Originally Posted by
FlightDetent
Counter question: If the gradient requirement was not met only formally but the true effect is not relevant handling wise, why did Boeing go through with MCAS and not just simply declaring the behaviour and asking for relief?
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Fair point. TBC was caught off guard by the A320 NEO, and having been led down the path of common type by the large fleet users, such as SWA etc, they were reticent in their planning to put out a greenfield design, which the big fleet customers would object to. To that end, TBC was a victim of their own success. The 737 design was in itself an outgrowth of the fuse sections that existed off the shelf, and plonking the JT8 underwing was a great idea at the time, but did come with complications for future large diameter engine use. Forget about the fact that they are miserable for cargo carriage underfloor, they were a great compromise in the 60s for a domestic short to medium haul jet. A shrink of the 757 was not a great option, it had relatively poor structural weight for its size. Pity, as it is still one of the fun jets to drive. Those that reminisce on the 727 remember the performance which was brilliant, but forget about the awful ailerons, the dutch roll, and the rest of the fun stuff). Stuck with the basic design of the gear/engine pylon, putting bigger blenders on was always an issue, have a look at the -3 engine cowl shape, the -7’s are slightly better but from raising the shaft height… and the top of the cowl v the wing LE. The MAX took that a step further, and the stability issue started to come out.
Going to the feds with a waiver request would have been embarrassing, but probably not pushed back by the feds, maybe. There are some good guys in the ACO/ transport office, but that horse has bolted. The aircraft still has to be acceptable within the guidelines of 25.173 by methods per 25.175 AC25.07 (Rev D at present) has a couple of interesting graphs on that matter. EASA and the associated comments suggest that the non-linearities were not substantial, but without the flight data and force measurements how close that was to being waivable is not quantified. The manner by which vortex interaction occurs would suggest that it was not a severe non linearity. IMHO.
Originally Posted by
FlightDetent
I think it links to your conclusion on the (lack of) other fixes apart from MCAS. They seem to have honestly chosen a solution that was readily available, required less R&D and cost as little as necessary, all that without penalizing performance As much as the internet likes to ridicule that decision, showboating and all [this thread is a great exception!!], what's being called clearly obvious in the laymen media sphere was for sure well known and thoroughly considered by the dedicated professionals yet AFTERWARDS they chose MCAS. No matter the pathetic killer gremlin MCAS 1.0 which was born later, the initial choice of picking the MCAS tool was a fair one. If it would be done again, there's absolutely no presentable evidence to deny that particular path. And as matter of fact that's what happened: The proper and agreed solution to control forces is MCAS 2.0 which is all that 1.0 wasn't and at the same time the exact thing they originally planned for.
Without getting carried away too far: Imagine the trailing edge modification had been chosen resulting in all the super critical geeky cool effects fdr explains. BUT THEN during the actual design and implementation aviation reality would be abused same as with MCAS 1.0. Such as failing to do ice contamination test and the additional load stress calculations. Resulting in flaps detaching a few years down the road - with crew performance same as on the second crash day, the death toll would have been identical.
Trying to say that selecting what is now disclosed and known as MCAS as a tool cannot be faulted. With extreme probability, it was well-reviewed against all the other options and chosen maybe even as a win-win.
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Mmmm’kay,
Nothing ever goes wrong with software changes.
- Like the PIO of the JAS 39 Gripen,
- Like the Mars climate orbiter,
- Like Ariane V,
- Bitcoins hack,
- Soviet Gas line explosion,
- The Patriot Missile in KSA,
- Airbus OEB 117
- Nissans airbags
- HSBC, and others customer lockouts.
And,
- just for stamps the near start of WW III on 26 SEP 1983, avoided by the actions of a single, fallible human,
Stanislav Yevgrafovich Petrov. We can chat about software, facebook, twitter and the rest of the inane stuff of this century because one man was smart enough to avoid Armageddon. On that day, at that time, I was sitting above a Yankee I, in the middle of nowhere.
Yup, computers, to mess up spectacularly and end the world takes software code.