*Sources
Boeing 737 Max 8 crash: Anti-stall system activated on Ethiopian plane
https://www.usatoday.com/story/news/nation/...crash...stall-system.../3308487002/
2 hours ago - In a preliminary finding, officials investigating the crash of an ... a flight control feature designed to prevent a stall was activated before the ... It alleges that Boeing had defectively designed the automated flight control system.
https://www.businessinsider.
Doomed plane's pilots apparently followed Boeing's directions Pilots of the Ethiopian Airlines 737 MAX hit the system-cutoff switches as Boeing instructed after the earlier Lion Air disaster, but couldn't regain control before the plane crashed. If investigators confirm that preliminary information, this is a nightmarish outcome for Boeing and the FAA. Lemme said the Ethiopian pilots most likely were unable to carry out that last instruction in the Boeing emergency procedure — because they simply couldn’t physically move that wheel against the heavy forces acting on the tail.
“The forces on the tail could have been too great,” Lemme said. “They couldn’t turn the manual trim wheel.”
could have been in an extreme position with two separate forces acting on it:
MCAS had swiveled the stabilizer upward by turning a large mechanical screw inside the tail called the jackscrew. This is pushing the jet’s nose down.
But the pilot had pulled his control column far back in an attempt to counter, which would flip up a separate movable surface called the elevator on the trailing edge of the tail.
analysis suggests the stabilizer trim wheel at the Ethiopian captain’s right hand could have been difficult to budge. As a result, the pilots would have struggled to get the nose up and the plane to climb.
If after much physical exertion failed, the pilots gave up their manual strategy and switched the electric trim system back on, MCAS would have begun pushing the nose down again.
1982 pilot manual for the old 737. As described in the extract posted by the Australian pilot, they require the pilot to do something counterintuitive: to let go of the control column for a brief moment.
this “will make the nose drop a bit,” but it will relax the force on the elevator and on the jackscrew, allowing the pilot to crank the stabilizer trim wheel. refers to this as “the ‘roller coaster’ technique”
Australian pilot also posted an extract from Boeing’s “Airliner” magazine published in May 1961, describing a similar technique as applied to Boeing’s first jet, the 707.
Clearly this unusual circumstance of having to move the stabilizer manually while maintaining a high stick force on the control column demands significant piloting skill.
Robert Jones 26 minutes ago
So all we needed to do was hit a couple switches and problem solved.......uh, no.....Boeing is in a heap of trouble.
the_eskimo 42 minutes ago
Even I know there should be at least two independent sensors - I easily figured this out after all the sensor-related plane crashes that occurred during the last four decades. I think my most recent count of sensor-related fatalities is up to 581 for just the last two decades
reading on a 'professional' blog that it takes about 25 turns on the wheel to move horiz stab 2.5 degrees. To do that one must fold out handles, reach down alongside knee, and crank - and and EASA document says that forces are such if speed greater than about 240 250 knots ... not really possible. Thus the old method of roller coaster method. But nowheere is mentioned how much altitude is lost during this process.
My guess is if AGL at start of process is less than 5000 feet- even with ' super pilot '- the result is shown in the pics ..:(((
another example of this generation failing to learn from the past. Those rules and regulations were not written arbitrarily, but because of blood and tears. This generation thinks it is so smart that they can re-write all the rules...well then don't be surprised when those same failures occur again.
glakers 1 hour ago
Boeing should never have built a system by which, in case of a sensor malfunction, the fix is for ALL pilots to have the where-with-all to know to try a bunch of manual maneuvers to trick the plane into doing what the pilot wants. Especially when there is only the one sensor to rely on and that sensor is randomly faulty.
Sky King Songbird 1 hour ago
Investigation of autopilot system should include the vendor Honeywell which the Seattle Time has yet to mention in any article.
Autopilot black box and software are built to specification by Honeywell from Boeing requirements.
MCAS algorithm is programmed by Honeywell.
dassss 2 hours ago
@cdt1 U.S. carriers require 10 to 15 thousand hours for a pilot to qualify for a left seat for passenger carriers. My understanding is these pilots only had 500 hours. It seems the requirement varies for most all these nationalized State run airlines since the State issues the regulations. I'm sorry but it looks like good old fashion incompetence trying to be masked and parsed by a third world propaganda department.
BTW - the captain of the Ethiopian jet had 8000 hrs. The Lion Air captain had 6000.
explanation for why disabling the MCAS system as instructed didn't resolve the problem. What happened?
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Guenter 2 hours ago
This article is misleading. Based on the partial info that’s been leaked to the press, they apparently did not follow the full procedure, which is to disable the system and most importantly, use the manual trim wheel to trim the airplane. This article leads the reader to believe they did the procedure and it wasn’t successful. I’m interested to get the full story, but there is a lot of sensationalizing going on by the media on incomplete info. The WSJ writeup on this was better than the stories that regurgitated its reporting as dumbed down versions of the original.
user14985274921364 3 hours ago
As a software developer, it's frustrating and scary that this wasn't caught in the simulator. Of course it's scary that such a fragile design was approved to move forward at all, but the simulator should have been the final check, and should have failed.
here are also investigations reported by Bloomberg of the FAULTY AoA sensor in Lion Air crash was a USED sensor repaired by a Florida company named XTRA Aerospace Inc. The sensor was made by Rosemount Aerospace Inc., of Minnesota, a subsidiary of United Technologies Corp. United Technologies declined to comment, citing the investigation.
Trail of negligence will go DEEP!
- Poor repair facilities
- Poor flight manuals
- Poor flight control algorithm safety design
- Poor pilot training
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