by National Transportation Safety Board

“ 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. ”

“ Tanker T130 flew down the east side of the drainage valley and proceeded to make a salvo fire retardant drop. Just prior to the completion of the drop, the nose of the airplane appeared to rise and the airplane started to initially arrest its descent and to level out. The nose of the airplane then continued to rise towards a nose up attitude and almost at the completion of the salvo fire retardant drop, the airplanes wings folded upwards and detached from the fuselage at the center wing box beam-to-fuselage attachment location. ”

“ 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 ”

“ The results of the service life calculations were that the service life endurance point and the structural action point for the center wing were 19,384 and 11,910 flight hours respectively. The structural action point was defined as that point where 10 percent of the center wings would be expected to have major repair or replacement due to fatigue cracks and the service life endurance point was defined as that point where 50 percent of the center wings would be expected to have major repair or replacement due to fatigue cracks. ”

“ The study, Operational Retardant Evaluation (ORE) , addressed all phases of aerial firefighting. Excerpts from the study addressed the potential for fixed wing airplanes exceeding their structural operating limitations. Recorders were installed on some airplanes for data collection. Airspeed and g-loading exceedences were recorded. Airspeed exceedences were associated with the normal practice of making downslope runs that result in an airspeed increase. ”

“ The latest revision to tanker T130s Operating Limitation sheet, dated June 1, 1998, required the airplane be maintained and serviced in according with the same USAF T.O. manuals as the previously issued Operating Limitations sheet and further added a requirement for the additional service and maintenance of the airplane in accordance with a company derived manual entitled H&P-C-130A Inspection Guide. The referenced H&P-C-130A Inspection Guide is also called the Inspection Planning Guide (IPG-182) , which was approved by the FAA Long Beach Aircraft Evaluation Group on March 22, 1995. ”

“ AIRCRAFT INFORMATION General Airplane History The USDA Forest Service promoted the transfer of military surplus C-130A airplanes to the contract fire tanker operators in an effort to update the fleet of airtankers to an all turbine fleet. After the USDA Forest Service facilitated transfer of an airplane, it became the operators financial responsibility to prepare the airplanes for the airtanker mission. ”

“ In summary, the paper said that it appears the current C-130A surplus military aircraft maintenance standards to which commercial operators are being held are not equivalent to minimum essential PDM inspection and TBO items necessary to sustain an aircraft in an airworthy condition regardless of the flight environment in which the aircraft is operated. ”

“ 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. ”

“ USFS Aviation Mishap Information System The Aviation Management part of the Forest Service has developed a reporting system called the Aviation Mishap Information System (AMIS) , which is an electronic data base encompassing all aspects of aviation mishap reporting within the Forest Service. A review of the data for the C-130A airplanes from January 1, 1988, to June 17, 2001, revealed a total of 11 entries, with two for N130HP. None of the entries were directly or indirectly related to the wings or any damage to the wings. ”

“ According to 14 CFR 21.41, a TC is considered to include the type design, the operating limitations, the certificate data sheet, the applicable regulations pertaining to records compliance, and any other conditions or limitations prescribed for the product. The Forest Service had listed SN 56-0538 on TC A15NM, revision 2 when T130 was first registered and an airworthiness certificate issued. The Safety Board was unable to obtain a copy of TC A15NM, revision 2; therefore, the date of issuance and the exact requirements outlined in the type certificate data sheet (TCDS) is unknown. ”

“ ADDITIONAL INFORMATION C-130A Certification, Airworthiness & Maintenance Issues In 1991, during inspections into the operation of large surplus United States military aircraft certificated in the restricted category, the FAA discovered that some confusion existed as to under what circumstances persons or property may be carried. ”

“ Based on these findings, Lockheed recommended that the C-130A fleet be inspected for cracks in the vicinity of WS 61 center wing lower surface with the initial inspection to be performed at 12,000 flight hours and a recurring inspection every 2,500 flight hours.
USAF Technical Order 00-25-4 addresses depot level maintenance of aircraft in the inventory and outlines the types and scope of program depot maintenance support. According to the order, depot level maintenance comprises a set of heavy inspections requiring skills, equipment, or facilities not normally possessed by operating locations. ”

“ In the 1990�s a Fokker F27 firefighting aircraft was analyzed as part of a Canadian airworthiness study, which found that, �The F27 firefighting aircraft operated in a firefighting role is exposed to a harsher loading environment than initially intended for a typical transport role aircraft�the time spent in the firefighting role is 5.7 times more severe that the typical Fokker transport role operation.� Because of these findings, the inspection intervals, limitations, mandatory replacement times, and remaining airframe life limits for the Fokker F27 firefighting aircraft were modified. ”

“ C-130A Maintenance Program USAF C-130A Testing, Restrictions, and Inspection Program In the late 1970s Lockheed performed a series of service life analysis tests on major components of the C-130 aircraft, one of which was the center wing and, in 1978, delivered their findings to the USAF. With respect to the C-130A center wing, three main areas were considered for analysis, each one constituting a major discontinuity in the center wing fuselage longeron carry thru at CWS 20L/R, fuselage-to-wing joint at BL 61, and outer-to-inner wing point CWS 220. ”

“ C-130 Operational Loads Recording Programs has shown the firefighting missions to be substantially more severe than typical military logistics operations and consequently, aircraft operated in this role would require inspection intervals as much as 12 times more frequently than typical military transport usage for meeting damage tolerance requirements.
Firefighting Tanker Airplane Flight Envelope Performance Study An industry study was conducted during the fire seasons 1983 through 1989. ”

“ The inspection provides a detailed preliminary nondestructive inspection (NDI) of the lower skin doubler, with the doubler still installed, using a portable x-ray unit. If cracks are detected using the x-ray, the doubler is removed and a backup eddy current inspection is performed. The outboard doubler inspection called for in CW 30 is not included in the set of center wings inspection called out in IPG-182.
Lockheed Service Bulletin 82-557 The C-130 models B through E had the doublers installed only outboard of BL 61L and 61R. The C-130J has no lower skin doublers at all. ”

“ At the time of the accident, the most recent revision of the TCDS, revision 4, had not been updated to include the IPG-182 or the additional maintenance manuals called out in the IPG-182.
Hawkins and Powers C-130A Center Wing Inspections General visual inspection of the wings occur at every check; however, detailed inspection of the wings are not covered in any particular check but are called out in section III of IPG-182, entitled Structural Inspection Program. Inspections for the wings are covered under zonal inspections 500 (left wing) and 600 (right wing) . ”

“ The original maximum-g load factor for the C-130A was +3.0 g/-1.0 g up to maximum level flight speed (Vh) at design gross weight (108,000 pounds) ; +2.0 g/-1.0 g up to maximum level flight speed (Vh) at maximum alternate gross weight (124,200 pounds) . Operational limitations are defined in terms of gross weight and airspeed limits at 2.0g, 2.5g, and 3.0g missions in Figure 5-5 of T.O. 1C-130A-1. The maximum load factor on the FAA approved N130HP airplane flight manual is 2.5g based on the FAR Part 25 (25.337) and Car 4b. (4b.210) requirements. ”

“ Flight Standards should issue an Advisory Circular specific to C-130A inspection program approval requirements (long) 4. AIR should establish an USAF/FAA liaison relationship for C-130A airworthiness necessary to establish a �core� list of T.O.s of the Programmed Depot Maintenance (PDM) inspection items (immediate/ongoing) 5. Flight Standards should issue a bulletin to FAA Field Offices on approval of C-130A inspection programs to ensure that the minimum �core� items are incorporated (immediate) 6. ”

“ An internal DOI information paper written after the FAA�s response to DOI�s request for assistance continued to raise the issue of the minimum and acceptable certification and maintenance requirements for C-130A aircraft. ”

“ This station also supplied surface pressure at 5-minute intervals, and during the hour preceding the accident, there was no significant pressure jumps reported. Mechanical and/or mountain wave induced turbulence and down slope winds most likely existed at the time of the accident. ”