Why not make plane-tires spin, before landing?!
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- Опубликовано: 7 ноя 2019
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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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I want to send a huge "Thank you!" to the channels that were featured in todays episode. You can watch the full, awesome, videos, using the links below:
Flugsnug (Closeup of landing gear)
• Touchdowns ultra-clo...
Tech insider (Why aircraft tires don’t explode)
• Why Plane Tires Don't ...
Bestdestination (A380 Aqua-planning)
• Airbus A380 Lucky Pilo...
aviafilmsproduction (aircraft taxying)
• Plane Spotting: airpla...
Karsten Eckert (Electric remote controlled tug)
• Airbus 320 with Mototo...
Cargospotter (A380 crosswind landing)
• Unbelieveable AIRBUS A...
I was a landing gear engineer with a major airline for 33 years and the tires were one of my responsibilities. Seeing the 2,617 comments below remind me of the MANY times I answered the same question. One of the major points you didn't mention is that the wheels spinning at touchdown speed with the tires out of balance would shake the airplane apart. With eighteen tires spinning on a 747 one can imagine the shaking that would occur and the passenger's reaction. Actually, B.F. Goodrich ran an exhaustive test on this problem a number of years ago and discontinued the test because of the vibration it set up.
Everyone believes that adding little flaps on the wheels or tires would solve the rotation problem but there is no way to control the speed of each tire so there would be no real benefit. In addition, not only spinning the tires but the brakes would also have to be spun up which would require considerable power. The brakes are designed to absorb the enormous energy of a rejected takeoff and not easily rotated.
Nitrogen is used to prevent the tires from exploding. We once had all four tires explode on a 727 after the pilot taxied the airplane up and down the runway trying to burn off the fog. The tires at that time were filled with air (80% nitrogen and 20% oxygen). The brakes became so hot with all the taxiing that the tire solvents mixed with the 20% oxygen and became hot enough to explode. We all converted to filing the tires with nitrogen after that. As an added note, when the Concorde was designed, they considered using nitrogen in the tires just to save weight.
The gyroscopic effect of spinning tires would also adversely effect trying to control the airplane during a critical time of landing.
Your video brought some interesting points from a pilot's perspective. I just thought I would add a few points from an engineering point of view and experience.
Wouldn't compressed air (or bleed air) work as, not driving the wheels, but shoot them up to speed, any speed would lessen the wear and tear more or less, doesn't have to be exactly the airplane speed.
thank God, someone who knows what he's talking about ... I'm not an engineer , but I've been working for a major airline for the past 30 years or so , and still am ... I must tell you that from my point of you , the biggest issue would be the huge gyroscopic effect , generated by large spinning wheels, especially on big aircrafts like B-747 or AB -380 ...
imagine trying to land in countries during the monsoon season ... there is no way the pilots could manage a landing with strong cross winds ...
Your reply and your point of view about this matter was very interesting and very professional.
Many times people comment only about the superficial not seeing the technical part of the subject. Congrats for your detailed information. Also I believe that you should be the person to publish videos about the technology of the landing gear.
The LG of any a/c is what seems to be one of the major issues in a/c design ... and the correct functioning ( maintenance + correct use, within parameters ) is mandatory ... think about the Concorde : it's the chain of events that led to catastrophe , and the key role was a non correctly rebuilt LG ... they forgot to put the spacer between the ballbearing ...
What would stop the addition of small fins to the wheel hubs so that they spin up in the airflow?
this has been tried on a plane from the 50s - Lockheed Constitution. turns out the rotating wheels caused some funny gyroscopic effects which made landings "interesting"
That, and passenger plane tires are really damn heavy and to "pre-spin" them would require really tough and heavy motors or engines, which means less payload, OR additional complexity to make the wheel spin using the turbine engines, which means more points of failure.
Edit: Both of which of would require additional maintenance procedures, which defeats the purpose.
@@grenzviel4480 i don’t think Motors would be necessary, some baffels to catch the air could start some spinning of the tires with less need for maintenance but i guess it would also add weight.
I can totally imagine that. 6 or 8 huge spinning wheels!
How interesting?
@@macflod I had the same idea
Peter, as always, nothing beats listening to someone who _knows_ what he's talking about [and in addition exudes his _passion_ for his profession], exactly like _you_ do! . . . ⭐⭐⭐⭐⭐⭐👍
Respect!🙏 🇳🇴
Another aspect to consider is that spinning tires would be one more thing for pilots to keep track of while landing. Landing is already the most intensive portion of the flight, and an extra checklist item really needs to provide some safety benefit to offset the additional mental load on the pilots.
Back in the eighties when I was in the Navy I brought this question up to my division officer it was an F-4 pilot and his reason for this not being a good idea was that a rotating wheel acts like a gyroscope and would induce adverse yaw on the aircraft and that's not something you want when trying to line up on a Runway or catch an arresting cable on an aircraft carrier deck.
Good point about the gyroscopic forces, I hadn't considered that.
do you mean that it will make pitch down !!!
@@tarekelgeidy1492 No, it would pitch it up ;)
But given the small mass of the tires I can't imagine that the torque would be that much (at least for a passenger plane)
The forces would negligible.. truth is airplane tires do spin up before landing. Its a Bush flying option to prevent rock/gravel ingestion
@@miallo What you discussed is a different effect, the angular momentum conservation when spinning up the wheel. It indeed is a minor effect. I believe what the F-4 pilot's point was that you need a very large twisting from the landing gear to change the heading direction of the fast-spinning tire (changing the direction of rotational axis of the wheel when turning the aircraft).
In all my years as a process improvement consultant, I have heard thousands of reasons why my improvement proposals wouldn`t work... until they did.
Impossible is one of the words I hate the most.
that's how i see it too..
some of the explanations don't really make sense to me as to why not implement wheel spinning.. the added weight most likely does not make sense, fuel consumption vs tire wear.
anyways,
~there's no need for "huge batteries by the gas tanks"
~the plane would not veer off the runway in case of cross-winds, as the wheel rotation ca be controlled to account for the 'side-ways' touchdown
Agreed. It's all about "attutude". Yes, more pun .. (cough)
I think he is over blowing the technical difficulty in implementing wheel spin. It definitely can be implemented and we have the technology to do so. But the things that he listed do make it less worthwhile to do so. So at the end of the day, there's no motivation to implement it.
The cost of development isn't cheap. It's not as simple as just spinning the wheel. A computer need to know the ground speed and crab angle which then actively adjust each individual wheel as the plane approach the runway. Then they need to fit the motors and batteries and computing systems somewhere safe without adding too much weight. Weight is a big deal because aviation fuel is really expensive, so any unnecessary weight will make each flight more expensive. Each addition need to have enough reasons to justify the added weight. TV screens for every seat attract passengers and that additional income justify the added weight and increased fuel consumption for example. Wheel spin is by all means possible but far from simple and so cost lots of money. Retrofitting would also means going through the regulatory bodies again.
New designs might be able to do it since they will have to go through a safety check anyways and the design can accommodate the system from the ground up instead of redesigning and retrofitting. But the airlines need to actually care and want that feature in the first place. If all else is the same, wheel spin feature might be nice, but more likely than not, fuel economy, seating and other features will not be the same and get most of the focus from potential buyers. If wheel spin isn't a attractive enough feature, designers won't incorporate it because it just adds development time and money. Instead that effort will be placed on better fuel economy and other more attractive design considerations.
I'm always impressed by your videos. You are much more than a commercial pilot -- which is no small thing, indeed! -- but also an excellent educator and presenter. Thank you for your excellent explanations!
While our host discussed the hazards of certification and electrical accessories, I thought of a few alternatives, like using the 100 mph slipstream to spin the tires. A set of rubber vanes glued to the sidewalls might be worth investigating.
Which type of glue would be better for that application- Elmers or Gorilla?
@@kamakaziozzie3038kamakazi glue!
@@kamakaziozzie3038flex seal will work best
They tried it... but to retract the wheels after takeoff... the wheels need to be stopped. The added wear on the brakes costs more.
@@wolphin732 That's a great argument against having vanes on the sidewalls. how about a shroud that covers part of the top of the wheel but not the bottom, spinning the bottom. The shroud wouldn't be deployed on take-off.
When I went through orientation at Boeing as young engineer in 1977, we were told they get many calls per week from the public suggesting pre spinning the tires for landing. Then they told us that the most tire wear is on take off when the plane is loaded with fuel. I think the problem is people seeing so many TV and movie B roll of a plane landing and seeing the puff of smoke.
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.
Ha. See my comment......
But now youre increasing drag even more than the landing gear already does and probably mess with the pitch of the aircraft
That´s not well enough thought thru, first a spinning wheel is not good for aerodynamics, second the problem with the speed is still there since the speed of the wind is not the same as the ground speed and third it still needs to be fail prof.
Not sure if the airspeed would have enough force to spin up the wheels at the cost of the drag. However some bleed air could help
That´s it! Adding that you do not need match ground speed, if it goes just half the speed, tyre useful life will double. Being passive, L/G will not "drive" the aircraft out of lane in case of crosswind. Added drag is not an issue during landing. Tractors (remote controlled or not) shold be driving airplanes to and from runways since last century.
I remember going on holidays with my parents many years back. As we got off the plane and walked towards the terminal I noticed two big airline tires propped against the wall. I touched one as I passed by. It felt more like a very hard plastic than regular tire rubber. Tough stuff !
I think... but I'm getting on in years these days that I had a professor that told us airlines (at least back in his day) leased the tires and they were rated for X number of take offs and landings which we all agree should be equal... but it was a physics class a long time ago and he said fuel load at take off is way worse on the tires than landing... he was a former bomber pilot so I can't support or refute his supposition
That huge thickness holds a lot of technology also. A 767 main gear tire is a 32 ply tire, the nose gear is 24 plies (ratings… ply numbers can vary by manufacturer). Their limiting factor is heat absorption during braking.
I love the way you personally speak about your sponsors instead of showing one of their commercials.
My Dad was a b17 mechanic during WWII. He said they tried putting vanes on the hubcaps to spin the tires up before landing. Didn't save the tires but was hard on wheel bearings and brakes. Had to use lot of brake to get the spinning wheels to stop before retracting gear.
But how are you solving that problem today? Retracting spinning tires into closed planes today is the same problem I guess.
I was wondering about this for years. Spinning tires can keep spinning inside the body, once retracted. If there is enough space. Small vanes to spin the tires a bit?
@@Deontjie I think small vanes are a good idea. But it does not work with Boeing 737. Tires and vanes are visible. Maybe you just could use special rills ... a profile like a tesla valve. It is almost a normal rill with small changes. This will bring a tire to turn by just using the speed of air (>250km/h). In a closed body they then are able to slowly stop without problems. (But probably they did test something like the tesla valve already.)
Probably tires are generating the moment of contact with the ground that much heat rubber is just burning. Slowing down the speed difference a bit could result in just getting hot tires but no destruction of the rubber molecules. This is science a series of tests should give you better knowledge.
@@Deontjie That is exactly the thing - There isn't space to retract spinning wheels - if you look at a gear well on a plane it is covered in hydraulic and power lines
The brakes are required to be engaged and the tyres decelerated as if they retract a fraying tyre into the well you have now pulled in a circuloar saw blade if you look they don't retract spinning wheels - they engage the brakes as part of the gear up
This increases brake wear as you can't turn off the vanes meaning after take off the wheels will still be spinning up to flight speed when you are trying to slow them to retract
Any vanes attached would need to be sizable to catch enough wind to spin them up - if a manufacture defect causes a vane to break free due to microfractures and fatigue you may have just catastrophicly compromized the plane
Say a wheel has a brake failure? Now you have a wheel runnaway which will be constantly accelerating to the speed the wind allows that you will never be able to retract - burning out the wheel bearings and runing faster until the vanes are thrown off as shrapnel
Finally, you have introduced an unknown variable in the flight controls - The mass of the spinning wheels while in the air generates a gyroscopic effect you can't account for - as the ammount of the effect will vary radically between and approch as you aren't going to be able to guarentee the speed of the wheels - as it's inherently a function of wind speed, altitude ASL and the fact that several wheels are partially or fully occluded from direct wind
This effect will be being added with very little possible control during the late stage of a stablized approch, which is specificly designed to reduce variables for safety
@@bengrogan9710 All very good points I hadn't thought about!
I thought too, that an aircraft when landing is trying to lose kinetic energy (speed), that by landing on stationary wheels a lot of energy is taken from the forward momentum of the aircraft and transferred into the rotational energy of the wheels. So this is a form of braking too, as soon as the wheels touch the ground.
good (overlooked ) point. quite a lot of KE would be transferred to rotational. a/c tires have a large radius (squared) and therfore loads of MI. I imagine theres also a bit of "differential feedback cotrol" in having wheels on both sides of the aircraft - effect like a car differential?
but i think they wont take much energy, considering the momentum of a 65 tonne machine coming at 300kmph.
@@abcdefgh6121 Every meter less in breaking distance is worth - not spinning up the tires prior to touchdown.
I always wondered about this! Great explanation and breakdown about its feasibility!
Also not having the wheels spinning at touchdown generates friction that helps losing a bit of momentum without destabilizing the plane, but rather helping the landing gear to "stick" to the runway. Having them rotating even at the exact right speed would generate some considerable bouncing in the case of a steeper approach.
Hi, thank you for addressing a question I always had in mind. However, two notes:
1) you don't need to match the speed exactly, getting 80% of it would already more than halve the energy lost in the impact.
2) you don't need electrical motors, a set of wind vanes/turbines coupled to the gear axles would do the job. Even if you decided to use motors, you could draw the energy from the APU or engine alternators.
It is true Petter insisted too much about matching the exact speed (when even only 25% of it would be already better than no speed at all), but he ended with saying this is not the main problem anyway. The main problem of spinning the wheels would be when crab-landing.
@@akseli9 Adding motors to the wheels doesn't decrease their abilities in any way. If it's safer, you can not use them when crab landing.
One correction: "Inert gas" means that is not reacting chemically with a lot of other elements while, for example, oxygen reacts easily with iron. It's not about pressure.
Indeed, oxygen gas and other gases (or mixes) follow the basic rule of temperature having a linear relationship with pressure. One problem with normal atmospheric air when it's subjected to large swings in temperature or pressure is that it contains water vapor, which could easily turn into liquid or solid under the temperature and pressure conditions that affect jet aircraft; liquid or solid water in the tires being undesirable for multiple reasons. I assume the process they use to separate nitrogen from air is sufficient to remove all significant impurities including water present in ordinary air.
Not true. The chemistry use isn't the definitive use of the word. Inert just means inactive. So his use here was appropriate.
What are you the inert gas police?
Inert gas must be non flammable is why gas lines are nitrogen purged as well as non corrosive etc
kefsound it’s about not supplying oxygen to burning brakes and tires following an aborted takeoff and consecutive pressure relieve valves releasing the gas rapidly. Every tire is equipped with a pressure release valve to avoid tires “exploding”. The Nitrogen released won’t feed the flames after such event.
I remember a solution to this problem in a P.M. Magazine a few decades ago.
At the wheel there was a cup anemometer like Thing to prespinn the aircraft wheels to reduce the tire wear.
I have been wondering about this for thirty years, I love that you covered it. Also cant believe everyone in here was wondering about the same thing, I thought I was the only one. lol
Me also
Tires are at take off speed on every take off. Most airplanes take off at a higher speed than on touchdown. So the argument of speed on tires is bad is just BS. I suspect paybacks from the tire makers and BS "Studies" by the tire makers too. Corruption.
This was actually tried on the Lockheed Constellation in the 1940's, a motor spun the main gear up to lessen the landing forces, apparently pilots found it harder to tell when they had actually touched down and the feature was dropped as unnecessary.
Plus it added weight & created maintenance issues. The idea sounds great but it was scrapped because it wasn't worth the trouble.
It was actually the Lockheed Constitution - a large cargo plane that never made it into production - that had this feature......
@Ian Brown was done, patented, dropped....safety issues
That's it exactly. Your can't sodding land. The tyres spinning up take enough energy out of the aircraft to stop it flying. Without which it just keeps skipping down the runway.
Actually, this concept was tried on the U.S. Army Air Force B-18, which was different from the B-17. This was probably around 1940. The concept was dropped, as I understand the facts, because little significant improvement in the landing procedure was found, and only a few B-18's were built.
Mentour thanks for all of your work! I am a 21 year old Canadian student in Switzerland, and I became a nervous flyer a year or so ago (even though I have flown about 40 times now). Your videos have made me much more confident in aviation as I understand what is happening.
I also wanted to thank to the Air Malta pilot flying Zurich to Malta on the 7th of November. He did a pa telling us to look out on the left as we were flying over Rome. The view was wonderful and it was a simple gesture that made the passengers even more confident in the pilot on a turbulent flight. It is pilots like him and Mentour, going over the minimum required that make flying such a special event every single time.
Dannick Giguère what’s it like being in the .01%?
Most of us will never fly let alone study in Switzerland, and my wife is Swiss.
Syudo Nem it might be fun feeling virtuous and blasting people online but I am unfortunately not a multimillionaire. I am in studying there only for a year, paying canadian tuition fees. I worked for many months saving up money while doing my degree at home and I live with minimal expenses in a small village so I do not pay crazy rents like in Zurich. Living 10 months in Switzerland plus all of my small travels in Europe will cost me less than 40% of the average yearly salary in Canada (or 25% of median family income).
No hard feelings, I just wanted to reply so you can see that it is not unachievable for most middle class Westerners, when you work hard and find different programs like student exchanges. If you or someone else has any questions, I will gladly answer them, but somewhere else, as this is unfair to Mentour. (It does boost interaction but not the type he wants I guess ahahaha)
Great Video. The video, and it's generated comments answered all the questions I have had since I entered Pilot training in 1971. Thanks!
In 1994, I made this suggestion to the USAF as a way of saving wear and tear on the tires. My idea required no motors. Instead, I suggested either the sidewalls or even the tread include several radial (center to outside) sawtooth half triangle ridges that catches the wind from one direction but is slipstreamed in the other direction. Result: Spin. In short, the wind is your engine, with this built-in turbine powered by the airflow over the tire itself. At normal takeoff and landing speeds, with the wheels spinning at an RPM commensurate with the aircraft's velocity, the additional air friction is minimal. And, YES, speaking as an aero engineer, you CAN design ridges such that the tire spins about about 80% of its forward velocity through the air. The ridges would be minimal, perhaps 1/2 inch high, and molded into the tire itself. The amount of weight would be small, perhaps 2 to 7 lbs per tire.
Answering Bill Witt's objections:
1. wheels spinning at touchdown speed with the tires out of balance would shake the airplane apart
Uh, no, for the very same reason that wheels spun up within 1/2 of a second after landing don't shake the airplane apart. Aircraft break/tire/wheel assemblies are balanced, same as your car tires, though with considerably heftier equipment. Did BF Goodrich balance the tires? Did they not balance them so they avoiding solving the problem thereby being able to sell more tires?
2. In addition, not only spinning the tires but the brakes would also have to be spun up which would require considerable power.
Again, no. While there is slight friction with the brake when the pressure is off, it's minuscule compared to the friction when it's even partially engaged. Furthermore, the inertial momentum of the brakes is a small fraction of the inertial momentum of the wheels and tires. Your 727 incident was the result of multiple stops from high taxi velocities, not from the mere act of taxiing.
3. Nitrogen is used to prevent the tires from exploding...
While true, that point has nothing to do with the issue of spinning up tires prior to landing.
4. The gyroscopic effect of spinning tires would also adversely effect trying to control the airplane during a critical time of landing.
Absolutely not. We not talking about a lightweight bicycle with a comparatively large radius wheel. We're talking about a large aircraft with a comparatively small radius wheel. The gyroscopic forces resulting from straightening the aircraft from a 20 degree right crab (rather large!) to straight down the runway, would only very slightly tilt the aircraft to the right, which actually counters the far larger left tilt induced by landing in a right crab.
It's feasible. It's unlikely tire manufacturers would adopt this for one simple reason: They would sell less tires and retreading services.
Sounds wise from every point of view, and just spinning up the wheels to 50% of normal rotational speed at landing would lower the wear a lot. Using bleed air to spin the wheels off could also cool the brakes, I guess.
as for your idea that wheels don't vibrate because they are balanced, yep when initially fitted they are but after use they can become out of balance, or shed a weight or...
These aren't as you say bicycle wheels, we are talking about a wheel up to several feet in diameter and a mass of several hundred pounds, in the case of a 747 there are 18 of them all spinning at various rates, why take the chance of spinning them up to high speed at THE critical point in the flight.. landing.
Spinning the brakes up.. brakes often bind quite hard so that wheel might be slow giving different forces than the others, why bother taking the risk for something that might only last one landing, you've probably seen the video of landings where they hit one leg first then slam the other down while the aircraft is sorting out which direction it wants to go, tyres are worked hard. As someone else said there are some aircraft where various systems may be initiated by the wheels spinning up to speed, like the brakes for instance, spinning them up early puts the brakes on before you land. Spinning them up is of course possible its just pointless.
~$1500 per tire, thats amazing, some luxury car tires cost this much. To me this was the most surprising fact
Bugatti charges ~U$20,000 per set for the Veyron
Standardization and big batches.
Car tires cost more because they are all custom made with lots and lots of different sizes and treads and compounds.
For one model of aircraft they essentially make a ONE SIZE FITS ALL tire and that can even go across a whole series of models or even a whole brand.
He said 15 000 per tire not 1500.
@키코kiko: That's not just the cost of the tires though. It's true that Bugatti charges that much but that includes picking up your Veyron from your home, flying it back to the factory in France for a full service of all the mechanical stuff, changing all the all oils, fluids and of course the tires, before delivering it back to your home. The tires themselves are only a small part of the cost.
@@niconico3907 Wrongo Wrongo
As an Aircraft Maintenance Engineer, I appreciate your presentation.
And just imagine the accumulative complications (parts, labour, inspection time, something more to ground the airplane!) going into just saving a bit of rubber to speed up wheels that you will be using energy to slow down right away anyway?!? Lol.
Small flaps like in ww2 would do the job
On the other hand if you mount electric motors on the wheels you could use them to charge the batteries onboard, and decelerate the aircraft at the same time! Using bleed air is probably much simpler. and just speeding up the wheels to 50% of normal landing speed would decrease tire wear a lot.
@@ErikssonTord_2 Electromotors are heavy and you need a lot of them. Also you need a large battery storage. And big batteries and planes don't go well together.
@@KneppaH what do you think the motors and batteries would be used for? traveling in the plane but on ground? how heavy do you think a motor and a battery needs to be to spin a wheel a little bit?
@@KneppaH no they are not. Jaguar has 350hp electric motor that weighs 16kg. The weight of a fat cat is not heavy
A friend of mine in High School wrote to the Air Force asking this same question for a Science Fair project he was working on in 1976. He wanted to spin the tires with a DC motor inside the aircraft before the landing gear was extended. They replied that they did not want the gyroscopic force to affect the aircraft's landing maneuvering capability in case of conditions other than a standard landing.
Jim Sim... thank s for answering a question I have had for over 42 y r s . I didn't consider adverse effects of inertia . This video explained it all .
Citations had this decades ago. There was an accessory spin-up kit used to reduce the stones thrown up when operating on remote dirt strips.
Just skip to 9:30 when he actually starts answering the question.
thanks
Thanks!
Thank!
thx mate
he is just busy pumping up his ego.
Nicely explained with additional info,thanks brother.
13:46 is the point for me: I thought about "why not change the rims, so the air spins up the tires before landing". Until you come to the point about crosswind landing. Thanks for pointing that out, 'cause everything else was more or less obvious, like "They would have done it if it would be cost efficient".
Back in A&P school (c.70's), one of the instructors claimed that Boeing had briefly piddled with gear spin up systems for the B-52... but abandoned the study when it was found to be much more trouble than it was worth. Also, I'm pretty sure one of the primary reasons for Nitrogen tire inflation is in the event of a wheel well fire, and wheel overheat 'fuseable plug/s' blow; it will be inert gas expelled into the wheel well as opposed to air containing Oxygen. (Just the other day I noticed a gas station offering Nitrogen for car tires... IIRC they were asking something on the order of $20.00USD!)
My father told me the exact same thing. He retired from USAF/SAC in 1965. Did not effectively extend the tire life cycle to be worth the bother.
Main reason for using nitrogen is to exclude moisture which stabilizes pressure over temeprature (nitrogen pressure will scale linearly with temperature while humidity can condense and evaporate and add a nonlinear characteristic over the service temperatures). The exclusion of oxygen is a side benefit which helps keep the rubber supple longer
Did you have to use 2 decimal places on the price? I read it as $20,000 with U as another 0.
My father who served in the Army Air Force durning the latter part of WWII as a radio operator on B29's flying missions over Japan, told me about another assignment he was on durning that time. He had crewed on a bomber (I don't remember what type) that had, for experimental purposes, been modified to spin the wheels up for landing, he told me that the gyroscopic effect of the spinning wheels made the airplane very hard to control durning approach and a good landing very difficult, (he might have said nearly impossible).
Thank you for explaining this issue so perfect !
FANTASTIC... I'm just about to watch this,.. only saw the first forty seconds but this is what I have been thinking for years. "Why not pre-spin the tyres... I'm about to be educated.. 😊go for it ".
AW NAWWW... So disappointed my idea was rubbish😪.. But I now appreciate the reason behind it.. and having read a comment from Bill Witt below he also explains the reasons.. big respect to you both.. Passionate in what you do and I daresay BOTH mechanically minded..👍
Thank you for addressing this issue. I pitched a REALLY simple air scoop design to Lockheed back in the 90´s that would spin up the tires at or near TAS on landing to help save the treads. They were not interested but never explained why. This video helped put that to rest. I did not realize that tires were so inexpensive and also we get the added benefit of having really good traction at the touchdown point!
All I can say is Great Mines think alike.
@@cvhawkeye6255 Yes. They all produce gold. (See what I did there?!)
@@ananda_miaoyin Sorry for the typo! Greater Mind! All Good.
@@cvhawkeye6255 I thought it was a brilliant play on words, if even by accident!
Thank you for explaining this. I often wondered about this. My idea was to create a RAT (ram air turbine) that comes out when the plane is landing to power a small motor to spin the tires on landing. The tires would just begin to spin 'freely' not in a motorized and controlled manner as to allow for crabbing, different speeds
Thank you, that was great, including the pitch for a filmmaking course.
I don't know why I didn't ever look that up, even though i have been asking myself why not spin the wheels for over 20 years!
Thank you for being on here and explaining things as u do.
Very interesting, some of these explanations I haven't thought of myself. I'm actually working in the aircraft tire business and my answer on this question is that you would not want tires rotating at those speeds on a landing gear when they are still in the air because of the centrifugal force and the unbalance these tires accumulate during use.
Air is around 78% nitrogen and rest of the gasses expand pretty much with the same rate. I think the more important part is to get all moisture out since steam tends to expand much more. Also probably good to have oxygen out since it can probably react with the tires and maybe even make small difference in case of an fire.
Also the tread on car tires is just for aqua planing not for any cornering stuff. The less you have pattern on your tires the stiffer and better they are on cornering. That's why you don't have offroad tires on track cars.
How has a comment from a channel with 2M subs been able to go 9 months without a reply? lol
you are correct. When working in the wheel shop the tires are inflated to pressure using normal shop air. However the shop air must be 100% free of moisture. We use helical air compressor with gas fired air dryer. Now the easiest way to add air in the line environment is to use nitrogen bottles. This guarantees moisture free air.
Also the more rubber on the ground the more traction you get as I understand
Good points. His understanding of physics is a little rough around the edges.
The use of nitrogen became law in FAA Airworthiness Directive AD 87-08-09. It requires that all transport category aircraft braked wheel tires contain no less than 95 percent nitrogen or other inert gas. The inertness of nitrogen has nothing to do with its physical properties. It expands and contracts with temperature just like any other gas. The required inertness is chemical. The AD was issued upon a report of a Mexicana 727 (flight 940) that crashed after having taken off with a dragging brake. The heat decomposed the tire rubber into flammable compounds, which combined with the oxygen in the tire to cause an internal fire and subsequent tire explosion. Google Mexicana flight 940 for details.
Very informative, thanks for sharing.
Bill, you've pointed the main reasons ,thank you ! and Captain you've explained it from the economic part very good ,thank you !
I only just realized the red pillow on the port side, and the green pillow on the starboard side of the couch...
Right because the dude with hard accent is an aircraft.
Is that with respect to the viewer, or the pilot?
Sean Whelan
There is a white tail pillow but you can’t see from here.
I freaked for a second when the pillow in the left background moved.
ha never noticed :)
0:56 Even this dog is sick of hearing Skillshare ads
Best comment of 2019!! xD
Yea, those major airline pilots barely make ends meet! He really has to do the paid advertisements in his videos to help pay the bills...
Just double click a few times on the right of the clip and skip 30 seconds a few times.. Skill share problem gone in two seconds and pilot still gets paid for the ad.
@@pickyourday joke mate chill out
@@pickyourday honestly, that is a positive joke to uplift people
The spinning up of main gear tires was tried on the B-36A which had enormous tires that were just over 9 feet tall. It was found that the initial touchdown caused an immediate drag on the airframe caused by the energy expended to spin the stationary tire which shortened the landing roll by a tremendous amount. The spinning tires resulted in very long roll out and excessive breaking being required to counter act that initial touchdown drag as well as stopping the inertia of that huge spinning tire. The spring gear on larger aircraft like the 747 result in, not only a smother, more cushioned landing, but also extends that initial drag portion as the tires contact the runway at different times. Also, the large spinning tires on the B-36A caused a gyroscopic effect that caused control issues when trying to change directions on base or final approach.
Well explained. Crystal clear. Thanks mate.Its been educational 👍
Great video Mentour I enjoyed watching it, have a fantastic weekend my friend.
You get feeling there would be less accidents if all pilots had the deep interest in their craft that this man has.
Not just a feeling
he has it so he can share that info with people like you and i
You do know that every pilot is risking their own life too every time they land, right?
You mean “even less accidents”.
@@alfeberlin Well, ACKtually, he means "even fewer accidents."
Extremely interesting video on a subject I never actually thought of until I got the recommendation from RUclips.
It's not often to find as enjoyable a video which is also as informative as this one, thank you for posting.
Thanks for an excellent explanation. I'd often wondered about this.
No need for motors, use the airflow which is freely available.
I remember that some 20-30 years ago a young girl suggested small flaps on the wheel in a youth competion ....
@@robertlaudensack376 tire industry is too powerful, i guess
@@robertlaudensack376 I heard 25 years ago that a patent like you describe was filled but immediately bought by a tire supplier and hidden. (Little curved blades or grooves on the rim that spin the wheel at high speeds)
Two problems. He mentioned that when landing with a crab angle, if the tires were spinning @ 200mph they would tend to push the aircraft in the direction of crabbing - towards the side of the runway not down the centerline. Could be dangerous. But probably most importantly, the fins would cause drag on takeoffs also, not just landings. That's potentially dangerous. If the fins were adjustable and made not a factor on takeoffs, that adjustable mechanism would be a potential point of mechanical failure.
Joe Sternhagen in my opinion angle landing with spinning tires is a negligible problem when you take the torque energy of small spinning wheels agains the linear Momentum of a 65+ tons Airplane. The second mentioned concern about the extra drag on takeoff doesn’t barely apply as the wheel spin on takeoff anyway and then soon disappear in the gearboxes.
Think outside the box folks and turn on the logic ;-)
One correction here: The pressure of nitrogen changes with temperature exactly as much as that of air (p*V=n*R*T).
Yeah I caught that too was gonna say the same thing :)
Air is 78 % nitrogen anyway.
pV=nRT applies to "ideal gas" which is hypothetical construct, not something existing in reality. "Real gas" is affected by multiple factors ideal gas equation doesn't consider, including various reactions on molecular level, compressibility of gas (or gas mixture as it would be in relation to air), varios molecular forces, and thermodynamics of it all. In other words pressure of pure nitrogen and nitrogen/oxygen/argon/CO2/various trace elements mixture (AKA air) do change differently with temperature. For most application that doesn't really matter mind you, ideal gas equation is reasonable approximation, but that doesn't make your statement any more true I'm affraid.
@@maciejkornatowski3026 actually, every element in gas form expands in the same way
@@maciejkornatowski3026 Oh my, I knew there was going to be someone pointing out that ideal gas is just an approximation. I know that. Nitpicking aside, the ideal gas model is absolutely fine for the point I wanted to make.
Amazing information. Well explained and in essence, common sense. A simple yet complicated problem with a basic yet complicated answer. Cheers for your great explanation.
I wondered about this when I was 8 or so watching 707s and 747s on 1970s TV landing. I forgot about that until this video at at age 56. I understand that many farmers buy old aircraft tires for implements that usually outlast the implement.
I remember seeing information about aircraft tires back in the 1960s or before. The information regarded spin-up on the tires for landing. The "fix" involved the addition of flaps on the tire sides. When the landing gear came down the flaps would engage the air and "Balloon out," causing the wheels to start spinning. The flaps would opening out only on the front bottom quarter to part of the aft bottom quarter. I thought the flaps were still incorporated in tire design to this day but wondered why they still smoked on landing.
I'm a Crew Chief in the USAF and I've been thinking about this question for quite some time. Thanks for the video and the explanation!
Crew Chief. Respect. However he just explained nothing to you or I. Ask yourself this. Has Boing Aircraft asked this question? Yep. They actually have. It is in the math that we don't spin tires. Hello Democrats.
Interesting. I wouldn't think they'd need to match the speed but have some spin. However er you're explanation of the difficulties and dangers makes it make a whole lot more sense why that's a bad idea.
Nice question. I thought about little flaps that spin the wheels with the landing air flow. Also, listening your reason about the landing in angle, i figure out that the flaps must give less speed than the landing one. It´s a passive way, without any complicated mechanism.
Tires are cheap numbers, but in my budget is the ingenuity the one that put the rules hahaha.
Thanks for all the great content of your channel, cheers!
Thanks so much for this explanation, I have always been shaking my head when I see the excessive amount of rubber on the runway touchdown zone and the smoking tires.
Regarding the accelerated wheels on landing ... you could use some modified standard gear that doesn't need electrical energy, you just had to change the algorithm of the anti-lock break system.
You could create a cast aluminum wind-shovel profile that is also working as a rim heat dissipation spreader that has a specific shape which accelerates the wheels by the ambient air pressure towards the RPM it needs to match the ground speed. The RPMs can be synchronised shortly before touchdown by the general braking systems anti-lock control by slowing the faster one down to equal RPMs. Since the wheels are turning with no load and you may let the gear down at maybe 180-130kts? (=333-240km/h) you should have plenty of ambient air pressure to be able to accelerate the giant wheels under no load to higher RPMs if using the right volume air-shovel profile in your rim-extensions. I have no clue if you could even get the tires up to near landing speed within the maybe 2 minutes while gear down, but e.g. 70% RPMs would already reduce your tire changing interval by a third while having much less tear and wear on the asphalt and a smother touchdown experience for the passengers. Even if the tires are not very expensive, the maintenance work, time and adjustments are summing up and this may be an relatively easy implementation. The breaking energy on the runway will be slightly higher but the heat that may be conducted from the brake disc towards the rim will be dissipated immediately from the air-shovel shaped aluminum rim extensions/cooling fins. So in other words if you can make these rim extensions in a shape that can be fitted into the regular gear box, the only thing you need is a modification of the autobreak circuit that has to equalize the RPMs with no load just before touchdown. Because some wheel might be running more freely than another, there might be differences that you don't need when touching down. No electric engine or high current wires needed, no extra RPM control sensors and mechanism ... just the air-shovel-rim extensions and the modification of the autobreak circuit!
What do you think, bullshit or does that idea have a possible future?
he already said that changing tires on airplane cost pennies compared to other maintenance and running costs.
The autonomous electric tugs is a good idea, I had it as well 😅. How much time would the engines need to warm up and show check readings showing that everything would be OK before takeoff?
Also, if tugs were big enough they could provide APU power, for the AC and all other systems. To have AC you would need compressed air. That could give you startup air to start the engines. This may sound huge but it would be a significant step for electrification of aviation. Tell me about your thoughts if you happen to catch this comment.
Well-done with the channel.
It sounds good on paper but aircraft needs the APU on board as well to have it there in case of emergency to keep power for flight instruments and create pressure for engine start up if air flow is not enough. You could use tugs to make the pull and have jet engines just idle and warm up while going to runway, not taking extra fuel to actually move the plane, this would also remove some break heating up if tug can provide braking forces on the ground, but to have them fully autonomous is kinda bad idea in my mind. Much rather have mentioned remote control by pilots and then ground operator takes control of it to get it back to gate. Having it being autonomous would cause dangers of thing deciding to just wroom on the runway while plane is coming in or stuff like that. There needs to be very least human operator supervising them even if its remotely, but even after that there must be system in place where by cutting power it can roll freely if there is no plane attached and another drone to be able to tow it away in case on malfunction all with in minutes to clear the paths. There is good ideas to this, but its needs further development to iron out any issues that can rise from it. For electrification of aviation... maybe when batteries can hold much power as fuels we use today. Electric systems are always bit iffy and i would not trust them specially in planes. EV's as ground vehicles, maybe, but even that is pretty horrid idea.. If you have seen how much effort it takes to extinguish EV fire... now add tons of fuel to that... then add row of 737's next to it.. yeah that is bad bad idea...
@@Hellsong89 further to your comments if you had a tug to tow the aircraft to the end of the runway then needed someone to return it to the gate you would need a tug and driver for lots of aircraft as opposed to one guy doing a quick push back then moving to the next plane, plus some of the taxi distances are pretty long and aircraft can end up in queues at the runway, so once again it would probably end up more expensive than a few thousand/hundred pounds of fuel, and would be far more complex to organise.
Certainly one of the best communicators on the internet as well as holding our interest what a treat.
Very well explained, thanks Captain Sir.
I would also think the inertia of the plane being transferred to the tires once the plane hits the ground is also partially a braking technique.
In ground tow ropes like they use on aircraft carriers could work for warm airports.
molding scallops into the sidewalls could act as vanes to help spin the tire when in the airstream.
I don´t thik the passagers would like arest wire landings. It´s kind of brutal. i read it´s like going 110km/h in to your driveway and make a compleat stop before you hit the garage wall.
The polar inertia of the landing gear is probably insignificant to other circumstances that make landing unpredictable.
@@exploatores There's no reason you'd have to have a brutal arrested landing, you could specify any amount of time or distance over which to reduce the speed. The wire may be impractically long though. :)
Thank You @Mentour pilot! I waited answer to this question for so long :)
Yet he didn't answer the question. The answer is the cost of the system is more than the tire use.
@@a787fxr actually he did mention that and also crab angle.
I have been thinking about this myself for a long time, so thanks for covering it. My idea was always, rather than having actively driven wheels, why not have them rather just spinning passively to a certain speed, using the natural air resistance. My idea would be, fitting the side of the rim with some sort of fan blades, like used in water turbines. As soon as they are subject to the air resistance, they would start spinning automatically. Would be quite fail save, as not using power, would not interfere with the navigation/direction, etc, just take away some of the tear on the tires during touch down.
I had basically the same idea about using the airflow to spin the tires many many years ago then I learned about gyroscopic forces and how any force applied to a gyroscope will result in a force 90 degrees in the direction of rotation.
@@OpusBuddly if a puny motorcycle engine spinning backwards (normally they spin forwards) changes the handling of the motorcycle so much as to be VERY noticeable, imagine the gyroscopic forces all those enormous wheels will create. All in all a very bad idea.
Good post but only the tip of the iceberg so to speak. What are all the issues1-Out side air temp. is -50 degrees F and the bearing grease is solidified. Fix with preheated lube oil at 50 degrees f with seal by pass and circulate with a small air turban pump.and pencil heater. Install push back springs in wheel disc brake cylinders This will help in free spinning. Wheel spin up via Pelton wheel hub caps and or tire cups in the moldings. Pilots can apply breaks until just before touch down to deal with Giro effect in cross winds. This is somewhat of a copy I use on Boat Trailers to prevent water intrusion. Pat pending?
dellori3
I have discussed this with a commercial pilot I know and he agrees this could work. The speed that would be achieved by rotors wouldn’t be as fast as the plane was travelling, in fact nowhere near as fast, but they would very much reduce the impact speed and tyre stress. The wheels are heavy despite the materials used and giving the wheels kinetic energy is like racing cars flooring the accelerator from a rolling start as apposed to a standing start, it’s difficult to get wheel spin from a rolling start! Speed of the wheel’s rotation could be controlled by computer slightly touching brakes to provide even speed. The centrifugal forces of the wheels would be minimal, given the weight of the plane.
When I trained as a Performance Engineer at Boeing, they said that only 10% of a tire's wear was on landing. Most of the wear and tear is taxiing, for example on an aircraft with walking beams. The tires don't want to turn and get scrubbed on all the turns.
The tires are filled with DRY nitrogen. According to the gas laws, the pressure in the tire will be mainly effected by temperature, as would any DRY gas.
I did fly an airplane that used bleed air to spin the nose tire. Citation II with a gravel kit. The idea was to spin the nose tire up before landing on gravel to prevent the nose wheel from spraying stones into the engines on touchdown.
A lot of airplanes apply the brakes automatically after lift-off to stop the tires from rotating before they are retracted into the wheel wells.
Most large aircraft have temperature monitors on each wheel and takeoff is not allowed unless the temperature is below a certain value so that so will have full rated braking available in a rejected takeoff. RTO. Becomes quite a problem if you have carbon brakes as they heat up very fast if you touch the brakes.
Hi.
I would add physics into the equation. The tire smoke shows a transfer of energy. In order for the aircraft to continue down the runway, it has to get its wheels up to speed very quickly. While this is occurring there is a form of resistance to the forward motion of the aircraft, therefore static wheels are another form of braking.
Pre-spinning wheels will add forward momentum - same as stepping off a travellator, the people who were standing, letting it do all the work simply step off. The people who were also walking on the travellator step off at a much faster pace. That's because your combining two driving forces in the same direction and not having to get your legs up to speed
The braking force is insignificantly small for a static wheel. We are talking a 80 tonne aircraft against a (what? guess) 250 kg wheel. Even when you multiply those wheels by six you only get 1,500 kg which is but a fraction of the total mass of the aircraft. And they will not be a constant stopping force as they start spinning rather quickly.
From the wheels perspective however... They are literally SCREAMING as they touch the ground.
Thats remould of the tyre, that is not what mentour means by retread. Retreading is using a heat cut and cutter to cut the groves in the existing tyre deeper. I've done this on lorries.
@@RealCadde
I know a static wheel isn't going to provide all the force necessary to slow the aircraft down, but every little helps!
I also know this isn't happening by design, more as a by-product of the reasons mentioned in the clip
@@miyahollands6136 You have a point. I see it now. Having pre- rolling tires would make the plane more tricky to stop since it will need more runnway.
@@GeordieBoy69 No, they're not cuts added to the tire. A retread for aircraft involves trimming the tire, then melting new rubber onto it. It is then placed in a hot mold to create the new tread.
6:20 They use nitrogen because air contains water, which can condense and evaporate which changes its volume by a factor of ~1000, and sloshing water (worse yet fumbling ice) can upset tire balance.
Mi 28 and regular air contains oxygen which in combination with moisture is a very bad thing to have in an area that can’t be inspected regularly. Nitrogen is inert and contains no oxidizing agents. That’s why we use it as a shielding gas for welding.
snee regular compressed air is also non flammable so that doesn’t seem to be a necessary argument. The second part of your response is what he explained in the video so good job
They use nitrogen because the FAA requires it to eliminate the possibility of explosions. From the FAA:
"This amendment to the Federal Aviation Regulations (FAR) requires that an inert gas, such as nitrogen, be used in lieu of air, for inflation of tires on certain transport category airplanes. This action is prompted by at least three cases in which the oxygen in air-filled tires combined with volatile gases given off by a severely overheated tire and exploded upon reaching auto-ignition temperature. The use of an inert gas for tire inflation will eliminate the possibility of a tire explosion."
Andrew Snow I think commentors on this thread are saying the same thing. Water in air freezes. And that causes problems that pure nitrogen doesn't have. The FAA requirements are based on simple physics, as well as accidents.
George W there are also a few that seem to be confusing explosions(needing a fuel and oxidizer) with rupturing(due to altitude change) nitrogen doesn’t expand at high altitude as much as compressed air. A ruptured tire in flight could cause an explosion just simply because of is location in the wing box.
this is one of the topics I´ve been wondering myself about for years. And I still can`t except the explanation your are giving us. It is like saying, that it is better for the tires to touch the ground with no rotation at all at the moment of touchdown versus having them rotate at least somehow near the real landing speed. I was always wondering why not give them at least some sort of rotation in advance bevor they actually touch the runway by for example having some sort of flaps or propellers attached to the axis of the landing gear that would make them spin in the wind in advance? It must not even match the real speed of the touchdown, but anything bigger (faster) than from zero to lets say 120 m/h should reduce the wear of the tires. I do understand the problems that would come with trying to get the tires rotating at the exact landing speed, but still, if you would be landing at for example at 120m/h it still should be better if the tires are allready rotating at for example 100m/h than touching ground with zero rotation. Most likely I just don`t get it, but....?🤔
Ive come to like the videos you present based on various questions from curious youtube viewers. this keep my interest in aviation at a peak though i pursue model hobby trains. the presentation of facts of airplane problems and crashes are of high quality in reference to Natgeo's aircrash investigation series which are good in their own way so for me to link the 2 different views and angles makes for great viewing thanx for bringing this highly interesting channel to us.
I've always wondered about this topic..thanks for shedding light on it.
One comment though..you've been using a 737 as a reference point in some of your examples so I'm assuming you were referring to a 737 when you mentioned an engine costs $12mm (I'm assuming you were suggesting a full performance restoration). A complete overhaul of a CFM engine would cost between $4mm-6mm. So, if you're saying it would cost $12mm for a pair of engines that would be correct..but not for a single engine. If we're talking about 777, 787 or an a350 I would agree that an overhaul could be well over $10mm.
Note: I buy/sell commercial aircraft & engines for a living.
I really enjoy your channel..please keep it up!
Also, the energy dissipated is helpful to slowing down!
Why not spin them backwards then!
That's actually a good point. Tires spinning at landing speeds would indeed increase the landing roll.
No it isnt. The less tyre slip, the better the braking performance.
Great video. Interesting questions.
Adresssing the problems:
1. you could use bleed air to accelerate the tires. The bleed air can be regulated until the terminal speed (= matching ground speed) is reached. No Batteries, no cables are needed.
2. measuring the ground speed: in order to get the current ground speed, the system can start when the ground proximity system calls out 10 ft. When the deviation angle between the aircraft axis and the velocity vector exceeds a certain amount, the system gets inhibited. The ground speed can be calculated by the difference of vectorial true airspeed and gps/irs ground speed, backed with an optical speed measurement system (like in modern drones or optical mice) as a redudancy backup. When getting contradicting values => inhibit the system.
3. safety: if the fms doesn't forward proper values to the system, it's operation gets inhibited.
4. landing distance calculation has to be done for the worst case, so it doesn't matter if the system is operational or not.
This is perfectly doable without any safety risk, when performed correctly, and it's much easier than engineering adventures like MCAS. However, it might not pay out. I agree in this point.
Draw a circle (this represents the rim). Now, divide that circle into 8 equal parts (these lines represent wind vanes). Next, shade the top half of the circle (this represents the shroud or fender). You should see where the air will be rushing by the rim and where the rim is shielded from the air rushing by. Once the gear goes down, the wheels should spin up to speed (or close to it) in the correct direction because the air forcing those wind vanes to move the wheel in one direction.
I had the same thought years ago, and even built a prototype with the blade from a squirrel cage fan mounted to the rim of a small tire.
I then tested it using my truck at 60 mph and it did indeed spin up, I dont think it matched my ground speed, but would have reduced the burn patch of the tire considerably.
I also thought of adding rubber vanes to the tire sidewalls themselves.
The one thing I didnt think of thats mentioned in the video, is how the spinning tires affect the crabbing maneuver.
Great minds think alike, even if not successful it can lead to huge innovations.
Keep that brain gearbox, well oiled
@@scottk6659 I take my lion's mane mushroom extract every day...or I would if I could figure out how to open the bottle.
Most aeroplanes do not have shrouds or fenders around the wheels, the Canberra had a shrouded nose wheel but that was to reduce stuff getting thrown towards the engines. A few GA aircraft do have guards around the wheels but most military and civil aircraft don't. Once again it is adding weight to the aircraft and its simply un-neccessary, even on the GA aircraft with guards they are more for aerodynamic effect on fixed undercarriages.
@@scottk6659 Absolutely agree. This seems like a no-brainer. And I think you could approach the actual landing speed by planning the geometry of the wind vanes. Even if it is half the landing speed, that would make a big difference in the stress and wear on the tires. If the vanes are built into the wheel, it would probably cost very little.
I have a suggestion. A simple retractable blade on the edge of tire (few blades per tire) would spin tires with outside airflow. They will not reach full speed but partial speed is enough to reduce wear and tear on tire. It also has another advantage. i.e. it will help in breaking as it provides additional air friction due to landing. This will make breaking relatively easy and less taxing on actual breaks. On the take off, simply retract these blades and take off with normal tires.
The blades would not be too big. Just few inches to side of tires (like ears).
It appears to be a solvable problem
damn - that was my idea decades ago, but with a small permanent feature on the tyres. I knew I should have patented it :)
How would you build a mechanism to retract these blades into a rubber tire that has 200 PSI or pressure in it? I can imagine it would require multiple holes in the tire which would seem to add a huge risk of tire failure. Would you make this mechanism something that is purchased with each tire? That would seem to add to the cost. Removing and reinstalling would add cost too. And whatever mechanism would have to be taught to withstand the tires flexing, and would also have to survive some huge centrifugal forces as the tired rotated at landing speed.
I may be missing your point though, if so, the idea sounds interesting absent a few problems.
Until you're retracting the gear after takeoff, when you want the wheels to have stopped spinning...
Another very interesting and enjoyable video! Thanks 🙂
You are very good at explaining difficult subjects
This question bothered me for YEARS. And even after tracking down the answer, my brains still resist it. It just feels so counter-intuitive. I used to imagine having paddle-blades attached to the sides of the tires, so no heavy motor would be needed, it'd just use the drag of the wind resistance to drive wheel rotation in preparation for landing.
verdatum it’s the same for me too, it’s kind of hurting my braid
I'll never accept it lol
But where would paddles go when wheels are retracted?
@@flyingark173 they'd remain parallel to the wheels at all time. The orientation relative to the wheels and the diameter of the turbine would be designed such that there's no chance of them scraping the tarmac, no matter how much the wheel is compressed on landing.
@@flyingark173 in the same place as the wheels??
Maybe the doors would need to be a bit wider.
My father, who was an aircraft mechanic on CV-33, said that some gear had a Pelton-wheel like turbine, that would catch air and pre-spin the tires before the controlled crash that was to come. Not sure about the details, but I remember him talking about it. Probably important in the early naval jet-age to maintain velocity in case they had a bolter.
Reading through the comments below regarding vanes etc. on the tyres/hubs to spin up the wheels using airflow I have the following observations -
1. The landing gear is down for landing far, far longer than after take-off. Therefore the extra energy imparted to spin speed after take-off and braking to stow the gear would be negligible.
2. Out of balance wheels spinning before landing would be just as bad after the first touch down and trundling down the runway for take-off.
3. The gyroscopic effect of the spinning wheels has to be overcome after the first touch down during a cross wind crab landing. If it can be controlled after the first bounce it can be controlled at any time..
$. I can see the 'vanes' being built into the tread design. The spin up speed can be very gentle and the terminal speed can be less than touch down speed as any spin is better than no spin. If the spin speed is too much there is always the brake to slow it down
Excellent idea. I can think of a patent to solve this problem but I am sure others will come up with the solutions sooner or later. Thank you for suggesting these cost saving solutions.
Another thought, if they are spinning you get less friction on touchdown. It may actually increase the landing distance.
I would think that would be the case, my seat-of-my-pants feel is it would not be terrifically significant. I certainly could be wrong.
Static friction is higher than dynamic friction. You get more friction between the tires if they are rolling along with the ground than skidding along it. This is why we have Anti-lock Braking Systems in cars - to stop the wheels locking up and skidding.
@@AtreidesOne0000 In cars it also helps with control while braking, as a sliding tire does not steer effectively (if you have driven cars without anti-lock brakes on snow or ice you are probably familiar with this).
You don't need a motor, you just need to add some shapes to the side of wheels so the airspeed will spin up the wheels for landing. And you don't need to match the airplane's speed. If you speed it up a little bit, now you will have less smoke and the tires will last longer and that is something.
I like the way you think
During WW-II many of the tires on the larger bombers were made with small flaps facing forward in the sidewall at the bottom of the rotation to use the airstream to start the wheels rotating before landing.
@@JimForeman so it's has already been done?
I guess it will add a lot of drag, thus making it harder to take off?
@@HenrikOlander But less wear on the brakes during landing.
Nitrogen doesn't have any special properties/stability with respect to temperature, or loading. it simply doesn't react chemically at normal temperatures. Love your channel!!
I love that you covered spinning the tires on a landing
Another factor: Anything that increases dry-weight decreases usable weight
1: Simple is better.
2: Don't fix what isn't broke.
3: Rubber is cheap.
3: Rubber is cheep. Only because of modern day slave labor
"if it ain't broke, don't fix it" must always be balanced with "there is always room for improvement".
Aldis Berjoza The guys to work at these plants are union and get paid fine.
@@mog882 "The guys to work at these plants are union and get paid fine."
He isn't talking about the guys at the tyre factory, but the ones producing the latex. They are commonly suffering.
Nothing beats simplicity
Back in the years just post WW2, piston engined aircraft (eg. Douglas D6B/Lockheed Constellation) were the large airliners, consideration were given to airflow (post gear down) airflow enabled 'spin up blades' fitted to each wheel. Many runways were shorter then and the braking effect on touch down was not deemed worth the braking effort and costs incurred. Some braking effect was noted, but it just wasn't enough on a cost to benefit ratio to fit aerodynamic 'spin up' tyres.
I worked in a military aircraft wheel and tire shop. the b52 tires were inflated over 700 PSI so that 8 of them could carry the weight. A fully assembled wheel for a b-52 was ~ 775lbs and we rolled them around every day inflated and deflated.
When I was a boy I often wondered about that... Do the wheels spin (or not) before landing?
Thanks for the confirmation. Brilliant idea on the Jetliner "TUGS"
@Ummer Farooq They would likely burst or the plane would slide off the no stability.
I always thought a tiny bit of rotation would make a big difference, like if the tires were rotating at 2 or 3 mph. That way there's less of a jolt on the tire taking all that weight from a dead stop. You could have little windmills on the tires that get them to spin up a little.
As somebody trained in physics and engineering, I'll can say this intuition of yours is wrong. The amount of energy to be gained and the time available to accelerate means it's essentially just the same as landing that 2 or 3 mph slower.
the idea of spinning wheels came to my mind and I searched about it and with this video I agreed that this thought can be more costly and not deficient to maneuvering the plan during landing. Then I thought about having one wheel on each side of the plane which can touch the ground first and this wheel can spin the other wheels on its side with the same speed before touching down but this thought can be also a big project or even more costly or maybe with some disadvantages . SO I want now to think out of the box a little bit with another thought which planes can touch on a wet surface only on the area of the touch down of the runway to reduce friction and heat which can save the tires from ruining in a short age. I appreciate any comment
I appreciate all the videos of the Mentour Pilot. I love them a lot in spite I am not a pilot but I love aviation
My 2c
*Re electric tugs to save 200kg of fuel used for taxiing: The saving is minute, as a large jet might used 200t of fuel for a flight. ie 1000x as much. To save that, you would have a fleet of very expensive tugs driving all over the tarmac, potentially getting in the way. I am hardly a seasoned traveler, but even I have been in a queue of 15+ aircraft at a large airport, which would mean 15 tugs. Or more. And you still burn the 200kg between landing and the terminal.
*Re bits of tyres on the roads: Car and truck tyres do not burst due to pressure either, and seem to be constructed the same as aircraft tyres. The debris you see on the road are the de-laminated treads of truck tyres, which are essentially bonded to the carcass of the tyre. Tubeless tyres do not 'blow out', as the 'blow out' from yesteryear was due to instant deflation of the inner tube. Tubed tyres go flat slowly, normally due to a screw in the tyre, then drivers drive on them flat, which overheats and physically damages them, THEN they disintegrate catastrophically, which some mistake for a 'blow out'. Yes, if you drive into a kerb, or a brick on the road, they could 'blow out', but then again, so can aircraft tyres. Just ask Concorde.
*Re car tyre treads. In all tyres, tread patterns are solely to evacuate water, and in dry conditions detract from grip. Of course, part of the pattern might be advertising flim flam, so let's not forget that possibility. But car tyres are constantly on the ground, are subject to lower forces, have to evacuate water and grip while subject to lateral loads, and no doubt have additional differences in application vs aircraft tyres. My assumption would be that aircraft tyres would benefit from more elaborate tread patterns IF water evacuation was the only consideration, but these other factors make the straight grooves the best compromise.
Okay Captain hold on! I love your videos but I'm a chemist and when you say inert gas you should be pointing at group number 18 or what is probably known to everyone as noble gases which includes Helium, xenon, neon etc.
The term inert mean that it is not reactive at all so you can't call nitrogen an inert gas because it is quite very reactive in some cases, the reason they use it is because of low cost simply because it's the most abundant gas in our atmosphere and because it holds it's pressure when exposed to changes in temperature, but believe me it is quite reactive gas if introduced to some chemicals but inert/noble gases won't react at all under normal circumstances even if exposed to the most reactive chemicals and I can talk forever about this lol. Thank you for your flight lessons and you're welcome for my chemistry one I just gave you lol.
We are all learning. Great thing you pointed that out
I understand where you are coming from (I studied chemistry in university as well), but nitrogen is often used as a substitute for the noble gases. While it is true that in certain situations it is reactive, most of the time nitrogen does not easily react with other substances (this requires breaking the triple bond in the N2 molecule - not easy to do). Guaranteed nobody would be using nitrogen in aircraft tires if there was any risk that it would be unsafe.
@@JustSomeCanuck you are 100% correct I was just commenting on the term "inert" which is a whole different group that is very difficult to react even in a lab and pushing the reaction towards it, I just wanted everyone to not get confused with the 18th group but you're absolutely right that triple bond is quite difficult to break in normal conditions. Thanks for your feedback 😊.
The video digresses a little from the title which is about pre-spinning aircraft tyres to reduce wear when touching down.
However the discussion about tyres is interesting. Filling tyres with nitrogen because nitrogen is 'inert' I think is a bogus point. The gas mixture of regular air is 78% nitrogen anyway. Removing the 21% oxygen that is in air might be advantageous, but I think removing moisture is an even bigger deal, particularly given the range of temperatures these tyres need to operate over.
I was lead to believe that dry nitrogen was advantageous because the nitrogen molecule was relatively large and diffusion through the rubber was reduced.
I think Mentour Pilot assumes that the motors to spin up the tyres are powerful (large enough to taxi with?) and you need to accurately match the rotation speed to the ground speed on landing. But even motors just large enough to spin the tyres up to 80% of the ground speed would reduce the tyre wear on landing. No need for a battery since the engines are running anyway (hopefully) when landing.
The point about costs and the relatively low cost of a tyre is the clincher though. If you get 300 landings from a $1500 tyre, that is just $5 per landing. Peanuts in the bigger scheme of things.
@@fredlodden1538 thank you for the physics behind that I really didn't know that like I said I'm the Chemist here lol, but you are right if it's $5 for each landing that's pocket change to the remainder of the costs to operate a passenger airliner.
"Why not make plane-tires spin, before landing?!" It would cost too much to feed all the gerbils it would take to spin all those tires up.
Ah but see..you could have a section for passengers that have to run on a treadmill that would transfer the spin to the tires. It would be less than the economy and the passengers would have to stand up.
Very interesting.
Thanks
I was really surprised that aircraft tyres were so cheap. As soon as I heard that, it was game over for the thought of saving the tyre life.
Very interesting and thanks for answering the question so thoroughly 👌