Comment by Reason077 4 days ago
The recalled aircraft include the latest A320neo model, some of which are basically brand new. Why would they be using flight computers from before 2002? Why is an old report from 2008, relating to a completely different aircraft type (A330), relevant to the A320 issue today?
I think you're confusing a type certificate (certifying the airworthiness of the aircraft type) with a type rating, which certifies the pilot is qualified to operate that type.
Significant internal hardware changes might indeed require re-certification, but it generally wouldn't mean that pilots need to re-qualify or get a new type rating.
No I meant designing a new aircraft with a new type certificate instead of creating the A320neo generation on the same type certificate. The parent comment wondered why Airbus would keep the old computers around, I tried to explain why they keep a lot of things the same and only incrementally add variants. Adding a variant allows them to be flown with the same type rating or with only differences training (that's what EASA calls it, not sure about the US term) which is much less costly.
Asking from ignorance: shouldn't the computer design be an implementation detail to the captain, while the interface used by who pilots stays the same for that type of airplane? I understand physical changes in the design need a retraining but the computer?
Since the new versions of the same ADIRU have EDAC, they have been using it on planes since 2002 and they have been putting the EDAC variant in whenever an old one was being returned for repairs, I don't think this is the reason. I think the reason is that they had 3 ADIRU's and even if one got wonky, the algorithm on the ELAC flight computer would have to take the correct decision. It did not take the correct decision. The ELAC is the one being updated in this case.
> Why would they be using flight computers from before 2002?
Why would you assume they're not? I don't know about aircraft specifically, but there's plenty of hardware that uses components older than that. Microchip still makes 8051 clones 45 years after the 8051 was released.
From a pure safety point of view, it's easier to deal with older, but well-understood products, only updating them if it's an actual safety issue. The alternative is having to deal with many generations of tech, as well as permutations with other components, that could get infinitely complicated. On top of that, it's extremely time consuming and expensive to certify new components.
There's a reason the airlines and manufacturers hem and haw about new models until the economics overwhelmingly make it worthwhile, and even then it can still be a shitshow. The MCAS issue is case in point of how introducing new tech can cause unexpected issues (made worse by Boeing's internal culture).
The 787 dreamliner is also a good example of how hard it is. By all accounts is a success, but it had some serious teething problems and still has some concerns about the long term wear and tear of the composite materials (though a lot of it's problems wasn't necessarily the application of new tech, but Boeing's simultaneous desire to overcomplicate the manufacturing pipeline via outsourcing and spreading out manufacturing).
The issue detailed in the linked report details why the spike happened in the first place on the ADIRU (produced by Northrop Gruman). The recalled controller is the ELAC that comes from Thales. The problem chain was that despite the ADIRU spiking up, the ELAC should not have taken the reactions it took. So they are fixing it in the ELAC.
For the same reasons that Honeywell is building new devices with AMD 29050 CPUs today[1] - by sticking with the same CPU ISA, they can avoid recertifying portion of the software stack.
[1] Honeywell actually bought full license et al from AMD and operates a fabless team that ensures they have stock and if necessary updates the chip.
Because the problem isn't just this. It's that the flight controller did not properly decide what to do when the data spiked because of this issue as well.
> Why would they be using flight computers from before 2002?
Because getting a new one certified is extremely expensive. And designing an aircraft with a new type certificate is unpopular with the airlines. Since pilots are locked into a single type at a time, a mixed fleet is less efficient.
Having a pilot switch type is very expensive, in the 50-100k per pilot range. And it comes with operational restrictions, you can't pair a newly trained (on type) captain with a newly trained first officer, so you need to manage all of this.