Why has someone not designed a landing wheel with a fin or fins on it so that the air will start the wheels turning before the wheels touch the ground? Wouldn't that preserve the tires longer from wear? Or would it make the control of the aircraft more dangerous in some circumstances, such as rain or snow, to have the wheels already turning when landing? If so, perhaps the fins could be manually or computer controlled for various weather conditions.
$\begingroup$
$\endgroup$
7
asked May 3, 2014 at 22:36
-
5$\begingroup$ You'd need to match speed exactly which is very hard. plus there is the weight issue, anything superfluous that is heavy will not get on board $\endgroup$– ratchet freakCommented May 3, 2014 at 23:08
-
65$\begingroup$ @ratchetfreak You wouldn't need to match it exactly at all! You'd just need to get closer to the actual ground speed than a stationary wheel is. Don't fall into the trap of failing to do anything just because a perfect solution isn't possible. (But I agree that the reason it's not been done will be that the advantages don't outweigh the costs.) $\endgroup$– David RicherbyCommented May 4, 2014 at 7:26
-
$\begingroup$ How do you spin the wheels in a way that does not affect their friction upon contact? I mean, if you use any kind of clutched drive, how do you ensure the clutch does not still contact the axle upon landing; any contact of the clutch would cause it to potentially burn out. If you use fins and airflow, would there possibly be enough airflow to overcome the inertial weight of the total tire/hub/etc. $\endgroup$– CGCampbellCommented Oct 15, 2014 at 12:47
-
5$\begingroup$ This guy claims to have designed some hubcaps with fins in then that catch the wind and supposedly spin the wheels up after the landing gear is deployed $\endgroup$– Matt HillCommented Mar 5, 2015 at 14:44
-
4$\begingroup$ I asked this exact question back in the old days when I was in the Civil Air Patrol. We were at an encampment at Chanute AFB in Illinois, and being given a tour of a B-58 they had on hand, whose tires were very badly worn. The instructor was telling us that the aircraft required new tires after about four landings. His response to my question was two parts: 1) anything that adds weight or complexity to a simple system is a bad thing, and 2) defense contractors don't make money by not selling you new tires. ^_^ $\endgroup$– RobustoCommented Sep 22, 2015 at 16:36
|
Show 2 more comments
3 Answers
$\begingroup$
$\endgroup$
9
This has been researched over the years, but it seems that the solutions did not find wide application. The oldest I could find is from 1941 (see page 112 in the September 1941 issue of Popular Science), and there have been several attempts to implement a spin-up turbine. See “Wheels with wings” on NewScientist Blogs or “Spin Wheels Before Landing”, a discussion thread on Eng-Tips forums, for more. The biggest problem seems to be the inertia of the spinning wheel because it makes the aircraft react in funny ways if the pilot wants to correct his approach.
The rough field package on the Cessna Citation 500 uses this technique (for the nose wheel only) to protect the fuselage from debris which could be kicked up by the wheel spinup.
answered May 4, 2014 at 6:19
-
12$\begingroup$ Control issues make sense! Gyroscopic precession is weird. $\endgroup$– egidCommented May 5, 2014 at 0:43
-
9$\begingroup$ So if gyroscopic precession is an issue, does it have the same effect during take off? $\endgroup$– MK YungCommented May 5, 2014 at 1:05
-
32$\begingroup$ @MKYung that's why people tap the brakes on takeoff $\endgroup$ Commented May 5, 2014 at 10:09
-
7$\begingroup$ Also, after take-off you mind less when the aircraft rolls a little when you yaw and vice versa. This is quite different to trying to line up with the runway during an approach in gusty air. $\endgroup$ Commented May 5, 2014 at 18:26
-
7$\begingroup$ And that's why Concorde had a disk brake on the nose wheel that was activated during gear retraction. $\endgroup$ Commented Sep 4, 2015 at 10:21
$\begingroup$
$\endgroup$
4
It's just not cost-efficient. Any weight-add produces more fuel consumption, any systems produces more maintenance costs. It's just easier to change the tires if they're worn out. source: Aerospace engineering
-
7$\begingroup$ could you expand your answer a bit? the content is fine, but expanding the reasoning would help. $\endgroup$– FedericoCommented May 5, 2014 at 9:03
-
3$\begingroup$ I thing Hubschr is correct. In general the more things you add or make complex, the more things break and drive up the cost of maintenance. Also when a tire goes the mechanic knows how to change it. When some fancy electric motor or its controller, or it's power supply , or ... it's a much bigger deal to troubleshoot and fix. This can result in more down time. Planes only make money when they are working, so keep it simple and get back in the air making money. $\endgroup$– JerryKurCommented Oct 15, 2014 at 20:24
-
2$\begingroup$ Well, this is a generalization and in this case I do not agree. ^^ Progress is most of the time not the effect of simplification. Systems are getting more complicated. (As an example: If you would build a special rim (when you have retractions wheels) which use the airflow for generating the spin it does not have to make the maintenance costs higher and it maybe also not produce more weight. And (maybe) the over-all cost is better, because fewer tires worn out.) Source: My two cents as an engineer $\endgroup$– TimKCommented Mar 16, 2019 at 18:16
-
$\begingroup$ A design based on the design of simple 3 cup anemometer would be lightweight, easy to understand and easy to maintain. $\endgroup$– KDPCommented Mar 26 at 16:32
$\begingroup$
$\endgroup$
A good summary of factors in this concept is SAE AIR5800 report. It lists the pros and cons as follows, citing several SAE and NASA documents, and Boeing NACA and AIAA papers:
Advantages:
- Reduces tire wear
- Potential to reduce touchdown loads
- Reduces debris spray on gravel runways
Disadvantages:
- Does not reduce tire wear significantly for most airplanes
- Not a reliable means to reduce landing loads, (and may even increase loads)
- If employed, motors add weight, cost, complexity
- Reliability expected to be an issue
- Failure mode requirements minimize potential loads benefits
- Additional maintenance
- If employed, special tires require more testing and spares (left and right tires)
- Causes noise and vibration at landing approach
- Adversely affects on-ground indication systems using wheel spin-up signals upon landing
A biref snippet from the summary section states:
There may be solutions to many of the issues associated wirh tire prerotation, but in the end, the main reason tireprerotation is not practical on most aircraft is that it is simply not effective in reducing either tire wear or landing loads, andwould create more problems than it would solve.
There may be applications where this conclusion does not apply, such as for airplanes operating on gravel runways, or for airplanes that land at extremely high speeds incurring a higher percentage of tire wear at landing.
Perhaps the most notable case of considering pre landing spin up was for the space shuttle, but even with wear reduction of up to 50%, the idea was scrapped.
the SAE report can be googled, I will not provide a link to it as it is made commercially availlable by SAE, and I do not wish to violate their copyright
