Kamuela, HI, USA
N902AF
MD HELICOPTER MD 900
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.
On December 27, 2008, at 1550 Hawaiian standard time, a McDonnell Douglas MD 900 helicopter, N902AF, sustained minor damage during an in-flight separation of the lower right endplate (vertical stabilizer) while landing near Kamuela, Hawaii. The helicopter is registered to, and operated by Vulcan Aircraft, Inc. The local flight was operated under the provisions of Title 14, Code of Federal Regulations (CFR) Part 91. The two pilots, the only occupants aboard the helicopter, were not injured. Visual meteorological conditions prevailed, and company visual flight rules (VFR) flight-following procedures were in effect. The flight originated offshore at 1512 with a planned destination of Kamuela. The pilots reported that a witness informed them that the helicopter had "lost a panel" during the approach. A postflight inspection revealed that the lower right endplate had separated from its mounting support bracket and was located approximately 70 feet from where the helicopter landed. The pilot seated in the left front seat, who was flying at the time of the incident, reported that he noted a slight momentary yaw approximately 15 minutes prior to landing. A representative from the operator reported that the endplate was later recovered; however, the two associated attachment bolts were not. Maintenance records showed that the endplate was removed on May 20, 2008, approximately 42 flight hours prior to the incident, to facilitate maintenance actions on the horizontal stabilizer. Following the maintenance action and inspection, the endplate was reinstalled using the original self-locking bolts (NAS6305LU12). The helicopter maintenance manual instructions for endplate installation (section 53-55-00) listed the following actions, in part, with respect to endplate installation: 1. Prepare endplate attach hole for electrical bond. 2. Position endplate on spar tube and align bolt holes. 3. Secure endplate to spar tube and torque bolts to 7-17 inch-pounds. 4. Test washer for electrical bond. 5. Environmentally seal washer to endplate with sealant. On April 11, 2009, following this incident, MD Helicopters issued Service Bulletin (Mandatory) SB900-111, titled Horizontal Endplate (Vertical Stabilizer) Installation. The service bulletin instructs operators, in part, to do the following: 1. Remove endplate attach bolts. 2. Clean threads of endplate attachment bolts. 3. Make certain thread lock device on bolts is serviceable. 4. Apply sealant primer to bolt threads. 5. Apply sealing and locking compound to bolt threads. 6. Install endplate attach bolts. 7. Make a record in the rotorcraft log book that indicating the service bulletin has been completed. 8. Complete Bulletin Completed Record form and forward to MD Helicopters.
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.
Source: NTSB Aviation Accident Database
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