F-35 pilot held 50-minute airborne conference call with engineers before crash

The article is somewhat sensationalistic. If you read the actual report you will find out that:

The pilot was not part of the conference call!

What froze was not hydraulic fluid for actuators (in some hydraulic line), but hydraulic fluid in the shock absorbers.

The last paragraph of the article and seems to be missing a few words and reads as the investigators blaming the people directly involved, which is essentially a complete opposite of what conclusions of the report say.

If you want to read the actual report, it's not linked from the CNN article, but it's available here:

https://www.pacaf.af.mil/Portals/6/documents/3_AIB%20Report....

Edit: While CNN says the air force blamed the crash on ice in the hydraulic lines, it's obvious that ice can't be legally culpable. The report actually says:

> Additionally, the [Accident Investigation Board] president found, by a preponderance of the evidence, that crew decision making including those on the in-flight conference call, lack of oversight for the Hazardous materials program, and lack of adherence to maintenance procedures for hydraulic servicing were substantially contributing factors.

They note further down that "The 355th FGS hazardous materials program (HAZMAT) program suffered from insufficient manning and frequent supervision changes at times relevant to the mishap." Basically, they had a barrel of hydraulic oil that sat outside and no one took care of it.

Also interesting is the 6 February 2025 incident, where another aircraft, barely a week after the one that crashed, had the same issue. They tested it inside a heated hangar, then outside in the 15F cold where they reproduced the weight-on-wheels sensor malfunctions, then brought it back in and drained the hydraulic fluid...there's a TON of water in those lines! I'm more familiar with industrial hydraulics in factories and earth-moving equipment, not with aviation...but we have water separators because a few drops of water can be enough to mess with the servo valves when you're near caviation limits. "...approximately one third of the fluid retrieved from the [landing gear] was water" is NOT RIGHT.

Also, I chuckled on reading "...the barrel tested with more than 1024 parts per million (ppm) particulates, which is more than double the allowable limit for particulates in hydraulic fluid... It is important to note that the test does not accurately measure contaminates above 1024ppm, so the contamination was potentially far greater than 1024ppm"

Gives strong "3.6 roentgen, not great, not terrible" vibes!

Of note to readers not familiar with hydraulic fluid, it is hygroscopic:

>Passenger safety requires that in commercial airplanes hydraulic actuators be powered by fire-resistant hydraulic fluids. As a downside, such fluids are hygroscopic which means that these tend to accumulate humidity from the environment

https://www.mdpi.com/2227-9040/8/4/131

The hygroscopic nature of hydraulic fluid is there for the same reason it is in car brake fluid-

it's better to evenly distribute water throughout the fluid, than to have it accumulate in a low point

That's actually a really cool way to deal with that problem!

It is. Right up until you go to hit your brakes hard and it all boils out and removes your ability to apply brake pressure in an emergency and you had no idea how much water was in your line because there's no easy way to check, like a low spot with a sight glass.

Or if you leave a barrel of hydraulic fluid outside until it is partially water and it's not easy to notice when you are handling it.

I think my mental model of hydraulic brakes is too simple. Where is there a low pressure region in a brake line? When I stomp on the brakes, isn't the working part of the hydraulic system going to be at higher pressure?