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  • 27

FAA says has no timetable for Boeing 737 MAX's return to service

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The Federal Aviation Administration said on Wednesday it does not have a specific timetable on when Boeing Co’s troubled 737 MAX jet would return to service after two fatal crashes (uk.reuters.com) More...

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mattwestuk
Matt West 4
Looks like their KC-46 is having a similar problems. They don't know how long it will take for them to correct technical deficiencies:

https://www.airforcetimes.com/news/your-air-force/2019/06/13/kc-46-refueling-system-flaws-will-take-years-to-fix-and-cost-hundreds-of-millions-of-dollars-gao-says/
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KobeHunte
Kobe Hunte 6
Boeing is in some pretty deep water. They need to resolve their problems, and fast.
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alexa320
alex hidveghy 4
Well, both AAL and SWA have already made provisions to their planning for NOT having the MAX in service this summer. That’s pretty bad. Not to mention the MILLIONS in compensation and deferred orders. This is now a major deal for Boeing, no doubt about that.
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tyketto
Brad Littlejohn 2
Well, seeing how Airbus is taking the orders to the bank right now at the Paris Airshow, Boeing is in some serious trouble. I wouldn't be surprised if Boeing doesn't get any orders for any of the MAX series, and that's despite the fact that the MAX10 doesn't have the same problem that the B38M and B39M have.

Boeing is in a world of hurt now, and will be for quite some time.
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alexa320
alex hidveghy 2
Yes, wouldn’t be surprised at all.
In fact, I just saw a news headline that it has not taken any new orders (not sure if that’s any Boeing aircraft because I didn’t read the full article) for the SECOND STRAIGHT MONTH. that cannot be good in anyone’s book......
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belzybob
belzybob 0
I bet they wish it was just water.....
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speshulk99
john kilcher 9
The Max 8 shouldn't have been awarded an airworthiness certificate. Enlarging the engines and changing the c.o.g was strike #1. Installing MCAS without proper training and/or being tight lipped of their existence was strike #2. The allowance of the FAA to authorize Boeing to self inspect this abortion was strike #3.
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hornet135
hornet135 1
The cg didn’t change, did it?
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E1craZ4life
Edward Bardes 5
The engines on the 737 MAX had to be installed further forward than on the 737NG to be able to fit under the wings, which needed to be angled slightly upward to accommodate the engines. That's what makes the plane prone to stalling, the difference in angle of the wings.
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hornet135
hornet135 -7
There’s no engine angling issue or issue with being prone to stalling. Not sure where you got your information, but it’s misinformed.
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tyketto
Brad Littlejohn 8
Actually, there is. And it's been documented many times. But yes, the engines were so big that they had to move them on the wings, which caused a lot of the problems contributing to the AoA issues that caused MCAS to be needed, and the subsequent issues from that.

https://flightaware.com/squawks/link/1/recently/popular/72846/How_the_Boeing_737_Max_Disaster_Looks_to_a_Software_Developer

https://spectrum.ieee.org/aerospace/aviation/how-the-boeing-737-max-disaster-looks-to-a-software-developer
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kd7eir
Jim Myers 5
You win the "Ignoramus of the internet" award today! Congratulations!
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hornet135
hornet135 3
Nuance is clearly lost on everyone in this thread.

The original poster said that changing the cg was strike #1 with mounting the new engines. There is no indication the cg changed. The leap engines are about 800lbs heavier each and situated farther forward than the engines on the NG, but the tail cone was also extended a small amount, presumably to counteract this increased engine weight forward of but very near to the cg.

The issue is that the increased thrust of the new engines increased the pitch up moment at high thrust settings. Although the engine has a larger diameter, being mounted higher helps mitigate this effect and gives it a thrust line very close to that of the NG engines. The real problem is that with the engine nacelles being larger and further forward of the cg, they create far more lift at low airspeeds/high alpha than on the NG. This combined with the pitch up from the increased thrust means that in those high alpha/low airspeeds/high thrust situations the MAX handles differently than the NG.

The reason why MCAS was needed was to make the stick forces in these situations similar enough between the NG and MAX so that they could be deemed to handle the 'same' and thus operate on a single type certificate. MCAS is not truly for stall prevention even though many reports call it a "stall prevention system" or similar, but merely to keep the elevator stick forces within parameters defined by regulations and similar enough to that of the NG. This doesn't mean the MAX is any more prone to stall than anything else; it just means that in certain situations it handles differently enough to warrant a new system to get a single type certificate with the NG.

The MCAS implementation was flawed, but it's important to understand the underlying causes that necessitated MCAS.
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rapidwolve
rapidwolve 1
The MAX 8/9 CG is nowhere near that of the NG. The thrust increase between a CFM56-7B27 and Leap 1-B is negligible, and the Leaps are almost 1k pounds heavier. The underlying cause is, as you said, the engine size moved forward and bigger nacells...thus moving the engines forward shifted CG. The MCAS is, in a sense, an anti stall device.
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bentwing60
bentwing60 1
While I will readily agree that the Leap vs. Cfm-56 thrust differential is not that great, I would contend that by your own admission the CG moved forward with the leap engine, Not aft! the MCAS system is specifically designed to drive the nose down in a stall event, the same result as moving the CG forward. If the CG shift was the sole culprit of MCAS, it would have provided nose up trim! Check. H135 is spot on.
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rapidwolve
rapidwolve 0
I never mentioned aft, and I was referring to H135's "There is no indication the cg changed." I also never mentioned CG was the reason for MCAS...bigger engines moved forward, and up, caused CG to change and bigger nacells, with shifted engines, provided unwanted lift to give a more nose up attitude! That more unwanted nose up attitude leading to a greater chance of a stall was 1 of the reasons MCAS was installed. Hence, I will say again the MCAS is, in a sense, an anti stall device.
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rapidwolve
rapidwolve 0
Also if you read up on his first comment, he talked about engine angling. Edward did not mention engine angling, he mentioned the wing angle. T
hat was also "tweaked"
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hornet135
hornet135 1
Just because the engines were moved forward and weigh more doesn’t mean that cg moved forward. That would be the case if nothing else changed, but landing gear were strengthened, nose gear extended, tail cone lengthened, etc.
There's a lot of design details we just don't know.
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rapidwolve
rapidwolve 0
The nose gear was extended but the landing gear were not lengthened and the tail cone received no major increase. The reason the engines were moved forward and and up is because the landing gear did not allow sufficient enough clearance between them and the ground. If they had lengthened the landing gear, they would not fit into their designated flight retraction area, and Boeing obviously did not want to spend time developing a rotational gear strut.
If you take an aircraft, redistribute its weight and flight characteristics such as moving engine forward and up, you change CG. It would be similar to taking cargo and not properly distributing it in the hold...place more of it forward and the aircraft's CG changes.
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hornet135
hornet135 1
Go back and read what I said, landing gear were strengthened, nose gear extended.

The point is that more could change the CG than just the engines, a fact that you seem to be blind to.

Yellow is NG, purple is the MAX.
https://leehamnews.com/wp-content/uploads/2018/11/737NG-vs-MAX-planform.png
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rapidwolve
rapidwolve -1
I am not blind to anything but I am done with this conversation..I misread what you stated, but you seem to completely misread mine and bounce all over.
"The cg didn’t change, did it?" Yes it did
"There’s no engine angling issue" No on said anything about engines but they did say wings.
"Just because the engines were moved forward and weigh more doesn’t mean that cg moved forward." I never stipulated the CG moved forward, bentwings did yet you inferred I stated it. CG changed.
And that planform is old as the tailcone is not that big and the engines are farther forward than that
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rarebear14
Dolf Brouwers 2
I would like to see the reports of the test pilots at Boeing , they must have encountered this problem during the program and what did they do to circumvent. (solve it ) ?
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rapidwolve
rapidwolve 1
According to a few reports, 1 from a former test pilot, "Boeing never flight-tested a scenario in which the AOA sensor malfunctioned."
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rarebear14
Dolf Brouwers 1
not a good test program then
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KobeHunte
Kobe Hunte 3
I am definitely a Boeing fan, but if they can't get the Max back into service quick and the 777 properly sorted out, I fear there might be a problem.
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rapidwolve
rapidwolve 2
Now they have the issue with the leading edge slat tracks on the MAX and NG
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alexa320
alex hidveghy 2
And also new issues on the 787-9! What’s going on at Boeing?.....
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E1craZ4life
Edward Bardes 1
Nothing that hasn't happened before.
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tyketto
Brad Littlejohn 1
I gotta say, flawed design issues of this magnitude is nothing that has ever happened at Boeing.

The worse that they have had to date outside of the supply issues for the B787 was the jackscrew issue with the B727 (though the MD80 and F27s also had the same issue; the B717 wasn't made at the time), and the B737 rudder issue (USA427) which caused Boeing to redesign the rudder and retrofit all B733s affected by the problem at Boeing's expense.

Outside of that, nothing relative to using Software to fix a hardware design flaw has ever happened before, especially of this magnitude.
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E1craZ4life
Edward Bardes 1
The DC-10 had a bumpy start with the cargo door design problems, and the FAA grounded the plane after AA191 crashed. Airbus also had a rough start with its A320 program, and the aircraft garnered a lot of scrutiny following the crash of AF296 with its software that could override pilot inputs.

I wasn't just talking about Boeing.
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rapidwolve
rapidwolve 1
Yes...the FAA grounded the plane after the first crash, but the design problem was not intentional and it was a hardware "fix".

After the investigation into AF296, the probable cause was "very low flyover height, lower than surrounding obstacles; speed very slow and reducing to reach maximum possible angle of attack; engines speed at flight idle; and late application of go-around power." Some questioned the computers role, but it did not want nose up attitude at such a slow speed and low altitude. And if I remember correctly, Airbus did not have to do a software update to the A320 family.
So no, using software to correct a hardware design flaw, and in itself, the software being flawed, has never happened before.
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