WPR24LA061

When the airplane’s tailwheel touched the ground during landing, the airplane immediately swerved and ground looped, causing substantial damage to the fuselage due to sideloads on the landing gear. The weather conditions were not a factor, and examination revealed that the tailwheel was jammed 45° relative to the direction of travel. Further examination revealed that the tailwheel assembly locking mechanism was significantly worn and had been incorrectly constructed, so a positive lock was not possible. Under this condition, with light side loads as are often encountered during landing, the tailwheel could unlock and be pushed into an over center position. This resulted in the airplane aggressively swerving as observed.

On December 26, 2023, about 1221 mountain standard time, an experimental amateur-built Glasair SH2, N29TT, was substantially damaged when it was involved in an accident near Prescott, Arizona. The pilot was uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, after an uneventful wheel landing, he held the tail off the ground until the airplane had decelerated to about 30 mph. As soon as the tailwheel touched the ground, the airplane swung hard to the right, ground looped, and came to rest on the runway edge. The airplane sustained substantial damage to the forward left fuselage, which had buckled and delaminated behind the firewall and just above the left main landing gear leg. Postaccident examination revealed that the tailwheel was jammed at a 45° angle to the left. The airplane was equipped with a free-castering tailwheel, designed to be locked in the straight position during takeoff and landing. It was controlled by a lever in the cabin that was connected via a cable to a spring-loaded locking arm in the tailwheel assembly. The locking arm, when activated, dropped down into a slot cut into the upper plate of the tailwheel trailing arm. The plate was a steel segment of about 90° arc and welded to the tailwheel arms. The pilot reported that, in accordance with the airplane’s operating instructions, he locked the tailwheel straight during takeoff with the cabin control and confirmed it was locked before landing. Postaccident examination revealed that both the cabin control and locking arm were in the locked position, but the tailwheel was jammed about the 45° to the left, rather than straight. Further examination revealed that the locking arm and associated plate slot were worn, and the locking spring had limited tension, such that with light force the tailwheel could be moved out of the straight position and jammed over center as the locking arm dropped down against the outer edges of the locking plate (see figure 1). Figure 1. Tailwheel in the overcenter position. Arrow indicates where the locking arm has dropped down against the outer edges of the locking plate. The construction plans specified that the control cable should be routed directly from the locking arm to a phenolic guide in the vertical fin shear web. However, the cable was routed from the locking arm down to a set of four cable ties mounted to the tailwheel strut (see figure 2). Figure 2. Tailwheel in the straight position; note the cable ties in top left restricting free movement of the locking cable.