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Revving Up The Wheels Before Touchdown  
User currently offlinefaro From Egypt, joined Aug 2007, 1572 posts, RR: 0
Posted (3 years 2 months 3 weeks 5 hours ago) and read 5474 times:

In order to save on tire wear, how about revving up airliners' wheels before touchdown so that less friction is generated once the wheels hit the tarmac? This may be achieved by a row of weather vane-like cups or paddles fixed around the outside rim of the wheels that present less drag on one face that the other:



Weight would not be a major consideration if you make the paddles from CFRP with a robust attachment point to handle dirt and/or FOD. Conceivably, and given the amount of tire smoke generated during landing, you could prolong tire life considerable with such a contraption...

Faro


The chalice not my son
24 replies: All unread, jump to last
 
User currently offlineflipdewaf From United Kingdom, joined Jul 2006, 1578 posts, RR: 0
Reply 1, posted (3 years 2 months 3 weeks 5 hours ago) and read 5460 times:
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Weight, complexity, another thing to check,another thing to go wrong. Most rubber I believe is scrubbed off when taxiing at high weights.

Fred


User currently offlinefaro From Egypt, joined Aug 2007, 1572 posts, RR: 0
Reply 2, posted (3 years 2 months 3 weeks 5 hours ago) and read 5443 times:

Quoting flipdewaf (Reply 1):
Most rubber I believe is scrubbed off when taxiing at high weights.

Funny then that aprons and taxiways are so clean compared to the touchdown area on runways. I agree thought that high-weight taxiing imposes heavier loads on the tire assemblies than landing, heavier vertical loads that is. When landing you have very significant longitudinal loading on the tires that subsides very quickly as soon as the tires are revved up and stop smoking.

Faro



The chalice not my son
User currently offlinehb88 From United Kingdom, joined Sep 2005, 817 posts, RR: 31
Reply 3, posted (3 years 2 months 3 weeks 4 hours ago) and read 5425 times:

The energy absorption via rubber loss and wheel acceleration on touchdown is an important factor in safely slowing the aircraft. Without this, you have increased brake wear and faster speeds on the ground. In short, you don't want to spin up the wheels.

This is one of the most common 'new inventions' relating to aircraft and also one of the most ill-conceived.


User currently offlinemandala499 From Indonesia, joined Aug 2001, 6951 posts, RR: 76
Reply 4, posted (3 years 2 months 3 weeks 4 hours ago) and read 5407 times:

Hmm... I wonder how those "vane cup wheel turners" would do in:
1. Very cold weather landings... on to a short runway, where the temperatures will rise up from minus something to a couple of hundred in less than a minute...
2. Very cold weather maximum energy rejected take off...
3. Hot weather landings... with hot brake temps, followed by a short turn around with brake fans...
4. Same as #3, followed by a maximum energy rejected take off...
5. Hot temp (brake fire) tire burst... these cups can end up becoming dangerous projectiles...
6. Rapid deceleration to stop as the wheels get retracted in take off... either in the well, or as the wheel stops before it gets into the wheel bay.
7. In hot brakes + water spray situation...

The wheels can be replaced easily and is cheaper than the brakes... more brake wear... it'll end up as more expensive...

Mandala499



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 5, posted (3 years 2 months 3 weeks 2 hours ago) and read 5372 times:

Quoting faro (Reply 2):
Funny then that aprons and taxiways are so clean compared to the touchdown area on runways.

Area. The area of all the aprons and taxiways is at least 2 orders of magnitude larger than the touchdown area so, even if you assumed the same rubber distribution in time you'd see *way* more of it on the touchdown area.

Quoting faro (Reply 2):
When landing you have very significant longitudinal loading on the tires that subsides very quickly as soon as the tires are revved up and stop smoking.

The loading to spin up a tire relates just to the weight of the wheel itself...that's very small (


User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 6, posted (3 years 2 months 3 weeks 2 hours ago) and read 5364 times:

Spinning the tires prior to landing using electric motors was a feature of the Lockheed XR6O-1 Constitution which flew in November of 1946. However the reason was not reduce tire where but to reduce the stress on the main gear struts.

User currently offlineflipdewaf From United Kingdom, joined Jul 2006, 1578 posts, RR: 0
Reply 7, posted (3 years 2 months 3 weeks 2 hours ago) and read 5342 times:
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Quoting tdscanuck (Reply 5):
The loading to spin up a tire relates just to the weight of the wheel itself...that's very small (

Sorry to nitpick, its the moment of inertia.   

Fred


User currently offlinediamondflyer From United States of America, joined Oct 2008, 1594 posts, RR: 3
Reply 8, posted (3 years 2 months 3 weeks 1 hour ago) and read 5296 times:

Some of the older Cessna Citations have a gravel kit, which one of the parts is a wheel spin up kit. Here's a decent pictures of it. Perhaps someone with more experience with the kit can talk about it.


View Large View Medium
Click here for bigger photo!

Photo © Alevik



-DiamondFlyer


User currently offlinemandala499 From Indonesia, joined Aug 2001, 6951 posts, RR: 76
Reply 9, posted (3 years 2 months 3 weeks ago) and read 5253 times:

Quoting diamondflyer (Reply 8):
Some of the older Cessna Citations have a gravel kit, which one of the parts is a wheel spin up kit. Here's a decent pictures of it. Perhaps someone with more experience with the kit can talk about it.

That nice metal cover on the nosewheel is the spin up kit... for nosewheel only... Reduces runway surface bits sticking to the wheels during initial nosewheel contact, which can end up damaging the fuselage or throwing FOD into the engine.

And there are no brakes on the nosewheel...   



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineBlueJuice From United States of America, joined Jun 2010, 249 posts, RR: 0
Reply 10, posted (3 years 2 months 2 weeks 6 days 16 hours ago) and read 5044 times:

On takeoff the wheels would be spinning as well. I'm thinking whatever savings from tire wear on landing will be eaten up by brake wear to slow down the spinning on takeoff. There would also be the extra wear on snubbers inside the wheel well.

User currently offlineFly2HMO From , joined Dec 1969, posts, RR:
Reply 11, posted (3 years 2 months 2 weeks 6 days 15 hours ago) and read 5001 times:

At least once a year somebody comes up with this great "new" idea.

In a nutshell (as with all other great new ideas) fuhgeddaboudit.


User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1656 posts, RR: 1
Reply 12, posted (3 years 2 months 2 weeks 6 days 11 hours ago) and read 4926 times:

Not going to bother looking them up but there must be 500 threads on a.net about this. It is a very bad idea; look it up to see why.

User currently offlinefr8mech From United States of America, joined Sep 2005, 5596 posts, RR: 15
Reply 13, posted (3 years 2 months 2 weeks 6 days 11 hours ago) and read 4912 times:

A couple of issues:
-wheel well clearance (space is at a premium in the wheel well
-weight
-drag on take off
-massive increase in FOD potential
-system inputs (some aircraft use wheel spin-up as an input to other systems)

Look, quite simply, this idea has been around for ages. If the cost/benefit analysis was on the plus side for spinning up the wheels prior to touchdown, it would already be done.



When seconds count...the police are minutes away.
User currently offlinebohica From United States of America, joined Feb 2004, 2736 posts, RR: 0
Reply 14, posted (3 years 2 months 2 weeks 6 days ago) and read 4768 times:

The only thing these so-called wheel spinners would do is cause more drag. More drag means more engine power which means more fuel burned which means money wasted.

On an airplane like a 737 or other aircraft which do not have gear doors, these devices would be sticking out in the airstream causing lots of drag.

Any money saved on tire wear will be lost burning more fuel to compensate for the drag.


User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9681 posts, RR: 52
Reply 15, posted (3 years 2 months 2 weeks 6 days ago) and read 4755 times:

The thing responsible for tire wear is braking. The tire is designed almost exclusively with the intent to get maximum braking efficiency. Part of the reason why main gear tires only last around 200 cycles between retreads is that the rubber is designed to wear off during the massive heat during braking. Main gear tires are huge because of braking. Nose gear tires also put off smoke on landing, but they do not wear anywhere near as fast as main gear tires (except the rare airplane like the 727s with nose wheel braking). All the energy of the airplane gets turned to heat. The brakes and tires heat up. Brakes are carbon fiber and are designed to perform at high temperatures. Tires are rubber, so they must wear to dissipate heat.

Taxiing at heavy loads puts stress on the tire as a whole, but that does not cause rubber to wear off.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlinenomadd22 From United States of America, joined Feb 2008, 1894 posts, RR: 0
Reply 16, posted (3 years 2 months 2 weeks 6 days ago) and read 4753 times:

I'm still waiting for the magnetic brakes that can double as motors for taxing. Sort of like what regenerative hybrids have. Spinning up the wheels for landing would be another function those could handle. They'd even feed a tiny bit of power back to the system when you stopped the wheel spin after takeoff.


Andy Goetsch
User currently offlineTSS From United States of America, joined Dec 2006, 3070 posts, RR: 5
Reply 17, posted (3 years 2 months 2 weeks 5 days 23 hours ago) and read 4738 times:

I suspect that the ability to spin the wheels up to speed before landing will be a feature of the 757 when Boeing restarts that production line.  


Able to kill active threads stone dead with a single post!
User currently offlineWingscrubber From UK - England, joined Sep 2001, 852 posts, RR: 0
Reply 18, posted (3 years 2 months 2 weeks 4 days 15 hours ago) and read 4493 times:

The KERS technology in formula one could be used for this - normally on gear retraction the brakes are applied (or the tyre contacts a skidpad in the wheel well) to reduce the risk of tyre-burst damage. If this energy was captured with a lightweight KERS flywheel or maybe a hydraulic accumulator, the tyres could be spun up prior to touchdown which would increase tyre life and reduce the risk of tyre-burst on landing.

Ultimately, the maintenance savings alone from increased cycle life of the tyres could easily sell this to the airlines, if a small weight trade-off could be justified.
I'm sure engineers at boeing/airbus etc have already made powerpoint slides on their own tyre-spin up concepts.
So, I have to disagree with those who think this is a bad idea - I think it's only a matter of time before it's implemented.



Resident TechOps Troll
User currently offlinefr8mech From United States of America, joined Sep 2005, 5596 posts, RR: 15
Reply 19, posted (3 years 2 months 2 weeks 4 days 4 hours ago) and read 4345 times:

Quoting Wingscrubber (Reply 18):
Ultimately, the maintenance savings alone from increased cycle life of the tyres could easily sell this to the airlines, if a small weight trade-off could be justified.

Once again, the concept has existed for decades. The trade-off is just not there. Increased weight and cost of maintenance is not adequately accounted for in the potential wear savings on the tire.

Have you ever seen a properly worn tire on an aircraft? They wear just about evenly all the way around, absent an anti-skid issue. That, at least at an anecdotal level, indicates that the majority of wear occurs during taxi, take-off roll and roll-out and not the landing.

Just my observation.



When seconds count...the police are minutes away.
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9681 posts, RR: 52
Reply 20, posted (3 years 2 months 2 weeks 4 days 1 hour ago) and read 4285 times:

Quoting Wingscrubber (Reply 18):
The KERS technology in formula one could be used for this - normally on gear retraction the brakes are applied (or the tyre contacts a skidpad in the wheel well) to reduce the risk of tyre-burst damage. If this energy was captured with a lightweight KERS flywheel or maybe a hydraulic accumulator, the tyres could be spun up prior to touchdown which would increase tyre life and reduce the risk of tyre-burst on landing.

The tires are braked so that a loose tread on the tire does not go spinning around in the wheel well after the gear is retracted. A loose piece of rubber moving at over 100 mph will do some considerable damage, and that's not good since the hydraulic systems are located partially in the wheel wells.

Quoting fr8mech (Reply 19):

Have you ever seen a properly worn tire on an aircraft? They wear just about evenly all the way around, absent an anti-skid issue. That, at least at an anecdotal level, indicates that the majority of wear occurs during taxi, take-off roll and roll-out and not the landing.

Flat spots on tires are from skids due to antiskid not working and not tire spin up. And in your list, you forgot landing roll, which is where it occurs as the airplane brakes.

Quoting Wingscrubber (Reply 18):

I'm sure engineers at boeing/airbus etc have already made powerpoint slides on their own tyre-spin up concepts.
So, I have to disagree with those who think this is a bad idea - I think it's only a matter of time before it's implemented.

In general unless it is very advanced technology, if it hasn't shown up on an airplane before, it probably won't. The easy simple ideas have already been implemented.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlinecobra27 From Slovenia, joined May 2001, 1028 posts, RR: 0
Reply 21, posted (3 years 2 months 2 weeks 4 days ago) and read 4259 times:

Somesort of hydraulic device could be used, electrical would also work, but woud probably be heavier. A small turbine you pictured coould also work.
I think than tires wear out at around 150 landings, and can be rebuilt afterwards


User currently offlinelonghauler From Canada, joined Mar 2004, 5121 posts, RR: 43
Reply 22, posted (3 years 2 months 2 weeks 3 days 23 hours ago) and read 4230 times:

I recall seeing a study many years ago with the same intent as the OP. However, in this case the actual tire was designed with rubber one-directional vanes on the side wall of the tire. This would spin the tire as soon as it was in the slipstream.

The conclusion was that it did not appreciably reduce tire wear.

As noted above, the majority of tire wear occurs on braking with hot tires.

Quoting RoseFlyer (Reply 15):
main gear tires only last around 200 cycles between retreads

Is this true? I didn't know that!



Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
User currently offlinefr8mech From United States of America, joined Sep 2005, 5596 posts, RR: 15
Reply 23, posted (3 years 2 months 2 weeks 3 days 22 hours ago) and read 4199 times:

Quoting RoseFlyer (Reply 20):
And in your list, you forgot landing roll, which is where it occurs as the airplane brakes.


Semantics, or a bit of ignorance on my part. I use roll-out and landing roll interchangeably.

Quoting RoseFlyer (Reply 20):
Flat spots on tires are from skids due to antiskid not working and not tire spin up.


That is what I was getting at. If the landing was that detrimental to tire wear, you would expect to see a more abnormal tire wear pattern.



When seconds count...the police are minutes away.
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 24, posted (3 years 2 months 2 weeks 3 days 21 hours ago) and read 4179 times:

Quoting RoseFlyer (Reply 15):
Part of the reason why main gear tires only last around 200 cycles between retreads is that the rubber is designed to wear off during the massive heat during braking.
Quoting cobra27 (Reply 21):
I think than tires wear out at around 150 landings, and can be rebuilt afterwards
Quoting longhauler (Reply 22):
Is this true? I didn't know that!


We did a survey about 25 years ago requesting the average landing each operator tires were achieving. The 150 to 200 range was what was reported.

Operators with long taxis and many turns were always on the low end. Taxing to takeoff with heavy loads and taxiing to the gate with hot tires from breaking accelerate tire wear. Additionally, when an aircraft turns the inboard tires skid/skip/scrub on the concert in a very tight arc scrubbing off tread.


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