Primarily for general aviation discussion, but other aviation topics are also welcome.
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By johnm
#1686704
We know how to deal with failed sensors and conflicting information and have done for years. The Air France problem was quite different, failed sensors caused the aircraft to hand back control to the pilots who had a flyable aircraft, but under fearfully difficult conditions. These poor blighters didn't have a flyable aircraft it seems from the report.
#1686707
My point started with a comment on the overall design. The sensors were a way down the chain. IMHO the problem started in the design office where they came up with a plane that, in highly simplistic terms, just looks wrong. You then put in place software to overcome the design issue and the software then leads to etc etc.

There’s never a single cause, but you can find a root cause in the chain.
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#1686709
It's reminiscent of Harrison's maritime clock #1 - add complications to fix a multitude of tiny problems, then add complications to complications to fix problems arising from problems.

Adding simplicity is extraordinarily difficult and (certainly in my trade) it's the difference between engineers and designers. You can train engineers, designers are a rarer breed.
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By kanga
#1686730
But, a veteran 737 pilot has told me, the Max merely exacerbates what was an issue with the 737 airframe design from the start: even the early (eg -200) versions produced a massive pitch up moment on application of full thrust, which stab trim devices (or software) in the autopilot were designed to overcome. With them switched off, the aircraft would be very unstable close to the ground after take-off. Presumably that feature was directly related to the low wing, in turn related to the short undercarriage legs, which to my inexpert eye look no or not much longer in later, even the latest, models, despite their much larger nacelle diameters.

I gather that, with the Max, the inherent previous autopilot software ran out of authority to cope with engines even more powerful and further forward, so MCAS was added to overcome this weakness. Then, there was nothing built in to overcome a MCAS malfunction, not even pilot brute strength and/or stab trim cutoff.

Happy, as ever, to be corrected
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By Josh
#1686732
The root cause of all these problems is Boeing’s decision (under the commercial pressure of the advent of the A320 NEO) to attempt another development of the 737NG and to keep it a common rating with the 737 300-900.

Contributing to the problem is the FAA’s policy of allowing grandfather rights in certification, with a large number of systems and design features that would not meet the current regulations, and not getting as involved in certification as previously.

My feeling is the engineers working on MCAS were far enough down the chain that they were required to implement the solution, rather than being involved in the conceptual decision to solve an aerodynamic stability problem with a kludge. I remember in a thread about vortex generators somebody (DaveW?) pointed out that the real solution is to design the wing better!

Instead, they’ve created a horrible halfway house between a conventional and an augmented FBW aircraft, with all the disadvantages of both concepts, and none of the benefits.
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By Dominie
#1686744
Josh wrote:The root cause of all these problems is Boeing’s decision (under the commercial pressure of the advent of the A320 NEO) to attempt another development of the 737NG and to keep it a common rating with the 737 300-900.

Contributing to the problem is the FAA’s policy of allowing grandfather rights in certification, with a large number of systems and design features that would not meet the current regulations...

Absolutely spot on in both cases.

One of the best things that can come from this is that Boeing realise that further development of the 737 on the same type certificate is just not feasible. And if the FAA realise that grandfather rights must have a time limit somewhere that would be great as well - the PA28 and Cessna 172 immediately come to mind as well as the 737, and there are many others that would not meet modern requirements. I'm sure there are many who could give precise examples.
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By Josh
#1686766
MCAS is a stability augmentation function and only works with the autopilot disengaged to provide the required stick force gradient.
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By Pete L
#1686791
The descriptions of the proposed fix didn't fill me with confidence. I thought Boeing philosophy was always to trust the pilot in terms of effect of direct control application.

As an IT person I've never trusted computers in aircraft :-).

I was impressed by the AAIB account of the Easyjet Airbus event where all of the screens went blank - in IMC. Just shows how good our commercial pilots are.
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By Gertie
#1686941
KeithM wrote:As is already being said, even if they claim a fix, how long before the passengers will be convinced?

I'm never going to fly in one.

And, if there are any other unstable airliners out there, whether or not they have similar sticking plaster bodges, could someone please let me know which they are, so I can avoid them too?
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By eltonioni
#1686961
It makes you hanker for the days of regulators when (for example) airliners needed at least three engines to cross the Atlantic, not just a type certification.

Dick Taylor, then Boeing's director of engineering approached FAA director J. Lynn Helms in 1980 about the possibility of an exemption, whose response was "It'll be a cold day in hell before I let twins fly long haul, overwater routes." [3][4] The Boeing 767-200ER entered service in 1984.
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By kanga
#1686975
eltonioni wrote:It makes you hanker for the days of regulators when (for example) airliners needed at least three engines to cross the Atlantic, not just a type certification.

Dick Taylor, then Boeing's director of engineering approached FAA director J. Lynn Helms in 1980 about the possibility of an exemption, whose response was "It'll be a cold day in hell before I let twins fly long haul, overwater routes." [3][4] The Boeing 767-200ER entered service in 1984.


Although in this case there seems not to have been any engine problem. They pushed the aircraft very reliably earthward .. :(

In 1988 (I think) I flew the Atlantic on 2 engines for the first time. It was on the inaugural Wardair Gatwick-Ottawa Airbus service, replacing DC10s. It was literally the airframe's second flight after its empty delivery flight from Toulouse.

In Ottawa I knew the RAF Air Attache at the High Commission, a Navigator, quite well. To return to UK he always flew down to Washington to catch the weekly RAF VC10 to Brize, although Wardair direct would not only have been more convenient but possibly not much more expensive after the flight to National, taxis, and a hotel night in Washington. When I asked why, he said that it was because it had 4 engines, 'and unfortunately they do not make them with 6'.

[my first transatlantic was in a BOAC Stratocruiser ..]
Last edited by kanga on Sat Apr 06, 2019 4:32 pm, edited 1 time in total.
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By eltonioni
#1687016
kanga wrote:
eltonioni wrote:It makes you hanker for the days of regulators when (for example) airliners needed at least three engines to cross the Atlantic, not just a type certification.

Dick Taylor, then Boeing's director of engineering approached FAA director J. Lynn Helms in 1980 about the possibility of an exemption, whose response was "It'll be a cold day in hell before I let twins fly long haul, overwater routes." [3][4] The Boeing 767-200ER entered service in 1984.


Although in this case there seems not to have been any engine problem.

Wasn't suggesting it, just alluding to how the type certification has been pushed past breaking by regulators that don't seem to be regulating properly at the behest of (a?) manufacturer(s) who are resorting to voodoo sticking plasters instead of good essential design.

Does that stripped out B737 still do the LCY - NYC route?
Edit: Just checked, it was an A319 with a fuel stop at Shannon. :roll:
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