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Comment by eismcc | Hacker News Reader

“unstart” - while a terrifying euphemism - is there is reason “stall”, or similar, is not used?

An unstart is a specific phenomenon where supersonic flow of air into the engine gets disrupted. It's very different from a compressor stall where the airflow _inside_ the engine is disrupted. Wikipedia has a pretty decent explanation: https://en.wikipedia.org/wiki/Unstart

In movies you see military folks with a very dry sense of humor. Doubly so for Airforce/Navy pilots, and then test pilots just bury the needle.

Having worked with a few different veterans over the years (army, Intelligence, and submarine) I don't have anything in my small but diverse sample size that disagrees with that mythos.

Golden Era NASA was mostly pilots and quite a few of them test pilots. "Houston, we have a problem" is iconic but as far as I can tell, not exceptional.

> Houston, we have a problem

A lot of people comment on this, but it succinctly relays the severity, in that the the pilot is alive, and the radio works.

I do wonder if the words should be further away from each other phonetically though - start … unstart seem close enough to be confused if the radio is noisy

Nobody is going to be talking about an unstart over the radio in an emergency situation. It took 2-3 seconds between the unstart and the aircraft disintegrating.

I get that but it’s not my point. I’m wondering in general about word choice to minimize collisions

I suspect the pilots and ground crew save their energy to fight about the things they are likely to say over a radio and let the engineers do whatever they want with the rest.

Unstart is a lot less evocative than “flameout” as used in the Top Gun movie. Flameout sounds like the plane is on fire. Especially if garbled.

Meanwhile, if your righter pilot sounds like he said engine start while flying? That’s only gonna happen if the engine already shut down. So that’s only ambiguous until the pilot keeps talking, in which case you know he was able to restart the engine before losing consciousness, versus the end of that conversation.

I read Chuck Yeager's autobiography when I was a kid. I remember from that that when a fellow test pilot fatally crashed, they'd say he "bought the farm".

“The Right Stuff” book evokes this atmosphere nicely.

Looks like it's a technical term for a particular type of supersonic behavior:

https://en.wikipedia.org/wiki/Unstart

The semantics is start/unstart are definitely more interesting in this context and seem less dramatic in the context of wind tunnel tests

> “unstart” - while a terrifying euphemism - is there is reason “stall”, or similar, is not used?

"stall" has a specific meaning, and it isn't what happened.

The supersonic shockwave-cone would enter the engine intake, which leads to an un-start. The weird cones that stick out the front of the engines can be manipulated to slow down the incoming air and keep it below supersonic at the intakes, which is normally done automatically with little analog computers that apparently failed somewhat regularly and in this case spectacularly during a banking turn.

In the course of helping an acquaintance do research for a book, I listened to hours of interviews with an 80 year old aerodynamics specialist who worked for Boeing for decades. It was fascinating stuff. One of his specialties was the design of the inlets for jet engines and, through the conversation, I learned that the inlet is the entire aerodynamic approach to the actual engine intake, starting before the air even encounters any of the structure of the aircraft. Turns out that certain designs cause turbulence out in front of the aircraft and all of that path to the intake must be taken into account.

He referred to the SR-71 inlet design and called the potentially catastrophic disruption of the air an "inlet unstart."

Because "inlet fart", while descriptive of what happens, wasn't socially acceptable.

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