MIA98LA192

On June 5, 1998, about 1615 eastern daylight time, a Cessna 310K, N366J, registered to the Matsui Aviation Company, experienced an explosion inside the left wing during takeoff from the Opa-Locka Airport, Opa-Locka, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 personal flight. The airplane was substantially damaged and the private-rated pilot, the sole occupant, was not injured. The flight was originating at the time of the accident.

The pilot stated that the flight was uneventful and after landing, he departed the area on a commercial flight, but returned the following day. Before departing on the commercial flight, he asked that the airplane be refueled and when he returned, he was advised by the line service personnel that the upper and lower skins of the left wing were displaced.

According to one of the co-owners of the airplane, he discovered the damage to the airplane 2 days after the accident. He also stated that they typically only filled the auxiliary fuel tanks in the summer to a level about 1 inch below the filler neck, but when he examined the fuel level in the left auxiliary fuel tank that day, it was down 1.5 inches. The pilot told him that he did not use fuel from the left auxiliary fuel tank during the flight.

Examination of the airplane revealed that the upper and lower wing skins were displaced upwards and downwards respectively, and a hole was burned through the upper wing skin aft of the battery box access cover. Soot was noted trailing the rivet holes in the upper wing skin where the skin was pulled away from several of the wing ribs. Soot was also noted exiting from the left wing root fairing. The battery was removed and examination of the positive battery cable revealed that it was not secured by a adel clamp, which by design, is secured to rib No. 23. Additionally, the PK sheet metal screw for the adel clamp was not located but the tinnerman nut on the clamp was in place. Examination of the clamp revealed evidence of electrical arching and also evidence of chafing on the insulation of the positive cable against the opened adel clamp. The left auxiliary fuel tank which had been subsequently drained before the NTSB examination, was fueled to the filler neck area. Fuel seeping from the fuel tank vent line outlet was noted. The outlet is located on the outboard upper section of the fuel tank. The fuel was determined to seep into the area aft of the battery box inside the wing then from that area around the sump. The lower skin surface in the sump drain area was found to contain a wax type residue on the skin. The fuel seepage stopped when the fuel level reached a certain point when tested several times. The left auxiliary fuel tank was then examined while in position and it was determined to be held in place by only two of the six hanger loop clips. One of the six hangar clips was not in place and a clamp which secures the fuel vent line to the vent nipple inside the fuel tank was determined to be in place and finger tight. The tank was removed and examination of the outside area near the fuel tank vent nipple revealed blistering of the reinforcing material. Additionally, examination of the ground where the airplane was routinely kept revealed damage to the asphalt beneath several areas near the left wing auxiliary fuel tank, including the area beneath the sump drain area. The damage beneath the left wing was greater than the damage beneath the right wing.

Review of the maintenance records revealed that the left and right auxiliary fuel tanks were replaced on December 16, 1990. Markings on the external portion of the left auxiliary fuel tank revealed that the tank was manufactured in April 1989. Additionally, the airplane was last inspected in accordance with an annual inspection that was signed off on July 10, 1997. The airplane had accumulated about 31 hours since then when the damage to the left wing was noted. Review of the checklist prepared and used by the mechanic who performed the inspection revealed in part, that the fuel tanks and plumbing are required to be checked. The mechanic stated that he could not recall removing the battery during the inspection and he did not drain or remove the left auxiliary fuel tank. He did verify that the fuel vent line was clear.

According to a representative of the tank manufacturer, it was manufactured under a Parts Manufacturer Approval (PMA) Letter, issued by the Federal Aviation Administration. Hanger clips are not typically included with the fuel cell when shipped to a customer and the tank was proper for the airplane application.

Review of the service manual for the airplane revealed there is a requirement to check the battery cables for condition, corrosion and security every 100 hours. The checklist lists only three types of inspections, a 50-hour, 100-hour, and as required.