Wheel spin-up pre touchdown

[Blue Sky Baron]

During discussions over dinner last night the following question cropped up:

Do any airliners pre-spin their wheels prior to touchdown?

If not why not?

Thought the answers would be found here for sure!

Thanks,

BSB :ok:

[Blip]

Actually BSB they had this conversation just last month.

The thread is titled "Is this a good idea" and the last post was made on the 25th April.

Cheers

[Flight Detent]

Hi BSB,
No, as far as I am aware!

Air driven and elecrically driven options are apparently uneconomical when compared to tyre useage.

This topic has been aired several times in the past.

Cheers

[oldebloke]

Some systems require immediate spin up after touchdown,spoilers, antiskid etc.Ergo it's beneficial to only have the spinup AFTER touchdown.The wheels are smaller than the big wheels of the WW2 bombers,that did investigate the feasability of having the Tires totating prior to touchdown to relieve the spinup shock on the undercarriage(sidewall pockets were installed to catch the airflow to start the spin)not sure how far this developement went as all tires today are smaller profile.:ok:

[Blue Sky Baron]

Thanks for that. I figured it must have been discussed somewhere but didn't know where to look.

Regards

BSB

[5150]

Even if you spin up a tyre prior to touchdown, it will still stop on contact with the surface and spin up again.

[John Farley]

Thanks for that. I figured it must have been discussed somewhere but didn't know where to look.

Search button?

[taffman]

If I remember the good old Trident of BEA fame had the system for a while along with ground run monitoring. GRM helped with finding taxi way turn off points in the fog. I can't remember which Tridents had but I think it was the 3's. May be some one with a better memroy could help.

[Tinstaafl]

5150, could you elaborate please? I disagree that the tyres will stop then start again. Perhaps there's something I've missed?

[Onan the Clumsy]

Must be on the VTOL aircraft ;)

[Willit Run]

The problem with pre-spinup is the gyroscopic forces induced on the airframe made them very hard to control in flight, especially on approach. This was tried back in the sixties and was determined to be a good idea, but had some bad results when actually tried. OOPS!

[Daysleeper]

The citation (550) had a gravel runway mod avaliable which included nose gear spin up. Had a little knob bit like on an oven which you set depending on the Vat. Not sure if anything larger had the same type of kit.

[Blacksheep]

oldbloke summarized it; systems such as auto-speed brake, anti-skid and auto-brake use spin-up as an initiating signal. These systems could be redesigned but there are no significant benefits to be derived from having the wheels spinning at touch down. Most tyre wear is caused during the braking sequence and eliminating the dramatic smoke puffs and tyre squeal at touch down would cause more trouble than it would fix.

[Slade Intl. Airport]

At touchdown a process that uses up a bit of kinetic energy is a good thing. The energy required to spin up the wheels must act to slow the aircraft down - anyone fancy making this calculation?!

Of course, you wouldn't want the wheels to be spinning faster than the aircraft groundspeed, or you would experience an amusing acceleration on touchdown!