Boeing 737 MAX

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The elephant in the room is Boeing's financial capability to shoulder the short and long term costs of remediation and product delays taking into account legal actions.

The knowledge exhibited on this thread is significant. So here is a question. What issues or inefficiencies did the Maxx 8's predecessors have that required the new designs now in question?
 
Larger diameter engines which are more efficient. I think some more passenger room. Move more people using less fuel, that is the name of the game.
 
Ski in NC said:
Larger diameter engines which are more efficient. I think some more passenger room. Move more people using less fuel, that is the name of the game.
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Understood. But the implementation of greater fuel efficiencies has heretofore been with seemingly more precise forethought. Suggesting Boeing did something different this time.
 
I thought the big difference is that on older models the engines hang directly below the wing, where to fit the larger diameter engines they had to be hung forward and higher, creating the increase in nose-up under power. Do I remember that correctly?
 
What issues or inefficiencies did the Maxx 8's predecessors have that required the new designs now in question?

The larger diameter engine was mounted further fwd , which with a very light aircraft and way aft CG exposed enough engine cowling bottom to add to the normal pitch change of adding power.

COPIED From Aviation Week 20 May page 24

" When we looked at JT 610 data and realized that the flight data showed the runaway pitch trim procedure WAS NOT DONE ...we knew that this needs to be emphasized"

" The ET 302 crew depowered the stabilizer trim motors , but did not counter the MCAS inputs with electric trim inputs before hand. They turned the motors back on , which the stabilizer runaway procedure says should NOT be done . This reactivated the MCAS and lead to an uncontrollable dive."

Flip the "stab cutout " switches to OFF and fly with the hand trim wheel as gramps did , problem solved.


This is a MEMORY procedure!!!
 
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FF said:
What issues or inefficiencies did the Maxx 8's predecessors have that required the new designs now in question?

The larger diameter engine was mounted further fwd , which with a very light aircraft and way aft CG exposed enough engine cowling bottom to add to the normal pitch change of adding power.

COPIED From Aviation Week 20 May page 24

" When we looked at JT 610 data and realized that the flight data showed the runaway pitch trim procedure WAS NOT DONE ...we knew that this needs to be emphasized"

" The ET 302 crew depowered the stabilizer trim motors , but did not counter the MCAS inputs with electric trim inputs before hand. They turned the motors back on , which the stabilizer runaway procedure says should NOT be done . This reactivated the MCAS and lead to an uncontrollable dive."

Flip the "stab cutout " switches to OFF and fly with the hand trim wheel as gramps did , problem solved.


This is a MEMORY procedure!!!
Click to expand...


This is all correct, but incomplete. ET302 did indeed turn off trim motors before counteracting MCAS with electric trim. But they didn't know that MCAS had done what it did, nor how to stop it, nor that it should be fully counteracted before turning off motor trim.


And yes, they turned the motor trim back on, but only because they couldn't get the manual trim wheel to do it's thing. It was the only way to get trim control. But they didn't know that motor trim also came with a third pilot who happened to be on crack at the time.



And gramps couldn't have moved the manual trim wheel either. Too much air speed creating too much force on it. And the recovery procedure is to go into a dive to relieve pressure, crank the wheel, recover, and repeat as necessary. But they didn't have the altitude to do that.


There really isn't that much to fault the pilots with, given what they knew. The big mistake was letting the air speed get away from them, which progressively took away all the tools they had to perform a recovery. They were super green, by comparison to US norms, but to me any pilot who thinks this wouldn't have happened to them is missing out on an important learning opportunity, and frankly isn't the kind of pilot I would want up front.
 
Except that with the MCAS system it is reported that as long as the pilots use the electric trim switches then the MCAS was inhibited for a few seconds after the switch was released. It would seem to me that all they had to do was keep retrimming the airplane every time the MCAS started moving the trim. I would've thought that the first thing to do when the airplane goes out of trim is to trim it back. It would be annoying and might not have made for the smoothest flight, but it should have worked.

Once the flaps came out for approach the MCAS would have stopped messing with things and then everything would go back to normal.

A common problem today is that pilots are taught to follow the book and the procedures. In a pilot's world, not following the published procedures is a huge no-no. They are often slapped down if they don't follow the manufacturer's flight manual, FCOM, or airline manuals. That's fine if there is a procedure for whatever situation you find yourself in (provided you can find it in the book fast enough). If the pilots find themselves in a situation not in the book, they no longer have the classic background information (detailed systems knowledge, aerodynamics, etc.) that will help them figure things out on their own. Plenty of accidents have been caused by pilots blindly following some procedure to no good end because that's what they were trained to do when such a situation arose.

On the other hand, there have also been a number of accidents that occurred because the pilots improvised their own procedure. But perhaps a more thorough knowledge of the aircraft might have either caused to pilots to think twice about what they were doing or to do something different.
 
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ssobol said:
Except that with the MCAS system it is reported that as long as the pilots use the electric trim switches then the MCAS was inhibited for a few seconds after the switch was released. It would seem to me that all they had to do was keep retrimming the airplane every time the MCAS started moving the trim. I would've thought that the first thing to do when the airplane goes out of trim is to trim it back. It would be annoying and might not have made for the smoothest flight, but it should have worked.
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I think that's correct, provided you know that MCAS is there and that it's the cause of the problem. And that you know that manual trim actions disable it for a little while. But by all indications, the pilots didn't know that, because they were never told. That's where the Boeing/FAA part of the problem starts to rear it's head.
 
twistedtree said:
I think that's correct, provided you know that MCAS is there and that it's the cause of the problem. And that you know that manual trim actions disable it for a little while. But by all indications, the pilots didn't know that, because they were never told. That's where the Boeing/FAA part of the problem starts to rear it's head.
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Even if you don't know about MCAS, if the system trims one way and you can counter it by trimming it back, why would you just stop doing that and let the trim run all the way nose down. Even when the MCAS first started doing its thing, the pilots did not run the trim back to where it started. The MCAS was putting in more ND trim than the amount of NU trim the pilots responded with. In the first crash the pilots countered the MCAS 26 times.
 
A couple links to Boeing.com for updates:

https://boeing.mediaroom.com/news-releases-statements?item=130434

CHICAGO, May 16, 2019 – Boeing has completed development of the updated software for the 737 MAX, along with associated simulator testing and the company’s engineering test flight. To date, Boeing has flown the 737 MAX with updated MCAS software for more than 360 hours on 207 flights.
Boeing is now providing additional information to address Federal Aviation Administration (FAA) requests that include detail on how pilots interact with the airplane controls and displays in different flight scenarios. Once the requests are addressed, Boeing will work with the FAA to schedule its certification test flight and submit final certification documentation.
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https://www.boeing.com/commercial/737max/737-max-software-updates.page

MCAS is designed to activate in manual flight, with the airplane’s flaps up, at an elevated Angle of Attack (AOA).
Boeing has developed an MCAS software update to provide additional layers of protection if the AOA sensors provide erroneous data. The software was put through hundreds of hours of analysis, laboratory testing, verification in a simulator and two test flights, including an in-flight certification test with Federal Aviation Administration (FAA) representatives on board as observers.
The additional layers of protection include:
  • Flight control system will now compare inputs from both AOA sensors. If the sensors disagree by 5.5 degrees or more with the flaps retracted, MCAS will not activate. An indicator on the flight deck display will alert the pilots.
  • If MCAS is activated in non-normal conditions, it will only provide one input for each elevated AOA event. There are no known or envisioned failure conditions where MCAS will provide multiple inputs.
  • MCAS can never command more stabilizer input than can be counteracted by the flight crew pulling back on the column. The pilots will continue to always have the ability to override MCAS and manually control the airplane.
Click to expand...
 
Since they pretty much hobbled MCAS, seems that the next question should be "Is MCAS really necessary at all?"
 
"There really isn't that much to fault the pilots with, given what they knew."

Had Boeing simply inserted the comment in the flight handbook

"Not following the approved procedure for runaway trim may KILL you ."

in 30 or 40 languages would perhaps have solved the problem as it did for other crews faced with the same problem.
 
ssobol said:
Since they pretty much hobbled MCAS, seems that the next question should be "Is MCAS really necessary at all?"
Click to expand...

My non-pilot guess is that MCAS was not necessary at all. It was only there so the Max was similar enough to previous models that it could be considered "in type". Not that MCAS was needed to make the AC safe, but to make it less different.

If it wasn't for how the rules were structured, MCAS probably would never have been there.

What a mess. Hopefully will get this sorted soon.
 
Ski in NC said:
My non-pilot guess is that MCAS was not necessary at all. It was only there so the Max was similar enough to previous models that it could be considered "in type". Not that MCAS was needed to make the AC safe, but to make it less different.

If it wasn't for how the rules were structured, MCAS probably would never have been there.

What a mess. Hopefully will get this sorted soon.
Click to expand...

That is a pretty good assessment. I can only say had it gone into production as it was originally designed, it would not have come to this.
 
It is an interesting article and the idea behind the site is also interesting. Monopolies.

However, he seems to be from another planet when he makes this statement:
The right policy path would be Congressional hearings to explore what happened to this once fine company
Click to expand...

Congress? Wonder what Congress, on what planet, is up to that job?


The "company run by engineers" is also what they said about Mercedes, after Mercedes forgot how to build a car.
 

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The right policy path would be Congressional hearings to explore what happened to this once fine company
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Need to find a "once fine Congress" first.

Most of the things the author says should happen will likely never come to pass.
 
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" The 737 started coming off the assembly line in 1967, and it was such a good design it was still the company’s top moneymaker thirty years later."

The first ones coming off the line could not go from LGA to ORD (NYC to Chicago)in bad winter conditions with out naming a fuel stop.

THe pilots called them FLUF, Fat Little Ugly Fellow ( last name changed to protect the kids)

The "good design " is now, transatlantic , no sweat.
 
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FF said:
" The 737 started coming off the assembly line in 1967, and it was such a good design it was still the company’s top moneymaker thirty years later."

The first ones coming off the line could not go from LGA to ORD (NYC to Chicago)in bad winter conditions with out naming a fuel stop.

THe pilots called them FLUF, Fat Little Ugly Fellow ( last name changed to protect the kids)

The "good design " is now, transatlantic , no sweat.
Click to expand...

That little FLUF was a GREAT plane. Dirt simple and worked quite well for what it was designed, and rarely had the LGA to ORD problem, which wasn't the problem. The problem was that there were situations where it couldn't hold the extra reserve fuel for a long hold because it would be overweight if that fuel wasn't burned. Had that catch me one time going between IND and ORD one bad weather night. Declared min fuel on takeoff after cleared to hold..... (Have a few thousand fun filled hours in that plane as captain).
 
A similar moniker, SLUF, was applied to the Vought A-7, a Vietnam era carrier-based attack plane. S as in short.
 
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Airbus has its issues too. Read up on Air France 447 that crashed in the Atlantic after pitot tubes iced up and the automation didn't have enough data to prevent an aerodynamic stall.

Air France Flight 447 and the safety paradox of airline automation on 99 Percent Invisible.

I don't fly these planes, as the Lear I fly has "delta fins" on the tail that provide enough lift in deep stall situations to push the tail up and "unstall" the wing if you will. At least it starts the pitch motion in the right direction. Its a super simple system that works on a smaller jet.

But I have many friend who fly the Airbus and they indicate that if the computer looses a sensor (airspeed/pitot) it will degrade to a lower level and basically "you are now flying the aircraft." So pitch and bank angle protections might not be there. From what I read the pilot in the right seat pulled the side stick fully aft and in normal "law" the plane should pitch to a maximum angle of attack and advance the auto throttles to prevent a stall. But they had flown through severe icing conditions at the top of a thunderstorm and iced up the pitot tubes.

My point being they relied on automation when it wasn't there. An otherwise perfectly good airplane was flown in a stalled condition with plenty of room to recover from the stall - if the crew had only realized it was stalled and acted on basic training from their early days of flying. Lower the nose and regain lift over the wing.

Boeing will get it right - but I agree the pilots need more simulator training on a newer aircraft. Most US pilots got an hour training program on an iPad.
 
IF anyone is interested this weeks issue of Aviation Week has a great in depth article on the MAX mess.
 
FF said:
IF anyone is interested this weeks issue of Aviation Week has a great in depth article on the MAX mess.
Click to expand...

Dammit.FF.....I am sure it is a good article and I need to find some time to sit down and read it!! Aviation Week is about the only publication I trust.
 
I'm a former FAA engineering test pilot from the Aircraft Certification organization. I also served in the senior management structure of the Aircraft Certification Service before retiring in 2006. The blame for this entire episode lies with early decisions that identified the failure mode of the MCAS as less than potentially catastrophic. Boeing and the FAA put the safety responsibility for a dangerous failure on the aircrew versus the airplane design. That determination amongst certification systems engineers and test pilots allowed Boeing to get by with a single string AOA sensor. It is mind boggling to me that it was allowed to happen, and it speaks to outright incompetence of the FAA individuals involved. It also suggests probable political pressure on the certification team from upper management (certainly in the case of the FAA). The MCAS would have been a tri-plex redundant system when the A310 was certified, for example...two systems vote out the third faulty input...or at a minimum two string where in the system would shut itself off in the case of a faulty input ....fail operational, or at least fail safe. My background is primarily rotary wing where artificial stability is commonplace. Catastrophic hardovers are unthinkable. That said, a helicopter pilot would have recognized and been able to deal with a PIO situation long before fixed wing types, as it's an inherent characteristic of unstabilized rotary wing aircraft

Every FAA person involved in this mess from the systems engineers, to the flight test pilots, and on up to the Director of the Aircraft Certification Service should be fired. A related issue is that within the past few years the FAA Certification Service reorganized it's internal structure such that the highly competent Transport Airplane Directorate in Seattle was gutted in order to consolidate decision making in Washington ...a transparant political move and power grab by senior managers in Washington. This is criminal.
 
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Rufus,


Wow, interesting post. And I need to get a copy of Aviation Week... but is that article online anywhere?


Agreed, heads should roll. The cert process has failed.



Question:
Has any decision that came out of Washington ever been any good? <g>
 
Rufus, I was under the impression that the final iteration of MCAS was never seen or scrutinized by the FAA??? Had the system the FAA signed off on was what went into the airplane, none of this would have happened. Mainly the .6 units per activation versus the 2.5 units per activiation. I think there was also a limit to the total units allowed versus full scale deflection.
 
The FAA would certainly want you to believe that. I seriously doubt that Boeing changed the type design without a signoff, unless it somehow happened through their Organization Delegation Authority (ODA). And if it happened there, it's still FAA. Regardless, even a slow hardover is ridiculous in that flight regime. Mitigating the hardover still puts a potentially dangerous scenario in the hands of the pilot, when a properly designed system eliminates it. Last I read, the new design is at least duplex. I'm a fierce opponent of covering up poor aircraft design by putting it on the crew via flight manual procedures.
 
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LearPilot said:
Airbus has its issues too. Read up on Air France 447 that crashed in the Atlantic after pitot tubes iced up and the automation didn't have enough data to prevent an aerodynamic stall.

Air France Flight 447 and the safety paradox of airline automation on 99 Percent Invisible.

I don't fly these planes, as the Lear I fly has "delta fins" on the tail that provide enough lift in deep stall situations to push the tail up and "unstall" the wing if you will. At least it starts the pitch motion in the right direction. Its a super simple system that works on a smaller jet.

But I have many friend who fly the Airbus and they indicate that if the computer looses a sensor (airspeed/pitot) it will degrade to a lower level and basically "you are now flying the aircraft." So pitch and bank angle protections might not be there. From what I read the pilot in the right seat pulled the side stick fully aft and in normal "law" the plane should pitch to a maximum angle of attack and advance the auto throttles to prevent a stall. But they had flown through severe icing conditions at the top of a thunderstorm and iced up the pitot tubes.

My point being they relied on automation when it wasn't there. An otherwise perfectly good airplane was flown in a stalled condition with plenty of room to recover from the stall - if the crew had only realized it was stalled and acted on basic training from their early days of flying. Lower the nose and regain lift over the wing.

Boeing will get it right - but I agree the pilots need more simulator training on a newer aircraft. Most US pilots got an hour training program on an iPad.
Click to expand...

Actually the sensors froze up and went unreliable for between 30 s and 1 minute. If the pilots had done nothing the plane would have carried on fine. Instead the pilots seemed not to understand what was happening, stalled the airplane, and held it in a stall until it crashed. The plane did not stall until the pilot inputs stalled it.
 
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