KC-135s at risk of vertical fin failure

Roughly 207 KC-135s are in danger of suffering vertical fin failures after non conforming parts may have been installed on them during routine maintenance. The inspections have been expanded to the RC-135 and WC-135 aircraft as well. The problem was found last year, when the 280 vertical terminal fitting pins bought from BlueDog Industries were found to be non conforming. A Quality Deficiency Report was filed in Spring 2022, and the pins were removed from supply. A total of 207 KC-135s were found to have gone through PDM from June 2020-December 2022, with at least some non conforming pins believed to have been used.

At each PDM both vertical terminal fitting pins are replaced, with one going on each side of the vertical fin. A metallurgical analysis was run on two non conforming pins in January, and they were found to have the wrong material, were undersized, had insufficient plating, and lacked shot peening. A more in depth analysis is ongoing to determine durability and the ability of the pins to tolerate damage. The two pins carry 90% of the vertical fin load. If one fails, the vertical fin will depart the aircraft. Each aircraft will require a 30 minute inspection to determine if they have the non conforming pins. Aircraft that do will then have to fly to a repair facility on a one time flight. Of 90 aircraft that had been inspected as of February 12, 24 were found to have non conforming pins. They will fly to Tinker to the Depot for replacement of the pins.

WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- The Air Force is directing inspections of KC-135 tanker aircraft for a non-conforming part in the vertical tail assembly. The Time Compliance Technical Order (TCTO) restricts flight operations until the approximately 30-minute inspection is completed.

The TCTO, issued February 14, follows a similar directive announced February 10 for each KC-135 to be inspected for non-conforming vertical terminal fitting pins (tail pins). While the initial requirement was for inspections to take place in the next 15 days, the new TCTO requires inspection prior to the next flight. The Program Office determined that non-conforming vertical terminal fitting pins, which have not been confirmed to meet technical specifications, may have been installed on some KC-135, RC-135, and WC-135 jets.

www.aflcmc.af.mil...

a reply to: Zaphod58

This may be a dumb question, but shouldn't such critical components be thoroughly inspected and tested for quality standards before being used?

a reply to: nugget1

It's possible they were. There have been several instances where new parts passed inspection when the contract was awarded, and later on when production started corners were cut and the parts were considered non conforming.

Oh, those can't be too important we only have 3 flying over the continental US right now that I can find and a couple in Europe, right....

I mean it's not like these were being used over and over the last 10 days ...

You can't forget the human element, I remember hearing about a woman at the Newport News Boatyard pushing falsified metallurgical tests and acceptance results/certification for a lot of the metals procured and installed on the Navy's fleet.

Accountability is a key factor and validation can be faked by those who just don't care.

a reply to: nugget1

originally posted by: nugget1
a reply to: Zaphod58

This may be a dumb question, but shouldn't such critical components be thoroughly inspected and tested for quality standards before being used?

From what I understand about aircraft parts, for every one made for use, you must test an identical one to failure to prove the part was good. That is one of the reasons why aircraft parts are so expensive.

Need a thousand pins, you also have to break a thousand pins.

a reply to: putnam6

There are something like 386 in the inventory. So there are 179 that didn't have the pins replaced yet and don't require inspection. Until today, the TCTO actually gave them time to complete the inspection, but when they found so many of the first 90, they pushed it up to before the next flight. There are currently nine up, but it's the end of the day, so day ops are winding down.

Depot unfortunately has a long history of pretty terrible behaviors, and darn few actual consequences for those screw ups.

At least this goes above them to the parts supplier, who most likely will face little to no consequences other than a public oopsie statement.

originally posted by: Zaphod58
a reply to: putnam6

There are something like 386 in the inventory. So there are 179 that didn't have the pins replaced yet and don't require inspection. Until today, the TCTO actually gave them time to complete the inspection, but when they found so many of the first 90, they pushed it up to before the next flight. There are currently nine up, but it's the end of the day, so day ops are winding down.

But only 17 surveillance ones? correct?

Still have one focused over North Dakota FWIW

a reply to: putnam6

Only seventeen in the RC fleet, but not all of them went through PDM between June 2020 and December 2022. Only a few of them will be affected, and they're being checked out of caution more than thinking that they got pins installed. PDM is generally every seven years or so, depending on airframe flight time.

Non-compliant parts (counterfeit) was something that was beat into our heads as Quality Assurance inspectors on our PDM lines in Coast Guard aviation. It's astounding how many aircraft parts/components tend to make it through from so-called vendors. Hopefully they can filter these pieces out of their program quickly.

originally posted by: Zaphod58
a reply to: putnam6

There are something like 386 in the inventory. So there are 179 that didn't have the pins replaced yet and don't require inspection. Until today, the TCTO actually gave them time to complete the inspection, but when they found so many of the first 90, they pushed it up to before the next flight. There are currently nine up, but it's the end of the day, so day ops are winding down.

The 2023 edition of FlightGlobal's World Air Forces publication lists 388 KC-135s in active service. The faulty vertical stabilizer pins noticed on many KC-135s is largely one result of the Stratotanker fleet being very old.

a reply to: Potlatch

There's already been at least one that has gone to AMARG this year that I've seen.

The faulty vertical stabilizer pins noticed on many KC-135s is largely one result of the Stratotanker fleet being very old.

No, it really isn't. Regardless of age of the fleet, the pins are replaced every PDM. Non compliant parts have absolutely nothing to do with the age of the fleet, and everything to do with manufacturers cutting corners and saving money.

The active RC-135 and WC-135 fleets have completed their inspections with no faulty pins found. At least one RC-135 at the Depot was found to have faulty pins. There are currently seven RC-135s at the Depot, but no word has been given on how many have faulty pins installed.

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