N119TGLockheed C-130A · 1957

On August 25, 2019, at 2224 Pacific daylight time, a Lockheed C-130A airplane, N119TG, was substantially damaged when it was involved in an accident at Santa Barbara Municipal Airport (SBA), Santa Barbara, California. The two pilots and five crewmembers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 positioning flight.

The operator reported that the airplane was stationed in Malaysia and was relocating to the operator’s home base at Phoenix-Mesa Gateway Airport (IWA), Phoenix, Arizona, for a maintenance C-check. The flight had made a refueling stop in Hilo, Hawaii, and another refueling stop at Santa Maria Public Airport (SMX), Santa Maria, California.

Soon after departing from SMX, the flight crew contacted air traffic control and cancelled their instrument flight rules (IFR) clearance when they broke out of the clouds. Shortly after cancelling IFR, the crew heard a loud popping noise and a loud bang. Simultaneously, the torque gauges provided unusual and fluctuating readings. A crew member in the cargo compartment announced misting hydraulic fluid mixed with smoke. The crew donned their supplemental oxygen and the cockpit crew turned off the bleed air from the four engines. At this time, they also noticed the utility hydraulic pressure fluctuating and a crew member advised that the landing gear should be lowered before there was a total utility system failure. The landing gear was lowered, and the crew observed three green lights from the landing gear. The flight crew then turned off the Nos. 2 and 4 hydraulic pumps. As they continued to troubleshoot the multiple failures, they diverted to SBA based on weather considerations.

While enroute to SBA the airplane began yawing back and forth and the Nos. 3 and 4 fire handles illuminated. The captain elected to feather the No. 4 engine, which stopped the yaw of the airplane. He elected not to shut down the No. 3 engine at that time to retain three-engine performance.

Upon reaching SBA and landing, the captain applied full inboard reverse thrust as soon as the nose landing gear touched down. The right wing began to drop, and the airplane drifted to the right, so the captain applied full left rudder and began using the No. 1 engine reverse to keep the airplane on the runway. The airplane continued to the right and departed the right side of the runway. The captain then intentionally ground looped the airplane, as it was continuing toward SBA's main terminal and parked airplanes. The airplane came to a stop about 270° right of the runway heading. The airplane undercarriage, right wing, and nose area were substantially damaged.

Federal Aviation Administration (FAA) inspectors inspected the airplane and identified that the No. 3 bleed air duct had failed.

According to the operator, the inner wing bleed air duct (part number 19-353632-14) had failed in a location close to the fuselage on the right side of the airplane, which allowed hot air to blow onto the surrounding electrical wires and hydraulic lines.

The failed bleed air duct and a flange remnant were sent to the National Transportation Safety Board (NTSB) metallurgical laboratory in Washington, D.C. The chemical composition of the flange and duct was consistent with 321 austenitic stainless steel. Examination of the bleed air duct revealed stress corrosion cracking preceded by corrosion pitting on the interior surfaces. This cracking proceeded circumferentially along the upper boundary of the weld between the flange piece and the duct end. The microscopic features observed were consistent with pre-existing cracking prior to the final circumferential fracture of the duct. This cracking was located adjacent to the welded joint between the flange and the duct. The cracking was manifest as mixed intergranular fracture with cleavage fracture, consistent with lowered ductility. The lowered ductility was due to the chemical attack inherent in stress corrosion cracking (SCC). The remainder of the duct remnant fracture was consistent with having plastically deformed and fractured from tensile overstress.