Currently, as far as I know, most modern (big) airliners do not pre-spint the tires before landing. The question is why not, as there are certain benefits. This question was asked here before Why are aircraft tires not pre-spun prior to landing to preserve them? , but I think not all benefits were mentioned there, especially not the passenger comfort.
Advantages: From most important to less:
- Comfort: At the moment of touch down, the gears are fiercely slammed backwards. The passengers won't experience this any more, which ads up to their complete flight experience.
- Safety: A slipping wheel has no grip, also not sideways. Also the aircraft will be more stable at the moment of touch down (see 1). When it does not work, we are just back to the currently accepted old situation. Even when it fails in the sense that the tires spin too fast!
- Tires last longer: This saves money for replacing them and the saves the time to do so. Most delays I personally experienced by interim maintenance on aircrafts were by maintenance that consisted of one tire replacement only! Still most tire wear does not come from the touch down moments.
Disadvantages: From most important to less:
- Costs: Of course it will come with a price and add extra weight to the aircraft, etcetera.
- Control: The gyroscopic effect of spinning wheels have their influence on the behavior of the aircraft. But this problem is already there just after takeoff. Would an A380 pilot really notice?? Or is it a minor issue at takeoff that would be a major one at landings? Please tell me!
- More difficult tire maintenance scheme: For each tire a log needs to be maintained of how many times the tire touched down where the system was both working and not working.
Design considerations: The system can take the time from when the gear is completely down to touch down to spin-up the tires. It is not a problem when the tires' speeds to not exactly match each other or the landing speed.
Simple implementation: Attach an electric motor to each axle of the main gears. At take-off they are disconnected, otherwise they would act as dynamic breaks. At landings they always just operate at full capacity. The size and power of these engines need just be enough to overcome slightly more than the resistance of the axle itself and should be just at the level that, after a minute, the tires keep spinning at an average landing speed (and don't speed up any more). For the (tire maintenance) logs each axle also should have a detection for if it is spinning above a certain speed, like faster than half the average landing speed.
What is the decisive reason something like this was never implemented on a modern (big) jet aircraft?
