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In this case there was probably little braking effect because either the tire was riding on a cushion of steam trapped in the footprint area by the sealing effect of the melted rubber, or an the melted rubber itself which would offer a smooth surface.
The third type of hydroplaning, viscous, takes place when very thin films of water are on smooth, or smooth acting, surface. This could have occurred in the touchdown area of the runway where large amounts of rubber from landing aircraft tires were deposited.
It is the Board's opinion that most if not all of these types of hydro-planing occurred in this case.
Based on the testimony of the witnesses, and statements from the psdsangers that they felt little or no deceleration after landing, it is probable that the braking coefficient on the runway was less than 0.15. The manufacturer computed that if the braking coefficient Were 0.05 it would take 6,700 feet of runway to stop, using-full reverse thrust to Zero velocity. At landing, the pilot had 5,950 feet of runway remaining. Calculations and testimony by the NASA technologist indicated that, under the conditions of the landing, the airplane could not have been expected to stop on the runway.
2.2 Conclusions
Findings:
a. The crew was qualified and certificated in accordance with existing company and FAA regulations.
b. The captain was flying the aircraft and the procedures employed by the crew were in keeping with the current company practices except that the crew exceeded the company's imposed maximum-landing weight for the conditions at Kansas City. They Were, however, Well under the FAA maximum gross landing 3 weight restriction of 175,000 pounds for B-707's.
c. Approach Control personnel did not provide the crew with all the available reported weather information.
d. Continental Air Lines, Inc., procedures for inspection and reporting runway conditions were not followed.
e. The crew of Flight 12 knew that TWA Flight 84 had landed about four minutes ahead of them, with no reported difficulties.
f. The final portion of the approach was made under visual flight condition
g. It was raining during the period of the final approach.
h. The crew of Flight 12 had no reason to believe that they would experience any difficulty during the landing.
i. The evidence and testimony established the aircraft touched down firmly on the runway in the area of the ILS touchdown point.
