Author of a fuel estimation program for 747 freighters here...

Yes, they take a significant amount of extra fuel, but that significant amount is very carefully calculated because carrying more than legally required adds up to a loss quickly, especially if your competitors are sharper at calculating these figures.

The are ~100 parameters that go into these calculations, ranging from almanacs with tables of various trade winds and densities to engine types, consumption at various altitudes and power settings and so on. And then the required hold time, first alternate, second alternate and legal reserve required on landing.

Getting that code certified still makes me break out in sweat, but good thing that this kind of thing is reviewed very strictly. That also makes me wonder how wise it was to have the software this article is about as a SaaS rather than something more integrated and less easy to mess up using an update. Maybe doing it as a SaaS is a kind of loophole that avoids certification? (not current on this stuff).

That's super interesting - I didn't realize that certification would be required for this.

I would suspect that certification would break down at some point; does a plain old calculator need to be certified? Certainly not, but I'd imagine the FAA or whoever if asked would prefer pilots use calculators than do everything by hand.

I'm curious about EFBs as well - I run W&B for my little bugsmasher in Foreflight. Has that gone through certification? Certainly someone from the FAA wouldn't have to review every release for that if so...

So when does certification come into play versus it just being another tool that pilots are responsible for validating?

Good question, I don't know the answer. But I can give you some more info on this project: the company, one of the largest freighters operating out of Schiphol already had such software but they had lost the source code. The assignment was to create a new piece of software that produced exactly identical output. That was the bar to clear. If not for a friend (who got me the job in the first place!) who managed to decrypt the original (it was apparently written in some variation of BASIC with an obfuscation layer but once you had it reversed it would actually list as source) I would likely have never managed to complete the assignment. But once I had that in hand it was much, much easier because I could read all of the original tables.

One of the bigger problems I encountered was that the original software wasn't perfect, so the first step was to replicate it, bugs and all and only then to fix the bugs. So the FAA never entered into it but the Dutch equivalent did. Also, I think there is a big difference in stuff in use in GA versus that which is used for commercial aviation. We're talking early 90's or so, so the details are a bit hazy by now.

Interesting job though, that's for sure, lots of good lessons from that one. I'd never been sent back four or five times by an auditor because my work wasn't up to their standards and every time they sent me back they had a valid point, it wasn't bs just to check a box somewhere, they had valid concerns and I had to rework some of it quite extensively. At the level of "I don't care if the answer is correct, I need to understand why it is correct".