From the news/reference thread:

Revelation wrote:

Reuters: Boeing 737 MAX certification flight tests to begin on Monday: sources says:

Pilots and test crew members from the U.S. Federal Aviation Administration and Boeing Co (BA.N) aim to kick off a certification test campaign for the 737 MAX on Monday, expected to last at least three days, people familiar with the matter told Reuters.

So Reuters has at least two sources saying the long (long, long, ...) awaited MAX test flights will begin Monday.

Gotta say, I feel a bit more nervous than I should that things will not go smoothly.

They have practiced this more than a few times, right?

Revelation wrote:

From the news/reference thread:

Revelation wrote:

Reuters: Boeing 737 MAX certification flight tests to begin on Monday: sources says:

Pilots and test crew members from the U.S. Federal Aviation Administration and Boeing Co (BA.N) aim to kick off a certification test campaign for the 737 MAX on Monday, expected to last at least three days, people familiar with the matter told Reuters.

So Reuters has at least two sources saying the long (long, long, ...) awaited MAX test flights will begin Monday.

Gotta say, I feel a bit more nervous than I should that things will not go smoothly.

They have practiced this more than a few times, right?

From the Reuters article:

“Based on how many problems have been uncovered, I would be stunned if the flight tests are ‘one and done,’” said another person with knowledge of the flight plans.

“(The FAA will) make sure they find enough stuff wrong to demonstrate they are putting this jet through its paces. The last thing the FAA or Boeing wants is for the Administrator to do his own flight and say ‘it’s not ready.’ Boeing wants Dickson’s flight to be a coronation.”

Regulators in Europe and Canada, while working closely with the FAA, will also conduct their own assessments and have pinpointed concerns that go beyond the FAA. They may require additional changes after the 737 MAX is cleared to return to service.

Sounds like this will be extremely intensive testing and I believe we will only know the future of the max once other regulators are done with their own testing.

So has the FAA moved away from their original "we want the final complete solution and just test that it's working as advertised"? Is this now more work in progress?

Revelation wrote:

From the news/reference thread:

Revelation wrote:

Reuters: Boeing 737 MAX certification flight tests to begin on Monday: sources says:

Pilots and test crew members from the U.S. Federal Aviation Administration and Boeing Co (BA.N) aim to kick off a certification test campaign for the 737 MAX on Monday, expected to last at least three days, people familiar with the matter told Reuters.

So Reuters has at least two sources saying the long (long, long, ...) awaited MAX test flights will begin Monday.

Gotta say, I feel a bit more nervous than I should that things will not go smoothly.

They have practiced this more than a few times, right?

I think they’ll go smoothly. Hopefully Boeing would’ve battered the plane time and time again in different scenarios. I do expect to a minor but just to make sure the FAA is really digging deep.

I

Noshow wrote:

So has the FAA moved away from their original "we want the final complete solution and just test that it's working as advertised"? Is this now more work in progress?

The Bloomberg article discussed on the last page says:

Conducting test flights is one of the final steps in the process of certifying a jetliner and aviation regulators wouldn’t have scheduled it if their review of Boeing’s proposed fixes had revealed significant additional issues.

So FAA thinks they are testing a plane that is a strong candidate for RTS with no outstanding significant issues.

The idea of having post-RTS fixes was floated as early as Sept 2019 ( ref: viewtopic.php?f=3&t=1445841&start=500#p22292469 ). It's not a surprise that Boeing, FAA, EASA and other world regulators have been negotiating on a lot of points. It's easy to say Boeing and FAA have been concessionary during the negotiations, but other posters here were keeping long lists of potential show stoppers that seem to not being addressed before RTS (dealing with containment upon jet engine failure was one I remember, I'm sure there were others) so maybe it's not as one sided as some think.

So to be clear, they have not perfected the model in the simulator but they are going to a test flight, and we are going to be shocked that all the problems generated in the simulator are replicated in the test flight?
I would have thought they would have gotten an all clear for the engineering model in the simulator first before going to test flight.

Revelation wrote:

From the news/reference thread:

Revelation wrote:

Reuters: Boeing 737 MAX certification flight tests to begin on Monday: sources says:

Pilots and test crew members from the U.S. Federal Aviation Administration and Boeing Co (BA.N) aim to kick off a certification test campaign for the 737 MAX on Monday, expected to last at least three days, people familiar with the matter told Reuters.

So Reuters has at least two sources saying the long (long, long, ...) awaited MAX test flights will begin Monday.

Gotta say, I feel a bit more nervous than I should that things will not go smoothly.

They have practiced this more than a few times, right?

It took a while to track down the now-retired engineers at North American who designed the ejection seats for the first two Space Shuttles and have them create a similar system for the MAX test aircraft

par13del wrote:

So to be clear, they have not perfected the model in the simulator but they are going to a test flight, and we are going to be shocked that all the problems generated in the simulator are replicated in the test flight?
I would have thought they would have gotten an all clear for the engineering model in the simulator first before going to test flight.

I'm pretty darn sure they've done everything they anticipate FAA will ask in the simulator multiple times, and probably on the same MAX7 with the same software installed a few times as well, but this program and this company seem to find ways to mess things up in very unexpected ways these days.

Revelation wrote:

par13del wrote:

So to be clear, they have not perfected the model in the simulator but they are going to a test flight, and we are going to be shocked that all the problems generated in the simulator are replicated in the test flight?
I would have thought they would have gotten an all clear for the engineering model in the simulator first before going to test flight.

I'm pretty darn sure they've done everything they anticipate FAA will ask in the simulator multiple times, and probably on the same MAX7 with the same software installed a few times as well, but this program and this company seem to find ways to mess things up in very unexpected ways these days.

I want to give them the benefit of the doubt that they know for sure this particular thing is the ONE thing they CAN'T mess up LOL

Opus99 wrote:

Revelation wrote:

par13del wrote:

So to be clear, they have not perfected the model in the simulator but they are going to a test flight, and we are going to be shocked that all the problems generated in the simulator are replicated in the test flight?
I would have thought they would have gotten an all clear for the engineering model in the simulator first before going to test flight.

I'm pretty darn sure they've done everything they anticipate FAA will ask in the simulator multiple times, and probably on the same MAX7 with the same software installed a few times as well, but this program and this company seem to find ways to mess things up in very unexpected ways these days.

I want to give them the benefit of the doubt that they know for sure this particular thing is the ONE thing they CAN'T mess up LOL

Hence the problem, we know they had issues in the simulator, no one crashed the a/c but they found different ways to safely land, we know the regulators opinions of those sessions.
We heard they updated manuals and procedures, no confirmation that all and sundry were happy with the updates, including the FAA.
Its not Boeing going to find new ways to screw things up, in my opinion, they are being set up to fail as the long list that the FAA and others can hold over the head of the MAX still exist.
As for the regulators allowing the MAX to RTS and fix outstanding issues later, my opinion again, since no one is taking new a/c now and Boeing has over 400+ a/c sitting down to modify before they can be delivered, nothing is going to change in the near future, at least nothing to positively affect Boeing's cash flow.
The a/c already delivered have to be modified, in itself that will probably be a few months, whether the airlines outside of the USA will use them is another story, as a lot of them are still closed to pax aviation traffic.
I guess I am being pessimistic but I get the feeling that too much emphasis is being placed on the test flights, my bigger fear is that once RTS is granted with a wish list of things to fix, at any given time, one of the regulators can go off and just ground the a/c again and restart the pissing match.

Please fly safe everybody. Do another flight the next day if needed.

par13del wrote:

Hence the problem, we know they had issues in the simulator, no one crashed the a/c but they found different ways to safely land, we know the regulators opinions of those sessions.
We heard they updated manuals and procedures, no confirmation that all and sundry were happy with the updates, including the FAA.
Its not Boeing going to find new ways to screw things up, in my opinion, they are being set up to fail as the long list that the FAA and others can hold over the head of the MAX still exist.
As for the regulators allowing the MAX to RTS and fix outstanding issues later, my opinion again, since no one is taking new a/c now and Boeing has over 400+ a/c sitting down to modify before they can be delivered, nothing is going to change in the near future, at least nothing to positively affect Boeing's cash flow.
The a/c already delivered have to be modified, in itself that will probably be a few months, whether the airlines outside of the USA will use them is another story, as a lot of them are still closed to pax aviation traffic.
I guess I am being pessimistic but I get the feeling that too much emphasis is being placed on the test flights, my bigger fear is that once RTS is granted with a wish list of things to fix, at any given time, one of the regulators can go off and just ground the a/c again and restart the pissing match.

The sequence being followed is the same one as was posted 19 Dec 2019 to Twitter:


Ref: https://twitter.com/LeehamNews/status/1 ... 3657516033

The "issues in the simulator, no one crashed the a/c but they found different ways to safely land" box is the first gray box, "Workload Evaluation", and it happened a bit after 19 Dec. It was always going to be an evaluation and not a test so did not block future events.

Tomorrow will be the next gray box, "certification flights". This could not happen till regulators felt all blocking items were resolved.

Then if/when the these flight tests happen successfully, then they go on to the JOEB "updated manuals and procedures, no confirmation that all and sundry were happy with the updates" resolution meeting. At that point they'll have all the info on the fixes, will have the feedback from the earlier evaluation session(s), have Boeing's latest and greatest training content, and "finalize training requirements" as the box says.

Again, the JOEB meeting could not happen till the set of fixes were frozen and had made it through testing, but the evaluation already happened and Boeing has sent around at least one set of training proposals, which of course now contains sim time.

Then once the JOEB "sets training requirements" the rest of the blocks are standard for any RTS activity.

I'm not too sure if too much emphasis is being put on the tests. The regulators didn't want to have them till all the non-training items had a resolution, either pre or post RTS. A whole sequence of glitches came up each step of the way. It *seems* at least FAA and EASA are on board with this being the set of things needed for RTS, and presumably some of the other regulators are on board as well. But yes, your fears could be true. It's pretty easy to project how one or more regulators will find one or more things they won't like and then we'll be back to the "need to perform certification test" phase all over again.

sgrow787 wrote:

beechnut wrote:

sgrow787 wrote:

IIRC, CAS is the airspeed corrected by angle of attack. I could be wrong.

The acronym "CAS" would be "calibrated airspeed". Wikipedia:

Calibrated airspeed (CAS) is indicated airspeed corrected for instrument and position error.

When flying at sea level under International Standard Atmosphere conditions (15 °C, 1013 hPa, 0% humidity) calibrated airspeed is the same as equivalent airspeed (EAS) and true airspeed (TAS). If there is no wind it is also the same as ground speed (GS). Under any other conditions, CAS may differ from the aircraft's TAS and GS.

Calibrated airspeed in knots is usually abbreviated as KCAS, while indicated airspeed is abbreviated as KIAS.

In some applications, notably British usage, the expression rectified airspeed is used instead of calibrated airspeed.[1]

Beech

Ok, thanks for that. From http://www.skybrary.aero:

https://www.skybrary.aero/index.php/Air ... 20altitude.

Remembering the relationship between the various speeds and understanding the conversion from one to another can be facilitated by use of the acronym "ICE T" in which the letters represent Indicated, Calibrated, Equivalent and True. The relationships between the speeds are as follows:

Indicated Airspeed is the speed shown on the airspeed indicator.
Calibrated Airspeed is indicated airspeed corrected for position installation error.
Equivalent Airspeed is calibrated airspeed corrected for compressibility.
True Airspeed is equivalent airspeed corrected for temperature and pressure altitude.

So 'I' feeds into 'C' feeds into 'E' feeds into 'T':
I-->C-->E-->T

No mention of AOA, so it's safe to assume that that correction happens at or near the airspeed sensor (eg Air Data Computer).

One mention of "Computed Airspeed" from DutchOps:
http://www.dutchops.com/Plane_Tech/Inst ... cator.html

The computer compensates also for position errors which is called the Computed airspeed. The Computed airspeed is used the calculate the CAS.

So if 'CO' represents Computed Airspeed, we have:

I-->CO-->C-->E-->T

All the AOA really does is just measures the aircraft AOA to and sends the aircraft systems cues that is its critical Angle is about to be exceeded which then activated whatever stall protection system that is onboard the aircraft to warn pilots that they are about to stall or activate the the stick pusher or MCAS whatever is onboard to force the aircraft to decrease its AOA to break the stall.

I wonder whether they will test the MAX with MCAS off, especially in tight turns. Didn't EASA explicitly ask for it? (I know, I know, by now I should know the EASA requests by heart... )

So we are back on this thing where MCAS has a switch that can be turned on and off?
If Boeing is going to give EASA a test flight with no MCAS they have to specially modify an a/c for that, the whole MCAS issue revolves about it being automatically added to the flight controls / systems where the pilots did not need to know about it, don't think we need to rehash all of that.

It's gearing up to be a monumental week for the BOEING COMPANY.......either they make progress to rectify this aircraft and return to the skies/it all goes to the dumps-program cancellation and lost of ALL credibility

par13del wrote:

So we are back on this thing where MCAS has a switch that can be turned on and off?
If Boeing is going to give EASA a test flight with no MCAS they have to specially modify an a/c for that, the whole MCAS issue revolves about it being automatically added to the flight controls / systems where the pilots did not need to know about it, don't think we need to rehash all of that.

LAX772LR wrote:

Another whistleblower steps forward with additional accusations against Boeing and allegations of flaws in 737MAX design.
https://www.seattletimes.com/business/b ... h-737-max/

Try reading the articles you cite. That guy stepped forward almost a year ago and there's nothing new in what he's saying.

par13del wrote:

So we are back on this thing where MCAS has a switch that can be turned on and off?
If Boeing is going to give EASA a test flight with no MCAS they have to specially modify an a/c for that, [...snip...].

logical :: ThisATestForEASA
! MCAS activation angle in degrees
real (kind=rdp) :: MCASactivationAngle

....

if (ThisATestForEASA) then
MCASactivationAngle = 100.
else
MCASactivationAngle = [whatever it is now]
end if

....

This is Fortran. Convert to your favorite programming language
voilà

IADFCO wrote:

I wonder whether they will test the MAX with MCAS off, especially in tight turns. Didn't EASA explicitly ask for it? (I know, I know, by now I should know the EASA requests by heart... )

I guess you mean this from the JTAR Report:

JATR Final Report wrote:

Recommendation R3.4: The FAA should review the natural (bare airframe) stalling
characteristics of the B737 MAX to determine if unsafe characteristics exist. If unsafe
characteristics exist, the design of the speed trim system (STS)/MCAS/elevator feel shift
(EFS) should be reviewed for acceptability.

JATR Final Report wrote:

Finding F3.4-A: The acceptability of the natural stalling characteristics of the aircraft should form the basis for the design and certification of augmentation functions such as EFS and STS (including MCAS) that are used in support of meeting 14 CFR part 25, subpart B requirements.

Finding F3.5-A: The nose-down pitch identified during Boeing flight tests for stall appears to the JATR team to be the product of system augmentation with flaps and gear up, and is likely due to stabilizer motion from the MCAS function.

Finding F3.5-B: The FAA-accepted Boeing flight test technique of freezing column deflection at the onset of EFS was perceived by the JATR team as possibly not meeting the requirements of § 25.201 for natural stall identification from nose-down pitch, not readily arrested. Column/elevator deflection data indicates that there may be an insufficient column input to attempt to arrest the nose-down pitch created by system augmentation.

And from the infamous Ky report:

EASA-Ky Report wrote:

Flight testson a modified B737 max [one full week -at Boeing Flight Test Center]
* MCAS operations (nominal behavior)
* Flight without MCAS (including high speed turns and stall)
* Scenario of stabiliser runaway (uncommanded MCAS activation, manual trim wheel forces)
* Approachto stallwithautopilotengaged

I was wondering about this as well, and whether Boeing/FA/EASA or any other party would publish the results of the unaugmented stall charateristics.
This had been heavily debated on here form day one, and it seems no concencus was found, just that ultimately it was agreed to disagree . . .

Wouldn't they need to test it without MCAS as the electrical system can be degraded? They need to know the unaugmented behavior.

First Recertification flight scheduled from BFI 10am on the MAX 7

You mean today? This is one flight where live streaming video from the cockpit would be useful...

AirlineCritic wrote:

You mean today? This is one flight where live streaming video from the cockpit would be useful...

Yes BOE701

AirlineCritic wrote:

You mean today? This is one flight where live streaming video from the cockpit would be useful...

Useful for whom though? Surely it would be quite a stretch to think Boeing, or Regulators, would countenance such a thing for the general public.

BOE701 is airborne.

Opus99 wrote:

AirlineCritic wrote:

You mean today? This is one flight where live streaming video from the cockpit would be useful...

Yes BOE701

in the air !

Interesting that the test flight is ending in Moses Lake. Odd that the testers and officials would want to have to ferry back to BFI. Anyone know the reason for this? Why not just fly back to BFI?

I get that MWH is a testing ground. So maybe they plan a series of take off and landing tests there this week.

If you have the fr24 (paid) 3d pilot view option you can be in the cockpit (almost)

DBCoop3r wrote:

Interesting that the test flight is ending in Moses Lake. Odd that the testers and officials would want to have to ferry back to BFI. Anyone know the reason for this? Why not just fly back to BFI?

It’s probably going to fly back today, it’s just how some of the test flights are filed.

ikolkyo wrote:

DBCoop3r wrote:

Interesting that the test flight is ending in Moses Lake. Odd that the testers and officials would want to have to ferry back to BFI. Anyone know the reason for this? Why not just fly back to BFI?

It’s probably going to fly back today, it’s just how some of the test flights are filed.

Next flight is scheduled for 12:25 PDT, MWH-BFI.

PW100 wrote:

I was wondering about this as well, and whether Boeing/FA/EASA or any other party would publish the results of the unaugmented stall charateristics.
This had been heavily debated on here form day one, and it seems no concencus was found, just that ultimately it was agreed to disagree . . .

Even EASA accepts that a review without MCAS requires a specially modified frame where the programming is removed.

Based on what has been revealed, they appear to have identified a need for augmentation during wind tunnel testing, when they did actual test flights, they found that the adjustments were not adequate enough thus they were increased.
In all the months after the bit flip disaster and the reprogramming of the flight computers, such an a/c could have been prepared, that they chose not to, says to me that they know it would have created more problems that it resolved.

If you have the fr24 (paid) 3d pilot view option you can be in the cockpit (almost)

par13del wrote:

Even EASA accepts that a review without MCAS requires a specially modified frame where the programming is removed.
... In all the months after the bit flip disaster and the reprogramming of the flight computers, such an a/c could have been prepared, that they chose not to, says to me that they know it would have created more problems that it resolved.

I am quite sure the MCAS functionality can be removed by a flick of a switch. Where that switch resides I cannot know but there is one. It can be at SW compile time or a setting in some service menu or a physical jumper or whatever. Probably not just one but multiple of those and most probably it is even more finegrained so that specific subparts of MCAS can be enabled or disabled independently from each other. This kind of functionality is necessary for SW development and testing and it is also totally inconceivable that Boeing themselves have not flown the plane without flicking these switches to disable MCAS at 10 different stages of the specification and testing of MCAS development. In testing phase there must have been also a flight time switch to disable MCAS if it starts to misbehave. Also there has been plans to disable MCAS if AoA inputs disagree and this MCAS disabling in the AoA disagreement case is 99% the functionality that is needed to disable it for other testing also. So there is zero possiblity that creating a plane without MCAS is in any way difficult task.

I am also very afraid that making this kind of plane available would have created more problems and that is the reason if it has not happened. The problems created could have been in the form of "This plane can never be certified".

Ertro wrote:

I am also very afraid that making this kind of plane available would have created more problems and that is the reason if it has not happened. The problems created could have been in the form of "This plane can never be certified".

Well since EASA now has more "power" as the FAA did a bang up job, time will tell if they will allow the a/c to fly in their jurisdiction.

Might be a silly question, but any reason why they chose the MAX 7 to begin test flights with? Or is it just random? I had assumed the MAX 8 would be the priority as it was involved in both crashes.

Continental767 wrote:

Might be a silly question, but any reason why they chose the MAX 7 to begin test flights with? Or is it just random? I had assumed the MAX 8 would be the priority as it was involved in both crashes.

I read recently that apparently MCAS acts faster and more abruptly on the max 7 as the AOA changes faster

Continental767 wrote:

Might be a silly question, but any reason why they chose the MAX 7 to begin test flights with? Or is it just random? I had assumed the MAX 8 would be the priority as it was involved in both crashes.

MAX 7 has all the testing equipment and my uninformed assumption would be that a 7 would be much more sensitive to MCAS input than an 8 or 9 due to shorter frame.

Looks like they just did a touch and go at MWH.

Someone please explain this to me:

The two crashes that led to the grounding were with 737-8 models. Now the certification flights are being done with a 737-7. Why? Wouldn't the longer fuselage of the -8 result in a bigger lever, which gives the trim inputs a bigger effect? Wouldn't you want to test that on an -8 so get data that can be better compared to the events that led to the crashes? Why would they do these tests on a variant with a shorter fuselage where the trim inputs would be less pronounced?

par13del wrote:

Ertro wrote:

I am also very afraid that making this kind of plane available would have created more problems and that is the reason if it has not happened. The problems created could have been in the form of "This plane can never be certified".

Well since EASA now has more "power" as the FAA did a bang up job, time will tell if they will allow the a/c to fly in their jurisdiction.

No, EASA's power has not increased in the slightest but up until the Max fiasco there was at least an element of mutual trust between regulators. Sadly, the FAA showed themselves, for a multitude of reasons, they were no longer to be automatically trusted. Other regulators, correctly, now want to satisfy themselves and which no doubt leaves Boeing rather uncomfortable.

[quote="par13del"
Even EASA accepts that a review without MCAS requires a specially modified frame where the programming is removed.
In all the months after the bit flip disaster and the reprogramming of the flight computers, such an a/c could have been prepared, that they chose not to, says to me that they know it would have created more problems that it resolved.[/quote]

Are you saying that EASA chose not to, or Boeing, remembering that it was Boeing who repeatedly refused to test without MCAS?

TropicalSky wrote:

It's gearing up to be a monumental week for the BOEING COMPANY.......either they make progress to rectify this aircraft and return to the skies/it all goes to the dumps-program cancellation and lost of ALL credibility

It's an important time for the program, but I think it would take a major calamity for there to be any risk of cancellation, and even then Boeing would do all in its power to fix whatever happened and try to find a path to RTS.

Vicenza wrote:

[quote="par13del"
Even EASA accepts that a review without MCAS requires a specially modified frame where the programming is removed.
In all the months after the bit flip disaster and the reprogramming of the flight computers, such an a/c could have been prepared, that they chose not to, says to me that they know it would have created more problems that it resolved.

Are you saying that EASA chose not to, or Boeing, remembering that it was Boeing who repeatedly refused to test without MCAS?[/quote]
EASA cannot modify a Boeing a/c for certification.
In their report EASA acknowledges that to have a test without MCAS they need a specially modified frame, the whole point of the post was that there is no switch to tun off MCAS, however, another poster said such a switch exist even if it is software code, so we are back at square 1 from a year or more ago.
It is what it is....

Revelation wrote:

TropicalSky wrote:

It's gearing up to be a monumental week for the BOEING COMPANY.......either they make progress to rectify this aircraft and return to the skies/it all goes to the dumps-program cancellation and lost of ALL credibility

It's an important time for the program, but I think it would take a major calamity for there to be any risk of cancellation, and even then Boeing would do all in its power to fix whatever happened and try to find a path to RTS.

Well so far we know that they are fighting back against some of the requirements being thrown out, so IF something else "comes up" I expect more of the same, and since Covid has made the situation even worse, they have additional items to affect resolution.

Anyone else picked up on the news that DY just cancelled their order for 92 MAX? Link in Norwegian only.
https://www.borsen.no/studio/borsenstudio/608?post=36739

DUSdude wrote:

Someone please explain this to me:

The two crashes that led to the grounding were with 737-8 models. Now the certification flights are being done with a 737-7. Why? Wouldn't the longer fuselage of the -8 result in a bigger lever, which gives the trim inputs a bigger effect? Wouldn't you want to test that on an -8 so get data that can be better compared to the events that led to the crashes? Why would they do these tests on a variant with a shorter fuselage where the trim inputs would be less pronounced?

Keep in mind I'm only a mechanical engineer, so my knowledge of aerodynamics is not up to par with an aerospace engineer or probably even most pilots, but I can speak to some of the points regarding control systems as well as overall dynamics. It could get complicated because of all the variables that change between the -7 and -8, but I believe you are correct that the -8 would have a larger pitching moment for a given stabilizer input. However, the problem with MCAS isn't that it is making the plane fly outside its envelope, so the additional pitch authority that the -8's and -9's have isn't really relevant. The two planes that crashed just happened to be 737-8s, but the problem isn't inherent to that variant only. The same thing could happen to a 737-7 but it might take a couple seconds longer to lose x-feet of altitude (assuming the trim activates the same amount across all variants). Furthermore, while I can't find an exact number breakdown of the deliveries of the MAX by type, but if we assume the 7,8,and 9 have a similar split to the 700,800,and 900, then the -8 was by far the most common MAX variant in service. Which again assuming that sales split held on the MAX, explains why the two crashes were both MAX-8s. Anyway what the engineers on the flight will be looking at is how MCAS responds to various flying conditions and most importantly different fault scenarios, which should be the same across all types.

There are also other non-MCAS related issues that have been discovered since the FAA is doing a fine tooth comb through the plane that should be identical across other models.

Just my thoughts on the matter, if anyone else has another view feel free to correct me.

Sales Source: http://www.b737.org.uk/sales.htm

DUSdude wrote:

Someone please explain this to me:

The two crashes that led to the grounding were with 737-8 models. Now the certification flights are being done with a 737-7. Why? Wouldn't the longer fuselage of the -8 result in a bigger lever, which gives the trim inputs a bigger effect? Wouldn't you want to test that on an -8 so get data that can be better compared to the events that led to the crashes? Why would they do these tests on a variant with a shorter fuselage where the trim inputs would be less pronounced?

Wouldn't the non-MCAS behavior be the worst case on the -7? I remember speculation that the -10 might not need it.

In a runaway the longer fuselage will be somewhat worse but they won't be testing a runaway since the new software limits the authority and allows pilot override. They'll be proving the software works I'm sure but if they haven't solved the runaway issue properly by now then their software team is incompetent.

Does anyone have any idea how many certification flights there will be? Will they someway fail the AoA sensor and see what happens or is that done in a simulator?

BowlingShoeDC9 wrote:

Which again assuming that sales split held on the MAX, explains why the two crashes were both MAX-8s.

Up to the two crashes only the MAX-8s were certified and delivered so there was no chance that any other variant of the MAX could crash as none were in service.

Here's a video of the 7M7 landing at Boeing field after its first cert flight. It's 17min long but it's a great shot.

https://komonews.com/news/local/faa-boe ... -this-week