Aerospace Stress Engineer
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Aerospace Stress Engineer… Jeez., sounds nerdy and complicated, what the heck do they do?
In simple terms:
- They help you stay safe in the aircraft in the air and on the ground
- Try to reduce your fuel costs by ensuring a light yet safe design that complies with all the required regulations.
Not the long winded answer you were expecting? Sorry, but that is pretty much all they do.
Well…. there is a BIT more to it, but that is the basic summary of it.
Technically speaking, the Aerospace Stress Engineer has a lot of power in the industry, especially the good ones. In some companies, they are the most dominant and highest paid group of engineers, influencing the program objectives and profit margins.
There is indeed a lot we nerds can do, and must do, to help out the management, the design leads, the project leads, and everyone else that relies on us for critical decisions. So let us dig deeper into it in this post.
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What is the role of an aerospace stress engineer?
As I mentioned above, the primary role is to ensure structural integrity and safety. The goal is that a structural member's failure in service is avoided under any circumstances. Or, at least the result of an unforeseen structural failure is not as catastrophic as shown in the picture below.
The safety regulations are mandated by the governing aviation authority that oversees a particular air space. They are there for precisely one reason, to keep passengers safe. Because, my friends, flight is a risky business.
In the USA and surrounding waters , it is the FAA. In Europe and surrounding waters it is the EASA. And there are other agencies across the world that essentially do the same. Generally speaking, there are a lot of similarities in the regulations no matter what agency it is.
In this case, luckily, the interiors of the aircraft were in tact enough that a majority of the passengers were able to escape the burning wreckage. And that safety aspect (safe egress under emergency conditions) is what the cabin structure stress engineers mainly focus on.
The aerospace stress engineer is responsible for ensuring that the structure of the aircraft meets or exceeds all of the mandatory regulations, in order to show compliance.
But what is compliance?
Means or Methods of Compliance (MOC, AMOC):
As part of the airworthiness compliance and certification procedures, the manufacturer must demonstrate compliance to all the applicable regulations. This is done by adhering to the primary method or means of compliance (MOC) according to the established guidance for each regulation.
Alternatively, an alternate means of compliance (AMOC) is also acceptable. However, a lot of supporting data and documentation will be required before approval is granted via AMOC.
In general, there is a long document or spread sheet that lists each and every applicable regulation or requirement. Various columns show how the manufacturer demonstrates compliance (MOC or AMOC). These columns must state how the regulation is complied with exactly as the regulation says, or by alternate means. It may also include responsible people, signatures etc.
Whether it is by test, by analysis, by comparison, or by service history or whether it may be not applicable needs to be identified and stated in the compliance document.
Well then.... Here comes the aerospace stress engineer who works out all the analysis and documentation required to show compliance.
Alright, here is a good link that describes AMOC in more detail, click here
And here is another nice FAA document that goes into the Product Certification
And one more really good document: Transport Airplane Cabin Interiors Crashworthiness Handbook
Cabin Interiors Advisory Circular:
The last link above (Advisory Circular - AC) goes into a lot of detail on Acceptable Means of Compliance (MOC) guidance for cabin interiors crashworthiness regulations and amendments. It includes guidance for 14 CFR Part 25 thru Amendments 25-112.
The amendments are very important. For example, you will notice how the minimum load factors have evolved. For emergency landing conditions (Part 25.561), they have increased in some directions with the amendments.
The bottom line is that the more familiar an aerospace stress engineer is with these different regulations, and AC's and MOC/AMOC requirements, the more valuable she will be as an aerospace stress engineer.
Bottom Line, Know Your Regulations:
So, my dear aerospace stress engineer, read reread and digest the regulations. Read them again, understand them, and study the guidance to become a star aerospace stress engineer. The same applies to the aerospace stress engineer working either primary, secondary, engine nacelle, interiors structures or any other part of the aircraft.
The best aerospace stress engineer knows the regulations and MOCs like the back of her hands, I am still working on it, 🙂