Fleetwide Replacement of Propeller Assemblies Pending

The U.S. Air Force has grounded most of its C-130H Hercules aircraft due to a problem with the storied cargo aircrafts’ propeller assemblies. Air Mobility Command (AMC) has confirmed the grounding, and states the repair timeline is unclear.

The exact nature of the problem with which the C-130H’s propellers are afflicted remains undisclosed, but AMC reports 116 of its 122 H-series Hercules airplanes were grounded on 27 September 2022 due to concerns their propeller assemblies may be defective. Inspections slated to occur over the coming days will show how many of the grounded aircraft are actually defective. AMC went on to say that the groundings are widespread, and affect primarily the Air Force Reserve and Air National Guard.

On Wednesday, 28 September, the unofficial Facebook page Air Force amn/nco/snco posted a screenshot of a time compliance technical order pertaining to the groundings. Two days later, the page posted a screenshot of a slide indicating the propeller assemblies in question had been installed in one-hundred C-130Hs, as well as the entire inventories of eight MC-130H Combat Talons.

In a public statement, Air Mobility Command asserted that a maintenance crew at Warner Robins Air Logistics Complex in Georgia had found a persistent leak emanating from a C-130H propeller hub while conducting a post-maintenance run-up of the plane’s engines. That propeller assembly was removed and sent to the complex’s propeller shop, where a technician discovered a crack in an as-of-yet unidentified component. Further inspections turned up similar malfunctions in two additional C-130H propeller assemblies.  

AMC ordered immediate field level visual inspections of all C-130Hs equipped with 54H60 model propellers. Metallurgical reviews and stress analyses were also ordered. Air Mobility Command subsequently authorized the replacement of all problematic propellers.

Newer C-130Hs and C-130Js upgraded with the eight-bladed NP2000 propeller system are not affected by the order.

Propeller woes have plagued the USAF’s C-130 fleet on former occasions. The prevailing issue with the 56H60 architecture is the second instance in three years that’s seen significant numbers of C-130Hs grounded due to malfunctions of their propeller governors, blades, or ice-protection systems.

In February 2019, the Air Force grounded sixty C-130Hs—nearly one third of the fleet at the time—for several weeks due to concerns that the aircrafts’ pre-1971 propeller blades could crack. The suspect blades were replaced over subsequent weeks.

In January 1998, the US Secretary of the Air Force directed the acting USAF Chief of Staff to conduct a broad area review (BAR) of the C-130’s safety record. The request derived of a U.S. Senate mandated investigation of the King 56 Accident—a 1996 tragedy in which ten lives were lost when a C-130 went down in the Pacific Ocean. The review took into consideration all C-130 aircraft systems with specific emphasis on safety-related issues, or perceived or known subsystem or aircraft deficiencies. The BAR concluded that the C-130 had been and remained a safe and dependable aircraft.

FMI: www.af.mil