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Spin Wheels Before Landing
5

Spin Wheels Before Landing

Spin Wheels Before Landing

(OP)
Everytime you see an airplane land, a large puff of smoke comes off the wheels as they skid before spinning up to speed.  I imagine this wear is the major factor in short tire life.  Some planes need new tires after just a few dozen landings.

Why not use an electric/hydraulic motor to spin the wheels up to speed.  Better yet - could a small series of vanes be formed on the tire itself - that when exposed to the rushing air would cause the wheel to spin up.  Might not be exact but might get it close enough.

Just a thought..

RE: Spin Wheels Before Landing

I suspect that it has been looked at before and the life-cycle cost advantage is not there.

RE: Spin Wheels Before Landing

you're right but the industry lives with it.  to my knowledge there have been only very few military/prototype planes have done this ... if there was every a plane for it, it was the shuttle (with it's very high landing speed).

RE: Spin Wheels Before Landing

Actually the model 500 Cessna Citation Corporate jet has a nose wheel spin-up scheme as part of a "unimproved" gravel runway package. I believe it's designed more to keep FOD from being kicked up by a static nose tire upon landing then any wear concerns. It uses ram air from a scoop & bleed air from the engines to drive a pair of turbines on the nosewheel. The air is applied through a swiveling duct, and the RPM is monitored by a simple monopole pickup.

Speaking for all lazy mechanics out there, I can say this is a royal PITA to work on.

There's also a bunch of Armour scabbed on the antenna's & flaps to deflect what rocks are thrown up anyway.

RE: Spin Wheels Before Landing

There were some tires molded with shell shaped scallops on the side ( No pun intended) to enable the tire to spin up to speed once the gear was lowered.
 I dont see these around any more. Apparently the spinning mass of the tire caused more problems than it solved.
Here is a related article: http://archives.sensorsmag.com/articles/0300/14/index.htm

B.E.

RE: Spin Wheels Before Landing

There was, many moons ago, a completely new concept of landing wheels that incorporated a pizeoelectric motor/brake.  The motor would spin up the wheel prior to landing, and once on the ground, the motor could depowered and act as a brake.  

Haven't head squat about it since then, so there must have been technical difficulties

TTFN

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RE: Spin Wheels Before Landing

I have advocated building biased ribs in wheels that act like turbine blades. The concept can be tested with clamp-on blades, four min to a wheel. Another approach is push-on blades made from spring material.

RE: Spin Wheels Before Landing

MiketheEnginurd...

SAE AIR5800 Tire Prerotation at Landing

Intro paragraph...

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.

There are a LOT of factors... intuitave and non-intuative... involved [for or against - depends].
 

Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

RE: Spin Wheels Before Landing

Air Force studies back in the 60's and 70's determined that only 10% of tire wear is a result of landing 'non-spinning' wheels on jet aircraft.  Yes, the ends of the runway looks like it contains a lot of rubber, but it is a thin layer.  The majority of tire wear occurs at the gate due to the scrubbing affect of tight turns.  The scrubbing affect, similar to tire wear on NASCAR tires, results in small balls of rubber which is difficult to see unless you are on the airport ramp.

As an airline Engineer back in the 80's, we received many letters from passengers that had ideas on how airlines could save money which we had to address - windows in the cabin floor to see the ground inflight (they didn't know the baggage was stored under the cabin), runways that sloped upwards to help slow down the aircraft, and of course the multitude of ideas on spinning the wheels just before landing.

Airlines are very concerned with two critical areas - reliability and weight.  Adding motors, vanes, or molded tires will increase aircraft weight (reducing revenue) and can increase flight delays and cancellations due to equipment malfunctions and normal maintenance (increasing costs).

The life of a bias ply tire is 350-500 landings and these could be retreaded multiple times to reduce costs.  Radial tires, while lighter in weight, have a life less than bias ply tires.  Additionally, they are for the most part not yet approved to be retreaded.  Yes, costs are higher with radial tires but a value analysis of adding 'devices' to spin the wheels to only increase the tire life by 10% is not economcal.

Another interesting Air Force study.  Brake wear can be different between the LH and RH landing gear not only due to which direction the aircaft turns a majority of the time but also due to the dominate leg effect of the pilot.  The study showed that right handed pilots tended to add more force from their right foot to the brake pedal than their left foot and they compensated with rudder input to balance the difference in braking force.  The opposite is true for left handed pilots.  For an aircraft that is flown mainly by the same pilot, the brake wear difference was measureable.

Regards,

ERAU82

RE: Spin Wheels Before Landing

An "unintended consequence" of extending tire life would be extending the time between inspecting the components associated with the tire change. Lubing & inspecting (or replacing) the wheel bearings, NDT on the wheel components themselves. Maybe the components are robust enough to go another 10%, maybe not.  

RE: Spin Wheels Before Landing

HI. Mike.. You can not change anything on an airplane until you get field approval for the work and any modifications and file form 337 with the FAA. You can spend thousands of dollars and submit your engineering data and try for an (STC), supplemental type certificate. If you can get the FAA to even read it!! The STC can only be used on that specific type and model of aircraft.. The STC for spinning wheels should be in the FAA files..(FAA.GOV/STC/WHEELS) The formula for the rubber was made long ago and the FAA will not change anything...  Oil is the same oil that was used back in the 1950's ,the FAA will not let us use any oil that has a modern day formula... However, there is one additive that has been approved and that is "CAMGuard" for use in aircraft engines..  Maybe there is hope out there yet!!..Thanks...Knightflyer!

RE: Spin Wheels Before Landing

ERAU82 - The automatic braking systems out there can be set to apply a selectable percentage of braking power upon landing and thereby eliminate LH-RH brake wear differences, at least as caused by the pilots.

RE: Spin Wheels Before Landing

At first glance, it would seem logical to spin up the tires prior to touch-down to alleviate tire wear and spin-up loads. Several methods have been devised to do this, and some have been tested with various degrees of success. One method uses an electric motor and another uses fan-like blades on the wheel or tire. However, the cost/weight/maintainability penalty must be assessed and traded off against the advantages gained. First, tire wear at spin-up is minor. Most tire wear is caused by breaking and turning. Secondly, spin-up loads do not usually design a great deal of the gear – usually parts of the torque links and pistons. Experience has indicated that tire pre-rotation devices are just not worthwhile. For further reading on this subject, reference should be made to "Prerotation of Landing Gear Wheels" by H. F. Shippel, SAE Journal, vol. 52, No. 10, October 1944.

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