N926LLCessna 180H · 1964

On October 12, 2021, about 1300 mountain daylight time, a Cessna 180 airplane, N926LL, was substantially damaged when it was involved in an accident near Kalispell, Montana. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot of the tailwheel-equipped airplane, she received a clearance to land on runway 20 but, because of a tailwind, performed a go-around. She then requested and was cleared to land on runway 02. Upon touchdown, the airplane veered abruptly to the right, skipped several times, and departed the runway to the right, where the left wing contacted terrain. The pilot reported that she did not know if a mechanical malfunction or failure had occurred.

A tower controller reported that the pilot was cleared to land on runway 20 and went around after bouncing the airplane a few times. The pilot then requested to land on runway 02. The controller cleared the pilot to land on runway 02, where the airplane then “skidded off east of runway mid-field.”

The airplane came to rest upright in open terrain adjacent to the runway. The left wing and aileron exhibited a sharp bend upwards from the tip to about 30 inches inboard. The right wing was bent downward, and the right strut buckled. The left horizontal stabilizer and elevator were bent upwards about mid-span. Examination of the landing gear revealed that the left landing gear assembly separated from the fuselage. The landing gear exhibited a wheel alignment shim on the left side-, and no-wheel alignment shim on the right side. According to Cessna, the wheel alignment shims are an “as required” item, and no wheel alignment shim would be acceptable. The pre-accident wheel alignment could not be determined due to the separation of the left landing gear.

A representative of the Federal Aviation Administration (FAA) traveled to the accident site and reported that the damage was consistent with a ground loop; he was unable to determine the alignment of the main landing gear due to the damage. Examination of the airplane did not reveal any mechanical malfunctions or failures that would have precluded normal operation.

The airport’s automated weather observation station reported that, about the time of the accident, wind was from 040° at 4 knots, and no reports of wind gusts.

According to the mechanic who performed maintenance on the airplane before the accident flight, he was approached by the pilot’s husband, who reported problems with the airplane’s handling on landings, and wanted different tires and rims installed. The mechanic replaced the tires, wheels, and brake calipers. He indicated that he set the alignment in accordance with the procedures for oversized tires.

A review of the maintenance logbook for the airplane revealed that, on October 7, 2021, the main gear axle spindles were aligned, and new ABI-1010 1.25/1/5 wheels with new 8.5-10 6-ply tires and tubes were installed per STC SA017655E. New ABI 30-52N brake calipers were installed, and the left tailwheel cable was reinstalled onto the pulley. The elevator and stabilizer movement were checked. STC SA017655E addressed the installation of Alaskan Bushwheel TSO-C26d wheels, part number ABI-1010, as listed in the approved model list (AML) SA017655E. STC SA01015SE addressed the “installation of eligible Alaska Tire and Rubber Company TSO-C62d Tires as listed in the approved model list (AML) SA01015SE. A review of the FAA Approved Model Lists (AML) SA01765SE, and SA01015SE revealed that the Cessna 180H airplane was approved to use the ABI 1010 wheel, and the 8.5-10 6-ply tires and tubes.

STC SA01015SE stated in part:

Tundra tires reduce the airplane’s directional stability and controllability during takeoff and landing ground rolls, increase its tendency to ground loop during takeoff and landing ground rolls, and increase its tendency to nose over during landings on paved surfaces more than during landings on gravel, grass, or other surfaces that allow the tires to skid more easily.

On September 30, 2020, about 1940 Alaska daylight time, a Cessna 180H airplane, N926LL, sustained substantial damage when it was involved in an accident near Tok Junction, Alaska. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot stated that she was landing her tailwheel-equipped airplane on an asphalt surfaced runway. After a normal touchdown in the three-point attitude, the airplane drifted to the left and right of the runway centerline but was corrected each time with the light application of the appropriate rudder pedal. As the airplane decelerated and rudder effectiveness diminished, the airplane veered abruptly to the right. Left rudder was applied but was unsuccessful in controlling the airplane. The airplane exited the runway, and the left main gear separated from the gear box, resulting in substantial damage to the fuselage.

Aircraft maintenance records revealed that on September 29, the day before the accident, the tailwheel had been repaired and the tailwheel bearings replaced.

A postaccident examination revealed that the tailwheel rotated freely to the right but was very stiff and difficult to rotate to the left. Disassembly of the tailwheel revealed that the steering arm inside radius (item #13 in figure 1 below) was heavily scored and worn. The compression spring (item #19 in figure 1 below) had sharp and damaged edges on the ends of the spring, and the spacer (item #20 or #21 in figure 1 below) was not present, which allowed for excessive movement of the spring in its assembly.

Figure 1 - Scott 3400 series tailwheel parts illustration.