AQUAPLANING OR HYDROPLANING

Defintion :

It is caused by a layer of water beneath the tire ,which became a wedge between the tire and the runway , this thin wedge of water effectively lifts the tire off the runway surface reducing the friction forces to practically zero (TIRE NOT ROTATING ) .

Therefore wheel braking has no effect and tire skating causing lost of directional control .

the stopping distance required significantly increased .

THREE major type of Aquaplaning :

VISCOUS:

It is particularly associated with smooth runway surfaces and is quite likely to occur in the touchdown area which is often liberally smeared with rubber deposits and when the surface is damp and provides a very thin film of fluid that cannot be penetrated by the tire .

it can occur at a lower speed than the dynamic one .

DYNAMIC Aquaplaning :

When there is a standing water on the runway surface , which causes the tire to be lifted off the ground .

Rubber Reversion( Tacky tire ) :

The heat that comes out of the friction between the tire and wet runway surface boils the water and reverts the rubber , which forms a seal that delays water dispersal .

the steam prevents the tire from contacting the runway , the melting rubber traps the steam causing the aquaplaning .

NOTES :

*Aquaplaning is extremely significant on jet aircraft .

*During one landing the 3 types of aquaplaning can occur if the conditions meet .

Controling the Aquaplaning

Thanks for Antiskid braking systems which releases the brakes if it senses a skid , which allows the wheel to rotate and push through the water layer to force a contact between the tire and ground .

In case of antiskid system is inoperative then the pilots should use the manual braking system with the same principle of the antiskid system .

if the pilot feels a slip , he then releases the brakes to stop the skid then reapply the brakes again.

How to calculate the Aquaplaning speed

For takeoff :

9 x square root of the tire pressure = minimum true ground speed

For Landing :

7.6 x square root of the tire pressure = GS