Primary finding
Probable cause
the disconnection of the tailwheel spring which resulted in the pilot's inability to maintain directional control of the airplane.
Investigator assessment
Analysis narrative
According to the pilot, the tailwheel began to shimmy during the landing roll and the tailwheel spring on the left side became disconnected. The airplane spun around 270 degrees and the left wing contacted the runway. The airplane traveled off the right side of the runway prior to coming to rest. The pilot stated the groundspeed was very slow when the spring disconnected which resulted in a lack of rudder authority to control the airplane.
Source record
Factual narrative
On May 7, 1997, at 1900 eastern daylight time, a Piper PA-18-150, N4056Z, operated by a commercial pilot ground looped during a landing roll at the Presque Isle County Airport, Rogers City, Michigan. The 14 CFR Part 91 flight was operating in visual meteorological conditions without a flight plan. The pilot and passenger were not injured. The airplane was substantially damaged. The flight originated from Alpena, Michigan, at 1700 edt. The pilot reported that during the landing roll on runway 09 (3,017' x 60', asphalt) the tailwheel began to shimmy. He reported that the spring on the left side of the tailwheel became disconnected which resulted in a loss of steering control. He reported the groundspeed was too slow to have any rudder authority. The airplane ground looped 270 degrees to the right during which time the left wing struck the ground. The airplane traveled off the right side of the runway into the grass prior to coming to rest. -