16 hours ago, Bobsk8 said:

Before that happens my guess is some orders of the Max will be switched to Airbus products. 

Not enough time. If you got a pilot rated on the max according to my knowledge its 3 Landings in 3 months or he's in he sim. 

I'm guessing the max is a simple differences course rating off the back of the  737 NG and not a separate LPC / type rating altogether? 

 

 

18 minutes ago, skelsey said:

To explain further:

This all comes about because of a certification issue: specifically FAR 25.173 which deals with static longitudinal stability.

(my emphasis).

As I understand it, this is where the Max encountered issues during flight test. Without MCAS, the Max does not meet the requirements.

This is flight tested at constant thrust (why would you do otherwise -- you would just be introducing an additional variable). So thrust coupling is not a factor (and in fact, given that the thrust/pitch couple is based on the amount of thrust and the lever arm -- i.e. the vertical distance from the thrust line to the CG -- I would not be surprised if with the higher mounted engines the thrust/pitch couple on the Max was actually less than on previous versions due to the shorter arm involved, but I couldn't say that for certain).

I understand what you are saying and the longitudinal stability requirements. I was just wondering where you heard or read of the nacelle lift being the primary cause of the mcas requirement. Because that is interesting and not touched upon at all by aviation week or my conversation with family that worked at boeing. I don’t doubt that there is a degree of lift provided by the nacelle, but all my sources indicate so far that the primary concern during stalls was from an even greater thrust coupling force.

Thrust coupling is always a factor unless the engine is mounted within the fuselage centerline. As long as the engine is working, there is always a force being imparted from below the cg. You just merely have accounted for it in your trimming out for level flight or constant climb or descent. The engines of the max are mounted from a higher point only because their increased diameter would have extended them to a lower point. Those engines aren’t sitting higher, they still just barely clear the ground. So I wouldn’t say that they have a shorter thrust coupling moment because you need to remember that the thrust from these high bypass engines come primarily from the bypass and not the core. So the primary thrust is coming from essentially the diameter of the entire nacelle. I’m pretty sure with the increased mass flow through the those big fans, the thrust coupling is still significant despite the higher mounting point.

Hi Kevin,

15 minutes ago, KevinAu said:

I understand what you are saying and the longitudinal stability requirements. I was just wondering where you heard or read of the nacelle lift being the primary cause of the mcas requirement. Because that is interesting and not touched upon at all by aviation week or my conversation with family that worked at boeing. I don’t doubt that there is a degree of lift provided by the nacelle, but all my sources indicate so far that the primary concern during stalls was from an even greater thrust coupling force. 

It came up in a number of PPrune discussions -- in particular from a chap who (claims to be -- and seems to have the credentials to back it up) a flight controls systems engineer in Seattle: https://www.pprune.org/rumours-news/619272-ethiopian-airliner-down-africa-43.html#post10415847 is a good explanation -- the other impact of relocating the engines of course is that they are now further forward of the CG which would add to the pitch-up effect as a result of nacelle lift.

This is backed up by this technical site which interestingly appears to have been amended recently -- when I Googled it there was something in the cached text about thrust coupling which appears to have now been removed from the live site.

One would think of course that Boeing might have published some technical info on this but all the official information seems to (still!) be extremely vague about the precise nature of MCAS and the problems it was intended to solve.

As mentioned, since the stick force gradient flight test is conducted with constant thrust it would be illogical to link thrust coupling to reduced longitudinal stability at high AoA -- if that were the case then the aircraft would longitudinally unstable at all angles of attack, not just at high AoA. Absolutely adding thrust will result in a nose-up moment, but as you say that is true of all aircraft with engines mounted below the CG including the 737NG (and even the Classic!) -- if certification required the aircraft to not pitch up when thrust is added at high AoA then basically every modern airliner in service would require some form of MCAS-like software, which clearly isn't the case.

37 minutes ago, tooting said:

I'm guessing the max is a simple differences course rating off the back of the  737 NG and not a separate LPC / type rating altogether?  

My understanding is that it's not even as formal as that -- here's an iPad, have a quick read and off you go.

More news published at the Aviation Herald: http://avherald.com/h?article=4c534c4a&opt=0

In summary:

F/O had a total of 350 flight hours.

After an uneventful departure, the flight was cleared direct to a waypoint, however, the crew requested to stay on runway heading citing flight control problems and eventually requested to return. There was no apparent distress in the voices from the pilots who sounded calm. The last transmission from the aircraft to ATC was a standby. No PAN PAN or MAYDAY calls. Contrary to early reports, there was no mention of unreliable airspeed by the pilots to ATC. Initial climb appeared to be very fast.

Following the Boeing bulletin from November in the aftermath of the Lion Air crash, Ethiopian included runaway stab trim lessons in the six month sim sessions only this March. The crew of the accident flight likely didn't have training on runaway stab trim in the sim.

In the NG, automatic stab trim movement can be counteracted and stopped by manual elevator control inputs into the opposite direction of the automatic stab trim movement. In order to allow MCAS to work, automatic stab trim in the MAX cannot be stopped in the same way. I'm sure without specific runaway stab trim training in the MAX this difference between the two variants could have added to probable confusion for the pilots on that flight who, considering the position that the jack screw was found in, appear not to have disabled the automatic stab trim system using the cutout switches. I'm still wondering why neither the Lion Air crew nor this crew did exactly that which I find especially strange in this case since a runaway stab trim on the MAX caused by a faulty sensor and the MCAS kicking in was fresh in everyone's minds after the Lion Air crash and Boeing's bulletin (which, according to the AH, had been passed on to their 737 flight crews). The crew of the Lion Air flight prior to the Lion Air accident flight flipped the switches and thus continued safely to their destination, according to reports.

 

 

2 hours ago, skelsey said:

My understanding is that it's not even as formal as that -- here's an iPad, have a quick read and off you go.

Correct. Which relates back to some prior comments. I don’t believe the MAX itself is an inherently flawed design, or is inherently unstable. An F-117 stealth fighter was as I understand it inherently unstable and incapable of being flown without computer assist. The MAX just exhibits apparently significantly different flying characteristics from the NG, in particular in certain situations, and in order to make it behave like an NG and therefore eliminate training (and increase its marketability) Boeing introduced software logic to make it behave like an NG. I don’t think think that in and of itself is a problem - all modern passenger aircraft are going to utilize computer logic based upon instrument readings to make adjustments to trim. 

What isn’t speculation is that we know that MCAS was a new system introduced to the MAX, and given the long safe history of the previous generation and the preliminary information that has been released so far seems to be a likely factor. What I do wonder is if true, is it an issue related to lack of redundancy with regards to AoA sensor readings, OR is it a problem with the MCAS logic? I read an interesting post elsewhere that made a compelling argument that it is the latter. The other question I have is whether MCAS is the only software/coding change made of a substantive nature between the MAX and prior generations. 

https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/#content

Cheers,

 

3 minutes ago, IUBrian said:

What I do wonder is if true, is it an issue related to lack of redundancy with regards to AoA sensor readings, OR is it a problem with the MCAS logic? I read an interesting post elsewhere that made a compelling argument that it is the latter. The other question I have is whether MCAS is the only software/coding change made of a substantive nature between the MAX and prior generations. 

It's both. The MCAS has been classified during testing and certification to fall in a failure category that requires the system to be dependent on two input sources rather than one because a failure of said system it can, as we have had to witness, have "hazardous" consequences. The goal is to eliminate just what happened: erroneous triggering of the system due to wrong input from one sensor which can't be compared to the other sensor's reading because, well, it's dependent on only one. The MCAS itself did just what it is designed to do. However, Boeing found during the flight tests that it has more authority than what was initially believed (an actual limit of 2.5 degrees as opposed to the assumed limit of just 0.6). Adding to the authority of this system is that it resets upon response from the pilots (by trim inputs via the yoke) and thus (still with false input from the faulty sensor) keeps applying nose down stab trim periodically which adds up over time and brings the aircraft into an attitude where the pilots can no longer work against it. On the Lion Air flight, this cycle of automatic nose down trim and pilot response happened over 21 times (24 in total if I recall correctly) until the aircraft crashed.

MCAS is a significant difference but not the only one. There are much more differences between the NG and the MAX than the same name of 737 suggests. A lot of work has gone into upgrading the MAX over the NG.

It was so funny, I had a dream that I had fallen asleep on a 737 MAX in a Southwest airlines hangar and I overheard them saying "nothing wrong with it, we are putting it back into service".  In the dream I gazed out the window as we taxied to the gate and I realized some other pax were aboard.  Then they announced we were flying to Anchorage Alaska which Southwest does not fly to from Phoenix, but they will be flying to Hawaii (I preferred my Hawaiian 767 widebody flight there with my ex wife and daughter, lovely airline, lovely set of roundtrip flights, lovely time).  I gradually woke from the strange dream to my still residual pain from my recent car accident.

It is so funny how these air crashes interweave sometimes with my dreams, because I have flown so much not only in sims but even more hours than sims in real life.  As I have said, three times I have come close to crashing on flights so I managed to skip the "third time's the charm" jinxed, and I have also had to go around as a pax from last second runway incursions twice, once at SFO and once at LAX I recall.

But thru it all I had the judgement of skilled pilots and I have no problem placing my faith and life in them on any airline fate asks me to fly on, same goes with the CFI's I have flown with who were stern, yet warm and kind people trying to teach me piloting skills.  I soloed just once, something I have forgotten about until now, in a fixed wing Challenger II in Prescott AZ, an aircraft I was looking to purchase but decided against because although the CFI trusted my flight skills, the aircraft was unregistered and I do not trust two cycle Rotax engines, one of which brought another friend and his friend, a CFI I knew named Jim Blumer, down near Lake Pleasant, AZ.

With the advent of new solid state, fast recharge, longer endurance batteries on the horizon I wonder if an electric airliner for short hops might become possible with ducted fan, brushless engines, more reliable than anything currently.  But such engines require electronic controllers which can have problems from radio interference.

What role do cell phones or a pax using electronic equipment during takeoff and landing play in these latest accidents?  I have seen pax use them as mp3 players and some forget to put them into airplane mode.  Heck, 10 years ago I brought a gps with me on a flight from Phoenix to Orlando to track my route and groundspeed, I had fun doing so, it was so accurate I was amazed although I had to sit on the south facing side of the aircraft which I intentionally booked to get sat reception, and I had to put the gps against the window.  My ex wife, daughter and I enjoyed that vacation so much, Disney voted us "Family of the Day" and bumped us to the Concierge level of the Beach Club resort we stayed at, such a nice place with the best hotel water park on the planet.  We had free breakfasts and lunches which saved us tons of money in an expensive place.

And, that was one of our last flights on America West, to briefly become US Airways, then American, who I worked for a while under contract, every flight buffs dream to say they worked for an airline at least once in their lives.

And what I learned, airlines are dedicated to safety, giving the best customer service they can under the constraints of customers/guests wanting low airfare, and when accidents like this crash happen, they are all in to help find the cause, and patient enough to wait for an answer before they taxi from the hangar and resume flights on suspect equipment.  Southwest in the US has had an amazing safety record, close to that of Qantas, so says Rainman, Cactus 521....  And so have all worldwide airlines in spite of accidents, they try and they try hard, with dedicated pilots who I like to call "*******" behind the stick and rudder.  Whatever happened to those souls in these crashes, I am sure every single one of them is in a better place than we are, which we will be when our bodies either wear out, or like mine are broken apart and put back together and mended after accidents by loving police, firefighters, doctors and nurses and my US government that sponsors them, or your governments that sponsor your health care.

Blessings,

John

 

Yes, I did read that MCAS had more authority as well as a reset and repeat issue. What I’m wondering is whether there is an issue with the software logic misinterpreting data from a non-faulty sensor. Clearly not consistently, but is it possible that a faulty sensor isn’t the issue, but how the logic is interpreting the data? Could that be part of the software change that Boeing is planning on rolling out? And yes. This is purely speculation on my part. 

23 minutes ago, IUBrian said:

Yes, I did read that MCAS had more authority as well as a reset and repeat issue. What I’m wondering is whether there is an issue with the software logic misinterpreting data from a non-faulty sensor. Clearly not consistently, but is it possible that a faulty sensor isn’t the issue, but how the logic is interpreting the data? Could that be part of the software change that Boeing is planning on rolling out? And yes. This is purely speculation on my part. 

From what has been reported about the two accidents so far, it seems MCAS worked exactly as it was supposed to - the faulty sensor in the Lion Air crash being what instigated the trouble and MCAS reacting 'appropriately' to the inputs it received. As far as I recall, the sensor has been found to have malfunctioned on the ground during taxi already.

The upcoming fixes include changes to how MCAS reacts to inputs, more precisely the limit of the nose down command will be lowered and MCAS will only activate once instead of resetting and engaging again. Also, it will depend on both AoA sensors rather than one. There are no changes to how it interprets the data.

1 minute ago, threegreen said:

From what has been reported about the two accidents so far, it seems MCAS worked exactly as it was supposed to - the faulty sensor in the Lion Air crash being what instigated the trouble and MCAS reacting 'appropriately' to the inputs it received. As far as I recall, the sensor has been found to have malfunctioned on the ground during taxi already.

The upcoming fixes include changes to how MCAS reacts to inputs, more precisely the limit of the nose down command will be lowered and MCAS will only activate once instead of resetting and engaging again. Also, it will depend on both AoA sensors rather than one. There are no changes to how it interprets the data.

I have to wonder though, why all this was added to the MAX.  What else does this automation do?  Does it improve efficiency in some way or does it improve stresses on the airframe in some way?  There must be some purpose for these improvements as pilots have input during aircraft design, otherwise they would have had a fit with the design of the MAX and the current competitors too worldwide.  I am still hoping I get to fly in this new hardware someday, especially the 787 for some reason, and that may be likely when I receive the settlement from my accident and take a vacation to recuperate.  I want to take a tour of China, which I have never seen. 

A friend of mine helped launch their modern tourism industry and he has invited me to come there as soon as I am well enough to travel again, so a 787 flight may be in my future this year.  I was so afraid I lost him in the 9-11 attacks, his name is Andrew Garcia and he was an employee of mine for about six months, and there was an Andrew Garcia who went down in PA.  Sadly, and unknown for me for years, another former colleague of mine and business systems instructor and mentor to us all, Nina Bell, was lost in the twin towers on 9/11.  I miss her so much I cry at times, hard for a man to admit but I do.  But I know she is in a better place now, my instinct, I know all my friends here and there will make it there.

I did not find out about Nina until thirteen years after 9/11, my closest friend and former colleague Mary would not tell me for fear I would break down when I share dinners with her.  We business systems instructors came from all creeds, all walks of life, and all faiths and that is what allowed us to interact so well in the international places we taught in, like me in Asia, Europe and South America.  I had a knack for teaching people from India, whether Muslim or Hindu, they worked together passionately as friends and software developers and we'd go out to lunch, and our boss would pay, that was just the way of the development workplace, especially when I worked at American airlines which outsourced to develop the merged crew scheduling software.

I remember when I worked for another company, I was lead on a software packaging suite we were rolling out and I had to go to Rockville MD to learn it along with two colleagues.  One was a kind married young Indian woman, her husband was in India.  I flew a Southwest 737-700 there into Baltimore from Phoenix, I love Baltimore as a DC Gateway, the friendliest airport I feel in the DC metro area with great runway views and an indoor observation deck.

One night I invited the woman who was longing to communicate something to her husband about our trip other than business to DC from Rockville via the Metro, I wanted to show off the capitol of a country I love.  She fell in love with my tour, and at each stop, the Smithsonian, the White House, the Vietnam Memorial and Finally, Lincoln, she'd call her husband.  And I heard her say "I love this country".

Made me so proud to hear I had been a good ambassador to my friends I still have abroad that day...  Flight==tourism==peace in our time.  As the Eddie Money song goes...

John

4 minutes ago, Jim Young said:

This is what I think happened but it is all a guess.  A couple of days ago I flew the PMDG 738 from KLAX to KSFO using ASP4.  In the FMC the only thing I did not set was trim.  I was at FL240 heading for FL290 when LNAV shutdown.  I enabled it again and I suddenly was off-course again with LNAV turning off.  Enabled again but this time the aircraft went into an uncontrollable dive toward some of the highest mountains in the area.  I tried to bring it under control by shutting down the AP but the aircraft did not respond and I soon hit the mountains.  A quick CTRL+C and I had P3D shutdown.  I've flown the 737 many times but this was the first time I experienced this.  Like I said, the only thing not set was the trim.  Another 20 years and I'll have this figured out....

Yes Jim

Same has happened to me at times with the sim autopilots.  Oddly though in each instance I pulled the plug on my web connection and regained control of my aircraft, so it sometimes makes me wonder if a burst of IP traffic can overwhelm the complexity of our sim software.  We know cyberhackers are constantly trying to test our web connections with DOS attacks.  When I was working for a home schooling software company as their IT risk lead, we were hit by a DOS attack once by a former student, my software was able to nail his IP but I cannot say what I wrote or how it works, since those rights are still owned by the company I worked for.  They gave me excellent job references until I retired even though I quit suddenly getting fed up not so much with them, but with my three hour commute to work one day when there was an accident on I-10 and the company frowned on telecommuting unlike my three previous employers.

My 99.9 pct success rate with autopilots on all my add-ons is I get myself trimmed in a stable hands on cruise climb for at least five minutes before engaging them unless I have complete faith in the aircraft, and only two aircraft, my Xplane11 Eclipse and my Carenado Citation 550, qualify under those circumstances, those autopilots have seemed foolproof so far although I did have the 550 get away from me just once with runaway trim in flight, a flight I was recording, to Socal.  So it may have been the recording that overwhelmed the capabilities of my system and P3DV4.4 install.  I heard the alarm of a pending stall, disengaged the autopilot, trimmed out the 550 back into stable cruise climb, and that was that, no more problems.

John

Got a couple of thousand hours with the PMDG 737 and never ever had an issue with trim or the AP.....

9 hours ago, KevinAu said:

No, they were nowhere near stall. The aoa sensor malfunctioned and gave the stall indication.

That is what is reported for the Lion Air flight.. did the Ethiopian flight also have a malfunctioning AoA sensor?  And if so, why did the crew not recognize it?    The Lion Air crash got lots of publicity... so they must have been aware..