Having seen and/or smelled the smoke of tires hitting the runway thousands of times while working at ANC, I often thought about a solution — not motorized wheels, as suggested in this video, but fins on the side of the wheels to get the wheels spinning.
This non-motorized solution is discussed in the comments. I post some of the most interesting comments beneath this video.
Why not make plane-tires spin, before landing?!
Nov 8, 2019
Why do aircraft manufacturers not invent motors that could start spinning the plane tires, before they hit the runway? Wouldn’t that save a lot of tire-use and money?
This is one of the most common questions I have ever had throughout the history of this channel so I thought it was about time to explain it.
In todays video, I will be talking about aircraft tires, how they are made, why they don’t burst and I will, finally, answer the question stated above in 3 different ways.
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Select comments, pro and con:
You don’t need an “electric/gas” Motor on the wheels to make it spin. You just need to redesign the landing gear rims where you have almost flushed side vents on the edge of the rims to draw air to small blades towards the inside of the rims to act like an air-motor that could pre-spin the free-wheeling tyres on landing. Almost like some of these aerodynamic hub caps (but with a purpose to pre-spin the wheels not just for aerodynamics). I wouldn’t recommend a clip on hub cap, but it could be hard designed into future rims or more securely secured light weight hub caps eg with bolts. The wear on the tyres would definitely be dramatically reduced. This is a passive solution so it doesn’t not have a complex point of failures like a conventional motor. The force would also be proportional to your air-speed so there is no mis-balancing of wheel speed mismatch or counter-acting magnetic forces an electrical motor might have if sudden changes in wheel speed happens.
CV Hawkeye the main issue with your solution would be when the aircraft would come in at an angle, like Mentour explained. Then, the side of the landing gear leading into the air would spin faster than intended and the trailing side of the landing gear would probably not spin at all, having the hub behind the air stream..
I have been flying over 40 years up to all versions of the 747, except for the 741 and had those ideas some 30 years ago; there are even patents established on similar ideas. Seems to me the low cost of tire replacement and the high cost of getting anything certified in aviation will keep those ideas on the shelf. .. even electric tugs to get you to the runway when you are # 75 for take off @ JFK where you burn 4 tons of Jet A1 to get to the #1 position just to taxi back to get more fuel for your 748 with a taxi weight of 440 tons seems like a total waste. In Africa there is a saying: TIA, “This is Africa” when things are not flowing to expectations .. I would say: TIA, this is aviation.
Actually no. This is an overengineered response. All you need are fenders to cover the top front quarter of each tire and the friction between the air and the lower half of the tires will cause them to spin. You literally only need to cover the tops of the tires to prevent the cancellation effect of the wind pushing over the tires against the wind pushing under the tires.
i think what you are speaking of is a voith schneider propeller integral with the hub of the tires.
Yes , I thought of something similar . But as he says on a cross wind landing . One wheel would be exposed to more wind so would be faster then the other and that would be the windward tyre . So the aircraft would be forced to the down wind side . Not a thing you would want !
@welshpete12 I don’t think it that’s much of a concern, because it happens all the time that aeroplanes touch the runway with only left or right landing gear, meaning the affecting force is very one sided.
@Halcyon Outlander Passive Centrifugal based spoilers can always be designed within the rims to regulate top wheel rotational speed to no greater than say 160-200knts if the wheels were rotating on the ground. BTW upon landing, air-speed would be approaching ground speed Typically 140-150knts.
A better written and explained version of what I came here to say. Thought it for years. On a v short runway you’d brake briefly just before touchdown to add the braking benefit of the touchdown smoky spin
@Annabelle M >The problem is not the drag, but the down force could be. The force would actually be up. Pressure would be less at the upper part of the wheel , because of higher speed relative to air.
@Halcyon Outlander Yeah, but it doesn’t have to match exactly. I mean, right now the difference between the ground speed and the wheel is TOTAL. So any speed you can get them closer together is a win anyway.
perhaps the effect would be minor but, a spinning mass is going to induce torque. To make things worse the landing gear is hung below the aircraft giving them leverage. this would induce a roll right force. I’m sure it could be trimmed out and handled with computers but it will mean that you will lose some roll left maneuverability. You might also find a difference in roll rates?
@Colin Southern The wheels have to be spun up for a very brief portion of the flight. As per the airspeed and wheel rotation issue, that could be calibrated with a retractable duct that allows for modification of airflow to the wheel based on airspeed/dynamic pressure. The bigger issue of gyroscopic yaw mentioned by other posters could be corrected by FCS. All in all, it seems the complications and risks are not worth the gain.
Colin Southern1 day ago (edited)
No Zack There’s no “gyroscopic issue”; if massive turbines spinning 15 times faster in the engines don’t cause an issue then the relatively slow turning wheels wouldn’t either. Ultimately it comes down to economics; too much cost for too little savings. Ducts capable of spinning up a wheel aren’t going to be small – and neither are the vanes they would have to blow on to. They’ll take up space – in an area that doesn’t currently have a lot to spare.
No Firstly you seem to be under the mistaken impression that these large & heavy wheels – complete with rotating parts of the braking systems – turn easily; they don’t. Secondly you’re going to have issues with middle and rear sets of tyres on bogeys getting non turbulent air. Third you’re going to have to deal with the complexities of failsafes; what would happen for example if a “variable vane” stuck in the “full force” position resulting in a tyre overspeeding to the point of destruction when lowered at Vle? At the end of the day these are all just pie-in-the-sky ideas that are about as unworkable as building a ladder to reach to ISS; some of the theory sounds fine … right up to the point where you start looking at real-world aerodynamic equations.