Definition
A condition that occurs during landing or takeoff on a wet runway when standing water is unable to escape from beneath a fast-moving tire, causing the tire to lift off the runway surface and ride on a thin film of water. While hydroplaning, the tire loses contact with the pavement, dramatically reducing braking effectiveness and directional control. The minimum speed at which dynamic hydroplaning can begin is roughly nine times the square root of the tire pressure (in psi) for a non-rotating tire.
Plain English
When a runway has standing water on it and the airplane is moving fast enough, the tires can skim across the water instead of touching the pavement. When that happens, brakes barely work and steering becomes very limited.
Context Anchor
Encountered during takeoff or landing roll on a wet runway, especially where there is standing water and the airplane is still moving fast.
Derivation
Hydroplaning combines the Greek hydro (water) with plane (to glide or skim). 'Dynamic' here means caused by motion — specifically, the speed of the tire generating enough water pressure to lift the tire off the surface. It distinguishes this type from viscous and reverted-rubber hydroplaning, which have different causes.
Why Pilots Care
It removes braking and directional control, greatly increasing stopping distance and the risk of runway overrun.
Analogy
It is similar to a water ski staying on top of the water when it moves fast enough. At lower speed it settles down, but at higher speed the water can support it.
Grounding Statement
Picture the wheels touching a wet runway, but the tires are riding on a thin sheet of water instead of pressing firmly onto the pavement.
Intuition Check
Do not read dynamic as meaning complicated or changing. Here it means motion-caused: the tire is moving fast enough for water pressure to lift it away from the runway surface.
Example Sentence 1
After touching down on the rain-soaked runway above the calculated hydroplaning speed, the pilot felt the airplane drift sideways as the tires began dynamic hydroplaning.
Example Sentence 2
After heavy rain the crew delayed landing until crosswind and speed allowed them to stay below the dynamic hydroplaning threshold.