NTSB launches investigation of firefighting aircraft crashes in California, Colorado

             

The National Transportation Safety Board recently released the following updated information on its investigations of two USDA Forestry Service firefighting airplane crashes. Both aircraft were registered to Hawkins and Powers, Aviation Inc., in Greybull, Wyo.

On June 17, a Lockheed C-130A, N130HP, broke apart in flight while executing a fire-retardant delivery near Walker, Calif. The three flight crew members were killed and the airplane was destroyed.

The airplane had departed Minden, Nev., at about 2:30 p.m., to participate in firefighting efforts near Walker. During the retardant drop the airplane's wings folded upwards at the center wing-to-fuselage attachment point and separated. The right wing folded just before the left wing. The crash occurred at about 2:45 p.m. PDT.

The second accident occurred on July 18 at 6:40 p.m., when a Consolidated-Vultee P4Y-2, N7620C was destroyed on impact into mountainous terrain near Estes Park, Colo. The two flight crew members were killed. A post-crash fire ensued. Prior to the impact, the airplane's left wing failed just inboard of engine number two. The left wing fractured at its wing-to-fuselage attachment point along the lower left spar cap.

Fatigue cracks were found in pieces of wing structure in both the C130A and the P4Y airplanes. Both investigations are closely looking at the fatigue cracks as well as other safety issues, such as inspection and maintenance procedures and operational factors.

In both investigations, the Safety Board is collecting data to determine why the cracks initiated and propagated to the critical length that caused the wings to fail catastrophically.

Although metallurgical examinations of both aircraft are ongoing the preliminary results for both have indicated that widespread fatigue was not evident over the entire wing but that in some locations current crack detection techniques may have been unreliable.

During a C-130A contract pre-award evaluation in 1991, the Department of the Interior's Office of Aviation Services inspectors concluded that essential inspection and maintenance services critical to sustaining the airplane in an airworthy condition under normal operating conditions were not being accomplished with the C130A. This prompted the DOI in 1993 to prohibit the use of the C130A on DOI land. The FAA and the DOI subsequently developed an action plan to address many of the same inspection and maintenance issues seen in the most recent C130A and P4Y accident investigations. Since that time, the DOI has dropped its restrictions on the C130A, and the NTSB is investigating how the FAA and the DOI followed through with the proposed action plan and what corrective measures were put in place.

Based on this information, the NTSB will explore whether the crashes were unique or a sign of systemic problems with military surplus aircraft now in public use operations. The investigations are reviewing continuing air-worthiness issues, including the original design intent, engineering support, mission profile, operating limits and inspection intervals, to determine if the airplanes' design and operational limits are appropriate for their current intended use.