Investigation Summary
The accident originated with the failure of the number four blade on the number two (inner-left) propeller. As the aircraft cruised at 20,000 feet, a circumferential fatigue crack caused the blade to liberate. The blade struck the left side of the fuselage and became embedded in the interior right wall of the passenger compartment. This impact sent a massive energy transfer through the airframe, causing an overload of the number three (inner-right) propeller drive shaft. The resulting failure of the number three reduction gearbox assembly caused that propeller to separate, strike the upper right fuselage, and then impact the right horizontal stabilizer, shearing it off. The loss of structural integrity led the forward fuselage and flight deck to separate approximately 19 feet forward of the wingbox. While the forward sections were destroyed by aerodynamic forces during the descent, the aft fuselage remained relatively stable until impacting the ground in a flat spin. Because the aircraft was carrying a large quantity of weapons and ammunition, explosive ordnance disposal (EOD) teams were required to secure the wreckage site before investigators could safely access the debris field.
Final Conclusions
The USMC investigation concluded the cause was the in-flight liberation of propeller blade P2B4 due to a fatigue crack originating from intergranular cracking and corrosion pitting. The presence of anodize coating within the pits proved the corrosion existed during the 2011 overhaul at Warner Robins Air Logistics Complex (WR-ALC) but was not removed. The failure was attributed to systemic deficiencies in the propeller blade overhaul process at WR-ALC that persisted until the facility's propeller line was shut down in late 2017.
Photographic Evidence (1)
Video Analysis
Marine Corps KC-130 Breaks Up in Mid-Flight | Falling Apart Over Mississippi — A detailed reconstruction and analysis of the structural failure and mid-air breakup of Yanky 72 over Mississippi.
If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
Propeller Blade P2B4
The specific blade on the inner-left engine that failed due to a fatigue crack originating from intergranular cracking.
Reduction Gearbox Assembly (RGA)
The assembly on the number three engine that failed due to shock-induced overload, leading to the separation of the right-hand propeller.
Horizontal Stabilizer
The right-hand stabilizer was struck and removed by the departing number three propeller, contributing to the loss of control.
Interesting Facts
- 01The aircraft was nicknamed 'Triple Nuts' due to its Bureau Number ending in 000.
- 02The aircraft was manufactured in 1992 and delivered to the Marine Corps in 1993.
- 03The debris field spanned a 5-mile radius from the main impact site.
- 04The aircraft was not equipped with a Cockpit Voice Recorder (CVR) or Flight Data Recorder (FDR).
- 05The aircraft was carrying weapons and ammunition at the time of the crash.
- 06The propeller blade that failed had been overhauled at Warner Robins Air Logistics Complex in the fall of 2011.
- 07The aircraft (BuNo 165000) was previously damaged on June 1, 2004, at NAS JRB Fort Worth when a storm flipped it onto its wingtip, but it was subsequently repaired and returned to service.
Safety Actions & Advisories
WR-ALC Propeller Line Shutdown
The propeller blade overhaul process at Warner Robins Air Logistics Complex was shut down in the fall of 2017 following the discovery of systemic maintenance deficiencies.