Nuts and Bolts of Safety

Thank you, Brian, for your thoroughness, persistence, and commitment to excellence and safety!
Brian Lewis, a YAJASI aircraft mechanic, and the YAJASI maintenance team were almost finished with reassembling a plane after finishing a paint job.

Throughout the assembly process, they had consulted the manufacturer’s Illustrated Parts Catalog (IPC) to ensure that all the hardware was correctly identified and installed. As they tackled one of their final tasks—reinstalling aileron counterweights—they took note of several service bulletins regarding this process.

The manufacturer had issued these bulletins due to reports of corrosion discovered on the counterweights. Corrosion and cracking could lead to failure of the counterweight resulting in loss of aircraft control.

Brian’s concern began to grow when, after installing the counterweight with the designated washer and bolt, he realized something was wrong. The bolt was too short. Even without the washer, it was too short. A quick check of the IPC confirmed he had used the correct bolt. But a borescope examination verified that the bolt was not properly engaged in the nut plate. It didn’t have the standard 1.5 threads projecting beyond the nut plate; in fact, it was recessed about 3 threads. It was only catching the nut plate by 2-3 threads.

They decided the counterweight should be installed with a longer bolt that would provide the proper, safe engagement. Brian’s borescope photos of the two bolts clearly reveal their difference in engaging the nut plate.

The shorter bolt lacks proper engagement.
Corrected installation with the longer bolt.

Brian immediately emailed photographs of the problem to the manufacturer and described the problem. Then, with his concern and curiosity fully aroused he examined the ailerons on all YAJASI’s aircraft of the same type and found that all the bolts were too short. Next he checked with the maintenance chief of a nearby mission that operates four of the same aircraft. Their examination of the aileron counterweights installed on the mission’s aircraft revealed … the same problem. Bolts installed with washers were too short.

He called to discuss the problem further with the manufacturer, receiving their promise to look into it. Within two days the manufacturer replied saying they had opened an investigation about the problem. Brian and his team then replaced all the bolts with longer ones to ensure safe flights for all: passengers, pilots, and the aircraft. Several months later his concern was further affirmed. The manufacturer issued a service bulletin alerting operators to the problem Brian had reported.