I was wondering if microcontrollers that hobbyists use, such as the 8-bit Atmel AVR ATMega328 which is used in many of my small projects, can be used in sensitive things, for example a life-dependent application such as an aircraft of space shuttle?
I am asking out of curiousity: I am a student in school.
Best Answer
There is a whole industry of reliability engineering which is how safety-critical electronics (and everything else) is made.
Amongst many other things, most chip manufacturers have special versions of their products which are specified for military, aerospace, medical and safety control purposes. This starts with simple things like extended temperature ranges. But the difference between these and ordinary products is mostly one of testing and certification, sometimes to the point where parts have individual serial numbers. You can imagine that such parts -- even if they run the identical code at identical speed -- are much more expensive that the kind for ordinary commercial products. As illustration, a given chip design might be rated with a particular clock rate, and perhaps the manufacturer tests 1 part every 10,000 to check it really does. They might sell you parts where each one has been numbered and tested and give you a certificate with it. The testing and tracking costs money. Another point of difference is doing something to make the part more reliable: such as using different packaging materials which have less background radiation, or radiation-hardening the device; all this prevents some of the causes of random behaviour of devices. The functional performance of these devices is unchanged, but you can see how they would be a better choice for safety-critical products.
You may have noticed at the bottom of the Atmel datasheet
This is how they tell you these are not specified for safety-critical applications. All manufacturers have this kind of thing on their datasheets.
The idea is that while the general specification of the part might make it suitable for a given application, it would be negligent to any particular chip in a safety-critical application without special testing. This is the case whether it's a piece of rope, a screw, or a CPU.
On top of this, there is many design practices, regulations, and certifications of design process which go to make safety-critical engineering. One place to start is the Wikipedia article Safety Engineering
Specifically about aircraft, here are a couple articles from Avionics Stack Exchange