Jump to content

800 MAX?


Recommended Posts

My rudimentary understanding  the new more efficient engines were wider diameter and thus required a higher  mounting position. The MCAS was then "tacked on" to the design because the engine placement caused excessive pitch up tendency in certain conditions when the autopilot is off.   The alternative would have been a long delay in entry to the market caused by  need for extensive redesign of the airframe, plus further decrease in competitive advantage from need for  extensive crew retraining. 

So could the problem be fairly summed up as market pressures driving a flawed air frame design into production, compounded by a disastrously failed attempt to use computer automation to protect against the consequences of a suboptimal design?  For transport category aircraft, should software  ever even be used in this way?  The market pressures seem to have driven a rather inelegant design philosophy. Saying that it's excessive automation or bad coding (which it very well may be) doesn't quite seem to capture the depth of the problem.

  • Like 1
Link to comment
Share on other sites

3 hours ago, jetdriven said:

Boeing design philosophy is not the same as airbus. The 737 NG and Max are very much cable and pulley airplanes. They have manual reversion for those and the trim as well.  There is a standby hydraulic rudder system as well. 

The Max does have the LAM, MCAS, and, I suspect, some active spoiler action going on for gusts and turbulence.  But it’s a cable and pulley airplane, hydraulically assisted, and there is some FBW spoiler and assisted trim going on. 

Thanks, Byron, I was hoping you'd submit something from your experiences (and kudos for remembering from OSH that I fly the Airbus!)

My question, then, is that in spite of the cables and pulleys, if the MCAS system gets erroneous information and commands a pitch down, how do the pilots override the system?  On the Airbus we know how to disable the responsible computers to force it to react to pilot inputs.  Is the MAX simply too new for this to become institutional knowledge?

(And, BTW, for non-airline pilots like Byron, the Airbus is incredibly safe and I don't know of any instances where this actually had to be done.  But we know how to do it just in case.)

Link to comment
Share on other sites

3 hours ago, jetdriven said:

Boeing design philosophy is not the same as airbus. The 737 NG and Max are very much cable and pulley airplanes. They have manual reversion for those and the trim as well.  There is a standby hydraulic rudder system as well. 

The Max does have the LAM, MCAS, and, I suspect, some active spoiler action going on for gusts and turbulence.  But it’s a cable and pulley airplane, hydraulically assisted, and there is some FBW spoiler and assisted trim going on. 

I'm glad you stepped in to the discussion to keep us honest Byron.

So you have mostly blown my discussion out of the water.  I was asserting that there may be no turning off the autopilot if the MCAS is there in some kind of fly by wire system.  But I take it you say I am wrong?  Do I understand?

Link to comment
Share on other sites

22 hours ago, tigers2007 said:

Yeah but if pilot Joe puts down he had 3.4hrs in N12345 on 02/01/2019 and the data shows N12345 only flying 2.4hrs that day and it shows the complete flight from point A to B, then there are some questions to be asked. YES I know that ADS-B data isn't completely accurate and sometimes is missing pieces but I'm quite sure that pilot Joe will be straining to do some explaining.

With no deference to airline pilots with many hours.  Perhaps we should have a column in log books for hands on controls(ie actually flying the plane). The balance of the time could go in a column “system monitor/analyst”.

Link to comment
Share on other sites

11 hours ago, Marcopolo said:

Technically yes....and no!  If you taxied out expecting to go flying and something changes that expectation then yes, the time is log-able, but taxiing out just to study the wildlife at the end of the runway, I'm guessing that's a no.  But you knew that!

 

Ron

Well crap, there goes half my hours.

  • Like 2
  • Haha 3
Link to comment
Share on other sites

This all seems like a solution in search of a problem.


That sums up the Federal government’s great ideas.

On a different note, I just watched this TV news report that aired in Nov 2018 that sums up the LionAir crash and they quickly point out how simple it is to disable the angry MCAS by toggling two switches near the throttles quadrant:





Sent from my iPhone using Tapatalk
  • Like 3
Link to comment
Share on other sites

How many accidents have been caused by faulty AOAis that are connected to the AP?

There have been a few battles in the cockpit recently... that haven’t ended well... and one that was a couple of years ago over the Atlantic...

Perfectly good planes bump into some weather.... something happens to the AOAi and then the battle begins...

fully powered, solid airplanes, excellent crew, possibly losing instrumentation....

 

1) Air France

https://www.telegraph.co.uk/technology/9231855/Air-France-Flight-447-Damn-it-were-going-to-crash.html

 

2) Amazon

https://en.m.wikipedia.org/wiki/Atlas_Air_Flight_3591

 

3) Lion Air

https://www.nytimes.com/2019/02/03/world/asia/lion-air-plane-crash-pilots.html

 

4) Ethiopian Airlines

https://www.nytimes.com/2019/03/14/world/boeing-737-max-ethiopian-airlines.html

 

5) Indonesia... 

https://en.m.wikipedia.org/wiki/Indonesia_AirAsia_Flight_8501

 

The data is going to be important... We see one set of data in the video above input of MCAS vs. opposite input of the pilot... for Lion Air...

 

Where this applies to Mooney flying...

1) Make sure you know how to turn the AP off... a few off switches for the AP and electric trim... then There are colored markers for CBs for this...

2) know how to trim manually, check it through the full range...

3) Expect that by the time you get the AP off... it might be jammed far forwards or far aft... know how to change the center of lift... add or subtract flaps... and landing gear... (nose wheel effect)... alter the power level...

4) expect holding back 35Lbs of force on the yoke is going to get unbearable after some time...

 

This is important because...

We have lost one MS Mooney via a stuck trim before... fortunately, the pilot was completely unharmed.... holding the nose up manually can be very tiring...

 

PP thoughts, and prayers for the lost... looking forward to getting the data to generate a proper solution...

Best regards,

-a-

 

 

  • Like 2
Link to comment
Share on other sites

I remember reading an article by Les Abend (Flying mag writer and AA captain) how he really wasn’t a pilot anymore but was a “Flight Systems Manager”. I’ve heard from several pilots that Emirates requires the use of the “autoland” feature by policy. I suppose membership as a professional pilot has its privileges. When I’m riding in a CRJ and we pull away from the gate and sit for an hour waiting for a clearance, for a 40 minute fight, I remind upset people the crew only gets PAID if they’re away from the gate. I suppose idling the APU on the tarmac continues their flight timer. Time to bring the microturbine APU idea thread back to life?


Sent from my iPhone using Tapatalk

  • Like 1
Link to comment
Share on other sites

Supposing this takes weeks and months to find the design error and certify the fix these planes would be grounded a long time.  Do the airlines have enough alternative airplanes to soak up the demand and keep up with demand?


I don't think so. The seat-sales optimization software is really good. There are just not that many seats leftover now.

This may be why my niece has just had 5 flights cancel on her in 24 hours. She's stuck in Denver.
Link to comment
Share on other sites

I've been logging my hours on the low side out of laziness I've been going to flight aware and logging my hours off the graph so I have stupidly only logging flight time oops.

Those of us with an autopilot, electric trim and integrated airplanes such as the G-1000, should get training in systems management, mostly is recovery in an advent of sometype of failure.

I like many have experienced runaway trim, my first encounter in my 88J was near fatal, in IFR at night climbing and near a stall before I fully recovered, being 30 years ago I've learned a little regarding handling problems such as that.

Never during a flight review or BFR has the CFI had me show recovery techniques, a failure in the system,

This is a chance to look at ourselves and determine if we are proficient in managing mishaps, I think I have a lot of work to do getting complacent.

Again MS has made us aware of safety issues when a crisis is made aware to us

 

 

Link to comment
Share on other sites

I feel compelled to chime in....

The B737-800 does not have a fly by wire control system.  However, a change on the MAX was to eliminate the mechanical spoiler mixer box with a digital control unit.  What this means is the roll control which uses ailerons and is augmented with the roll spoilers (for additional authority) has an electrical component.  I think it is primarily a function of wheel position - not a closed loop on attitude - like fly-by-wire.  The alpha vane is used primarily by the stall warning computer.  The autopilot doesn't use it much.  The MAX MCAS uses the vane data.

The autopilot is probably a Collins autopilot.   Boeing provides design specifications, Collins builds the product including writing the software for the box.  It a collaboration.

Jets with engines under the wing, below and forward of the CG tend to pitch up with the addition of power.  Especially so with substantial addition of power.  The MCAS was added to protect against accelerated stalls (in the bank) when the aircraft was being hand flown.

All the Lion Air pilots had to do was engage the autopilot or use the trim cutout switches.  The autopilot will not engage with the trim disabled by the cutout switches.

It remains to be seen about the Ethiopian crash.  It may be related to the CWS (control wheel steering) mode which sometimes confuses pilots.   It has happened many times that pilots became distracted by something and crashed a perfectly good airplane - think L-1011 and the everglades.

  • Like 1
Link to comment
Share on other sites

1 hour ago, Danb said:

I've been logging my hours on the low side out of laziness I've been going to flight aware and logging my hours off the graph so I have stupidly only logging flight time oops.

Those of us with an autopilot, electric trim and integrated airplanes such as the G-1000, should get training in systems management, mostly is recovery in an advent of sometype of failure.

I like many have experienced runaway trim, my first encounter in my 88J was near fatal, in IFR at night climbing and near a stall before I fully recovered, being 30 years ago I've learned a little regarding handling problems such as that.

Never during a flight review or BFR has the CFI had me show recovery techniques, a failure in the system,

This is a chance to look at ourselves and determine if we are proficient in managing mishaps, I think I have a lot of work to do getting complacent.

Again MS has made us aware of safety issues when a crisis is made aware to us

 

 

Do you have those marker rings on the circuit breakers for electric trim and autopilot?

Clarence

Link to comment
Share on other sites

3 hours ago, Wayne Cease said:

 


I don't think so. The seat-sales optimization software is really good. There are just not that many seats leftover now.

This may be why my niece has just had 5 flights cancel on her in 24 hours. She's stuck in Denver. emoji853.png

 

Nope, apparently they are still having winter in Colorado.  And a bad storm on top of it.  Here in Atlanta I had the top down on my convertible yesterday.  :D

 

Link to comment
Share on other sites

1 hour ago, skykrawler said:

I feel compelled to chime in....

The B737-800 does not have a fly by wire control system.  However, a change on the MAX was to eliminate the mechanical spoiler mixer box with a digital control unit.  What this means is the roll control which uses ailerons and is augmented with the roll spoilers (for additional authority) has an electrical component.  I think it is primarily a function of wheel position - not a closed loop on attitude - like fly-by-wire.  The alpha vane is used primarily by the stall warning computer.  The autopilot doesn't use it much.  The MAX MCAS uses the vane data.

The autopilot is probably a Collins autopilot.   Boeing provides design specifications, Collins builds the product including writing the software for the box.  It a collaboration.

Jets with engines under the wing, below and forward of the CG tend to pitch up with the addition of power.  Especially so with substantial addition of power.  The MCAS was added to protect against accelerated stalls (in the bank) when the aircraft was being hand flown.

All the Lion Air pilots had to do was engage the autopilot or use the trim cutout switches.  The autopilot will not engage with the trim disabled by the cutout switches.

It remains to be seen about the Ethiopian crash.  It may be related to the CWS (control wheel steering) mode which sometimes confuses pilots.   It has happened many times that pilots became distracted by something and crashed a perfectly good airplane - think L-1011 and the everglades.

Thanks for chiming in.  Clearly I didn't/don't know the details of these machines but I was talking in generalities and what if it were a fly by wire system AND there is a bug.

You do say all the lion air pilots had to do was...  now with a second crash and the stronger possibility that this second crew was well aware of all they had to do, that something is specifically wrong with the the system, again a fault and the system is not doing what it is supposed to do, a bug, so that when the crew may have done exactly what you described they should have done, nonetheless the plane did not do what it was supposed to do?

Link to comment
Share on other sites

3 hours ago, Wayne Cease said:

 


I don't think so. The seat-sales optimization software is really good. There are just not that many seats leftover now.

This may be why my niece has just had 5 flights cancel on her in 24 hours. She's stuck in Denver. emoji853.png

 

Oh boy - I feel her pain.  Been there done that.

Just 6 weeks ago I spent 36 hours at Dulles airport.  First flight to Plattsburgh delayed for weather at Plattsburgh then we went and then 5 min from landing the airport closed for freezing rain so with wide spread freezing rain they returned to Dulles.  Then after a few hours it cancelled for the day.  Next day...that flight was delayed 9 hours for an entirely different reason - there was a medical emergency on the flight which turned out to be a crew so I heard by rumor.  SO that airplane had to emergency divert before arriving at Dulles to pick us up, and then they had to find a new crew member.  So two back to back delays that were entirely unrelated.  (and I have no idea how serious that medical emergency was and hope they are well). ...and then when I got to my car in Plattsburgh it was literally encased in like 2 inches of ice and I spent like 30 minutes banging on it with my little plastic scraper trying to clear the windows.

  • Sad 1
Link to comment
Share on other sites

9 hours ago, Wayne Cease said:

 


I don't think so. The seat-sales optimization software is really good. There are just not that many seats leftover now.

This may be why my niece has just had 5 flights cancel on her in 24 hours. She's stuck in Denver. emoji853.png

 

This is why she had that many flight cancel on her in Denver. This was Tuesday 3-12-19. 

 

38D6911D-DF0E-440A-942F-5ACB125ECECC.jpeg

Link to comment
Share on other sites

The video from Nov 2018 that @tigers2007 posted showed what to do when the system calls for nose down and the crew believe it may not be warranted.  Solution? Turn these off. 

0314_boeing_737_max8_trim.jpg.504c425d874e5f2a6d755d14b3826633.jpg

The same solution is shown, in part, by the latest AOPA entry into the discussion at https://www.aopa.org/news-and-media/all-news/2019/march/14/faa-grounds-boeing-737-max-fleet

It appears that modifying operations manuals, modifying crew training, and one software modification (apparently due out in April) may resolve the issue altogether.  But maybe that is just me being hopeful.

Link to comment
Share on other sites

On 3/13/2019 at 7:18 PM, KSMooniac said:


I can't believe that what seems to be the failure of a single sensor (AOA in this case) can wreak such havoc with the flight controls. I think someone screwed up with this system architecture as well as passing it thru certification. I'm especially curious to learn if the FAA knew every detail under the hood here, or if company designees signed off instead.


 

I highly doubt it is a single sensor.  I cannot speak for Boeings, but the Gulfstream G650 is fly by wire and it has 4 independent AOA sensors.  I cannot imagine Boeing having any less than 2.  I would further imagine that if 1 failed the FC LAW would drop down a lower level of protection... for example if the G650 drops even 1 level down (there are 4)then Stall protection is lost and it is on the pilot to fly the aircraft.

 

From what I have read... and I could very well be wrong, but this is my speculation based on what I have read so far.

It sounds like other pilots had already stated there was a safety issue with the aircraft as it is and had had experiences that resulted in similar control issues during departure( from which they recovered).  One said that the Auto throttles had brought power to idle rapidly when un-commanded/unexpected.  This caused the MCAS to begin trimming the aircraft due to the power change, however upon manually reintroducing power the aircraft became difficult to control.

I think something like this is probably what is happening.  I have seen even a G550 reduce power to idle during initial climb.  I wont go into details but the systems were working exactly as designed, however the designers cant imagine every real world scenario.  I can see the MCAS system and the pilot becoming out of sync with one another and a sort of  PIO occurring where the PIO is being caused by the interaction between the pilot moving the power levers and the MCAS stab trim lagging behind the inputs.

 

as stated, I could be 100% wrong.  Just speculation.

Link to comment
Share on other sites

https://www.bloomberg.com/news/features/2019-03-13/two-737-max-crashes-in-five-months-put-boeing-s-reputation-on-the-line

"Following the latest crash, Boeing sent engineering leaders and sales executives around the globe to answer questions and explain a software upgrade they hope to roll out in coming weeks. The update, which takes about an hour to download, will make sure the MCAS compares data from two angle-of-attack vanes instead of relying on a single potentially faulty sensor. There will be limits to the number of times the system can nudge the nose down and to the amount of force it exerts. The redesign has been tested in multiple flight-simulator runs and flights, but it must also be certified by the FAA."

 

I am flabbergasted that the inputs into this hidden system relied on a single sensor!  I cannot imagine how this passed a rigorous review, FMEA, etc from any controls engineer, much less the FAA. 

  • Like 1
Link to comment
Share on other sites

How many G650’s have been lost due to AOA sensor failure? I’m curious if there is a way to find out how many times -8 and -9 drivers have had to flip those trim switches down due to an urgent situation. Especially the US carriers.


Sent from my iPhone using Tapatalk

Link to comment
Share on other sites

1 minute ago, tigers2007 said:

How many G650’s have been lost due to AOA sensor failure? I’m curious if there is a way to find out how many times -8 and -9 drivers have had to flip those trim switches down due to an urgent situation. Especially the US carriers.


Sent from my iPhone using Tapatalk

none that I am aware of.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.