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Open Roads Forum  >  Around the Campfire  >  General Topics

 > Boeing 737 crashes..........why ?

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jseyfert3

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Posted: 11/01/19 06:35pm Link  |  Print  |  Notify Moderator

akaPedro wrote:

Why were the MCAS controls installed in the first place ? I read 3-4 months ago, somewhere, that Boeing retrofitted the 737 with new engines. Heavier but more fuel efficient.

The added weight affected the wings...causing the plane to dip down.... and the MCAS was added to keep the plane level.

Did not work apparently. Anyone else have info as to why the MCAS was added ?

In short, to compete with Airbus on fuel efficient planes, they updated the 737. This primary involved more efficient engines, which are much bigger. The 737 wasn't designed for engines this large, so they put them in a weird position. Because of this, it no longer handled like the 737s made previously.

Pilots are type rated, which means they have to be certified to fly a particular type of airplane. The handling changes caused by the new engines meant that any airline that wanted to buy the new 737 would have to put all the pilots for the new 737 through type training on it, an expensive proposition given that (from what I've read) it takes 1-4 weeks of classroom and simulator training to become type rated.

This cost makes airlines less likely to buy a different type of airplane than ones they already have. That's why Boeing has made sure 737's have handled the same since they first came out (if I understand correctly). So the new 737 handling different means it won't sell nearly as well as if it handled the same.

So, what is MCAS? It's computer flight assistance, with one purpose. To make these new 737's that handle differently on thier own handle just like any other 737 made to date, so airlines don't have to send all their pilots through type training, so they are more likely to buy it.

The crashes happened due to a single point of failure. An instrument MCAS relied on malfunctioned, causing MCAS to push the nose down. The pilots could not override it by pulling up the stick. The only override was to turn MCAS off, but the pilots didn't know that, much less how to disable it. It seems likely they didn't even know MCAS was a thing. My reading gets flakey here but I think MCAS was not even in the manual for the plane.

Questions remain about why it had single point failure, why instruments to make it more robust were optional, why it wasn't mentioned in the manual, if the FCC and Boeing got a little too cozy and the FCC signed off on it without robost review or requirements, etc.


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Posted: 11/01/19 10:55pm Link  |  Print  |  Notify Moderator

This is all a pretty accurate assessment. It is true that there was a lack of pilot training pertaining to the MCAS system as Boeing’s mistake was to hide this little pitch enhancer to run in the background.
There is a switch to turn off the horizontal stabilizer trim in a case like this but the flight crew has to recognize the problem first.
I know that in one of the accident scenarios the trim switch was turned off but then turned back on again and in the meantime they weren’t paying attention to the power setting/airspeed and basically dug themselves a big smoking hole.
So in a nutshell it’s Boeing trying to keep upgrading this model aircraft while trying to maintain the same type rating for the aircraft. Go look up a picture of a 737-200 model and you will see how the aircraft was initially designed with the JT-8 Pratt and Whitney engine design. Nicely tucked up under the wing with no ground clearance or adverse nose trim handling characteristics. I’ve got a ton of hours flying them. The aircraft sits pretty close to the ground and with the upgrade to a high bypass engine in the -300 model changed some handling characteristics and ultimately with the latest engine iteration causing more issues.

* This post was last edited 11/02/19 07:24am by an administrator/moderator *   View edit history

Cloud Dancer

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Posted: 11/02/19 06:16am Link  |  Print  |  Notify Moderator

As a retired pilot of high performance, multi-engined, jet aircraft IMO the wrong questions are being asked, in this case. IMO it's not difficult for a pilot/aviator to sense that the emergency is a "jammed stab" trim system, and that the problem is in the jack screw. I survived a full nose-up jammed jack screw. Keep in mind that the stab jack screw is turned by electric motor. With power engine power levers set for minimum flying speed both pilots did not have the strength to keep the nose down sufficiently. It was a dire emergency. I had to find a way to kill lift. I deployed the spoilers and crossed controlled the aircraft into a forward slip, and were able to reach the runway,....for the hard landing.
So, my first question is, in the subject 737 MAX, what does the tab data say about handling a jammed stab jackscrew in the full nose down position....?
Was the FAA involved in certifying "the book". Does the FAA plan on junking all the 737 MAX aircraft? What are they doing?


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atreis

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Posted: 11/02/19 07:11am Link  |  Print  |  Notify Moderator

Cloud Dancer wrote:

Nose-heavy aircraft is nothing new. Setting ALL trims according to the take-off weight-and-balance data is nothing new. Hand flying during takeoff, and and trimming the aircraft as necessary during climb-out is nothing new. Granted, in order to do it safely, you not only need to be systems knowledgeable, but you also need to be an experienced aviator,...not just a pilot. An aviator knows the limits of elevator and stabilizer authority, and the difference between full power and takeoff power, and the limits of rudder authority,.....plus hundreds of other important related things.
In aviation, it's easy to learn that if you go too slow, you might fall out of the sky. It takes a lot more time to learn that if you go too fast you might go into Mach Tuck, from which you will problably NOT recover.


Yes, nose heavy aircraft, etc ... Quite true, but part of the goal with the Max was to have pilots be able to go from other 737 models without having to relearn the plane. (Why? It's good for sales to airlines, who want pilots to be able to fly a variety of similar planes and minimize training time.) So, they put in a software system aimed at taking care of those adjustments for the pilot, didn't tell the pilots, and messed up the implementation.

Somehow I doubt that passenger 737 Max pilots spend a lot of time worrying about Mach Tuck. [emoticon]


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JRscooby

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Posted: 11/02/19 07:34am Link  |  Print  |  Notify Moderator

Who can justify selling planes that charge extra for safety equipment? Or not letting the flying public know which airlines did not buy?

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Posted: 11/02/19 08:36am Link  |  Print  |  Notify Moderator

Obviously, we need better pilots/aviators. If someone needs me to upgrade to a different/better model of the airplane I'm flying, I will insist on studying the documents which describe the nature of all the changes, BEFORE I agree to fly it. My life is worth more than the job.
*
*
"Good judgement with knowledge is great. Good judgement without knowledge,.....is still good judgement."

* This post was edited 11/02/19 09:44am by Cloud Dancer *

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Posted: 11/02/19 09:43am Link  |  Print  |  Notify Moderator

Cloud Dancer wrote:

Obviously, we need better pilots/aviators. If someone needs me to upgrade to a different/better model of the airplane I'm flying, I will insist on studying the documents which describe the nature of all the changes, BEFORE I agree to fly it. My life is worth more than the job.


But if the book tells you all is the same do you just enjoy the new car smell?
And at this time, knowing that Boeing and FAA resisted grounding the plane after the 2nd crash, who can tell you or me it is safe to fly one?

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Posted: 11/02/19 10:07am Link  |  Print  |  Notify Moderator

The "book" did NOT say that it was all the same. But, if it had said it was all the same, ONE look at the airplane, and I would've walked away,..because it sure doesn't look all the same.
The chief pilot at Southwest knew already the MAX had many differences, and demanded CHANGES.
If you were buying one, would you not want to know all about it? And, more so if you were going to fly it.
Remember the Concord that would not let the pilots command the airplane to climb out (after takeoff) and crashed into the trees?

* This post was edited 11/02/19 01:54pm by Cloud Dancer *

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Posted: 11/02/19 08:42pm Link  |  Print  |  Notify Moderator

Cloud Dancer wrote:

The "book" did NOT say that it was all the same. But, if it had said it was all the same, ONE look at the airplane, and I would've walked away,..because it sure doesn't look all the same.
The chief pilot at Southwest knew already the MAX had many differences, and demanded CHANGES.
If you were buying one, would you not want to know all about it? And, more so if you were going to fly it.
Remember the Concord that would not let the pilots command the airplane to climb out (after takeoff) and crashed into the trees?


I believe that was the Airbus A-320 incident?

* This post was edited 11/02/19 09:06pm by Jetstreamer *

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Posted: 11/03/19 07:23am Link  |  Print  |  Notify Moderator

Cloud Dancer wrote:

The "book" did NOT say that it was all the same. But, if it had said it was all the same, ONE look at the airplane, and I would've walked away,..because it sure doesn't look all the same.
The chief pilot at Southwest knew already the MAX had many differences, and demanded CHANGES.
If you were buying one, would you not want to know all about it? And, more so if you were going to fly it.
Remember the Concord that would not let the pilots command the airplane to climb out (after takeoff) and crashed into the trees?


The book did not say they where the same? I'm sorry, I mis-understood. I thought Boeing told their customers and FAA the plane flew enough like earlier planes the pilots did not need re-certified.

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