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Rookie question: nose over with BW's

hotrod180 said:
I know two different skywagon drivers (both good sticks) who ended up upside down on paved runways,
they both said that along with goofy winds their "grabby" tires (shaved 29's) seemed to be a factor.
Those heavy tires take more spinning up when landing, I can see where that might present an issue on pavement.
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I’ve heard that excuse used a few times, by guys who simply didnt handle conditions. Yes, if you touch down solidly at warp speed, as some are won’t to do, those tires will grab…..a LITTLE. But, that alone should not result in a nose over. I’d bet that a bit of grab, followed by a shove on the brakes was the actual dynamic.

I really like big tires for the very reason that they grip. But I don’t touch down at 1.9 Vso. The grip is just another tool.

MTV
 
Steve Pierce said:
Seen a lot of poor pilots blame the brakes locking up but I always find it interesting that the brakes tend to lock just before they end up in the river. ;)
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I'm glad I've never been put in that position but if (when) it happens to me I take it all back, it was the brakes fault!

I retract my previous answer. I have to go with small tires flipping over easier if you're talking about a taxiing incident. Lots of good points brought up in this discussion.
 
DavePA11 said:
Heard of a lot of nose overs with pilots landing on wet snow with the big tires rather than landing with skis. Just to through that into the discussion…
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We get guys landing in snow with small tires also. Few years ago we had a CFI take the company plane with friend out to Lake George saw all the ski track and thinking it was OK to land (year before windblown ice and 206's brought people out for pictures) well snow was a few feet deep and he flipped it. Same year a 180 or 185 landed short on ski tracks 20R Birchwood was able to get the spinner on the tar. Then small tire 172/182 decided they would try the ski strip instead of the tar at Soldotna and flipped. About 10 years ago I found an active ELT. It was a Base Aero club small tire 172 flipped in fresh snow next to Dr Seuss house. Not to just mention small tire trikes I did have a friend a few years back flip because he landed on soft ski strip to instead of the dry runway next to it trying to save his bushwheels. Last night I slept with my brothers sister in law and her husband managed to land on a gravel bar with Federal AWB skis wheels down and dig a tip in resulting some impressive one flight prop wear and an 200 hr engine teardown. Soooo snow don't care if you got nose wheel, tailwheel, big, or small, tires if it gets it gets ya.
DENNY
 
Glen has a very good point. So how many note a ground loop point and side (Right vs left) when you are working a short strip? How many have practiced ground looping the plane? I want to Willow last summer and worked on it, hard to get exact speed but locking tire and hard ground loop at 15 mph was not bad at all. Get closer to 20 and you get a lot of lean. I prefer my brakes work and work well, they can save you if you know how to use them.
DENNY
 
aeroaddict said:
Is it easier to induce a nose over due to overly aggressive braking with larger tires (say 35's) or smaller (800/850's) tires.

And why (whatever your answer may be)? I can't quite work out the mental physics with this.
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aeroaddict said:
Thanks.

Should have been more precise in the parameters. Level dry pavement, taxi (not landing) in 3 point attitude (obviously).

Again, just a general question as I could not come up with any mechanical/logical answer.

Speed, CG and inertia then rotating mass come into play. Not trying to a make a science fair here, but thought I would ask the collective/brain trust/gray beards which have more knowledge than myself.
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Instead of being concerned with tipping on the nose due to braking and tire size under your described conditions, you should practice not using any brakes at all. Under most circumstances they are not needed for landings.
 
What do you suppose would be the answer if, as I proposed, the aircraft with the large tires was subject to the same deceleration as the aircraft with the small tires?
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Then the higher CG would matter (very slightly). But to obtain the same deceleration would require greater braking effort.
 
Big tires really don't change the angle all that much - you can get the actual angle change by using the arctan function in your hand held. With big tires your CG goes up, with very little offset from the additional distance the tail must move to get above the CG.

It isn't the effectivity of the brakes or the size of the tires - it is the lack of flow over the stabs/elevators that will get you. It can happen - it does happen - at extremely low speeds.

We had one go over on a hot start procedure. As the engine started, the aircraft moved. Pilot of course hopped on the brakes. I don't think the aircraft moved more than three feet. Boom. Fifty grand.
 
My two cents: brakes are not really the reason airplanes flip, pilots are. Tire size is not really the reason airplanes flip, pilots are.

However, I will say that the biggest risk of brakes and tires contributing to this event is if the pilot does not properly plan or manage the airplane operation including to consider the differences in handling characteristics, whatever those might be, and identify those handling characteristics by doing some reasonable level of currency type work when in a new configuration. One of the areas that can be a surprise to pilots is when they buy their big new fancy tires, find the brakes are ineffective, put on more powerful brakes, then sometime in the future end up with smaller tires on the airplane. The power of those souped up brakes can be a real eye-opener on a set of small tires...

I always find braking as little as possible is the best plan, especially when you are trying out new equipment and trying to get a feel for it.
 
aeroaddict said:
Great responses, thanks.

So I kinda hearing that it is smaller tires that would be easier to nose over?

Can I use this thread as a justification for the CFO (Chief Financial Officer) that bigger tires are safer and I should get bigger tires?
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Be careful with that conversation. She might decide you are not safe in the Carbon Cub and buy you a C-150. [emoji848]

Do you already have 3x3 gear? That would make more difference than the tire size. So would 20 lbs of lead near the tailpost.


Sent from my SM-G965U1 using SuperCub.Org mobile app
 
I agree it is a pilot experience issue. For new pilots one thing to remember is the plane really doesn't care it is on tar, cement, gravel or grass. So just because your CFI has claimed that the world will end if you get 3 ft from the centerline most aircraft (especially with bigger wheels) will happily leave the runway taking a light or two in the process and roll just fine as long as it does not hit some ditch or other large hard object. I had a new pilot friend that managed to get off the dirt strip and instead of just turning back on to it locked the brakes and put it on its nose. DENNY
 
I started this thread because I saw a plane on it's nose that had big tires (on a taxi way). I'll confess that I'm a retired engineer and a thought occurred to me wondering if tire size has any effect on a possible nose over. It is a physics question, not how to fly/taxi a plane. And no I do not have 'legacy death gear' on my plane. 8)

Great answers though.
 
I'll confess that I'm a retired engineer and a thought occurred to me wondering if tire size has any effect on a possible nose over. It is a physics question
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Haha! Well, Denny and 'slumber' kinda veered from that for a moment, didn't he? Good stuff - sent you a PM.
 
BW's aint your friend in certain soft or deep snow. Hard packed or frozen slush maybe. Lots of planes end up on their back when skis were essential for the mission.

Airplanedownheresomewhere_zps92f27c93.jpg
 
scout88305 said:
BW's aint your friend in certain soft or deep snow. Hard packed or frozen slush maybe. Lots of planes end up on their back when skis were essential for the mission.

Airplanedownheresomewhere_zps92f27c93.jpg
Click to expand...

This needs picture an explanation more than the above sentence. What is the back story here please?
 
scout88305 said:
BW's aint your friend in certain soft or deep snow. Hard packed or frozen slush maybe. Lots of planes end up on their back when skis were essential for the mission.

Airplanedownheresomewhere_zps92f27c93.jpg
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I just saved this picture to my photo gallery. Anytime someone asks me if wheels are ok I'll send this and say " your choice "

Glenn
 
Litecub,

That photo was from an earlier April 2009 thread and I think there may have been some discussion of events surrounding it. I remember there was a little photo shop variations that occurred but can't find the actual thread.

bushwheels_2.jpg
bushwheels_5.jpg
Jerry
 

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aktango58 said:
Don't forget fuel load. You have more chance of nosing over with half tanks than full tanks- the fuel sloshes froward adding to the momentum.
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I agree that partial fuel could be an aggravating factor. Under hard braking all the fuel that would have been at the back of the tanks in 3 point attitude will move to the front of the tanks. This moves the CG forward and higher. There is also a brief impulse in the nose down couple as the fuel stop moving forward.

I wasted a few minutes yesterday creating this picture which shows how the CG moves with a change from small to large tires (CG position, red dot, is a WAG but absolute location doesn't influence the relative change):
 

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Nice.

I would offer the opinion that the distance between the CG and axle does not change, but the distance from the tire contact of the ground to CG does change with tire size. Implying the this is the true point of rotation: tire contact at the ground.

I should have better set parameters when first posting: constraints; same exact plane with 'magic brakes' that compensate for tire size. The only difference is the diameter of the tires.

Cheers
 
It really does not take good brakes to lock up a wheel at low speed. Even a crummy cable operated brake will put a Champ on its nose if you jump on them at low speed. When the tail comes up, get off the brakes.
 
Don't forget a little wind on the tail and a quick hit to the brakes- tail comes a bit up and you yank back allowing wind under the tail...

Yea, a little wind is a big deal!
 
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