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Accident Investigation Board Determines Cause of the Puerto Rico Air National Guard Crash

By MS. ALLISON BROWN, HQ AMC Occupational Safety

On May 2, 2018, a WC-130H from the 156th Airlift Wing, Puerto Rico Air National Guard, crashed shortly after takeoff, killing all nine personnel on board. The mission was to fly the aircraft to the 309th Aerospace Maintenance and Regeneration Group at Davis-Monthan Air Force Base, Arizona (known as the “Boneyard”).

The aircraft had been in Savannah, Georgia for nearly a month for prescheduled fuel cell maintenance and unscheduled work on the #1 engine. During takeoff roll, the #1 engine speed fluctuated and did not provide normal flight RPM when the throttle levers were advanced for takeoff. Eight seconds before aircraft rotation, engine #1 RPM and torque dropped significantly. This loss of power initially went unrecognized by the crew. Moments before takeoff, the pilot applied rudder input to keep the aircraft on the runway’s centerline. As the aircraft rotated, it veered left and nearly departed the runway onto the grass. Approximately 15 seconds into flight, engine #1 regained partial power. As the landing gear retracted, the RPM and torque from the #1 engine dropped again, and the pilot called for #1 engine shutdown. The pilot banked left into the inoperative engine, rather than continuing acceleration to three-engine climb speed, while the crew successfully shut down the engine. As the aircraft attempted to climb and turn left, the crew did not retract the flaps to reduce drag and the aircraft never achieved three-engine climb speed. The banked turn into the failed engine was well below the minimum air speed needed for proper control of the aircraft. The left wing lost lift and stalled, and the aircraft departed controlled flight and impacted the ground less than two minutes after takeoff onto Georgia State Highway 21.

The Accident Investigation Board determined:

  • Engine fluctuations had been identified during a previous flight. Maintainers from the 156th Maintenance Group performed two engine runs on the aircraft, but did not follow Technical Order procedures. The #1 engine malfunction was misdiagnosed and the aircraft was cleared to fly without the appropriate repairs completed.
  • The flight crew did not brief coordinated emergency actions or an emergency return in accordance with the Before Takeoff checklist.
  • Although there were several opportunities prior to takeoff for crew members to recognize the #1 engine malfunction, they did not reject the takeoff.
  • After takeoff and upon engine failure, the crew did not complete the Engine Shutdown procedure, Takeoff Continued After Engine Failure procedure, or After Takeoff checklist. These procedures would have called for flap retraction after raising the landing gear, which would have increased airspeed, and recommended to avoid banking left into the malfunctioning engine.
  • Ultimately, the pilot’s improper application of the left rudder, which resulted in the subsequent skid and left-wing stall, caused the aircraft’s departure from controlled flight.