Posts Tagged ‘stoping hydroplaning’
The viscous hydroplaning due to the characteristics of the water slimy. A thin film of liquid over a thousandth of an inch in depth is all that is necessary. The tire can not penetrate the liquid and the tire rolls over the movie. This can occur at a rate much lower than the hydroplane dynamic, but requires a temporary flat or smooth surface such as asphalt or a touchdown area covered with rubber accumulated past landings. Such a surface can have the same coefficient of friction than wet ice.
When confronted with the possibility of hydroplaning, the best land in a grooved channel (if available). The touchdown speed must be as slow as possible consistent with safety. After the wheel bow down the runway, braking should be applied moderately. If the deceleration is not detected and hydrofoils is suspected, the nose should be lifted and used aerodynamic drag to decelerate to a point where the brakes become effective.
Inverted rubber (steam) that hydroplaning occurs during heavy braking which results in a prolonged skid locked-wheel. Only a thin film of water in the channel is required to facilitate this type of hydroplaning. The tire skid generates enough heat to make the rubber in contact with the channel fresh investment to its original. Inverted rubber acts as seal between the tire and the runway, and retards the flow of water in the area of the footprint of the tire. The water heats up and turns to steam which supports the tire of the channel.
The inverted rubber hydroplaning often follows an encounter with dynamic hydroplaning, while the driver can lock the brakes in an attempt to slow the plane. The plane eventually slows enough to where the tires make contact with the surface of the runway and the plane starts to skid. The remedy for this type of seaplane pilot is to throw the brakes and let the wheels do spin up and apply moderate braking. Inverted rubber hydroplaning is insidious in that the pilot may not know when it starts, and may persist groundspeeds very slow (20 knots or less).
Dynamic hydroplaning is a relatively high speed that occurs when a film of water on the runway that is at least one tenth inch deep. As the aircraft speed and depth of water increased, the layer of water builds up an increasing resistance to dislocation, resulting in the formation of a wedge of water under the tire.
At a certain speed, called the hydroplaning speed (VP), the upward force generated by water pressure equals the weight of the aircraft and the tire is removed from the surface of the channel. In this condition, the tires no longer contribute to the directional control and braking action is nothing.
Dynamic hydroplaning is related to the inflation pressure of the tire. The data obtained during hydroplaning tests have shown the minimum dynamic hydroplaning speed (VP) of a tire to be 8.6 times the square root of the tire pressure in pounds per square inch (PSI). For an airplane with a head pressure of 24 PSI tire, the calculated hydroplaning speed would be about 42 knots. It is important to note that the rate referenced above is calculated for the beginning of dynamic hydroplaning. Once hydroplaning has begun, may persist to a significantly reduced rate depending on which is experienced.
To recover while traveling in a straight line, the driver should not turn the steering wheel of a car or applying the brakes. Any action could put the car into a skid from which recovery would be difficult or impossible to. Instead, no change in steering input, the driver should gently ease the throttle pressure. The control should then return. If braking is unavoidable, the driver should lightly pump the brakes until hydroplaning has stopped.
If the rear wheels and cause hydroplaning oversteer, the driver should steer in the direction of the skid until you gain traction following links, and then goes rapidly in the other direction to straighten the car.
Prevention by the driver
The best strategy is to avoid as many contributors to hydroplaning as is possible. Proper tire pressure, narrow tires and not spent, and slow speeds of those deemed suitable will moderate dry mitigate the risk of hydroplaning. Avoidance of standing water is another effective strategy of prevention.