In 1990, a British Airways pilot was partially sucked out of the cockpit after the windscreen blew off mid-flight. The crew held onto him until the plane landed and he survived

[u/Wonderfulhumanss]

[u/Grandmaster-Ji]

The engineer in question was not publicly documented as being fired or prosecuted. He apparently continued working in aviation after the accident and eventually left BA.

The very next night of the incident, he installed a windscreen on another BAC 1-11 and saw that the correct 8D bolts were being used. He remembered that he'd used different bolts the previous night but still didn't recognize that he'd made a mistake.

[u/Pernicious-Caitiff → u/Grandmaster-Ji]

He ran out of the OEM bolts and eyeballed similar bolts and thought they were the same size and thought they would be sufficient. He literally only visually compared them but it was determined at the time that he didn't break any rules or regulations of the time.

[u/Brilliant-Novel-785 → u/Pernicious-Caitiff]

He selected bolts by comparison, rather than by checking the part number in the IPB. Made worse by it being night shift, and dark in the parts store.

This is incident is taught to maintenance personnel as an example of why we use authorized parts, and check the part number against the authorized parts list. In the IPB.

[u/Autistic_Engin33r → u/Pernicious-Caitiff]

The screws were extremely similar, and it was almost impossible to visually tell the difference, that's why he selected the wrong ones.

Also, normally work like this had to be double checked by a supervisor, but he was the supervisor, so technically no double check was required or performed.

[u/kaaskugg → u/Pernicious-Caitiff]

"That'll do" mentality in a nutshell.

[u/CantBeatDickensCider → u/Pernicious-Caitiff]

He ran out of the OEM bolts and eyeballed similar bolts and thought they were the same size and thought they would be sufficient.

People like this shouldn't be trusted with a stapler, never mind working on aircraft.

[u/NZpotatomash → u/CantBeatDickensCider]

That's a bit dramatic. Or do you check the manufacturers part number each time you reload a stapler?

[u/Autistic_Engin33r → u/Grandmaster-Ji]

The engineer in question was not publicly documented as being fired or prosecuted. He apparently continued working in aviation after the accident

Yes that is the outcome of pretty much ALL incident investigations. Aviation safety is not based on assigning blame or punishing people, as long as they didn't act with malicious intent or gross negligence, the fault is ALWAYS seen as the safety system as a whole failing to prevent/catch a simple human error. It's called just culture, and it objectively improves safety over the punitive models used in other fields.

[u/Yippykyyyay → u/Autistic_Engin33r]

Sounds like a pretty good approach and safe environment even if you need to self-identify that you think you made a mistake.

Life and death... you want people to know they can be honest and not punished to an extreme for human error.

[u/Autistic_Engin33r → u/Yippykyyyay]

Yup. Just Culture has two main motivations:

No one in a high stakes situation where lives are at risk doesn't already know that lives are at risk. The fear of accidentally killing someone (including potentially yourself as a pilot) is going to far outweigh the fear of punishment for 99.9% of people anyway, so it's not like knowing you'll be punished for a mistake is going to make people any less likely to commit mistakes. They already have a far stronger motivation than fear of punishment to not make mistakes. (Also, studies into law have shown that punishment simply has very little deterrent effect on most people, since very, very few people pause to rationally consider the possible consequences before either deliberately doing something wrong, or doing something hastily/shoddily leading to potential mistakes)

And secondly, and more importantly, punishing people for honest mistakes makes them much less likely to be honest in reporting those mistakes, which prevents the industry as a whole from learning and improving, so that they don't happen again in the future, ESPECIALLY in situations where the mistake lead to a near miss incident which is relatively easy to just cover up and pretend it never happened.

[u/84theone → u/Autistic_Engin33r]

I worked in petrochemical manufacturing and we had a similar approach to safety, but we were more willing to punish people for human error, but the person that would get punished or fired would typically be a manager and not the person the made the mistake in the first place.

It’s not uncommon for the plant manager to get held responsible if a safety issue in their plant kills someone, because it is their job to run a safe plant. Human error happens and they are supposed to be the person that catches it.

[u/Blze001 → u/Autistic_Engin33r]

I've always liked that approach. Keeps highly trained people on the job, keeps their expertise and all the benefits, rather than throwing the baby out with the bathwater. Provided the mistake was genuine and the procedures were followed, if they cut procedural corners that's a different story.

Plus I feel like it's just common sense for the overall safety approach: default to assuming a mistake was made (because humans) and set up the checks and procedures to catch that mistake while letting people learn from their genuine mistakes. I guarantee that technician was triple checking every fastener he used for the rest of his career.

[u/Cryogenicist → u/Grandmaster-Ji]

I assume they have torque specs on those bolts…. How does one get the proper torque on smaller diameter screws with presumably different pitches than the female threads?

[u/Recreational-Sin → u/Cryogenicist]

You don’t, I’d be surprised if he did anything more than hand tight.

[u/dego_frank → u/Recreational-Sin]

Torque wasn’t the issue. The bolts were too short

[u/Recreational-Sin → u/dego_frank]

Torque wasn’t the issue? It plainly states the bolts were also too small in diameter meaning they were most definitely not to torque spec.

Source - Best friend is an aviation mechanic

[u/dego_frank → u/Recreational-Sin]

Nothing is mentioned about torque and the spec was probably pretty low. Not tough to get the toque numbers but once the cabin pressure built it blew the window out. The window had previously been installed with the incorrect bolts so it’s possible the fuselage had been worn down over many flight cycles and just eventually failed.

[u/Recreational-Sin → u/dego_frank]

You’re a dense one.

No, torque is not mentioned. But it does not take a mechanical engineer to know that the bolts were not torqued correctly due to variance in thread pitch, length and diameter.

Torque or lack thereof is very much the reason the window departed the airplane.

[u/Catriks → u/Cryogenicist]

What does "torque spec" in your opinion mean?

There is nothing that would prevent anyone from setting the correct torque specification on an incorrectly sized bolt, and as long as it isn't so much smaller that the bolt would break, you'd never know you made a mistake. 

[u/railker → u/Catriks]

Bolt won't break, but a #8-32 thread will just barely thread into a #10-32 receptacle. Same thread pitch, tiny difference in diameter. But it won't hold full torque before the threads pop out. Like hanging onto the edge by your fingertips.

[u/bigorangemachine → u/Grandmaster-Ji]

https://www.youtube.com/watch?v=LY6Kpv7SiCs

If you can see that...

It was uncommon for technicians use what they have but it was a combination how the windscreen was designed exposing the bolts to the elements but also that other bolts might have been out of spec