On December 21, 1997, at 1515 central standard time, an unregistered amateur-built Quicksilver GT-500 airplane sustained substantial damage when it impacted the ground during an uncontrolled descent following the failure of the left leading edge wing strut fitting near Bat Cave Field Airport, San Antonio, Texas. The two-place kit-built airplane was being operated as an ultralight vehicle under an exemption to Title 14 CFR Part 103 granted to Aero Sports Connection, Inc., of Marshall, Michigan, to provide a means for single-place ultralight pilot training. The ultralight instructor pilot, who was the owner of the airplane, received serious injuries, and the student pilot, who was the owner's son, sustained minor injuries. No flight plan was filed and visual meteorological conditions prevailed for the local instructional flight that departed from Kitty Hawk Ultralight Field, San Antonio, Texas, at 1415.

In a written statement, the pilot reported that he had taken his "son/student for an orientation flight" and was passing over Bat Cave Field on the way back to Kitty Hawk "when the left leading edge strut bracket broke," and the airplane "entered a violent left hand spin." The pilot further reported that he "was able to deploy the Ballistic Recovery System [parachute] after several tries." Although the parachute slowed the rate of descent "somewhat," the airplane "continued down in a nose down spiral to the left until [it] struck the ground."

A witness, who was at Bat Cave Field, stated he heard a "loud pop" as the parachute deployed, and then saw the airplane descending under a partially inflated canopy. He reported that the airplane was "nose down approx. 45 degrees spiraling left" and "contacted the ground in this attitude" at an estimated speed of "25 to 30 mph."

The FAA inspector who examined the airplane reported that the nose section of the fuselage was crushed aft, the bottom of the fuselage was deformed upward and aft, and the nose landing gear was folded aft. The inspector further reported that the main line fastening the Ballistic Recovery Systems (BRS) parachute to the airplane was wrapped around the propeller drive shaft of the rear-mounted (pusher) engine. According to the inspector, the right wing appeared to be undamaged; however, the left wing was twisted with the leading edge displaced upward. The forward lift strut was detached from the left wing, while the rear lift strut remained attached to the left wing.

Closer examination of the left wing by the inspector revealed that the left leading edge wing strut fitting had separated from the leading edge spar and remained attached to the upper end of the forward lift strut. The cuff-shaped fitting was designed to slip around the tubular spar and fasten to the spar with three bolts inserted first through holes in the front of the fitting, then through holes in the tubular spar, and finally through holes in the rear of the fitting before being secured by nuts. On the accident airplane, the three bolts remained in place in the left leading edge spar with each bolt secured by a nut. Each of the three bolt holes in the front of the fitting was elongated in a direction perpendicular to the longitudinal axis of the wing spar to a point where it appeared that the bolt had torn out along the upper edge of the fitting. The three bolt holes in the rear of the fitting all appeared to be round and undistorted.

Examination of the undamaged right leading edge wing strut fitting by the inspector disclosed that the strut fittings were installed after the wings were covered with fabric. (Review of the "GT 500 Assembly, Maintenance and Parts Manual" confirmed this to be the recommended installation method.) A zipper in the fabric on the lower surface of the wing provided access to insert the fitting inside the wing and rotate it into position. The inspector noted that the rear side of the fitting was not visible without the aid of a flashlight and mirror.

In the section of the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) entitled "Recommendation (How Could This Accident Have Been Prevented)," the pilot wrote:

Bracket was not installed correctly on initial construction of aircraft. Three bolt holes were missed completely. This bracket was in an area that could not be seen even with a very through pre-flight.

Records provided by Aero Sports Connection (ASC), Inc., of Marshall, Michigan, indicated that on March 27, 1996, the pilot was issued an authorization to operate under ASC's "2-Place Training Exemption No. 6080" for a 2 year period. Additionally, two certificates were issued by ASC to the pilot on March 27, 1996. One of the certificates indicated that he was awarded a "Basic Flight Instructor" rating, ASC number BTX000388, and the other certificate stated that he was issued vehicle registration number A10HDN. According to the "Vehicle Registration Request Form" submitted to ASC by the pilot, the registered vehicle was a 1995 Quicksilver GT-500.

During a telephone interview, conducted by the NTSB investigator-in-charge (IIC), and in fax communications, the Chief Executive Officer (CEO) of ASC stated that in January 1997, ASC adopted a policy requiring its authorized instructors to provide training only in vehicles which have a recorded condition inspection, current within the last 100 flight hours or 12 calendar months, whichever occurs first. The CEO further stated that in December 1996, a letter explaining the new policy and a suggested condition inspection checklist based on Title 14 CFR Part 43, Appendix D, were mailed to all ASC instructors.

Copies of the pages containing entries from the "Ultralight Aircraft & Engine Log" for the accident airplane were provided to the NTSB IIC by the FAA inspector. Review of the entries indicated that the airplane was first flown on February 19, 1995. The section of the log entitled "Ownership Records" showed that ownership of the airplane was transferred to the pilot on June 30, 1995. No entries were found in the log indicating the performance of any condition inspections on the airplane. The pilot did not complete the blocks on the Pilot/Operator Aircraft Accident Report asking for the date and time the last inspection of the airplane was performed or for the airframe total time. An entry in the log dated June 6, 1997, stated, "master switch left on, 24 hrs run up on Hobbs." Based on this entry and the hour meter (Hobbs) reading at the time of the accident (121.7) as reported by the FAA inspector, the total time on the airplane was calculated to be 97.7 hours.

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