They are so big and it seems like so much could go wrong yet they are statistically extremely successful.
In: Engineering
Passenger aircraft safety regulations, technologies, and procedures are literally written in blood.
With regard to the Electronics and PCB Assemblies used for important equipment on aircraft these are designed and built to IPC Class 3 standard. Class 3 is defined as life/system critical equipment that must function on demand with no down time, or ” **high reliability or harsh environment electronics where acceptable downtime is zero**”
Every step of the design and manufacture has to meet Class 3 IPC standards from design, to manufacture of the bare board, assembly of the board, testing and inspection.
This is quite a high standard to achieve and comes at an increased cost.
A pilot buddy of mine told me that each aircraft is actually about 4 aircrafts smushed into one. Because there are usually at least 3 lines of redundancy in case any particular component fails.
Every crash is investigated for the cause so it can be corrected or new procedures put in place so they don’t happen again.
There’s lots of great answers in here, and I’ll just add a fun anecdote. I worked for one of the big companies that supply Wi Fi on planes. They were always trying to have 99.99% uptime or better. That wouldn’t have qualified to be a system used in standard aircraft operations because it wasn’t reliable enough.
Four nines is less than an hour of downtime over a whole year.
designs are thoroughly tested, any small change needs to be approved.
There are backup systems for everything that is critical, often with different design so it nearly never fails the same way, at the same time. A multi-engine plane can fly with one or even 2 off vs a car that has 1 engine and one steering wheel.
The pilots are highly trained and evaluated regularly on a simulation that presents different scenarios. There are usually a pilot and a copilot who can question decisions or take over if needed. There are mandatory rest time and no tolerance for alcohol and a medical check regularly. Compared to a driver who needs to pass a test once, can drive even after drinking and staying up all night.
The current level of aviation safety is built on the back of decades of follow up and investigations of past failures, and by focussing the investigations on eliminating the cause instead of finger pointing.
Mentour Pilot on youtube does absolutely FANTASTIC in-depth, technical recreations of aviation incidents if you want to see the extent that incidents/accidents/near misses are investigated.
Aerospace manufacturing engineering technologist here.
Very early in the history of flight, it was felt that safety was the most important factor. To achieve that, it was decided that when an accident happened, it should be investigated with the aim of preventing it from happening again. People won’t be honest with investigators if they felt that what they say may get them arrested, or lose them their job, so these investigations do not hold people responsible. This allows maintenance technicians to honestly give accounts of what was done, knowing that even if they were negligent, they won’t go to jail. This allows investigations to not only find the exact chain of events that led to what happened, but also make a recommendation to prevent it from happening again.
That is why, when an engine pylon cracks, the maintenance team can look up the paperwork for it. Not just things like who worked on it last, but they can see exactly which batch of aluminum it was, who made it, the results of the testing on that batch, the smelter than made the aluminum, the mine that got the ore, etc… Because at some point in the past, that information was important, so it is now all collected, and in order to go onto an aircraft, every part needs to have all the required documentation filled out properly. When I went to school, we had some massive blocks of aluminum (.5M X 1M X 3M) that were donated to the school by an aircraft manufacturer, because the paperwork wasn’t complete so they couldn’t use it..
For decades, every time there was a crash, there has been a legally-required investigation to determine the causes of the crash. This does not aim at charging anyone with a crime; but rather at making clear statements on how the crash happened and how it could have been prevented. These then are turned into requirements for making airplanes safer.
Repeating that process *over and over* means that more and more causes of crashes get eliminated.
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Suppose that you make a pie, and the pie turns out to be not very good. You figure out *why* it was bad (“the crust is soggy”) and you do some research and figure out *what could be done* to make it less bad (“parbake the crust before adding the filling”).
The next time you make a pie, you make that change! So even if the new pie is still not perfect, at least it doesn’t have the *specific problem* that the first pie did. Maybe the second pie is not very good because it’s too sour and needs more sugar — but at least it doesn’t have a soggy crust!
So you keep figuring out what’s wrong, and fixing it, and trying again.
But you don’t forget the lesson you learned from the first pie. Every time you’re dissatisfied with a pie you made, you figure out *why* and you fix it the next time. Over time, you build up a whole bunch of rules for how to avoid pie problems.
After making lots of pies this way, eventually you get a reputation as the person who always makes really great pies. It’s not that you started out perfect; it’s that you kept finding problems, fixing them, and not forgetting the lessons of your earlier mistakes.
Historically, the airline industry has been very regulated. The pilots required training, the planes require a minimum level of maintenance, the people in the “tower”, the flight traffic controllers require training, and the exact expected path of a plane must be declared long before the plane takes off. Drivers on the road typically don’t make it their job to understand their vehicle and allow themselves to be distracted. The airline space’s regulations simply eliminate many of the conditions that lead to the types of accidents you see between automobile drivers.
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