Maintenance-Caused Cracks Ground Hercs


The Air Force has grounded 116 C-130Hs, more than 20 percent of the fleet, after it was determined that inscriptions scratched in the propellers documenting inspections for cracks actually caused cracks. “The process used to engrave serial numbers on the propellers likely contributed to cracks that are being found on the C-130Hs,” Maj. Beau Downey, an Air Force spokesperson, told Defense One. “That process, which involved an electric arc pen to incise digits into the surface of the metal, was stopped about six months ago and will not be used going forward.”

Some of the aircraft have been returned to service but the Air Force won’t say how many. The cracks and aircraft groundings came to light in October, but the cause wasn’t released until this week. Downey said the Air Force is studying how the cracks spread from the inscriptions and is working on getting the Hercs back on the line. “This will be an incremental process based on operational priority and our focus remains the safety of our crews.”

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  1. Really? Really? It’s not like advice on the matter has not been around for YEARS!

    These propellers and blades are generally susceptible to fatigue failure resulting from the concentration of stresses at the bottoms of sharp nicks, cuts, and scratches.

      • The USAF is becoming political, when they should be focusing on mission readiness and troop morale. The Air Force mission actually ended when the Soviet Union fell, but like many huge entities, it was ‘too big to fail’ (Even though the BRAC Commission shut down Air Force bases by the gross during the 1990s, including the base I worked at as a civilian.) Now our military is used to experiment with social engineering, along with being a repository for hideously expensive, functionally useless weapons. If we didn’t have so many bellicose public officials clamoring for more foreign conflicts, we could actually function with the National Guard as our defense posture.

    • Props by their nature are susceptible to weaknesses. Nicks can grow into cracks, and these newer carbonated varieties scare me. I remember examining the prop on a Darter (Aero Commander) with a 3/8 inch deep, filed down, roughly rectangular notch about halfway up the blade. I don’t think that plane would have passed an annual……

  2. Every time my mother (A WWII Veteran) tried to number her children, she’d lose track somewhere between #2 & #5. That always caused the next child to crack. Finally, after the youngest was sent to the principal for disrupting the class with prolonged laughter, she gave us names.
    She solved the cracking problem, and gave us our props.

  3. More confirmation to feed my biases. Lovely.

    Children are taught early and often that the appearance of hard work gets rewarded more than accomplishment. Institutions that cannot figure out how to measure actual effectiveness will quickly start measuring the ability to please the leaders. The leaders will then replicate themselves. Within a couple generations you now have a shadow of the original organization.

  4. How many times as a pilot AC owner were we told about dangers of nicks and scratches on our props and what could happen? Every annual my prop came back smooth and clean with all the nicks and dings cleaned up. Supposedly such cleanups were to be done by a prop specialist but the shops deemed removal of such flaws of very high importance, and someone in the shop did the job because they all knew not doing it was potentially dangerous or at least very expensive down the road. Be interesting to know how much a Herky bird prop blade costs.

  5. All these comments about the ‘stoopid’ air force and how obvious it is not to stamp, nick, or scratch a prop seem to forget that when a typical GA prop is repitched, the old pitch is X’ed out and the new pitched is… wait for it… stamped into prop.

    The article above doesn’t have enough detail. Were these new numbers engraved into the prop blade? The shank? The face end inside the hub? I expect a full telling of the story would show that the location and type of engraving were in a seemingly non-critical area. Except, of course, to the team of prolific commenters led by Captain Hindsight.

  6. I’m no expert in prop stress, but I do know that in other rotating machinery, there is a right and wrong way to imprint or form the device. That’s one reason why some threaded parts have rolled threads instead of cut threads. There is also a procedure for how to imprint data into the surface of pressure vessels to avoid the stress risers caused by a simple pin punch. I would hope that someone checked into the process of electric arc engraving to see if it would cause stress risers before approving it for this application. Maybe the procedure was acceptable for certain locations, but was applied in the wrong place? The Air Force seems unwilling to provide enough detail to fully explain the issue.