Another Country Grounds The 737-MAX

[sometimewoodworker]

Boeing's argument appears to be that MACS was introduced/added into the plane as a safety measure software, to prevent the plane from stalling during Take Off? Am I correct or is there more to Boeing's argument
pipoz4444

I don't know anything about Boeing's argument. I also don't know anyone who's suggesting the accidents/incidents happened during takeoff. They happened during the climb out not during takeoff. Takeoff finishes when the wheels leave the ground. Both planes had a completely normal takeoff

However the MCAS was not designed for that purpose. It is designed to make a stall recovery possible when the pilots controls become less able to correct a stall situation. It is turned off during takeoff while the flaps are extended and only becomes operational after the flaps are retracted during the climb out after takeoff.

It was required because if the airspeed drops low enough to get near enough to the stall point the natural and trained reaction is to increase power to increase airspeed and in many other planes this is an uneventful procedure. However with the Max due to the position, size and power of the new engines so that they will pull the nose of the plane up when increasing power, if this were not countered this would make the stall worse as the normal control surfaces will not be sufficient to counter the effect. Thus the trim function had to be linked and MCAS adjusts the trim to counter the tendency for the engines to pull the nose up and put a recoverable stall into a catastrophic stall.

The tail trim can, and unfortunately did, override all the other control surfaces.

I would suggest watching the Mentor Pilot's video for an overview of the need for MCAS and the way it works. He exclusively talks about MCAS in flight and nothing about takeoff, that is where my assumptions come from.

Boeing quote on MCAS design and usage

to compensate for some unique aircraft handling characteristics during it’s (sic) Part 25 certification” and help pilots bring the nose down in the event the jet’s angle of attack drifted too high when flying manually, putting the aircraft at risk of stalling,

Further reading
https://www.nytimes.com/2019/02/03/worl ... ule=inline

According to Boeing, MCAS does not control the plane during normal flight but "improves the behavior of the airplane" during "non-normal" situations.
These could be steep turns or after takeoff when a plane is climbing with flaps up at speeds that are close to stall speed.


Read more at: https://phys.org/news/2019-03-ethiopian ... 1.html#jCp

So when the flaps are down MCAS is disabled.

One pilot's comment on flap retraction in 777s

Below is sample screen of a Boeing 777's Primary Flight Display. See those flaps marks on the speed tape?

IMG_7071.GIF (17.32 KiB) Viewed 3970 times

Here's the thing: you don't want to retract the flaps from 5 to 1 when you're slower than the stall speed at flaps 1. So in terms of flaps retraction schedule, you'll:

Accelerate to (at least) the minimum speed for flaps 5 in the takeoff roll.
Pitch up really high (e.g. 12.5 degrees)
Upon reaching acceleration altitude (a.k.a. flap retraction altitude), pitch down a bit (e.g. from 12.5 to 10 degrees) and let the aircraft accelerate.
When the speed passes the "1" mark on the speed tape, set flaps 1.
When the speed passes "up" on the speed tape, fully retract the flaps.
Acceleration altitude is usually 1,000 feet or 1,250 feet. So that really steep climb right after takeoff roll lasts only about 30 seconds.

This ties in with the problems happening after the flaps would have been retracted.

Usage of flaps
Usually retracted by 3,000 feet

http://www.boeing.com/commercial/aeroma ... icle05.pdf

[pipoz4444]

STWW

Buy Take Off, I was actually referring to the time from ground to leveling out, so yes include the term/duration of flight - Climbing

Either way there does no appear to be any previously reported accidents of a Boeing 737 crashing due to problems experienced during the Climbing stage, until recently.

Re. "to compensate for some unique aircraft handling characteristics during it’s (sic) Part 25 certification” and help pilots bring the nose down in the event the jet’s angle of attack drifted too high when flying manually, putting the aircraft at risk of stalling". - Sounds like a way of saying we F..ked up the design of the plane and now need to retro fit a design correction? I don't see how it helps the Pilot bring the nose down, since it actually does that for them

The question still remains, if the 737-8 Max is/was properly designed, why can't the 737-8 Max be flown without the MACS system during Take Off & Climbing??? given the fact that most of the Pilots flying them have spent many hours flying the older 737 version. Just doesn't make sense to me, as Pilots have been Taking Off and Climbing for years without issue, unless I have missed something in Boeing's argument of "Add for Safety during Take Off/Climbing"

pipoz4444

[pipoz4444]

Opps

[tamada]

The car accessories you list aren't life-savers. They aint BASIC and yes, they cost more. They're OPTIONAL. The MCAS isn't a reversing camera. It's something that's supposed to keep the plane in the air. The system, it's redundancy of AOA sensors (now suddenly two instead of one) and the 'idiot light' shouldn't ever have been an item where its usefulness was decided by the accountants on EITHER side.

I never said that the safety features were life savers, just examples of safety equipment that costs more, for a life saver some cars don't have airbags or have fewer, you have to pay more for them. Is that a suitable example?

There have always been two AOA sensors, one on each side of the plane. The MCAS system as originally delivered used the information from only 1 I haven't seen anything suggesting that any earlier changes started using both.

And no the MCAS wasn't designed to keep the plane in the air, but to make recovery from a near stall possible. I don't have the data but wouldn't be surprised to find that in almost all flights it never activated.

It is possible that the fix may include information from both, that is pure guesswork. The logic of the software having to try to decide on which information is accurate if they disagree is not simple, get it wrong and you will have another plane falling out of the sky.

In all probability the rush to market has a significant bearing on the lack of sufficient testing.

Lack of an air bag in a certain automobile market where they aren't mandatory is a good analogy. But there's similar fudging in jurisdictions where they are mandatory that allows manufacturers to fit what they determine is the bare minimum air bag requirement.

I stand corrected on the AOA sensors in that there has always been two. However, the fact that the default configuration of MCAS is to use the data from only one of these sensors makes it harder to fathom why the 'difference' indicator, the visible warning of significant difference between the data from each separate AOA sensor, should be optional. It gets back to the immediate post- Lion Air 'defence' from Boeing that maybe they didn't want to overload the more novice pilot with data. Right, lets NOT tell him anything but just let MCAS automatically and anonymously wind the jackscrew on the tailplane anyway... he'll be able work it out but failing that, he can always hit the circuit breakers, no?

The larger engines and shorter engine pylons have altered the centre of gravity of the Max 8, something that is probably more critical during take-off. I understand that MCAS was developed to address this. Looking at the FAA's own wording on what the MCAS functionality is, they said a fault condition with the AOA sensor (data input to MCAS), "if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain." If you want to split hairs and suggest that this does not suggest any functionality with regard to "keeping the plane in the air", knock yourself out. The plane stalls, the plane crashes, end of.

[tamada]

Why is it Boeing's fault for making them options? Why aren't the airlines to blame for choosing not to buy them?

Separately, United apparently doesn't use them. UA released a statement saying that their pilots get this information another way.

Spoken like Boeing's legal counsel?

The other guys manage OK so why can't you guys?

Back to my contention that if something is available that makes this 737 derivative behave more in line to previous models with regard to safe take-off, then it shouldn't be left to the beancounters at any airline or LCC to decide if it's non-essential. It's elimination and subsequent cost saving should not be used as a sweetener by the salesman.

BTW, the UA statement is so incredibly light on detail, it's hard to see the relevance. I mean without looking at their chronometers, how do UA pilots know it's getting late in the day ? When it starts getting dark maybe?

[Udon Map]

Back to my contention that if something is available that makes this 737 derivative behave more in line to previous models with regard to safe take-off, then it shouldn't be left to the beancounters at any airline or LCC to decide if it's non-essential. It's elimination and subsequent cost saving should not be used as a sweetener by the salesman.

What makes you think that there will be any cost saving? If it's mandated to be included, you think that Boeing's not going to build it in to the base price? They're not giving anything away free.

[tamada]

Back to my contention that if something is available that makes this 737 derivative behave more in line to previous models with regard to safe take-off, then it shouldn't be left to the beancounters at any airline or LCC to decide if it's non-essential. It's elimination and subsequent cost saving should not be used as a sweetener by the salesman.

What makes you think that there will be any cost saving? If it's mandated to be included, you think that Boeing's not going to build it in to the base price? They're not giving anything away free.

If something isn't installed, connected up and tested in the first place, then beyond the cost of the uninstalled hardware, there are labor costs savings for the manufacturer as well.

Moot point moving forward since Boeing have recently decided to fit the AOA sensor 'difference alarm' as a no-cost, standard safety feature. Now was that decision driven by cost, safety concerns or ongoing loss of shareholder value?

The FAA appears to have let Boeing self-certify for a fair while now. I guess that's the customers fault as well?

[sometimewoodworker]

The larger engines and shorter engine pylons have altered the centre of gravity of the Max 8, something that is probably more critical during take-off. I understand that MCAS was developed to address this.

Sorry MCAS isn't functional during takeoff. It is disabled by the flaps being extended. It only comes into play once the flaps are retracted. As I have said it can only function during climb out, though that may well have been caused by A faulty AOT sensor (probably was in Lion Air), and during flight when the autopilot is off.

[sometimewoodworker]

Re. "to compensate for some unique aircraft handling characteristics during it’s (sic) Part 25 certification” and help pilots bring the nose down in the event the jet’s angle of attack drifted too high when flying manually, putting the aircraft at risk of stalling". - Sounds like a way of saying we F..ked up the design of the plan and now need to retro fit a design correction? I don't see how it helps the Pilot bring the nose down, since it actually does that for them

If the nose is going up the pilot will be using his control surfaces to bring the nose down, so yes MCAS is helping it isn't supposed to do the job independently.

The question still remains, if the 737-8 Max is/was properly designed, why can't the 737-8 Max be flown without the MACS system during Take Off & Climbing??? given the fact that most of the Pilots flying them have spent many hours flying the older 737 version. Just doesn't make sense to me, as Pilots have been Taking Off and Climbing for years without issue, unless I have missed something in Boeing's argument of "Add for Safety during Take Off/Climbing"

pipoz4444

In the majority of flights it is unlikely that MCAS was activated.

And the Max is sufficiently different to fly that an untrained older 737 pilot flying it without the autopilot and without MCAS would, in the wrong circumstances, have reacted in a way that makes a catastrophic uncontrollable stall a strong possibility.

You really should watch the Mentor Pilot video.

[Jing Jing]

Here is another video from Mentour Pilot. In this video he discusses a runaway stabilizer. MCAS has a role in activating the stabilizers during stall conditions and may cause a runaway stabilizer.

https://youtu.be/xixM_cwSLcQ

[pipoz4444]

Hi and this part I know "and the Max is sufficiently different to fly that an untrained older 737 pilot flying it without the autopilot and without MCAS would, in the wrong circumstances, have reacted in a way that makes a catastrophic uncontrollable stall a strong possibility"

Actually, I opt not to put my faith in info from a Mentour Pilot Video. Prefer to communicate direct with a seasoned Pilot, who has spent his last 5 years training other Pilots on the Airlines Simulator. Anyway, how do we know if this Dude in the Mentor Pilot Video, dressed in a Pilots Shirt holding a plastic plane, is actually an experienced Boeing 737 Pilot. Yes he appears in the Simulator but.............

Anyway back to the question, "If the 737-8 Max is/was properly designed, why can't the 737-8 Max be flown without the MACS system during Take Off & Climbing?? Why does it need MACS, other planes don't seem to need it"

I would have thought it reasonably logical that you don't just go and develop and put Safety Systems, such as the MACS, into a plane, arguably for use during the take off to end of climb, unless of course their is an inherent reason for it or a significant control risk. But then that is just me

Regards

pipoz4444

[the-monk]

Boeing tragedies expose cosy ties with regulator
US FAA delegated extensive authority for safety checks to aircraft manufacturer

https://www.bangkokpost.com/news/genera ... recent_box

[sometimewoodworker]

Anyway back to the question, "If the 737-8 Max is/was properly designed, why can't the 737-8 Max be flown without the MACS system during Take Off & Climbing?? Why does it need MACS, other planes don't seem to need it"

Other planes don't have the same system because they don't have high bypass engines mounted in a position that lifts the nose as much when applying thrust. Other planes do have an automatic stabiliser system, though not needing anywhere near the amount of control that the Max has as they don't pitch up as mich as the Max

Yes the system should have had longer testing and probably the plane itself shouldn't have been rushed out to compete with the airbus.

It certainly seems that the fact that after each pilot input the system reset and was able to make another 9.6 second adjustment of 2.5 degrees and that pilots seldom apply that amount of correction when making a trim adjustment was a prime reason the plane could not be covered.

If you take a look at a manual trim adjustment and how long it takes compared to the electric adjustment it's clear that any delay in turning off the power to the trim motor will take so long to correct that a low level you don't have enough time.

[pipoz4444]

True STWW, most of us have conveyed the same opinion that being the positioning of the engines is a contributing factor, given along with the thrust, pushing that nose upwards.To me its comes across as an over engineered design fault, that Boeing attempted to correct with the MACS.

I don't see Airbus having the same issue on their near equivalent planes

Let's see what the experts come up with? if they do ever issue a Report

pipoz4444

[sometimewoodworker]

True STWW, most of us have conveyed the same opinion that being the positioning of the engines is a contributing factor, given along with the thrust, pushing that nose upwards.To me its comes across as an over engineered design fault, that Boeing attempted to correct with the MACS.

I don't see Airbus having the same issue on their near equivalent planes

Let's see what the experts come up with? if they do ever issue a Report

pipoz4444

Does the new airbus have such low wings and larger engines that they need to move them forward and up? I hadn't heard that.

The MCAS system itself is a continuation of similar systems rather than a correction to a design fault.

Most probably it was the lack of testing including: The MCAS command authority, the resetting after each pilot trim command, the changing of the trim for each operation from 0.6 degrees to 2.5 degrees, the fact that there was no absolute limit to the trim adjustment along with being fed faulty data.

[tamada]

The larger engines and shorter engine pylons have altered the centre of gravity of the Max 8, something that is probably more critical during take-off. I understand that MCAS was developed to address this.

Sorry MCAS isn't functional during takeoff. It is disabled by the flaps being extended. It only comes into play once the flaps are retracted. As I have said it can only function during climb out, though that may well have been caused by A faulty AOT sensor (probably was in Lion Air), and during flight when the autopilot is off.IMG_7073.JPG

Good posts. For the layman traveler, take-off ends when the seatbelt light goes off and the plane is (almost) at cruising altitude. Deployed flaps disable MCAS but depending on how quickly the aircraft is being taken through climb-out, the flaps will be retracted sooner, no? Do you know if MCAS automatically senses the amount of flap and kicks-in unannounced or does it only activate once the flaps are fully retracted? The Lion Air flight had issues during climb out and the same issues may have affected the Ethiopian flight which, due to the altitude of Addis, thinner air and other aerodynamics, may already have been on a more accelerated climb-out?

[saint]

So as a layman am i correct in assuming that there was a basic design fault with the plane , and Boeing decided that this MCAS thingy was a quick or cheap fix ?

[sometimewoodworker]

So as a layman am i correct in assuming that there was a basic design fault with the plane , and Boeing decided that this MCAS thingy was a quick or cheap fix ?

No design fault AFIK, the characteristics of the planes design made certain actions of the pilot cause the plane to pitch up quite a lot which in a different plane would not have caused such degree of inclination.

MCAS was part of the original design. It originally only worked in 0.6 degree increments, this was increased during flight testing to work in 2.5 degree increments as the amount of increased angle of attack was found to be greater than was assumed during the design stage.

[Jing Jing]

Whether the MCAS was part of the original design does not help the fact the whole project was wrong. Boeing did not want to build a new airplane due to cost and timing. Boeing stuck larger more fuel efficient engines on a plane that was not originally designed to take this size engine. Airbus also did the same thing with their A320 Neo. By sticking larger engines on an existing plane Boeing hoped to cut the certification and trading process. These were selling points to the airline. A more fuel efficient plane that did not require pilot certification. Training in some cases consisted of using a tablet towatch videos.

[tamada]

So as a layman am i correct in assuming that there was a basic design fault with the plane , and Boeing decided that this MCAS thingy was a quick or cheap fix ?

No design fault AFIK, the characteristics of the planes design made certain actions of the pilot cause the plane to pitch up quite a lot which in a different plane would not have caused such degree of inclination.

MCAS was part of the original design. It originally only worked in 0.6 degree increments, this was increased during flight testing to work in 2.5 degree increments as the amount of increased angle of attack was found to be greater than was assumed during the design stage.

To put this technical jargon in layman's terms, the rate of nose-down that MCAS forced on the tailplane jackscrew was several orders of magnitude higher than any amount of counteracting, manual spinning of the trim wheels in the flight deck by the flight crew.

That's the point where the revised manual says they're supposed to flip the MCAS breakers and pull up.