Md Helicopter MD 900 N902AF incident near Kamuela, Hawaii

Probable cause

The separation of the endplate bolts for undetermined reasons, resulting in an in-flight separation of the right endplate. Contributing to the accident was the manufacturer's failure to provide sufficient guidance for endplate bolt installation.

NTSB analysis

A witness informed the flight crew that the helicopter "lost a panel" during landing. Inspection of the helicopter revealed that the lower right stabilizer (endplate) separated and was located approximately 70 feet from where the helicopter landed. The endplate was later recovered; however, the two associated attachment bolts were not. Without the bolts, it could not be determined if the attachments were not properly torqued or if the bolts' locking mechanism was no longer serviceable. The operator reported that the endplate was removed approximately 42 flight hours prior to the incident to facilitate a maintenance action on the horizontal stabilizer. Following the maintenance action and inspection, the endplate was reinstalled using the original attachment bolts. The applicable maintenance manual instructions for endplate installation directed maintenance personnel to secure the endplate to the spar tube and torque bolts to a specified value; however, it did not direct maintenance personnel to apply sealing and locking compound to bolt threads prior to installation. Following the incident, the manufacturer issued a mandatory Service Bulletin requiring the inspection of endplate bolts for serviceability and application of thread locking compound.

Text from the NTSB. Open the NTSB docket for WPR09IA070 for the full record.