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Flying back from Belfast this morning on a small Flybe plane with a seat level with the landing gear. As the tyre hit the runway there was the puff of smoke as it spun up to speed, made me think, why do they not spin the wheel up to approximate rpm, with a motor or turbine,to match landing speed and reduce stress put on the tyre? Would it affect the stability of the plane on landing?
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I guess cost and something else to go wrong. Motor would need to be pretty impressive to spin the wheels up to >100mph.
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Interesting coincidence - the other night I saw a short piece of film showing an airliner landing. Nothing special about that, but, in this case it was shot from above and I saw, for the first time, a great smudge of rubber across and along the runway where the planes touch down.
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Cost really, the extra weight is a fair bit plus to get a wheel up to speed would need a very heavy axle stub. The weight would be 'unsprung' it's on the other side of the oleo, which in any suspension isn't a good idea. Tyres aren't really that expensive anyway, if they land with high angle of attack then the wear isn't great. Tyres will be 4 maybe 5 figures which sounds a lot but in the grand scheme of things it's not.
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I have a similar question that I was going to put to Fursty Ferret (the pilot?)
A month or so ago we were landing in Warsaw and maybe less than a minute from touchdown it decided to hit the gas and shoot off, doing a huge circuit and try again. I was treated to a low and wonderful scene of the old town that I’d never seen from the air before. Just wondered why the pilot might have done it cos it wasn’t windy or foggy.
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My suggestions.
The runway was not clear - due to an aircraft slow to cross it or exit it, the guy already on the runway too slow commencing his run, aircraft on the runway had aborted his/ her take off or another vehicle on the runway etc.
Air traffic control instructed him for a variety of reasons.
Your pilot was not happy with the approach.
FF will have many more when he is back on the forum.
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Pretty much what Henry says.
The pilot might 'go around' of his own volition because the approach wasn't working out as it should or because he saw something ahead, another aircraft with a problem or a warning light about landing gear, brakes, flaps or whatever.
ATC might have had an issue, debris on the runway, problem reported by another aircraft. If they say 'Go Around' then you go around and ask questions later.
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>> I have a similar question that I was going to put to Fursty Ferret (the
>> pilot?)
>>
>> A month or so ago we were landing in Warsaw and maybe less than a
>> minute from touchdown it decided to hit the gas and shoot off, doing a huge
>> circuit and try again. I was treated to a low and wonderful scene of the
>> old town that I’d never seen from the air before. Just wondered why the pilot
>> might have done it cos it wasn’t windy or foggy.
>>
Either runway not clear or going to fast!
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>> Cost really, the extra weight is a fair bit plus to get a wheel up
>> to speed would need a very heavy axle stub. The weight would be 'unsprung' it's
>> on the other side of the oleo, which in any suspension isn't a good idea.
>> Tyres aren't really that expensive anyway, if they land with high angle of attack then
>> the wear isn't great. Tyres will be 4 maybe 5 figures which sounds a lot
>> but in the grand scheme of things it's not.
They don't quite hit 5 figures, but they get remoulded - for most tyres 3 times is not uncommon. A lot of airlines will have contracts for tyre supply so the real cost is not that easy to work out
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> They don't quite hit 5 figures, but they get remoulded - for most tyres 3
>> times is not uncommon. A lot of airlines will have contracts for tyre supply so the real cost is not that easy to work out
>>
Some really are that expensive, yes.
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A quick google says that various methods have been tried, the lightest and most promising involved fins on the hub caps so that air-flow turned the wheels,
But the over-riding objection to any method is the gyroscopic effect of the spinning wheels on plane control, especially significant if the pilot has to change direction at the last moment for any reason.
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Yes, aircraft tyres are 'consumable' parts. Lots of big black skidmarks on the smooth bitumen runways found in rich, heavily-trafficked countries.
Third world dirt airstrips can be very hairy indeed. Not everyone will remember the 707 (I think) that missed the main runway at Kano, bounced into the air a few times and crashed with a lot of deaths.
Bukoba in Tanzania had last time I saw it a red laterite earth airstrip at a peculiar angle, quite steep too, with a hillside at one end and Lake Victoria at the downhill end. It was quite exciting taking off there, and a bit buttock-clenching. I sometimes wondered how many aircraft had ended up in the lake.
Red laterite bakes hard in the sun but becomes very slippery when wet. But aircraft once they get moving are really 'flying along the ground' using aerodynamic control surfaces. The wheeled chassis only counts at very low speeds.
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>> A quick google says that various methods have been tried, the lightest and most promising
>> involved fins on the hub caps so that air-flow turned the wheels,
>>
>> But the over-riding objection to any method is the gyroscopic effect of the spinning wheels
>> on plane control, especially significant if the pilot has to change direction at the last
>> moment for any reason.
>>
>>
Tyres are cheap.
Go arounds for any number of reasons... ATC, speed, configuration, vertical position, lateral position. Most airlines insist the aircraft is in the landing configuration (gear, flaps, spoilers abd speed) at 1000ft above the ground on the approach. There's no leeway in this, so even if the landing gear locks down at 990ft we have to fly a missed approach.
No questions asked about the decision to go around regardless of fuel burn etc. Choosing to continue without good reason (fire in the cabin etc) would result in invitation for tea and biscuits with fleet management. Except without the tea. Or the biscuits.
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>>Tyres are cheap.
Its all man maths: "Tyres are expensive at 4 or 5 figures"...
A quick google suggests that they cost between $2 and $4k each for a 747 and there are 18 of them.
Now assuming an average of $3k each x 18 = $54k against a cost for a new plane of $147m.
Its the same maths as a friend who brought a new £35k car because the road tax was £0 compared to £180 a year on the old model!
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"Now assuming an average of $3k each x 18 = $54k against a cost for a new plane of $147m."
Yes but doing some advanced man maths if the tyres last for 100 landings (guess) and the plane makes 10,000 landings in its lifetime (guess) that's a hundred tyre changes that's £5.5 million which is significant
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>> A plane is quite a bit more than $150k if this is to be believed
>>
and a plane is quite a bit more than $150m!
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>>Its the same maths as a friend who brought a new £35k car because the road tax was £0 compared to £180 a year on the old model!>>
He or she isn't the first by a long chalk to adopt such logic. Annual fuel cost would be a much more significant factor....:-)
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>> Some really are that expensive, yes.
>>
Sooty - I used to buy commercial aircraft tyres so I have a fair idea of the market place - which ones are into 5 figures?
Last edited by: VxFan on Sun 11 Dec 16 at 19:26
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Tyres for military aircraft.
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I used to collect new aircraft tyres, half a dozen or so at a time, from the Dunlop Aircraft Tyres factory in the shadow of Fort Dunlop in Birmingham. They were marked with the maximum landing speed - ISTR some were marked around 150mph, some 200mph or more. Big, heavy but manageable, very inflexible things. They were for onward transport by road to the Faroe Isles.
Entering the despatch warehouse was like taking a step back in time; it looked as though it hadn't been updated since the 1960s. Ancient time clocks, separate offices, whitewashed brick walls throughout. And several hundred huge, treadless tyres in 4-foot high stacks. A fascinating place to be allowed into.
Last edited by: Dave_ on Mon 12 Dec 16 at 21:12
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General Question - Aircraft landing wheels - zippy
