NTSB Identification: CHI08IA200
Nonscheduled 14 CFR Part 91: General Aviation
Incident occurred Thursday, July 17, 2008 in Rockford, IL
Probable Cause Approval Date: 04/15/2009
Aircraft: Eclipse Aviation Corporation EA500, registration: N875NA
Injuries: 2 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The positioning flight was in cruise flight and had just encountered light turbulence when the left-hand wing-to-body fairing separated from the airplane. The panel had been last removed by company maintenance personnel performing maintenance relating to the autopilot system. The forward flat portion of panel had four screw holes in the underlying structure, but the fairing had only three screw holes. Inspection of the operator's other EA500 airplanes showed that some fairings made use of four screw holes while others made use of three screw holes even though four screw holes were available in the underlying structure. An inspection of the airplane revealed that all of the screws were intact except for three screws located at the forward flat edge of the fairing. The respective nuts for these three screws were in place. All but one of the screws and grommets for the curved fairing piece had pulled through the fairing and were attached to the underlying structure. Two and possibly three screw holes at the forward edge of the flat piece of fairing did not have grommets in place and radial cracking of the finished coat was observed at these holes. Also, a delamination ring was observed on the backside of the flat piece of fairing at the screw holes. With the absence of grommets there is a reduced force necessary to pull through the fairing. The outer diameter of the screw head and grommet differ by 0.040 inch. Larger grommets with an integral flange are used in other areas of the airplane, which provide more surface area, distribute contact forces, and improve adhesion to the screw hole. According to the operator, the repetitive removal of screws would result in the countersunk metal grommets loosening from their adhesive bond to the composite fairing.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The improper installation of the forward edge of the left-hand wing-to-body panel, causing the fairing to separate from the airplane during an in-flight encounter with light turbulence. Contributing to the event was the use of small-head screws and grommets in securing the fairing. Full narrative available
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