# AOPA Online Members Only -- AOPA ePilot Flight Training Edition -- Vol. 5, Issue 33AOPA Online Members Only -- AOPA ePilot Flight Training Edition -- Vol. 5, Issue 33

 Volume 5, Issue 33 • August 19, 2005 In this issue: National Aviation Day: Spread the joy of flight AOPA Twin Comanche winner keeps on learning 'Google it' on AOPA Online

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 Training Tips DYNAMIC HYDROPLANING Maintaining your aircraft tires at the correct pressure for performance and safety was the message of the August 12, 2005, "Training Tips." One risk amplified by soft tires, but always present when landing on a wet runway, is a phenomenon called dynamic hydroplaning. This occurs, says Chapter 9 of the Pilot's Handbook of Aeronautical Knowledge, when the tires "ride on a thin sheet of water rather than on the runway's surface. Because hydroplaning wheels are not touching the runway, braking and directional control are almost nil." The chapter also contains an interesting and easy mathematical formula to determine the minimum speed at which dynamic hydroplaning could occur. To use it you will need to know your aircraft's tire pressure. Landing during or shortly after a rainstorm should make any pilot alert to potential hydroplaning. Standing water or puddles on a runway are other warning signs. Grooved runways minimize the problem by facilitating drainage. Check the runway surface of your destination as part of your flight planning. The possibility of dynamic hydroplaning is another incentive to make your landings to exacting standards of directional control and touchdown airspeed. Note that if hydroplaning begins, it may continue down a speed lower than the one determined by the formula referred to above. Numerous accidents in which aircraft have run off the end of grass runways have been attributed to excessive speed and dynamic hydroplaning-so keep this in mind when landing on a soft field. "By their nature, soft-field landings invite hydroplaning when wheels touch down on wet grass or soggy runways," advised Dave Wilkerson in "Checkride: Soft Touch" in the May 2001 AOPA Flight Training. Dynamic hydroplaning is a risk for any size aircraft. Sharing one pilot's recollection could spare you a similar experience. "I knew lots of fancy terms for the problem and could quote the details from memory. It never made much of an impression on me until I experienced that no-brakes feeling as we were rolling out after landing an airliner on Runway 5R at Mexico City," AOPA Flight Training contributor Karen Kahn wrote in her April 2003 feature "Learn By Doing: Every Flight Helps to Build Good Judgment." Dynamic hydroplaning is another reason to make every landing your best landing.