NTSB Identification: CHI06LA260.
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Accident occurred Monday, September 11, 2006 in Durand, MI
Probable Cause Approval Date: 05/29/2007
Aircraft: Endless Skies Aviation Inc. L164, registration: N2627J
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The experimental amateur-built airplane sustained substantial damage when a wing spar failed during cruise. The pilot executed a forced landing to a nearby field. The airplane had accumulated 40.6 hours of flight time. The pilot's accident report, in part, stated, "When the aircraft reached 135 MPH indicated and was at that airspeed for a minute or two in calm stable air it suddenly developed an aileron flutter. Both ailerons fluttered. ... [The passenger] noticed the flutter before [the pilot] because the stick did not shake. The flutter started at the trailing edge of the wing and progressively got worse. Wing tips traveled 4 to 5 [inches] up [and] down. [The pilot] saw the right wing fail in an up position. The flutter stopped at approx 120 MPH. The nearest airport was 8.5 miles away. That was too far away. [The pilot] elected to land in a farmer's field straight ahead before we experienced further wing failure." An on-scene examination revealed that the aileron hinge brackets were not attached to the ailerons as depicted in the kit drawings for the airplane. This airplane kit's aileron hinge brackets were not pre-drilled by the kit manufacturer. Subsequent to the accident, the kit manufacturer issued a service bulletin (SB). That SB, in part, stated, "As of January 2004, Parts L370 R & L are delivered to customer pre-drilled for bolt holes as per attached drawing. Compliance method: Customers who have received the above parts un-drilled should note that the center to center distances of the bolt holes are critical. Particularly those which are for the bolts holding the assembly to the aileron spars. The attached drawing dimensions must be respected."

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The kit builder's improper installation of the aileron bracket leading to the aileron flutter during cruise that resulted in the wing spars' failure.

Full narrative available

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