The offending AoA Sensor.
Posted on 03/14/2019 2:33:55 PM PDT by rickmichaels
Lion Air Flight 610 plunged into the sea off Indonesia because the pilot “lost (the) fight with his software,” Canadian Transport minister Marc Garneau chillingly told a Wednesday press conference announcing the grounding of the Boeing 737 MAX 8.
There is nothing wrong with the basic mechanics of the aircraft: Its engines, wings and control surfaces are all believed to be working fine. Rather, the passenger jet may have killed 346 people for the terrifyingly modern reason that human pilots were unable to override a malfunctioning computer.
The cause of the Lion Air crash — and the suspected cause of the recent downing of Ethiopian Airlines Flight 302 — is a little-known piece of software known as MCAS, the Maneuvering Characteristics Augmentation System.
The 737 MAX 8 has heavier and more fuel-efficient engines than prior editions of the 737, a change which causes the aircraft to pitch upwards ever-so-slightly after takeoff.
Rather than instructing airlines to warn their pilots of this quirk, Boeing simply equipped the MAX 8 with MCAS, a program that would automatically tilt the nose downwards to compensate.
In normal circumstances, the system is not a problem, but it only takes a minor maintenance error to turn MCAS into a deadly liability.
In the case of Lion Air Flight 610, the 737 MAX 8 had a faulty “angle of attack sensor”; a small blade sticking out of the cockpit that records the angle of the aircraft in flight.
The sensor was wrongly telling the MAX 8’s flight computers that the aircraft was climbing much more sharply than it was. As a result, pilots were left wrestling with an aircraft that was repeatedly plunging itself towards the ground for no reason.
(Excerpt) Read more at nationalpost.com ...
“... Boeing says the are going to rewrite their software so that it uses inputs from other available sensors “
Boeing should have been doing that all along — checking for consistency among its inputs. Can’t believe they didn’t.
Yeah. I've wondered about that, too. Both of these planes crashed just a few minutes after take-off. Was there time to make a judgement and take appropriate action?
Why the need for MCAS at all? Isn’t that what trim adjustments are for?
There’s a huge difference between a high performance military plane that need to be unstable to accomplish high-G and tight high-speed maneuvers and a passenger jet designed for steady low-speed flight.
I was wondering the same thing.
If a single faulty sensor can precipitate a catastrophic event, it’s a computer problem.
Proof that we will never obsolete human beings. The problem with machines is that they have to be trained and have “experienced the event” in order to know how to react to it. Humans are really good at adapting to brand new situations.
The nav system in this airplane is probably a complicated control system. A control system that is only as good as the design engineers who designed it. One of design rules in a control system is convergence and stability and an oscillation, which apparently happened, is a major no-no.
So the engineers must design the system to account for this possibility and failure and when it happens, switch to a minimal known state, whenever there is a problem. In other words, turn off autopilot and the control system itself and allow the pilots to take control of the aircraft. The aircraft must be able to be flown in this minimal state (in all conditions) so that the aircraft can be returned to the airport.
This requires a pilot trained in this contingency. As you mentioned, the pilots may have not been well trained.
Of course, it is easy to armchair quarterback.
B-2. B-1 is a fairly conventional design.
Engines close to fuselage probably isn’t an issue, there’s plenty of jets designed that way.
The position of the wing is said to contribute to this plane’s tendency to tip its nose up.
I’ve read that in the most recent crash, investigators found a screw jack and it was in a position that would have caused the plane to dive.
Things go wrong on planes all the time. Cars too. That’s why we have mechanics. You deal with mechanical defects. This was a pilot problem.
Not really familiar with airplanes or software, are you?
Your premise is wrong from the start, computers don’t fly planes, pilots fly planes. Think about it.
The offending AoA Sensor.
An angle of attack sensor pictured on an Embraer 145.
Sorry, I didn’t notice until after I Posted the Picture above.
A to D problem
It’s Ok: He probably owns Boeing stock as well (he’s a Musk cheerleader).
He’s dumb as a rock on this one, too. MCAS was an add-on system which intervenes in normal flight in the critical moments immediately after takeoff. There is no excuse for Boeing to have utilized a single sensor for its input when a fault can cause a departure from flight with critically-short reaction time (40 seconds). Training is one thing, but anyone with half a brain who reads how the system operates can see that MCAS was added haphazardly.
The overarching question is “Why?”
What incident during flight testing could possibly have prodded them to butcher a well-designed flight control system with an add-on?
Better, how did it get certified without thorough testing?
There’s no other tangible explanation for this other than they found a defect in flight handling for which the risk was sufficient to patch the system but deemed too expensive to redesign the flight control system.
Other than the obvious critique of failing to design a safe fix, the root of this is lousy engineering. I can’t imagine how this might have occurred, but the fact is that the 737 MAX 8 was not an all-new aircraft: With all the design changes it should have prompted a very strict certification process rather than the fast-tracking it obviously received for being an existing/updated model.
Nailed it.
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