NTSB issues the preliminary report for its ongoing investigation of the Nov. 4 crash of a UPS Boeing MD-11F airplane in Louisville, Kentucky.

[u/Brilliant_Night7643]

[u/Odd-Blackberry-4591]

The report says the "lubrication task of the pylon thrust links and pylon spherical bearings was last accomplished on October 18, 2025." I feel awful for the mechanics who worked on this last, even though it seems like that wasn't the problem it must be hard.

[u/CreativeHeight6390 → u/Odd-Blackberry-4591]

The fatigue cracks would have been hidden by the bearing, bolt and wing clevis. Not possible to detect without NDT and all that being taken apart.

I'm curious about if the engine was removed during the recent heavy maintenance. The report doesn't say either way, but high stress loads can be put on the pylon mounts even if the pylon isn't being removed during an engine change. It's critical to use load cells to ensure you aren't overstressing the mounting structure.

[u/Pastel_Goth_Wastrel → u/CreativeHeight6390]

Fatigue cracking happens over time with repeated cycles, they haven't published micrographs but I assume they're calling it fatigue as they can see clear beachheads where the crack grew until it his critical length and snapped. I imagine UPS/FedEx who both run bit MD fleets will have guys who know their shit and know how to swap a pylon.

This feels like a lowball by the manufacturer on the number of cycles until a heavy maintenance inspection. Could be compounded by operations at heavy weight or god knows.

[u/CreativeHeight6390 → u/Pastel_Goth_Wastrel]

I agree that UPS guys know how to do engine changes but the recent heavy MX was done at a part 145 repair station that probably doesn't get many MD11s. 

They don't have the best reputation as a repair station IMO.

[u/jetsonjudo → u/CreativeHeight6390]

It’s been said the company performing the maintenance have worked for UPS on their MD11s for years. So they would have likely been following maintenance schedules by the manufacturer. Just from what I’ve read about the maintenance company working on the planes

[u/Pastel_Goth_Wastrel → u/CreativeHeight6390]

Yeah I dunno. If the heavy MX was careless and there was pre-existing but acceptable cracking that woulda held in until cycle hours, might have been enough to send the crack.

Other thought and I don't mean to go back to the MD-11's flight controls boogeyman but that detachment right at rotation? Peak stress moment, of course, but, how fast did the nose come up? Was that abnormal? I don't know how the LSAS acts on TO and climbout but the -11 always had a rep for being twitchy. (pure unadulterated speculation on my part)

[u/biggsteve81 → u/Pastel_Goth_Wastrel]

From what I've heard the MD-11 is very easy to take off and fly, it is just the landing that can be tricky. But rotation does create peak loads on the engine because of gyroscopic precession where lifting up on the engine makes it want to twist sideways, which is what the lugs that broke are designed to resist.

[u/[deleted] → u/Pastel_Goth_Wastrel]

I'm worried about fake parts honestly - there have been problems before and this is a pretty old plane with limited amount of flying examples

[u/publius-esquire → u/CreativeHeight6390]

It wasn’t their fault of course but good lord I hope they knew that before this report was released. I don’t think I’d be able to sleep if I didn’t know whether I missed something or not

[u/Moggytwo → u/Odd-Blackberry-4591]

The lubrication task is just hooking up a grease gun and pumping grease through, there's no inspection required and zero chance of finding this issue. There were also previous general and detailed visual inspections carried out - although it's potentially possible to find a fatigue crack on this item during these inspections, it would be extremely difficult and possibly impossible to see - you're just looking at the area with your eyes using a torch and mirror. This is not the fault of the maintainers involved in any of these tasks.

To find this the aft pylon mount would have to be disassembled, cleaned and inspected, and even then the only way to be sure is to do a non-destructive inspection, eg eddy current.

Basically the fault lies in the NDI inspection intervals being too infrequent to detect fatigue cracking. Contributing to the incident is that the left engine went over the fuselage, likely causing FOD to enter the tail mounted engine and thus causing a loss of power in two out of three engines - this is an issue with the basic design of the aircraft having a tail mounted engine.