If you're new here and you're wondering who the heck I am and what I've done, here are some threads I've written about my experiences. First, the pain that was testing the original F-35C tailhook, and testing its redesign:

https://x.com/the_engi_nerd/status/1748929186108997841

The flight test instrumentation systems used on F-35 test aircraft:

https://x.com/the_engi_nerd/status/1757243336941871159

Two photos here from the USAF. The first is from 2013, with a maintainer opening an F-35's Maintenance Interface Panel (MIP). The second photo is more recent, showing a maintainer performing the same task. But something's changed: the MIP now has marks near each fastener. Why?
The answer is: to give the maintainer a visual confirmation that they've properly closed the door prior to flight. And like everything, there's a story about what happens when that door ISN'T closed.

This is not a dumb question. I will answer it as well as I can in tweet form.

In combat survivability we talk about kill chains (putting all the things together that you need to do in order to put warheads on forehads) and live chains

https://twitter.com/rmcentush/status/1938723949099291075

Live chains are everything you need to do to keep the other SOB from putting his warhead on YOUR forehead.

To kill something, we have to find it first. Then, we have to determine where it is in relation to ourselves. We must update this idea of its state over time to track it.

Time for another F-35 flight test story, because why not.

Fall of 2010. I had been on the program for a few months as a flight test instrumentation engineer. That job involved supporting the several thousand sensors (temperature, pressure, vibration, strain, etc) on the jets. We also captured information from the jet's digital data buses. A subset of this information was sent via telemetry to the ground to support monitoring during test. No one monitors the situation without FTI.

One day I was in the control room supporting a test of aircraft BF-03.

On Thursday, October 10, the California Coastal Commission rejected the Department of the Air Force’s plans to give SpaceX permission to launch up increase the number of allowed launches at Vandenberg Space Force Base from 36 rockets per year to as high as 50 rockets per year. Among the justifications for this decision were remarks about the political activities that Elon Musk, majority owner of SpaceX, conducts as a private citizen. But what truly sent me was this howler, uttered by Commissioner Dayna Bochco:

I've told this story before, but I had a smaller audience then.

I was once in a meeting with the lead engineer for the F-35 navigation system. I asked a question I had always wondered about: why are many of the F-35's antennas a different color than the rest of the jet?

https://twitter.com/JarodMHamilton/status/1833509490618200331

Context: Northrop Grumman is the contractor responsible for the F-35 Communications/Navigation/Interrogation (CNI) suite. This engineer had worked on the CNI suite for years. So I thought he would know. His answer:

"That's the color the jet was originally supposed to be."

Okay, so in a few replies to people here today, I've said more or less this:

"The F-35 is a great aircraft but it's a terrible program."

I could write some lengthy thread where I cite a bunch of systems engineering stuff, but here's a better way to explain things. One explanation for the problems of the F-35 program has been "There are too many cooks in the kitchen."

Let's take that metaphor farther.

The F-35 program is like a restaurant. But the restaurant is very strange.

Let's put a bookend on the V-22 thread from the other day and tell the story of why I hated the NVH-3A test aircraft. 🧵

https://twitter.com/the_engi_nerd/status/1784937394891899153

This is BuNo 150614 (614 for short). Delivered in 1962, it served as a transport for Presidents Nixon and Ford. It was then sent to the boneyard, where it stayed until 1984. Returned to service, it found its way to NAS Pax River by 1988, where it served as a test aircraft.

On June 1, 2009, the VH-71 Presidential Helicopter program was terminated after years of delays and cost overruns. But we still needed a replacement for the NVH-3A as "Marine One".

Here's the story of how I learned that the V-22 wouldn't be that replacement. 🧵

📸 US Navy With the VH-71 cancelled, the program began looking for solutions. Maybe an existing platform could be used. So the program decided to do a study to see if any existing platforms would work. Part of that was an acoustic survey to see just how loud existing platforms are.

On April 24, 2024, a CH-53K transported an F-35C, tail number CF-01, from its storage site Naval Air Station Patuxent River, Maryland, to to a Navy unit located at Joint Base McGuire-Dix-Lakehurst, New Jersey.

📸 Kyra Helwick Some of you had questions: why not fly the jet? Wouldn't it be more economical to just update CF-01 to the latest F-35 configuration?

To shed some light on these questions, let's look at how the F-35 program used its test aircraft.

📸 Kyra Helwick

As I've just spent a while riffing on in the replies, being a telemetry engineer on the Sounding Rocket program was...an experience. Read the first few paragraphs of this article.

The scenario being described was literally my job during launch. archive.is/oGqY6 These were the kind of computers being used. Luggable, single board computers. 486s, the "new Dolches" we had were equipped with Pentium 1s @ 66 MHz.

I had to cannibalize three of them to get one working.

I installed Windows 95 on one of these in the year 2013

You go to an air show and see one of these on display. An F-35A! But...what's the deal with the black and white stickers all over it? Let's go down the rabbit hole and talk about weapons separation testing on the F-35 as we did it during the SDD days. A 🧵
📸:@Jack1nthecrack Once again, our references are my own experiences and "The F-35 Lightning II: From Concept To Cockpit", specifically Chapter 16, "F-35 Weapons Separation Test and Verification". This chapter is also available standalone if you have AIAA access: arc.aiaa.org/doi/10.2514/6.…

F-35 Flight Test Instrumentation Thread 🧵 Once again, I'm riffing from "The F-35 Lightning II: From Concept to Cockpit". Specifically, Chapter 6, "F-35 System Development and Demonstration Flight Testing at Edwards Air Force Base and Naval Air Station Patuxent River".

But also, I was an instrumentation engineer at PAX.

Hell with it, it’s on internet archive

My thoughts as I read. Down the rabbit hole we go Normalize the salty, hyper competent engineer.

F-35C Tailhook thread 🧵 Primary source here is “F-35C Carrier Suitability Testing” by Tony “Brick” Wilson, who gives us one of the greatest flexes in an AIAA paper I’ve ever seen.

I've been thinking about this tweet all day, because it's hilarious. "S400s don't care if it [the F-35] identifies as invisible." Except, they do, because of the radar range equation, which gives the aircraft engineering team a direct say in how threat radars see the F-35. A 🧵 The radar range equation was developed in the late 1940s by a US Navy engineer, Lamont V. Blake, as he was trying to evaluate competing contractor proposals. It's gone through a lot of changes over the years as our knowledge of radars has grown.