Posted on 03/20/2019 5:18:38 AM PDT by csvset
JAKARTA/SINGAPORE/PARIS (Reuters) - The pilots of a doomed Lion Air Boeing 737 MAX scoured a handbook as they struggled to understand why the jet was lurching downwards, but ran out of time before it hit the water, three people with knowledge of the cockpit voice recorder contents said
The captain asked the first officer to check the quick reference handbook, which contains checklists for abnormal events, the first source said.
For the next nine minutes, the jet warned pilots it was in a stall and pushed the nose down in response, the report showed. A stall is when the airflow over a plane’s wings is too weak to generate lift and keep it flying.
The captain fought to climb, but the computer, still incorrectly sensing a stall, continued to push the nose down using the plane’s trim system. Normally, trim adjusts an aircraft’s control surfaces to ensure it flies straight and level.
“They didn’t seem to know the trim was moving down,” the third source said. “They thought only about airspeed and altitude. That was the only thing they talked about.”
(Excerpt) Read more at reuters.com ...
Talked to a Corporate Pilot who knows some 737 MAX Pilots.
There are two switches (forget what he called them) located in the lower Console next to the Copilot that have to be flipped off to overcome the MCAS Flight Control Computer.
On a regular 737, it can be overruled by hitting a Button on the Yolk. The MCAS system on the 737 MAX is independent from the Auto Pilot function.
The new Engine Mounting location which changed the Airframe angle of attack caused all this.
The theory for what happens rests with a Sensor malfunction.
“If the failure of a single sensor can send the aircraft into a dive toward the ground, it is not “pilot error”
First, the software did not send the plane into a dive. It lowered the nose a few degrees which was easily compensated for by the captain over 20 times. He could have simply turned on autopilot or turn off the stab and it would have been fine.
Next, the crash was not caused by the failure of single sensor. Items malfunction in planes all the time - from sensors to engines and everything in between.
Pilots are there to deal with these in the right way. A runaway stab is something every airline pilot in the world should recognize and deal with in seconds. Is it Boeing’s fault if some low hour pilot reacts to an engine problem by turning off fuel to the good engine?
I put the blame for this 100% on the awful mistakes made by lion air mechanics and lion air pilots and also lion air culture. Remember, the pilots on the previous flight kept flying to their destination after they turned off the auto stab system. Any American airline would require such a plane to turn around and return to airport.
Each of the 2 Stall Warning Computers receive data from both angle of attack sensors. They also continually crosscheck each other. An erroneous input from one vane triggers an event message on the display along with an audible alarm.
The Capt should have disconnected the autopilot (if engaged) in the early stages of flight problems. Each yoke has a A/P disconnect switch plus excessive manual force on the yoke disconnects the autopilot. Being that airspeed, aircraft attitude and engine power were NOT in a stall envelope, the Stabilizer Trim Setting should have been noted as way out of the normal setting for stable flight. A manual trim readjust would have saved their lives.
This is pure ‘Pilot Error’.
‘Runaway Stab Trim’ is in the crews Quick Reference Guide
So, how many planes have to crash before it is safe to say there is a problem here?
We’re up to two. Will three do it for you? Is 750 dead passengers enough? Or is it necessary to break 1,000 before it is time to get serious?
The manual trim adjust only lasts for 10 seconds, and then the MCAS lowers the nose again.
from what I’ve read that MCAS software only ran when the plane was in manual mode. Ironically autopilot would have disconnected it.
“How much muscle power does it take to pull back the yoke if the trim tab is set to nose down? Seems to me my arms would NEVER get tired.”
You likely would have fallen into the same trap as the doomed pilots appear to have done:
“To counter the MAX’s lower stability margins at high AOA, Boeing introduced MCAS. Dependent on AOA value and rate, altitude (air density) and Mach (changed flow conditions) the MCAS, which is a software loop in the Flight Control computer, initiates a nose down trim above a threshold AOA.
“It can be stopped by the Pilot counter-trimming on the Yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the Pilot pulling the Yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the Pilot pulling so hard on the Yoke that the aircraft is flying close to stall.
“It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the Pilots pulling against it. The faulty high AOA signal was still present.
“How should they know that pulling on the Yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the Pilot’s manual, the FCOM. This has created strong reactions from airlines with the 737 MAX on the flight line and their Pilots. They have learned the NG and the MAX flies the same. They fly them interchangeably during the week.
“They do fly the same as long as no fault appears. Then there are differences, and the Pilots should have been informed about the differences.
200 hours total time for a Boeing pilot is just crazy. Insane, actually.
“Altimeter tells the computer we’re at 1000’. Computer still trims the nose down?”
The MCAS program appears to have been designed to activate upon the decision of a single Angle Of Attack sensor.
Please.
How many of these Boeing 737 Max 8 were owned and flying around the world?
How many successful flights were completed by this new jet?
If this plane was so bad why were their only 2 crashes by 3rd world airlines?
+1
Boeing has a problem
FAA was wrong
Not good
True but plane should not be doing this with out of control auto avionics like this so commonly
That so many lives need Chuck Yeager talent at the helm
FAA and BOEING both screwed the pooch on this plane....
A lot of heads should be rolling over this mess...
Boeing created a system that overrode pilot input, and didn’t adequate inform or train pilots about it...
To further eff it up, they made a version of this plane that could take over control dependent on ONLY 1 SENSOR... No REDUNDANCY ... now a version with redundant sensors is available, but you had to pay extra for it.
So, if you happen to be in a plane with only one sensor, and that sensor failed or malfunctioned, the flight systems would believe the plane was in stall, and push the nose down no matter what the pilot did.. other than of course turning it off, which they didn’t inform pilots this thing would do this, let alone how to turn it off.
The FAA should have NEVER certified a plane without a redundancy to such a system for commercial use... Boeing should have never BUILT a plane without redundancy in these systems...
In the end you are going to find, my guess is, a lot of crony capitalism at work behind the scenes of this planes certification for airworthiness.
Freepers love to beat up so called third world pilots some of whom have more experience flying in crap weather and poor airports than some milk train driver from DFW to LAX has
This bird should not be willing itself into crash scenario pell mell due to automated avionics
Quit blaming the pilot
Right after take off essentially new plane decides to dive in the ocean and doesn’t respond to yoke and hey dang it you forget to engage trim override as you’re going down the role coaster
And it’s shown now these pilots were not warned since Boeing soft pedaled this roll outs issues
Boeing is going to get hit on this
Lawyers gonna get rich
Boeing and the FAA BOTH have problems, see 118....
Culture of complacency at both organizations, was at least in part to blame for this.
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