Hydroplaning is caused by a thin layer of standing water that separates the tires from the runway. It causes substantial reduction in friction between the airplane tires and the runway surface and results in poor or nil braking action at high speeds. High aircraft speed, standing water, slush, and a smooth runway texture are factors conductive to hydroplaning.

• Dynamic hydroplaning occurs when there is standing water or slush on the runway deeper than the tread depth of the tyres. A wedge of water builds up, lifting the tires away from the runway surface. The speed of the airplane, the depth of the water, and the air pressure in the tires are some of the factors that affect dynamic hydroplaning.

HYDROPLANING SPEED CALCULATIONS:

• Rotating Tyres formula (applies to rejected take-offs): V = 9 √ P
• NON-Rotating Tyres formula (applies to touchdown): V = 7.7 √ P
  Where V stands for velocity (kt) and P is tyre pressure (PSI)

In this case, the aircraft is landing: V = 7.7 √ 200 = approx. 109 kt

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=> We must make sure that the reference landing speed (V_REF) is below 109 kt. Referring to the provided table, the flap setting is FLAP 30.