Air Force grounds over 100 cargo planes over defective propeller barrels that could CRACK

The United States Air Force has grounded more than 100 cargo planes over concerns that they had been built with faulty propeller barrels that could burst and leak fluid.

The Air Force Mobility Command confirmed that: Defense News that a large number of its C-130 Hercules cargo planes — of which there were 128 at the beginning of the fiscal year — are now unable to fly.

On Tuesday, 116 C-130 Hercules aircraft and even more of its variants were grounded as they investigate how many have been affected.

The propeller barrels in question were installed on 100 C-130Hs, as well as the full inventory of eight MC-130H Combat Talons, seven EC 130H Compass Calls and one TC-130H, according to the unofficial Air Force amn/nco/snco Facebook page.

Mobility Command has since confirmed that the groundings are “widespread” and will primarily affect operations of the Air Force Reserves and the Air National Guard.

It remains unclear how long it will take for the Air Force to replace all affected propeller barrels.

The announcement comes after a maintenance crew at the Warner Robins Air Logistics Complex in Georgia discovered a persistent leak from a C-130H propeller while testing the aircraft’s engine after it had undergone maintenance.

Authorities told Defense News that the propeller assembly was then removed and sent to a propeller shop, where a technician found a crack in the barrel assembly.

Further inspections revealed that two more propeller assemblies had the same problem, Mobility Command said, and it ordered an immediate inspection of all C-130 Hs with the older 54H6 model propellers and performed metallurgical assessments and stress analyses.

Mobility Command then issued a new order to replace the propellers immediately, although a timeline has not yet been established.

It said newer C-130Js and C-130Hs whose propeller assemblies have already been upgraded with the eight-blade NP 2000 system are not affected by the defect.

This is the second time in more than three years that the cargo planes have been grounded due to problems with the propeller system.

In February 2019, the Air Force grounded 60 C-130Hs — nearly a third of the fleet at the time — for several weeks over concerns that their pre-1971 propeller blades could burst.

That fear arose after a KC-130T crashed in 2017, killing 15 Marines and a sailor.

An investigation found that the crash was caused by a deteriorating propeller blade, which had already corroded when the plane entered an Air Force maintenance depot in 2011.

The corrosion eventually deteriorated into a crack, which had doomed the aircraft.

In the aftermath, the Air Force reviewed the propeller blade overhaul process as a senior review board met to review the crash investigation findings, according to the Air Force times.

It found that there were 23 cases where propeller blades showed some form of intergranular cracking, almost all of which were manufactured before 1971 — the year the Air Force switched to a different manufacturing process that resulted in more uniformly made, reliable propellers.

All those older propellers have since been replaced.