level flight. I start my descent after I have turned base and then add the rest of the flaps to 40 deg., again retrimming the plane to level attitude. I maintain 80 mph as I descend on final, watching my glide slope as I was taught to do ( pick your touch down spot and keep it in your view). Adding power if my speed decays or my touch down spot rises or decreasing power if my spot falls too low, always trimming accordingly. Keep that stick light. I pull out the power on very short final and ease back the stick to set the mains on the ground. With the plane properly trimmed, stick forces necessary to keep the nosewheel off the ground are easy. Easing the plane down with the speed controlled helps you reach that touchdown zone at a speed that will help prevent the plane from balooning into an uncontrollable attitude resulting in a bad landing or accident. Holding the wheel off the ground gives you dynamic braking allowing you to stay off the brakes. Getting on the brakes too soon forces the nose wheel down too soon. Planning and finesse are KEY!!! Always be ahead of the plane and don't strong arm it.

Roberta
N2447A 0-360 A1A with Hartzell BA prop

Click to expand...

Some very good advice from Roberta on approaching. As usual a most considered opinion.

The problem I see with many low time pilots is that once they kill the power prior to the flair they become emotionally committed to the landing and unable to reapply power. In fact if things start to go awry the last thing they want to do is reapply power..they just want to get the gear on the ground. Sometimes when I have a long runway ahead of me I practice what I call the "hover taxi". Instead of letting the plane settle to the strip I reapply just a little power to prevent the plane settling. In ground effect it's amazing just how little power is required to keep flying. The idea is to keep flying the plane in ground effect just above the stall with the gear just off the bitumen. It's virtually impossible to stall the plane in ground effect. Then eventually just a small reduction in power lets the ship settle to land. This is good practice in cross winds also as it hones control skills. Sometimes I practice this during touch and go operations (I just don't "touch").

The idea is to train the mind to be receptive to applying and using power at all stages of flight until a landing is effectively executed. Power is the key when the final stages of the landing comes unstuck because it puts you back in control, particularly after the flair. Don't take that hand off the throttle.

Another good method to hone those landing and slow flight skills, Bob. As you said, keep that throttle in your hand, the other on the stick and your feet on the rudder pedals. Just a little throttle can get you back in control, or a lot to get you out of a bad landing.

You are right about not being able to stall in ground effect. What does happen is pilots sometimes balloon out of ground effect at too low an airspeed, then stall in.

More great advice to better landings,

Roberta

Out of interest how soft was the field?

To my mind, as an ex -9A owner, I was unimpressed by the -9A's ability to handle soft ground. With its long leg, drag on the gear puts a considerable load onto the noseleg since the moment tips it forwards. My main concern was takeoff, but it could slow down very abruptly on landing once I could no longer hold the nosewheel off.

The -9A has longer main legs than the -6A and this clearly (to me) exacerbates the issue.

Steve

I noticed this report in the NTSB database:

Accident occurred Friday, August 12, 2005 in Palmer, AK
Aircraft: Brabandt RV-9A, registration: N63EB
"During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on August 15, the pilot reported that he landed with full flaps on runway 21 at the Cardwell Airstrip, a gravel surfaced runway, which is about 1,200 feet long, and about 50 feet wide. He said his touchdown speed was about 56 mph, and about 500 feet after touchdown, the nose wheel landing gear began producing scuff marks on the runway surface. The nose gear fork eventually dug into the runway surface, and bent the landing gear strut aft. The airplane subsequently nosed over, and received structural damage to the fuselage, the left elevator, the left wingtip, the rudder, and the vertical stabilizer."

Seems like something was impeding rotation of the nosewheel, and it got worse until the fork dug in. Plausible? Has anyone here ever heard of gravel getting inside a wheel pant and causing trouble? I guess it could also have been the old problem of the fairing rubbing on the tyre.

Does anybody have any further info on the following nosegear failure. Apparently happened at the Reklaw Fly-in, Texas, in late October. The grass strip where the skid marks are looks pretty good to me.

http://img394.imageshack.us/img394/7231/planeafterrecovery8ug.jpg

http://img394.imageshack.us/img394/2553/tnskidmarkpriortovaulting7sy.jpg

Bob,
Believe me, you can't tell from the pictures. I landed there at Reklaw the same day as the accident. The first third or so of the strip was smooth, but after that it got pretty rough and dipped down hill a good bit past the mid point. I landed there in my RV-7 and as I decelerated I remember the thought entering my mind that I was going to rip my wheel pants off. Having said that, hundreds of planes landed there that day including other "A" models with out any problems. For some reason the accident is not on the NTSB website. BTW, post #68 on this thread is a picture I posted(I didn't take the photo) which shows the plane having just flipped over. They occupant is still inside the plane and the battery switch is still on as noted by the right landing light still being on.

Tobin

Nose fairing skid plate

I've implemented a nose gear skid plate based on epoxy-flox.
The idea is to have any load on the nose cone transferred to the gear weldment, thus preventing nose cone collapse and digging in of the axle nut.

I did this by packing the epoxy-flox mixture into a small plastic bag, compressing iit between the nose cone and weldment. After removing the bag, I glued the casting to the nose cone and enlarged the area around the nut to allow free rotation.

Finally, I sprayed the weldment in oil, put some filler on the casting to fill the creases and gaps, and fit it together again. After a bit of shaping and adjustments, I got an acceptable result.

It's not pretty, but I think it will give a bit more margin of safety.

BTW I used a flox/micro-balloons mixture, rather than glass fibers. Flox is more flexible and less likely to crack, and is lighter. The casting will only be in compression, so this should work fine.

I hope to never be in a situation to test this skid plate out, but if I find the nose cone bottom ground off one day and stay upright, I'll let you all know.

Vern Little
RV-9A

Record postings

As far as I'm aware no Vans Airforce thread has ever had more postings than this one. With over 200 postings this is a record....by miles (and nautical miles too). What does that tell you. It says that a looooot of RV builders, and flyers, are concerned about the shortcomings of the Vans nosegear.

What's even more impressive is the number of views of this thread. As of now, over 7,300.

Tobin

Skid plate design

Since this thread is getting pretty big, it's hard to find postings.
Therefore, I posted details of my nose gear skid plate design on my web site.

Tips Page


Vern Little RV-9A

Ive had shimmys in a Tomahawk, C172, C210 and a GlasairIII on landing. Each time I thought the nosegear was going to colapse it was so severe.
Only once ,was there damage, on the Glasair when the limiting pin sheared off.

Could this not be part of the nose wheel colapse issue with the "A" ???

Any of you who have experienced a shimmy can attest to how violent it feels from inside the cabin

The NTSB Preliminary Report ...

... for this incident has been published to their web site. http://www.ntsb.gov/ntsb/brief.asp?ev_id=20051219X01990&key=1

Full narrative is at:

http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20051219X01990&ntsbno=DFW06CA009&akey=1

Another One Flipped Today 3/13/06

Don't know any details but you can see a picture and a report at www.wsoctv.com . This was near Charlotte, NC. The airplane is flipped on grass. The flaps are down and the nose wheel is bent back.

JR

New flip over

WSOCTV.com said:

Private Plane Crashed Near Mooresville Airport

POSTED: 10:54 am EST March 13, 2006
UPDATED: 11:52 am EST March 13, 2006

Emergency crews are on the scene of a plane crash near Mooresville in Rowan County.

Officials have reported a private plane crash and a request for an ambulance.

The crash happened Monday morning near Miller Airport.

Click to expand...

Damage

All:

A question was asked about pass compartment damage. This is not related to the above incident but happened to me a couple years ago. My RV flipped while taxing about 10 MPH. I had no idea that this was about to happen. While landing my RV settled in a little fast and bounced back into the air. Instead of adding power and going around I tried to recover form the bounce without adding power. Big mistake!!!!!! I had no idea that the nose gear was even bent. All I can say is that while taxing the nose went down and the RV ended up on her back.
Go to my web site: www.wparvbuilders.nstemp.com.. On the bottom of the home page is a picture that I just posted for all to look at. Need I say that canopy breakers are not necessary???? Also I now have the canopy with the big fat steel roll bar in the front.

There's nothing wrong with the design guys. Just keep the nose light.

Tom Emery N193RV

Hey, Tom!! Glad you are OK and were able to rebuild. Doublely glad you're not ranting about the design. Like I said earlier, if I ever flip my RV-7A over, I'll look for the cause in the mirror.

CAVU.

Roberta

A glob of turf and bent back and to side

Looks familiar, no attempt at glibness intended. PS thanks for the aftermath picture. I have a slider, but thank goodness you are OK. I also have a taildragger (not that they can not flip also, please no debate), but wonder what a flip would do the the roll bar canopy. Any pictures out there? Thanks George

Perhaps Grass and Nose wheels don't mix

Yes, I know, I *don't* know what I'm talking about.... But hopefully some observations. BTW, this really isn't a nose wheel vs. tail wheel start to a debate.

a) this observation starts actually in looking at the Vans tail wheel designs. Ever noticed how low the trailing arms are? As most will tell ya, this causes this design to "get stuck" on larger asphault or concrete edges and I suspect soft grass strips, but that isn't acknowledged because you are puling it and it comes unstuck easily on landing.

b) looks like Vans carried the same basic design to the nose wheel. Trailing arms that are very low to the centerline of the wheel. At first glance, a trailing linkage is probably necessary in a "free castering" design. BUT, that also lowers the leading edge of the nose strut to what I would consider an unacceptable distance from the ground, especially when landing on soft/grass strips.

I suspect that the wheel pant gives a little and if you stub the nose wheels "toe" you are asking it to dig in.

If you want to see the most exaggerated view, go look at a 10's nose strut. I still don't know how the physics work with it, but I certainly would *never* land one on grass.

While I'm sure a confrontational comment.... I think the "A" models should keep off GRASS strips, and especially "SOFT" grass strips. Even hard, rough strips probably don't allow the "reflex" of the nose strut enough recovery time to prevent digging in.

From my perspective, i'd be just as happy to take an insurance break and sign and agreement that I'll always land on a hard suface runway, unless an off airport emergency landing is needed.

My .02, and like I said, I *don't* know what I"m talking about, but it seems to happen enough to cause you to go "hmmmm"

I hope you always land safely on hard surface strips, too. That way the insurance rates of those of us who do land safely on turf, with our "A" models, will not suffer higher rates due to those who don't.

Roberta

Living on a grass strip with my 7A and loving it.

No Room for Discussion?

Roberta,

I normally agree with your well reasoned input but I can't go along with your last comments regarding the "A" model nose gear design. Your comments seem to imply that poor technique or pilot error can explain all of the reported problems with nose gear failure. I suspect that many of the failure events did indeed begin with "less than ideal pilot performance". On the other hand, good design requires that the product be able to withstand the conditions it is likely to encounter under reasonable conditions. Common sense says that RV's are likely to encounter less than perfect landings on occasion and should be able to survive this without undue danger of flipping the airplane.

A bent landing gear which could be straightned or replaced would not be an unreasonable, though vexing, penalty to pay for a botched landing. However, a fllipped airplane, probably totaled, along with possible injury is a serious "gottcha!" I think the serious consequences of this type of failure requires an objective study of the problem. Each data point is costing $50,000 to $100,000!

I doubt that the nose gear failure issue can or will be resolved in this forum. My concern is, your comment about the "problem being in the mirror" tends to brush aside what might be an issue of vital concern to RV builders. What is badly needed is an orderly study of the facts of each incident, not opinions. I would hope that Van's would take care of this but so far they seem to be agreeing with you....pilot error. I am not quite so certain.

John R.

John, If you have followed all my comments regarding this problem you would see that I have listed other probable causes of nose gear mishaps. They include, low tire pressure, inadequate tire to wheel pant clearance, and nosewheel bearing preload being excessive. I have addressed and continue to address these issues with my airplane. If the only other variable left is me, then I would have to conclude that I was the fault, if this mishap should
befall me.

I thought the comments about the "A" models should not land on grass inappropriate and unfair. Several flip overs occurred on hard surface runways. Some were probably pilot error. Some were due to mechanical errors. And maybe some were a combination of errors.

Yes, the RV nose gear could be made sturdier, but properly maintained, it is adequate when safely and properly managed. I have made less than perfect landings with my RV. I have also had the tire grab due to all of the above factors. I recognized problems and corrected them. Both in the plane and myself.

Roberta

Not that it really matters, but... How many of the planes that flipped were totalled? Most of the stories I've seen did *not* end with the plane being totalled. Major damage, yes, but repairable.

Personally, I'm building an A ...not because I fear tailwheels (the second plane I build will be a bearhawk...probably)... and I intend to use it on dirt or grass. I also intend to follow soft field procedures when I'm on a soft field.

More info

robertahegy said:

I hope you always land safely on hard surface strips, too. That way the insurance rates of those of us who do land safely on turf, with our "A" models, will not suffer higher rates due to those who don't.

Roberta

Living on a grass strip with my 7A and loving it.

Click to expand...

Roberta,

I didn't mean to imply that I *always land perfectly*. But, I did mean to imply that a better design would allow some "error" to be handled and not to cause a serious accident. Hard surfaces have other challenges, but digging a nose wheel into them, isn't usually one.

*warning* I'm going to make up numbers, cuz I don't have nose wheel in front of me.

If the diameter of the rim is 5" a 5X tire, and there is 2" of diameter of tire on each side of the rim, that basically a 9" diameter wheel/tire combo. That leaves somewhere around 4+" of clearance between the "flat" ground, and bottom edge of the nose strut and trailing arms. Any sort of "rising terrain" even so small, decreases that distance.

Ok, so lets look at the rest of the angles. I would expect that most pilots who land a Tri gear, land tail low, so you would think that that would help. But think about it.

Rising terrain (think crossing ripples in the turf), you land tail low, drop the nose to steer, compress whatever spring action is in the nose strut, it recovers (causes the nose wheel to press down") and do all of that on a soft field or a non-hardened grass strip and that 4+ inches becomes probably less than 2" (nose strut compression, wheel compression due to increased weight, and tire sinking into the grass/soft dirt.

There really are only a hand ful of TRI designs (maybe less than that) that use a trailing link design. Cessna doesn't, it's "fork" is slightly trailing, but there is nothing directly in front of the wheel like the Vans.

It's just a logical conclusion to suggest that a nose wheel airplane, has more things that can cause an issue on soft/grass strips than a tail wheel airplane. Now complicate that with the design of the RV and I believe you compound the problem, not make it simplier.

BTW, Yup, just my .02,

You make the point exactly!

robertahegy said:

John, If you have followed all my comments regarding this problem you would see that I have listed other probable causes of nose gear mishaps. They include, low tire pressure, inadequate tire to wheel pant clearance, and nosewheel bearing preload being excessive. I have addressed and continue to address these issues with my airplane. If the only other variable left is me, then I would have to conclude that I was the fault, if this mishap should
befall me.

Roberta

Click to expand...

I think you missed a variable.... The Design.

Roberta, again, you make the point exactly. All of the above problems reduce the percentage of a successful nose wheel landing on soft/grass strips.

Doesn't matter that you address them or not, it's the one time that you don't/didn't.

Perhaps I'm being too black and white, but if all those things that *you* mention *could* lead to a mishap in a nose wheel airplane, I don't think any of them apply to a tail wheel one...

Like I said, you made the point for me.

I'm not making the statement that "A" models are not made for grass, what I *am* saying is that given the current design of the trailing link nose wheel that vans uses, that "A" models using that design *could* be more prone to this problem than non-A models.

Alan, you aren't being "too black and white", you are missing the nature of the solutions Roberta has enumerated. Most of what was mentioned is basic construction (e.g. wheel fairing clearance) and basic maintenance (e.g. tire pressure)... they are not pilot skills to develop. If you preflight your plane before each flight, the only "one time that you don't/didn't" is next time you build a plane. Not what you'd call a sacrifice.

As for your hypothetical rising terrain... why are you dropping the nosewheel for steering with a free-castoring nosewheel? That's just silly. I was taught that you don't drop the nose on a 152 in those conditions....you certainly wouldn't drop a non-steering nosewheel.

I haven't flown many planes, nor all that much, but I've never encountered a plane that liked being on its nosewheel. All of my instructors wanted me to lighten the nosewheel by elevator back-pressure when taxiing on pavement. One of them preferred that I taxi a 172 on two wheels whenever possible. We are not talking about grass, here... just hard pavement. Nosewheels shimmy, cause stick-slip pedal feel problems, get caught in potholes, slam on transitions between paved areas, and so on. They are still more versatile than tailwheel planes.

indirectly related I suppose

While at our EAA chapter's pancake breakfast Saturday morning, I watched two Cessna 152s and a 172 doing touch and goes. Out of the three pilots, only one was making proper full stall landings and holding the nosewheel off as long as possible. The other two were landing on all three wheels at about the same time. Nice smooth landings, but lousy technique. To top it off, the instructor was aboard in the 172 and no apparent attempt was being made to correct the student's landing technique through the series of landings I observed. If this is the quality of flight instruction being given these days, it's no surprize that we have RVs on their backs. The poor damned students won't know the difference if they are not being shown.
My wife is currently learning to fly. The above is the reason she is learning in a Cessna 120. For her landings to look good thay have to be good.

Bob Severns

Really

avaviat said:

One of them preferred that I taxi a 172 on two wheels whenever possible.

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A CFI told you to TAXI with the nose wheel OFF the ground on hard surface (any surface for that matter)? I would never do that, I mean I could, but I recall in a C172 that would be a pretty good forward speed to do that.

George CFI

subtle complexity?

aadamson said:

Yes, I know, I *don't* know what I'm talking about.... But hopefully some observations. BTW, this really isn't a nose wheel vs. tail wheel start to a debate.

a) this observation starts actually in looking at the Vans tail wheel designs. Ever noticed how low the trailing arms are? As most will tell ya, this causes this design to "get stuck" on larger asphault or concrete edges and I suspect soft grass strips, but that isn't acknowledged because you are puling it and it comes unstuck easily on landing.

b) looks like Vans carried the same basic design to the nose wheel. Trailing arms that are very low to the centerline of the wheel. At first glance, a trailing linkage is probably necessary in a "free castering" design. BUT, that also lowers the leading edge of the nose strut to what I would consider an unacceptable distance from the ground, especially when landing on soft/grass strips.

I suspect that the wheel pant gives a little and if you stub the nose wheels "toe" you are asking it to dig in.

If you want to see the most exaggerated view, go look at a 10's nose strut. I still don't know how the physics work with it, but I certainly would *never* land one on grass.

While I'm sure a confrontational comment.... I think the "A" models should keep off GRASS strips, and especially "SOFT" grass strips. Even hard, rough strips probably don't allow the "reflex" of the nose strut enough recovery time to prevent digging in.

From my perspective, i'd be just as happy to take an insurance break and sign and agreement that I'll always land on a hard suface runway, unless an off airport emergency landing is needed.

My .02, and like I said, I *don't* know what I"m talking about, but it seems to happen enough to cause you to go "hmmmm"

Click to expand...

"The case of the flippin' A model" is probably not so simple as nosewheel design. Are these planes nose heavy? The reason I ask is that my 8A has landed without incident in 3" of snow, on gravel, on turf(well-manicured and nasty clump grass), and steep uphills. If this were strictly a design problem, then surely a low time pilot like me landing on turf, gravel, snow would have flipped by now? Or maybe I've just rolled "7" a hundred times in a row?

Roberta mentioned several problems that could have serious impact. Perhaps the flipped planes had some combination of problems.

Pilot error cannot reasonably be removed from the list of possible contributing factors simply because all of the aircraft have the same wheel configuration. To do so would be just plain silly.

As far as keeping A models off the grass, are you suggesting the posting of "Keep Off The Grass" signs on all turf strips or perhaps posting FAA policemen?

gmcjetpilot said:

A CFI told you to TAXI with the nose wheel OFF the ground on hard surface (any surface for that matter)? I would never do that, I mean I could, but I recall in a C172 that would be a pretty good forward speed to do that.

George CFI

Click to expand...

Well, "when possible" was the operative phrase. He was definitely the speed demon of the bunch, but we rarely went fast enough to do more than tilt the plane back a few degrees unless there was a strong head-wind. A few degrees is enough to stop a noswwheel shimmy, but not really enough to lift the nose wheel. The Zenith is a different matter...you can lift the nose on the CH2000 at fairly low speeds.

Learning to maneuver a plane on two wheels was a *major* confidence booster for me actualy. I wish my first CFI had run me through soft field techniques before I soloed. Knowing I could have the nosewheel off the ground (CH2000), roll onto the runway on two wheels, steer to the center-line, and take off really helped me get a handle on p-factor yaw and a PIO problem I was fighting (and shouldn't have been...fighting, that is).

Nose gear

I have 450 Hrs on my 7A. I have read about most of the A model flip overs. Its scary to me. I treat my nose gear like it was made out of glass. I think Vans nose gear design could be improved but that will not save your bacon if you land hard on the nose on grass or pavement. I only land on unimproved strips out of necessity. I have to much money invested in my plane, and besides I get grumpy if I don't have something to fly.