Pre-rotating of aircraft wheels before landing?
Discussion
Here's a question.
Every time an aircraft lands, the tyres hit the runway at over 100 mph, which obviously takes a large amount of the tyre was, as evidenced by the tyre smoke.
Would it not be possible (and presumably not too expensive) to have the tyres "pre-rotating" at the ground speed of landing?
You would obviously lose a very small amount of retardation that you get currently, and there is a cost involved, but presumably there would be a net gain over the life time of the aircraft in terms of tyre costs?
Every time an aircraft lands, the tyres hit the runway at over 100 mph, which obviously takes a large amount of the tyre was, as evidenced by the tyre smoke.
Would it not be possible (and presumably not too expensive) to have the tyres "pre-rotating" at the ground speed of landing?
You would obviously lose a very small amount of retardation that you get currently, and there is a cost involved, but presumably there would be a net gain over the life time of the aircraft in terms of tyre costs?
I always wondered why the tyre manufacturers didn't mould fins on to the sidewalls - that would let the tyre spin up using the airflow as the plane came into land. The only downside I can see is that it would put a bit more load on the brakes when they stop the wheels before the undercarriage retracts after takeoff. I guess it would also mean that aircraft tyres would become rotational rather than being fitted anywhere (assuming they're not rotational already, obviously!)
alangla said:
I always wondered why the tyre manufacturers didn't mould fins on to the sidewalls - that would let the tyre spin up using the airflow as the plane came into land. The only downside I can see is that it would put a bit more load on the brakes when they stop the wheels before the undercarriage retracts after takeoff. I guess it would also mean that aircraft tyres would become rotational rather than being fitted anywhere (assuming they're not rotational already, obviously!)
What would the fins look like to allow rotation?For large passenger airframes, i believe the tyre life limitations are primarily load/fatigue based, rather than "tread wear" in most normal cases (when operating from long, well surfaced 1st world r/w). Each time you land or take off, those tyres are supporting hundreds of tonnes of airframe traveling at nearly 200mph, and those stresses lead to a slow degradation in the tyre integrity. And whilst you could make a tyre strong enough to last indefinitely, it would be so heavy and bulky it would cost you more in terms of payload & drag!
dr_gn said:
alangla said:
I always wondered why the tyre manufacturers didn't mould fins on to the sidewalls - that would let the tyre spin up using the airflow as the plane came into land. The only downside I can see is that it would put a bit more load on the brakes when they stop the wheels before the undercarriage retracts after takeoff. I guess it would also mean that aircraft tyres would become rotational rather than being fitted anywhere (assuming they're not rotational already, obviously!)
What would the fins look like to allow rotation?This was posted in a similar discussion elsewhere and seems plausible
internet said:
The articulated main landing gear of most "heavy" type aircraft (747, A320, MD-11, etc.) already serves to minimize touchdown tire wear, and reduce blowouts, by providing some articulated initial "soft" loading of the tire clusters at touchdown. You can see this working as the rear most tires, "hanging" lowest immediately prior to touchdown, first contact the runway, and the landing gear then is quickly compressed/rotated slightly to bring additional tires, farther forward, into ground contact.
There is also this summary of a technical document that costs $70aircraft industry said:
Standard: AIR5800
Issued: 2009-10-29
Issuing:
A-5c Aircraft Tires Committee
Committee Information
Scope:
This SAE Aerospace Information Report (AIR) applies to landing gear tires and airframe structure for all types and models of civil and military aircraft having tires as part of the landing gear. This report describes the advantages and disadvantages of prerotating tires prior to landing, and explains why this practice is not generally adopted. Two potential benefits of this practice are considered: 1) Tire wear and 2) Spin-up loads on the landing gear and aircraft structure.
Rationale:
The idea of tire prerotation at landing to reduce tire wear and spin-up loads has been proposed many times in the past, and continues to be proposed for new airplane projects. Yet, this practice has not been adopted in the aircraft industry. This report explains why this is generally not a feasible idea, and also discusses situations where it may be beneficial. This report is a compilation of all of the information available to SAE A-5, and comprises the general consensus from the aircraft and landing gear industry on this subject.
Issued: 2009-10-29
Issuing:
A-5c Aircraft Tires Committee
Committee Information
Scope:
This SAE Aerospace Information Report (AIR) applies to landing gear tires and airframe structure for all types and models of civil and military aircraft having tires as part of the landing gear. This report describes the advantages and disadvantages of prerotating tires prior to landing, and explains why this practice is not generally adopted. Two potential benefits of this practice are considered: 1) Tire wear and 2) Spin-up loads on the landing gear and aircraft structure.
Rationale:
The idea of tire prerotation at landing to reduce tire wear and spin-up loads has been proposed many times in the past, and continues to be proposed for new airplane projects. Yet, this practice has not been adopted in the aircraft industry. This report explains why this is generally not a feasible idea, and also discusses situations where it may be beneficial. This report is a compilation of all of the information available to SAE A-5, and comprises the general consensus from the aircraft and landing gear industry on this subject.
dr_gn said:
Driven mainwheels for taxying are currently being investigated (to save fuel), and these would also allow pre-rotation and regenerative braking for landing.
Was going to mention that. The large aerospace company I work for has such a product. Don't know too much about it other than the electric taxiing to save fuel but I don't see no reason why the wheels could not be spun up on landing with such as system if it is safe to do so.Why take something that works well, lasts a long time and doesn't cause safety issues and lumber it with extra complication.
The cost savings would be minimal, extra weight carried just for one phase of flight burdensome on fuel consumption and the extra equipment an added maintenance burden.
Thats without even considering that dangling 20 huge gyroscopes under the aircraft may have some small effect on handling during this critical phase of flight (20 in the case of an A380 main wheels)
I personally think its a non starter as all airlines are looking to strip out any unnecessary weight to save fuel rather than add more weight in. In the grand scheme of things tyre wear due to touchdown speeds isn't a huge cost, more damage is done braking on grooved runways and taking high speed exits from the runways. A lot of tyre wear also occurs when turning tight intersections and during pushback.
The cost savings would be minimal, extra weight carried just for one phase of flight burdensome on fuel consumption and the extra equipment an added maintenance burden.
Thats without even considering that dangling 20 huge gyroscopes under the aircraft may have some small effect on handling during this critical phase of flight (20 in the case of an A380 main wheels)
I personally think its a non starter as all airlines are looking to strip out any unnecessary weight to save fuel rather than add more weight in. In the grand scheme of things tyre wear due to touchdown speeds isn't a huge cost, more damage is done braking on grooved runways and taking high speed exits from the runways. A lot of tyre wear also occurs when turning tight intersections and during pushback.
blueg33 said:
If I was a tyre maker for aircraft, I think I would be happy not to do something that would reduce the wear rate.......
The company next door to us does very nicely out of doing remoulds for aircraft. Imagine how much cheaper a set of remoulds are for a 747?http://www.monaflex.com/products/
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