Aquaplaning on takeoff????

[PFM]

Is it possible? If the tread is unable to displace the water on landing, (Dynamic aquaplaning), why would it be any different accelerating through the affected speed range?

[Victor Hotel]

Yes, aquaplaning on take off can and does occur but as it only really becomes a problem when stopping it doesn't rate much of a mention. However some operators do reduce their V1 on a wet runway for exactly this reason (i.e. the effect the aquaplaning will have when the takeoff is aborted).

[A and C]

In the sim try using a dry V1 on a wet runway and then try to stop at V1 you will go off the end but i doubt that the aircraft will aquaplane at a speed under the wet V1.

As the post above sujested that is why we have a wet V1.

[mutt]

I would be weary about saying that the V1 wet runway decrement accounts for hydroplaning. The data is based on the following:

Slippery Runway (Wet or Icy)
 No effect on acceleration
 Engine out accelerate - go
– Go to 15- ft screen height
 Accelerate - stop
– Reduce tire to ground friction
– Credit for reverse thrust

I dont see any accounting for Hydroplaning on wet runways.

Mutt :)

[Victor Hotel]

But Shirley you're joking Mutt? Methinks that reduced friction between tyre and runway would include aquaplaning would it not?
But I wary of this thread and will not slip in another reply. ;)
However, before slipping away I might add for the enlightenment of PFM and A and C that total dynamic aquaplaning may occur when the water depth is between 1/10th of an inch to 4/10th of an inch (2.5mm to 10mm) and at a speed (in knots) of 9 times the square root of the tyre pressure in p.s.i.. That comes out at around 129 kts for an average weight B747 which is incidentally below the balanced V1 at those weights.
Please note that the type of tread makes no difference (much to the chagrin of Messrs Bridgestone, Pirelli and Goodrich!)

[ 30 August 2001: Message edited by: Victor Hotel ]

[shakespeare]

A & c. An a/c will indeed aquaplane at a speed much lower than V1 if the appropriate conditions exist. An a/c can aquaplane at taxi speed if the brakes are applied too abruptly or the nose wheel turned excessively on a contaminated surface or painted line etc.

DYNAMIC HYDROPLANING is the sliding effect caused by low coefficient of friction from standing water.

VISCOUS HYDROPLANING is the effect at low speeds caused by the lack of tyre penetration of a thin film of water.

REVERTED RUBBER HYDROPLANING causes tyre damage that results from prolonged lack of tyre rotation and friction generated super heated water.

We sometimes do not give wet surfaces the respect they deserve. I am inclined to be extra vigilant when runways/taxiways are wet. They can be a statistic waiting to happen.

[ 01 September 2001: Message edited by: shakespeare ]

[slapfaan]

Good textebook answer,shakespeare!!Must have read HTBJ???

[john_tullamarine]

The mechanics involved in hydroplaning are not in my areas of professional expertise... but I always was under the impression that the 9 root P bit applied to bald tyres and, I guess, a treaded tyre in sufficient water depth ?

[A and C]

So if the aircraft can aquaplane at a speed under the wet V1 why are wet V1 speeds not based on the aquaplaning speed ?

[m&v]

Aqua planeing is just that.Planeing on the top of the water.It came into being whilst trying to stop aircraft after landing on 'wet'runways,with the tire not in contact with the surface!!!
The tire does not spinup the spoilers,or the reversers and the aircraft goes off the end..If the brakes are on the rubber boils with the friction and steam..
In the takeoff case the tire is in contact with the surface,the water night constitute a drag(more tham 3mm)but in this case skimming the top would help the takeoff case!!It's only when one wants to stop we're back to square one-Aquaplaneing,thats why the V1 is lower-to give you more room to stop. :eek: