CHI00LA149

The airplane veered off of runway 34 in a sharp turn to the right while back taxiing for takeoff. The pilot reported that there were light to moderate rain showers located 15-20 miles west/southwest of the airport prior to his preflighting the airplane. He also reported that the wind velocity changed in magnitude and direction during the taxi. The pilot also reported that following the accident, the winds increased from the east/northeast to 12-15 mph and that there was convective activity in the area.

On June 1, 2000, at 0700 central daylight time, a Piper PA-36-200, N2329Y, operated by Cooperative Agricultural Services Incorporated, was substantially damaged during a back taxi for takeoff on runway 34 (5,000 feet by 75 feet, asphalt) at the Oakley Municipal Airport, Oakley, Kansas. Visual meteorological conditions prevailed at the time accident. The 14 CFR Part 137 aerial application flight was not operating on a flight plan. The commercial pilot reported no injuries. The local flight was originating at the time of the accident.

In a written statement, the pilot reported the following: "...I arrived at the airplane's hanger at 6:10 a.m. to preflight the plane and pushed it out of the hanger to load it for spraying that morning. Winds were light and variable out of the north/northwest at 5 to 7 mph. Thin cloud cover with light to moderate rain showers to the west/southwest of the airport about 15-20 miles away. The direction I was to spray was about 20 miles southeast of the airport. After pre-flight and loading the plane I checked the radar and wind speed/direction again and conditions were still favorable for flight. I started the plane, let it warm up, all systems and controls were functioning correctly and fully operational. I then let the plane idle while I checked weather conditions once more. The wind was a little more east/northeast about 8-10 mph with light showers about 10 miles away to the southeast. I proceeded to taxi to the runway, did my run-up again found all systems and control operating correctly and rolled out on the runway 16 to back taxi for departure on 34. I was proceeding very slowly with my feet on the rudders and stick to the left to compensate for the crosswind. I had rolled less than 300 ft. when the tail whipped suddenly to the right and the airplane veered to the left. I instantly tried to bring it back to center to no avail. The plane left the runway in a sharp turn to the right... Once back at the hanger, I checked radar and winds finding winds had increased to E-NE 12-15 mph with a moderately strong thunderstorm in the area."

Weather radar indicated an area of 40 dBZ returns to be present in the area at 0715.

The accident airplane was equipped with a tailwheel landing gear arrangement. Advisory Circular 61-21A, Flight Training Handbook, states under Taxiing-Tailwheel Type Airplanes, "An airplane with a tailwheel landing gear arrangement has a tendency to "weathervane" or turn into the wind while it is being taxied. This tendency is much greater than in airplanes equipped with nosewheels... The tendency of the tailwheel-type airplane to weathervane is greatest while taxiing directly crosswind: consequently, directional control is somewhat difficult. Without brakes, it is almost impossible to keep the airplane from turning into any wind of considerable velocity since the airplane's rudder control capability may be inadequate to counteract the crosswind. In taxiing downwind the tendency to weathervane is increased, due to the tailwind decreasing the effectiveness of the flight controls. This requires a more positive use of the rudder and the brakes, particularly if the wind velocity is above that of a light breeze. Unless the field is soft, or very rough, it is best when taxiing downwind to hold the elevator control in neutral or slightly forward."