CHI06LA260

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."

History of flight

On September 11, 2006, about 1015 eastern daylight time, an experimental amateur-built airplane, registered as Endless Skies Aviation Inc. L164, N2627J, sustained substantial damage when wing spars failed during cruise near Durand, Michigan. The pilot executed a forced landing to a nearby field. The personal flight was operating under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed at the time of the accident. No flight plan was on file. The pilot and pilot rated passenger reported no injuries. The flight originated from the Livingston County Spencer J. Hardy Airport, near Howell, Michigan, about 1000, and was destined for the Bismarck Municipal Airport, near Bismarck, North Dakota.

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 pilot immediately]

pulled the power back to slow the aircraft. [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. The landing was

uneventful.

Personnel information

The pilot held a commercial pilot certificate with single-engine and multi-engine land airplane ratings. His most recent Federal Aviation Administration (FAA) second-class medical certificate was issued on February 20, 2006. The pilot reported having accumulated a total of 7,950.9 hours of total flight time, 200 hours of flight time in the 90 days prior to the accident, and 80 hours of flight time in the 30 days prior to the accident.

Aircraft information

N2627J was registered as an experimental amateur-built Endless Skies Aviation Inc. L164 airplane, serial number CA004-90. The airplane was reported to be powered by a 180-horsepower ECI Titan O-360 engine. The airplane was constructed from a BushCaddy L164 kit. The airplane had accumulated 40.6 hours of flight time.

According to the kit manufacturer's data, it was a four-seat, tailwheel, externally braced, high-wing airplane of all metal construction with a fiberglass nosebowl. The airplane was designed with a 2,500-pound gross weight. The airplane had two main doors. The cabin construction started from a cage. The cage was built from 6061-T6 aluminum angle and gusset reinforcements and it was pre-jigged and pre-drilled. The airplane's fuselage was reinforced with stringers that span the entire length of the bulkheads to the tail section. Rear bulkheads were designed for tailwheel and float operation. All four corners of the fuselage were reinforced with interior and exterior sandwich construction. The leading edge of the vertical stabilizer was designed with a forward pitch, eliminating the need for strakes. Elevators were trimmed from within the cockpit by means of a spring mechanism. The high lift wing design is a NACA 4412 modified airfoil. The 63-inch constant chord wings were designed with both dihedral and washout. Landing gear was constructed from welded 4130 steel tubing. The airplane was equipped with Frise ailerons and flaps. This airplane kit's aileron hinge brackets were not pre-drilled by the kit manufacturer.

Meteorological information

At 0953, the recorded weather at the Bishop International Airport, near Flint, Michigan, was: Wind 080 degrees at 8 knots; visibility 10 statute miles; sky condition overcast 9,500 feet; temperature 12 degrees C; dew point 8 degrees C; altimeter 30.29 inches of mercury.

Wreckage and impact information

FAA inspectors performed an on-scene examination of the airplane. The front and rear spars failed. The examination revealed that the aileron hinge brackets were not attached to the ailerons as depicted in the kit drawings for the airplane. The bracket's fastener holes were drilled at spacing different from depicted.

Additional information

The pilot's safety recommendation, in part stated:

The cause that lead to the aileron flutter was incorrect placement of 4

holes that bolted the control lever to the aileron spar which allowed it

to flex. ... There was a S.B. [service bulletin] on the install of this part

but [the kit builder] missed it. I also missed seeing it on the

manufacturers web site. ... [The kit builder] ... had the airplane

inspected as per [Canadian] rules and no sqwaks were found. He also

worked with his local [Experimental Aircraft Association] in Michigan

and [an airframe and powerplant mechanic]. All parties missed it. The

factory [kit manufacturer] now pre drills these holes to prevent builder

error.

Subsequent to the accident, the kit manufacturer issued SB-2. That SB is available from the www.bushcaddy.com website. SB-2, BOLT HOLE CRITICAL DIMENSIONS, 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 FAA was a party to the investigation.