Posted on 05/03/2019 8:50:09 AM PDT by billorites
Even Airbus wants Boeing to survive. That duopoly keeps China and others from successfully breaking into the business and wrecking the market for both of them.
“But they should have used the electronic trim switch on the control wheel to neutralize the trim before cutting off the trim power.”
They did. See 5:40:38 of CVR.
They didn’t. That wasn’t nearly enough to neutralize the trim. See page 26:
https://leehamnews.com/wp-content/uploads/2019/04/Preliminary-Report-B737-800MAX-ET-AVJ.pdf
They were pulling back on the control wheel rather than achieving neutral trim.
“They were pulling back on the control wheel rather than achieving neutral trim.”
Again, see 5:40:28 of the CVR.
At 05:40:27, the Captain advised the First-Officer to trim up with him.
At 05:40:28 Manual electric trim in the ANU direction was recorded and the stabilizer reversed moving in the ANU direction and then the trim reached 2.3 units.
At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out.
At 05:40:41, approximately five seconds after the end of the ANU stabilizer motion, a third instance of AND automatic trim command occurred without any corresponding motion of the stabilizer, which is consistent with the stabilizer trim cutout switches were in the ‘’cutout’’ position
I don’t have to look at it again. The key phrase in my previous post is ACHIEVING NEUTRAL TRIM. They didn’t trim the nose up nearly enough. They had to continue applying back pressure to the control wheel to counter the nose down trim. They eventually got tired and that’s when they nosed into the ground.
If you need help reading the charts on page 26 let me know.
There is no indication they got tired and relaxed the yoke columns.
They turned the stabilizer trim system back on and that is when they nose into the ground.
If you need help reading the charts on page 26 let me know.
They turned the stabilizer trim system back on and that is when they nose into the ground.
...
That’s when they relaxed back pressure on the control wheel. They couldn’t take the last bit of nose down trim from MCAS. They did increase back pressure again as they saw their lives about to end, but that wasn’t enough.
Using elevator to control all that nose down trim at high speed required a lot of effort.
It's not the ejection seat that allows the fighters (F-16, F-22, & F-35) to be unstable. They are all fly-by-wire.
The mission computer flys the aircraft. The pilot is merely providing inputs to the computer. If the pilot tries to pull 10 Gs, the computer will only pull the max G allowable based on gross weight, CG, etc.
Also, the FAA does not certify fighters. The USAF and USN/USMC are certifying authorities.
You can find the information here: https://leehamnews.com/wp-content/uploads/2019/04/Preliminary-Report-B737-800MAX-ET-AVJ.pdf
The captain should have transferred control to the first officer, because the stick shaker going off on one side indicates a bad sensor on that side and the instruments may not be reliable on that side.
Why didn’t the pilots diagnose why the stick shaker was going off?
It wasn’t an emergency at that point, so that’s not an excuse.
1. As I said before, It's not easily possible to determine which stick shaker is going off because they are connected, and both columns shake.
2. The instrument that failed is the AOA sensor. The AOA is not presented on the flight instruments on the flight deck of Boeing Aircraft (Unlike all U.S. Navy carrier aircraft that fly by AOA). Although, a failure of the AOA system may (or may not) display on the Primary Flight Director.
3. Getting the Stick Shaker is an Emergency:
a. If the sensors are accurate it indicates a stall.
b. If the sensors are inaccurate, the Emergency Procedure is the Airspeed Unreliable Procedure:
Autopilot off
Autothrottles off
Flight Director off
Set pitch and power.
Setting the pitch however was not possible because of the run away stab trim which is also an emergency procedure:
Same as above with the addition of putting the STAB TRIM Cutout Switches to Cutout.
Depending on when that was done, the aircraft may or may not be flyable at that point. Switching pilots would have made no difference whatsoever.
“Using elevator to control all that nose down trim at high speed required a lot of effort.”
MCAS was designed to over ride their elevator demand actions.
They tried the electric trim again but it didn’t work. I guess they forgot they had turned it off. Turned it back on an the MCAS drove them into the ground.
b. If the sensors are inaccurate, the Emergency Procedure is the Airspeed Unreliable Procedure:
Autopilot off
...
Why do the captain turn the autopilot on with the stick shaker going off?
Why did the captain retract the flaps with the stick shaker going off?
MCAS was designed to over ride their elevator demand actions.
...
MCAS controls the trim only. Elevator still works, but it takes a lot of effort. The plane dove into the ground when the pilots no longer had the strength to counteract the nose down trim.
MCAS was designed to over ride their elevator demand actions
Nope.
MCAS was designed to compensate for the nose up pitch caused by the engines on the 737 MAX.
All it checks is the angle of attack, whether the autopilot is on, whether the flaps are extended, and whether the engines are above a certain level of thrust. MCAS uses trim to control the pitch. The elevators are still under the control of the pilots.
“The redesign of the 737-800 Max resulted in an aircraft that was unstable in pitch around the lateral axis when flown at high angles of attack and under conditions of high thrust. “
Um, no. The plane was dumbed down for untrained, inexperienced pilots by suits around conference tables and they also made the decision to leave test pilots out of the loop.
I still maintain the plane is safe in a trained, experienced pilot’s hands, but that Boeing screwed the pooch in handling the redefined flight characteristics and attempting to oversimplify the plane toward what is obviously a drive to autonomous flight.
Big mistake. Yuge.
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“Cheap way to prevent a stall when the inexperienced pilots punch it,” or CWTPASWTIPPI, system."
Fixed it.
“The scale of this negligence makes all its designs from the period of the 737 Max onwards suspect.”
UGH you mean like this next offering?
https://interestingengineering.com/the-boeing-777-xs-folding-wings-are-they-safe
OH dear and here’s their latest design offering, coming in 2020...read the fine print:
https://static.interestingengineering.com/images/APRIL/sizes/boeing_777_x_resize_md.jpg
The MCAS was designed to over ride pilot control of the elevators by stabilizer trim control.
“I still maintain the plane is safe in a trained, experienced pilot’s hands, but that Boeing screwed the pooch in handling the redefined flight characteristics and attempting to oversimplify the plane toward what is obviously a drive to autonomous flight.”
MCAS was not put in as a drive to autonomous flight. It was put in to keep the pilot from taking the plane out of its operating envelope during high-g turns.
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