Lockheed C130 N119TG accident near Santa Barbara, California

Probable cause

The failure of the No. 3 bleed air duct due to corrosion, which resulted in numerous system failures and the pilot’s inability to maintain directional control during the landing roll.

NTSB analysis

During the final leg of a cross-country flight, the flight 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. The crew subsequently diverted to a nearby airport and trouble shot multiple anomalies, including engine fire warning lights from the N0s. 3 and 4 engines and the loss of normal hydraulic pressure. The captain elected to feather the No. 4 engine but did not shut down the No. 3 engine at that time to retain three-engine performance. During landing, the captain was unable to maintain directional control and the airplane departed the runway. The captain then intentionally ground looped the airplane to avoid hitting the main terminal building and airplanes that were parked on the ramp. The airplane undercarriage, right wing, and nose area were substantially damaged.

Postaccident examination of the airplane revealed that the No. 3 bleed air duct had failed. Further examination of the bleed air duct revealed stress corrosion cracking preceded by corrosion pitting on the interior surfaces. The microscopic features observed were consistent with pre-existing cracking prior to the final circumferential fracture of the duct. When the duct failed due to corrosion, hot air was directed onto surrounding electrical wires and hydraulic lines, which subsequently resulted in numerous system failures. The captain was subsequently unable to maintain directional control during the landing roll.

Text from the NTSB. Open the NTSB docket for WPR19LA242 for the full record.