Screaching Tyres

[Jinkster]

Screaching Tyres

I am a poor ATPL student and the closest I get to big fast jets is either holiday or watching them at the local airport.

I wonder how much wear and tear the tyres of say a 737 get every time it lands.

My question is - if the tyre was to accelerate with the airflow when on approach instead of the tyre accelerating when it touches the tarmac wearing the tyre and possibility risk of blowout.

How much money would it save a company in tyres each year and would it be a cost effective design?

Does anybody catch my drift :rolleyes: ?

Jinkster

[PAXboy]

If you search the archive of Pprune you may find a similar thread as this was discussed at some stage of the last year (I think).

In a nutshell, the weight penalty of carrying electric motors to spin up the tyres does not justify the savings on wear. There is also the issue of adding further complications and equipment to the machine that has to be designed and built and then maintained. Simplicity usually wins.

I understand that designers have done many tests over the years on this point. What they found was (again, if I recall correctly) that you have to match the rotation of tryres closely to what they will be a second after touch down. If the tyre is rotating slower or faster than it will be after touch down - it still suffers wear in adjusting from it's speed to the actual one.

Something like that!

[Jinkster]

I understand what you are trying to say - my idea uses the airflow to speed up the wheels so little extra electrical equipment is needed - however more drag would be created.

As you said Pax - trying to match the speed of the wheels to the speed of the approach is the more difficult part of the problem - anyone know?

Jinkster

[Golden Rivet]

Its a big enough pain in the butt to remove brake fans prior to a wheel removal - let alone some multi-airfoil thingy to spin up the wheel.

Having a nice simple gear is the way to go. Bear in mind most operators have less than 1 1/2 hours for a turn-around - normally a lot less.

GR :confused:

[avioniker]

You don't want the wheel spinning in the air because you don't know the condition.
If it's out of balance the vibration is pretty wild.
If it's blown it'll cause damage.
The gyroscopic action of a spinning tire causes side loads on the bearings with lateral gear retraction motion adding to their wear.
The speed match problems have already been mentioned.
It all comes down to money and there's no relative savings to spinning up the wheel for landing.
That's just a couple of reasons there are spindown braking systems on the wheels and not spin up for landing systems.

[pigboat]

I believe Cessna tried that - wheel spin in the air - on the nose wheel of the Citation as part of a gravel kit. The idea was to save the belly of the aircraft from flying rocks on touchdown. I don't believe it worked worth a sh!t for all the above reasons.

[Tinstaafl]

Spin up won't stop wear caused by not being exactly aligned with the direction of movement during touchdown ie some amount of drift/crab angle - so why bother with the complexity/expense/failure issues?. All the skill in the world won't guarantee a perfectl alignment each & every time.

[Flight Detent]

Hi all,
and, of course, you will want to stop the wheelspin after take-off, so if aerodynamic means are used to spin the wheels on the approach, then these same aerodynamic thingys, now overcome by the automatic inflight brakes, will cause significant extra drag during the departure, until the wheels are fully retracted!
Then there's the nose wheels!!

I'm just full of good news!!

Cheers

[Golden Rivet]

Variable pitch aerodynamic thingys should cure that problem.

[Self Loading Freight]

I seem to remember a bloke from the US Patent Office saying that gizmos to spin wheels up prior to landing were the single most common submission from inventors. Everyone sits at home, sees a movie with that 'Scrrrrrtch!" noise dubbed over a landing, and goes "Oooh! I bet you could save loads of wear if..."

Said officer went on to say that, unsurprisingly, there were a number of methods on file, and that nobody from the airlines or manufacturers had ever found them economical to implement.

R

[Smoketoomuch]

Most tyre wear happens during taxying, esp when heavy prior to take-off, and braking, however;
http://www.afmc.wpafb.af.mil/HQ-AFMC/PA/news/archive/2002/feb/Edwards_Tireinvention.htm

[Onan the Clumsy]

Jinkster and SLF - That was my idea too. :8 I guess I can shelve it for good now :(

[Michael111]

'Evening all

Back in the '70s I remember a couple of flights from Jersey to Alderney with Aurigny. We were approaching the Tarmac runway and on both occasions about 50 yards short of the runway, we briefly touched the main wheels down on the scrub before continuing in the air to the runway itself.

On both occasions I enquired with the Captain as to why this was and both responses were "to save the tyres my boy".

OK on a Trilander I suppose but perhaps a little different on a 777!!

Michael

[Jinkster]

Ok - shelved for the moment

Jinkster