by National Transportation Safety Board

“ The fatigue propagated rearward in a low stress manner in the skin for about 1 inch. Aft of the spar area, the fracture propagated on various slant planes through the skin indicative of high stress propagation. Scanning electron microscope (SEM) examinations found that the slant region was made up of mostly ductile dimples with interspersed regions of fatigue and arrest failures. Many of the arrest features, particularly toward the aft end of the cracks were consistent with mechanical damage on the fracture due to fracture face closure and recontact. ”

“ It is critical that thorough documentation of the information recorded by a flight data recorder be available for foreign- or U.S.-registered air transport airplanes that fly into or out of the United States. ”

“ Approximately 25 feet east-southeast of the remains of the fuselage center section and right wing sections was the beginning of a debris field containing the forward fuselage and cockpit sections of the airplane. The debris field extending outward in a 110-degree arc for approximately 150 feet, beginning at 145 degrees and extending south through southwest to approximately a 255 degree heading. The majority of the debris fanning outward in the area approximating a 155 to 170 degree arc consisted of bulkheads, stringers, skin, and broken wood floor panels from the airplane's nose section. ”

“ The first fatigue region was found in lower wing skin, on a flat, 90-degree plane relative to the skin surface, and extended from a rivet hole between stringer 14 and 15, aft for about 0.6 inch, before transitioning to overstress. The region had been covered by a 9.6-inch-wide doubler that extended from the forward edge of stringer 14 to the aft edge of stringer 15. ”

“ The inspection and maintenance programs employed by H&P were based on an established military program developed in the late 1980s when this airplane was first delivered to the Forest Service. Review of these programs revealed that they were based on the original design intent and military mission profile, and that no continuing airworthiness program had been established to determine if the current inspection and maintenance programs were appropriate and effective taking into account the increased age of the aircraft and the new low level firefighting mission. ”

“ Flight 801 departed from Kimpo International Airport, Seoul, Korea, with 2 pilots, 1 flight engineer, 14 flight attendants, and 237 passengers on board. The airplane had been cleared to land on runway 6 Left at A.B. Won Guam International Airport, Agana, Guam, and crashed into high terrain about 3 miles southwest of the airport. Of the 254 persons on board, 228 were killed, and 23 passengers and 3 flight attendants survived the accident with serious injuries. The airplane was destroyed by impact forces and a postcrash fire. ”

“ As part of the March 26, 1992, internal memorandum, OAS recommended that DOI notify the FAA of the findings and solicit their assistance in resolving the airworthiness problem, with specific help in providing some standardization among operators. The memorandum further recommended that DOI's use of these C-130A aircraft should be based upon an inspection and maintenance program, which incorporates all the inspection life-limited component overhauls/replacement and maintenance requirement for continued airworthiness. ”

“ Visual examinations of the wing pieces from the rear spar found that all separations were typical of overstress separations with no indications of fatigue or other progressive cracking. The deformation associated with the spar as consistent with the leading edge of the wing rotating downward about the rear spar area.
Visual examination of the tubular strut-type mount legs from the number 1 engine mount showed features consistent with overstress separations on all fractures. No evidence of preexisting cracking was uncovered. ”

“ The Korean Civil Aviation Bureau was ineffective in its oversight of Korean Air's operations and pilot training program.
34. The Federal Aviation Administration's International Aviation Safety Assessment program (which evaluates a foreign civil aviation authority's ability to provide adequate oversight for its air carrier) is not adequate to determine whether foreign air carriers operating into the United States are maintaining an adequate level of safety. ”

“ The two body fuel tanks, two wing tanks at the carry-through section, catwalk, and slurry tanks were broken open, charred, melted, and consumed by fire. Sections of the slurry tanks, slurry tank doors, doors uplocks and actuator arms, and fuel tank baffling fanned outward from the center fuselage section in a 30-degree arc extending along a 265 degree heading. Fire retardant chemical also fanned outward along the ground in this area. Fire retardant was observed on the east-facing sides of tree trunks in the area, extending from the roots of the trees upward approximately 15 to 30 feet. ”

“ According to Lockheed Study LG81ER0148, the forward underside region of the center wing, at CWS 185.5, was known to be susceptible to fatigue. However, the location was slightly aft of the area examined. In addition, the study cited that the critical size for a crack growing in the wing skin alone was 1.72 inches, while the critical size for a crack growing in the wing skin and stringer together was 0.86 inch. ”

“ WRECKAGE AND IMPACT INFORMATION Safety Board investigators examined the wreckage at the accident location in a pasture along the east side of Highway 395, 31.47 miles east southeast of the departure point at Minden. There were two debris fields separated by a barbed wire fence. The first debris field consisted of the wings, engines, and propellers, and started 250 feet east of Highway 395. It was measured about 500 feet in length on a magnetic bearing about 090 degrees. A post accident fire consumed major portions of the wing structure and engine magnesium components. ”

“ The challenges associated with operations to Guam International Airport support its immediate consideration as a special airport requiring special pilot qualifications.
8. Although the captain apparently became confused about the glideslope's status, the flight crew had sufficient information to be aware that the glideslope was unusable for vertical guidance and should have ignored any glideslope indications while executing the nonprecision localizer-only approach.
9. Navigation receivers other than glideslope receivers may be susceptible to spurious radio signals. ”

“ The Forest Service conducts a pre-use inspection of the aircraft, personnel, and facilities prior to executing the airtanker contract. The Forest Service does not maintain qualified inspectors dedicated to examine the company's maintenance procedures or practices, nor do they have personnel trained and dedicated to conduct oversight inspections of air tanker operators. ”

“ Concerning the detectability of the cracks, Lockheed reported that, �Non-destructive inspection methods could have detected the existing fatigue cracks in the wing lower surface skin panel prior to this accident occurring.� The company noted that a directed radiographic inspection in the area of each lower surface doubler is capable of detecting fatigue cracks in order of 0.50 to 0.75 inches with high confidence, providing skilled inspectors are used. Inspection intervals appropriate for this detectable crack size can be determined from a damage tolerance crack growth analysis ”

“ Although the supporting structure was fractured or consumed by fire, the engines retained their relative positions on the right wing. The persistent odor of ammonia was detected in and about the No. 3 engine. ”

“ The captain was fatigued, which degraded his performance and contributed to his failure to properly execute the approach.
16. Korean Air's training in the execution of nonprecision approaches was ineffective, which contributed to the deficient performance of the flight crew.
17. U.S. air carrier pilots would benefit from additional training and practice in nonprecision approaches during line operations (in daytime visual conditions in which such a practice would not add a risk factor) . ”