Book Description

Results of helicopter clearing experiments conducted at the Greenbrier Valley Airport, Lewisburg, West Virginia, during the period 7 to 29 Sep 1969, are presented and discussed. Thirty-five hover experiments and runway- clearing experiments were performed on 10 separate days with fog layers ranging from 125 to 525 ft in depth. The hover experiments, which were successful in virtually all cases, yielded clearings that varied from 400 to 2800 ft in length extent. The largest clearings occurred with the shallowest fog during tests conducted within one hour or so of the natural dissipation time of the fog. The runway-clearing experiments were successful in clearing the full 6000 ft extent of the runway on two occasions, were partially successful on four occasions and were unsuccessful on 12 occasions. Six helicopter landings were accomplished through artificially-created clearings. Quantitative information is described concerning the wake penetration distances of the helicopters, the steady-state clearing times, the total entrainment (mixing) values and the persistence times of the clearings following helicopter departure from the test sites. The temperature, humidity and wind speed values within the cleared zones are also given for certain of the experiments.