BALL
Thread Starter
Join Date: Oct 2007
Location: london
Posts: 59
Likes: 0
Received 0 Likes
on
0 Posts
BALL
Following my EFAT O topic recently, I would think that the plane would have a load of fuel just after takeoff, meaning that should a landing be on land with rough grooves, the chances of flipping over would be high, with resultant fire risks.
It got me thinking...how can we prevent the plane flipping over (I am talking about normal tricycle with front steering)? The thing to cause the flipover would be, I guess, grooves that the front wheel cannot climb.
Is there any merit in having the front wheel as a ball, you know, along the lines of a barrow-ball or a Dyson Ball vacuum cleaner? I am not an engineer and haven't got the foggiest how such a thing would be made, but I think a ball type wheel would just roll over most ridges, especially if it was out- sized (thing penny farthing in reverse, although not so big).
To reduce drag, maybe have pimples, like golf balls do?
Anyway, over to the folks with the brains....
It got me thinking...how can we prevent the plane flipping over (I am talking about normal tricycle with front steering)? The thing to cause the flipover would be, I guess, grooves that the front wheel cannot climb.
Is there any merit in having the front wheel as a ball, you know, along the lines of a barrow-ball or a Dyson Ball vacuum cleaner? I am not an engineer and haven't got the foggiest how such a thing would be made, but I think a ball type wheel would just roll over most ridges, especially if it was out- sized (thing penny farthing in reverse, although not so big).
To reduce drag, maybe have pimples, like golf balls do?
Anyway, over to the folks with the brains....
Moderator
Keeping such a "ball" balanced, and free of shimmy could be a challenge. Drag might be a factor too! I'd stick with the original design.
Some types do offer "tundra tires", but these are more common, and better suited to taildragger aircraft types.
Some types do offer "tundra tires", but these are more common, and better suited to taildragger aircraft types.
Join Date: Feb 2007
Location: Amsterdam
Posts: 4,598
Likes: 0
Received 0 Likes
on
0 Posts
Is there any evidence of nosewheel aircraft flipping over on EFATO landings on rough ground, assuming they land more-or-less under control? I would think that the chances are not that big.
The CofG of an aircraft roughly lies in the spar box. Slightly higher in case of a low wing, slightly lower in case of a high wing. And for your typical light aircraft that's approximately 1 meter of the ground. Maybe 1.5 meter in case of a high wing, but let's go with the 1 meter for now.
The point of rotation in this scenario is the place where the nosewheel meets the ground. That's something like 2 meters in front of the CofG.
For the vectors to work out so that the aircraft indeed flips over, with the nosewheel as its rotation point, the nosewheel needs to generate at least approximately 2G in horizontal deceleration. Multiply this by the mass of the aircraft (say one ton), you're talking about at least two tons. (Less in case of a high wing, but still a considerable amount.)
My gut feeling is that if the nosewheel snags on something, the nosewheel assembly simply breaks off. It's nowhere near strong enough to handle something like twice the aircraft mass in the horizontal. The aircraft will then continue to slide on the engine cowling. And that cowling, coincidentally, has more or less the ball shape you were looking for in the first place.
Further supporting my gut feeling: What I've seen so far about water landings in nosewheel aircraft (see for instance the Equipped to Survive site) is that even in a water landing scenario the aircraft will dig in, but in the majority of cases not flip over.
Taildraggers, on the other hand, are a totally different thing. The horizontal distance between their CofG and the rotation point (the mainwheels) is so short that they can sometimes be put on the nose by simply braking too hard.
The CofG of an aircraft roughly lies in the spar box. Slightly higher in case of a low wing, slightly lower in case of a high wing. And for your typical light aircraft that's approximately 1 meter of the ground. Maybe 1.5 meter in case of a high wing, but let's go with the 1 meter for now.
The point of rotation in this scenario is the place where the nosewheel meets the ground. That's something like 2 meters in front of the CofG.
For the vectors to work out so that the aircraft indeed flips over, with the nosewheel as its rotation point, the nosewheel needs to generate at least approximately 2G in horizontal deceleration. Multiply this by the mass of the aircraft (say one ton), you're talking about at least two tons. (Less in case of a high wing, but still a considerable amount.)
My gut feeling is that if the nosewheel snags on something, the nosewheel assembly simply breaks off. It's nowhere near strong enough to handle something like twice the aircraft mass in the horizontal. The aircraft will then continue to slide on the engine cowling. And that cowling, coincidentally, has more or less the ball shape you were looking for in the first place.
Further supporting my gut feeling: What I've seen so far about water landings in nosewheel aircraft (see for instance the Equipped to Survive site) is that even in a water landing scenario the aircraft will dig in, but in the majority of cases not flip over.
Taildraggers, on the other hand, are a totally different thing. The horizontal distance between their CofG and the rotation point (the mainwheels) is so short that they can sometimes be put on the nose by simply braking too hard.
Last edited by BackPacker; 17th Jan 2012 at 07:54.
Not, in my opinion, a good idea - but nonetheless would be interesting to have a play with and find out.
I can't see why a ball nosewheel will skip over runway bumps and holes any better than a tyre of the same diameter, but what I think it probably will do is offer much poorer natural directional stabilisation (that is of-course what the ballbarrow is designed to do).
I have seen a very experienced tailwheel pilot enter an uncontrollable groundloop with a tundra tyre NOSEWHEEL aeroplane (with a castoring nosewheel), the ball just strikes me as making it more likely.
That said, as a flight tester an an eternally curious aviation researcher, I'd enjoy running a test programme to find out if I'm right or not.
Incidentally, the ballbarrow was also invented by James Dyson.
G
I can't see why a ball nosewheel will skip over runway bumps and holes any better than a tyre of the same diameter, but what I think it probably will do is offer much poorer natural directional stabilisation (that is of-course what the ballbarrow is designed to do).
I have seen a very experienced tailwheel pilot enter an uncontrollable groundloop with a tundra tyre NOSEWHEEL aeroplane (with a castoring nosewheel), the ball just strikes me as making it more likely.
That said, as a flight tester an an eternally curious aviation researcher, I'd enjoy running a test programme to find out if I'm right or not.
Incidentally, the ballbarrow was also invented by James Dyson.
G
Join Date: May 2001
Posts: 10,815
Likes: 0
Received 0 Likes
on
0 Posts
There are I think a whole heap of issues with wheel stability at high speed and a ball doesn't actually give you better grip.
And the further out the axle support is the beefer the attachment needs to be. Then if you go for two wheels the control forces get higher and thus things need beefed up.
As with all things its a historical compromise. I have no doudt there have been several iterations of nose gear design which were done years and years ago. And the one we have now turned out to be the best option for light aircraft. Just as the 2 wheeled live axle turned out to be the best for bigger things.
And the further out the axle support is the beefer the attachment needs to be. Then if you go for two wheels the control forces get higher and thus things need beefed up.
As with all things its a historical compromise. I have no doudt there have been several iterations of nose gear design which were done years and years ago. And the one we have now turned out to be the best option for light aircraft. Just as the 2 wheeled live axle turned out to be the best for bigger things.
Incidentally, the ballbarrow was also invented by James Dyson.
Join Date: May 2011
Location: Glasgow
Age: 40
Posts: 642
Likes: 0
Received 0 Likes
on
0 Posts
With a ball on a hard surface, surely the surface contact area would be reduced, therefore reducing grip and so making its use for directional control pretty much useless? It may as well be a skid! Unless its an inflatable ball that is - or not a true ball but have it contain a flat center region.
The ball would also need some sort of tread to allow it to expel standing water. With a wider shape, this could be more of an issue, increasing the tendency to aquaplane.
My Dad has a wheel barrow with a round ball, my Grandpa one with a traditional tyre. On soft ground the tyre cuts through leaving a furrow, the ball stays on top. Works nicely for a wheel barrow but in a plane I would normally want to cut through standing water. So for grass use only?
Also - if a hard ball was used, there may need to be changes to the oleos to absorb more of the ruts in undulating ground.
Just some more things to think about!
The ball would also need some sort of tread to allow it to expel standing water. With a wider shape, this could be more of an issue, increasing the tendency to aquaplane.
My Dad has a wheel barrow with a round ball, my Grandpa one with a traditional tyre. On soft ground the tyre cuts through leaving a furrow, the ball stays on top. Works nicely for a wheel barrow but in a plane I would normally want to cut through standing water. So for grass use only?
Also - if a hard ball was used, there may need to be changes to the oleos to absorb more of the ruts in undulating ground.
Just some more things to think about!
Thread Starter
Join Date: Oct 2007
Location: london
Posts: 59
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for the comments, guys....I am glad I am not an engineer and have to worry about all the possible flying/ ground conditions to which it would be subjected!
The more usual approach to this problem is of course retractable landing gear. I seem to recall that the question of whether or not to extend the gear for an off field landing is right up there with LOP vs ROP as a controversial topic, though I haven't seen it for a while. Intuitively it seems that it would be better to land gear-up if you are not sure about the surface where you are landing, but iirc there are pretty sound arguments for NOT doing this.
