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 ATTACHMENT NO. 4 Page 3 C O P Y FEDERAL AVIATION AGENCYWASHINGTON D. C. 20553

May 23, 1966

We share the concern as expressed in your letter of May 11, 1966, over the problems associated with operating on wet runways, and particularly the perplexing problem of aguaplaning. Although this subject has been covered for sometime in a general sense, we have recently again directed the regions to assure that all air carrier training programs cover the subject of aquaplaning in as definitive a way as the state of the art will permit.

Very frankly, as stated in the preamble to Amendment 121-9, the recent 15 percent Increase for wet runway is designed to account for lubricating wetness and not for the more adverse conditions such as aquaplaning or snow and slush, This 1c an extremely complex problem involving water depth, airplane speed/tire pressure ratios, tire design tread and condition, undercarriage arrangement, runway surface texture, and variations in runway contour which may develop with use.

As you are no doubt aware, research and study have been continuing on this problem since 1960. At present, NASA is actively investigating the possibility of reducing or eliminating aquaplaning by the use of a directed stream of air ahead of the tire. They have Just fitted their test equipment with a Boeing 727 type tire which will be the first actual aircraft tire tested. They are also working on the possibility of surface texturing.

We shall, of course, keep the industry fully informed of any important findings or breakthroughs, and will advise you of any significant developments.

,

Honorable Charles S. Murphy

Chairman, Civil Aeronautics Board

Washington, D. C. 20428.