“Shall” used to be like any other word for me. “You shall not pass” was a famous line from the Lord of the Rings movie. “Shall we go?” A legitimate question. No big deal until I worked with legal documents.
The word shall implies assured action. “The contractor shall complete the project by October 8.” There is no room for discussion. A date is set.
If you read a typical contract, you will see the word everywhere, like a gun inserted into every sentence. “The contractor better do what they are supposed to, or I will shoot them. Yeah, take that!”
However, a contract did not introduce me to this word. I used to be employed by a company that produced commercial aircraft parts. At some point, the FAA required careful tracking for the specifications. This process takes some explaining to get a total dose of the madness.
The process begins when an aircraft company produces a set of requirements for the subcontractor. We took these requirements and entered them into an awful program called Doors. We converted the aircraft company requirements into Doors and made a new set of requirements that mirrored the aircraft company requirements. We then linked them to each other. This linking is like opening a door from one room to the next, where the program got its name.
Then, we made a proposed set of specifications (to answer the requirements) linked to the requirements (linked to the aircraft company specifications). When we checked the links, we developed a design plan that met our specifications, which was then linked. Then, we developed a test requirement covering all the specifications linked to everything else. We developed a test plan, recorded the results, and linked everything. I skipped 10+ steps for simplicity, including manufacturing, quality, shal reviews (we actually called them that), and back-linking.
The documentation process took over 3,000 hours for an effort that should have been 100, but this was not the worst part. Because the Doors linking was so tedious, we went out of our way not to change any documents. This translates to knowingly using a poor design because we did not want to change any documentation. Happy flying!
Each Doors statement had a single shall per sentence. For example, “The radio shall work between 0 and 50 degrees Celsius.” We could not combine topics or use other words. “The radio shall work between 0 and 50 degrees Celsius, 0 to 80% humidity.” “The radio operating conditions are specified between 0 and 50 degrees Celsius.” “The radio must work between 0 and 50 degrees Celsius.” While clear to the reader, the FAA did not permit such text. The reviewers were laser-focused on each shall and the surrounding sentence.
There was another enormous problem with this system. The aircraft company set its requirements to meet its performance goals. Yet, the subcontractor had broader requirements to attract more customers. Is it reasonable to use superior parts? Yes, but no.
Using shall statements, let’s link a requirement, specification, test, and test result. “The radio shall work between 0 and 50 degrees Celsius.” “The radio shall work between -20 and 80 degrees Celsius.” “The radio shall be tested working between -25 and 85 degrees Celsius.” “The radio testing results shall state operation between -27 and 88 degrees Celsius.”
Wow, that last sentence was awkward, but that is not the real problem. When looking at the links between specifications, testing, and requirements, they do not match. Most of us understand using a superior part (a radio that works at wider temperatures) is better, but the link reviewers do not accept mismatches. That is the point that the FAA demanded to be addressed. To satisfy the FAA, we made the statements match. “0 and 50 degrees Celsius.” Thus, the aircraft received a part tested to less stringent requirements. Happy flying!
The heart of this process was understanding and linking shall statements. I must have seen 50,000 of them. This intense studying messed me up because when I read something like, “The radio works between -25 and 85 degrees Celsius,” it looks all wrong. And people make claims all the time. “I’m going to the post office around four today.” That sentence is understandable, but there is no shall statement. Thus, no commitment. I do not believe you.
This word indeed messed me up, and I rarely use it. Is it wrong to be afraid of a word? Yeah, it is. I should cowboy up and use it like any other. It SHALL be done!

PS, I know this shall linking mess has led to a genuine safety issue. My former company made a fan controller for the Airbus A380 that was installed under the main fuel tank. It occasionally shorts out because of botched requirements and bad design. This causes burned-up wires. Burning wires under the main fuel tank? Nice! We did not update the controller because of documentation and testing costs. Happy flying!

You’re the best -Bill
February 21, 2024
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