737 max nacelle lift generation
Tdracer
(...No, you completely misunderstand MCAS...)
No, I don't think so...
I am thinking of abnormals, let's get on the same page?
A primer on Nacelle lift is not required.
Was Boeing trying to reinvent AB FBW?
A progressive linkage to the Yokes would enhance back pressure... MCAS completely unnecessary.
As the engine raises, more of its bottom presents to the airstream, less of its Nacelle top
Are the pro Nacelle lift guys counting the blown wing affect of the gas path on the ventral nacelle?
Coanda?
How did Boeing "Fix" MCAS?
tdracer... MCAS uses the THS to provide "feel".. Why import a massive trim surface architecture if all you want is a bigger bicep?
Failing the smell test. One thinks The Nacelles May be a red herring... No mention of moving the engines forward five feet and up two???? Magic?
No, I don't think so...
I am thinking of abnormals, let's get on the same page?
A primer on Nacelle lift is not required.
Was Boeing trying to reinvent AB FBW?
A progressive linkage to the Yokes would enhance back pressure... MCAS completely unnecessary.
As the engine raises, more of its bottom presents to the airstream, less of its Nacelle top
Are the pro Nacelle lift guys counting the blown wing affect of the gas path on the ventral nacelle?
Coanda?
How did Boeing "Fix" MCAS?
tdracer... MCAS uses the THS to provide "feel".. Why import a massive trim surface architecture if all you want is a bigger bicep?
Failing the smell test. One thinks The Nacelles May be a red herring... No mention of moving the engines forward five feet and up two???? Magic?
Last edited by BugBear; 23rd Jun 2024 at 22:17.
Correct, no involvement in the MAX other than attending a couple propulsion related design reviews. A new clean sheet design would almost certainly have incorporated FBW - rather than conventional cable control of the flight controls. With FBW, increasing the forces necessary to pull back into stall is simply modifying a few lines of code (which I suspect is what Airbus did on the NEO).
Airbus FBW: Not sure they have aerodynamic feedback into the sidestick at all. More like linear forces along the sidestick deflection from spring load. (And since you only command a change in g-load, reducing the speed towards stall speed does not need input at all. FBW keeps current g load (Edit: in high speed range) which means no change in vertical speed. Edit: in low speed range however FBW commands pitch rate, so there pilot must pull with decreasing speed)
Here I'm really unreliable guesser, look for reliable sources if you want to know!
Last edited by waito; 23rd Jun 2024 at 22:52.
I won't even attempt to evaluate the proposed solution(s) in context, but the next time I need a thorny design problem brainstormed, I'm calling MechEngr.
The following 2 users liked this post by OldnGrounded:
(...No, you completely misunderstand MCAS...)
No, I don't think so...
I am thinking of abnormals, let's get on the same page?
A primer on Nacelle lift is not required.
Was Boeing trying to reinvent AB FBW?
A progressive linkage to the Yokes would enhance back pressure... MCAS completely unnecessary.
As the engine raises, more of its bottom presents to the airstream, less of its Nacelle top
Are the pro Nacelle lift guys counting the blown wing affect of the gas path on the ventral nacelle?
Coanda?
How did Boeing "Fix" MCAS?
tdracer... MCAS uses the THS to provide "feel".. Why import a massive trim surface architecture if all you want is a bigger bicep?
Failing the smell test. One thinks The Nacelles May be a red herring... No mention of moving the engines forward five feet and up two???? Magic?
No, I don't think so...
I am thinking of abnormals, let's get on the same page?
A primer on Nacelle lift is not required.
Was Boeing trying to reinvent AB FBW?
A progressive linkage to the Yokes would enhance back pressure... MCAS completely unnecessary.
As the engine raises, more of its bottom presents to the airstream, less of its Nacelle top
Are the pro Nacelle lift guys counting the blown wing affect of the gas path on the ventral nacelle?
Coanda?
How did Boeing "Fix" MCAS?
tdracer... MCAS uses the THS to provide "feel".. Why import a massive trim surface architecture if all you want is a bigger bicep?
Failing the smell test. One thinks The Nacelles May be a red herring... No mention of moving the engines forward five feet and up two???? Magic?
If you want to be taken seriously you need to take a step back.... The engines moving forward is exactly what lead to MCAS. Because the nacelles are attached to the engines...
How difficult is it to see that a 737-200 and a 737 MAX8 would have a different feel with increasing AOA, everything else being equal?. And I personally think strakes on the tail would have been a better solution, but you know what, I am not an aeronautical engineer, and the B1900/D was still way worse to fly than the original King Air.
This is what happened:
The design requirement is that the pilot have to increase back pressure to maintain higher AOA. Absolutely normal behavior is expected from a conventional aircraft. The AB is exempt from some of those rules because of flight envelope protections. So in an A320, in level flight, with the AP and AT off, you can pull the Thrust levers to idle at 340kts, and get all the way down to Vls without having to put back pressure on the stick, and wont lose altitude. The magic that makes that happen is the computers using the trimmable horizontal stabilizer to keep the aircraft level.
In plan B, the pilot is supposed to be in the loop, so the THS needs to be adjusted by the pilot to trim away yoke force. This trim input is normally done with the switches on the yoke. There are other 737 systems that have an input on the THS, for instance STS, which will trim ANU while you are trying to accelerate after T/O. Pretty much always opposite to what you want, so always have to trim AND.
With The MAX the engines were even bigger than the NG, so had to be moved even further forward, to be able to be mounted higher and keep ground clearance., and yeah, so did the nacelle...... MCAS was there for a small corner of the envelope where if you were hand flying, and got slower, the aircraft would not feel as nose heavy as required, so Boeing decided to have a few units of AND added by the trim system would be a good idea. This was not necessarily bad. Not telling anybody about it, and using only ONE input to decide if it needed AND trim, without any failure protection or warning was obviously a disaster waiting to happen.
The question about abnormals is a good one. But every trim abnormal in the 737 can be solved by switching the trim off, a luxury not afforded to the A320 crowd.
"A primer on Nacelle lift is not required.
Was Boeing trying to reinvent AB FBW?
A progressive linkage to the Yokes would enhance back pressure... MCAS completely unnecessary.
As the engine raises, more of its bottom presents to the airstream, less of its Nacelle top
Are the pro Nacelle lift guys counting the blown wing affect of the gas path on the ventral nacelle?"
Coanda?"
This, I honestly have no clue what you are talking about.
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hansbrinker:
"...With The MAX the engines were even bigger than the NG, so had to be moved even further forward, to be able to be mounted higher and keep ground clearance., and yeah, so did the nacelle...... MCAS was there for a small corner of the envelope where if you were hand flying, and got slower, the aircraft would not feel as nose heavy as required, so Boeing decided to have a few units of AND added by the trim system would be a good idea. This was not necessarily bad. Not telling anybody about it, and using only ONE input to decide if it needed AND trim, without any failure protection or warning was obviously a disaster waiting to happen...."
This has been my thesis thru out... Your red ink you misread my post... Rather than Nacelle lift, the compliance involving MCAS was to correct unwanted lightness in NU created by the engines. My position exactly.
THIS:
"Failing the smell test. One thinks The Nacelles May be a red herring... No mention of moving the engines forward five feet and up two???? Magic?"
Airbus' flight path is Pitch Stable.
Boeing is Speed Stable.
My remark about Boeing copying AB had to do with MAX THS trimming to level, a pitch stable characteristic..It doesn't stay level, seeking speed stability
"...With The MAX the engines were even bigger than the NG, so had to be moved even further forward, to be able to be mounted higher and keep ground clearance., and yeah, so did the nacelle...... MCAS was there for a small corner of the envelope where if you were hand flying, and got slower, the aircraft would not feel as nose heavy as required, so Boeing decided to have a few units of AND added by the trim system would be a good idea. This was not necessarily bad. Not telling anybody about it, and using only ONE input to decide if it needed AND trim, without any failure protection or warning was obviously a disaster waiting to happen...."
This has been my thesis thru out... Your red ink you misread my post... Rather than Nacelle lift, the compliance involving MCAS was to correct unwanted lightness in NU created by the engines. My position exactly.
THIS:
"Failing the smell test. One thinks The Nacelles May be a red herring... No mention of moving the engines forward five feet and up two???? Magic?"
Airbus' flight path is Pitch Stable.
Boeing is Speed Stable.
My remark about Boeing copying AB had to do with MAX THS trimming to level, a pitch stable characteristic..It doesn't stay level, seeking speed stability
Last edited by BugBear; 24th Jun 2024 at 09:46.
Distraction
If the Nacelles are generating aerodynamic Lift, I would like to see the chord. If the lip of the Nacelle is creating upforce, it is doing so about the circumference, including downward. If this force is Nacelle wash flowing over the leading edge of the wing, I can't see anything but turbulent flow streaming over the part of the leading edge that is blanked by this novel airflow..
I have considered the MAX as a different type than the 737. It doesn't fly like the Certificate demands.
The issue is not controls "feel". The issue is more powerful engines, mounted in a way that causes the aircraft to want to overrotate onto it's back.
This aberrant behavior is dangerous. It is a hot design, and Boeing tried to shoehorn this plane into an existing Certificate of Airworthiness.
Tortured explanations and distractions are not a good defense.
Respect to all
I have considered the MAX as a different type than the 737. It doesn't fly like the Certificate demands.
The issue is not controls "feel". The issue is more powerful engines, mounted in a way that causes the aircraft to want to overrotate onto it's back.
This aberrant behavior is dangerous. It is a hot design, and Boeing tried to shoehorn this plane into an existing Certificate of Airworthiness.
Tortured explanations and distractions are not a good defense.
Respect to all
Last edited by BugBear; 24th Jun 2024 at 14:22.
Anything with the appropriate angle to the airflow can generate a lift force. Heck, even "drag" - in an upward direction - can be considered lift. When that force is forward of the center of pressure (usually ~25% of the wing Mean Aerodynamic Cord), that lift will create a nose up moment. The engine nacelles - located forward of the wing (and hence well forward of the MAC of the wing), create a force that tends to push the nose up at high angles of attack. Note that this is not new to the MAX, it was also the case on the NG and the "classic" 3/4/500 series (which also had engines located forward of the wing) - just not to the extent that occurred on the MAX. On the MAX, that force was enough to create a pitch up moment at high angles of attack that it negated the 'normal' increase in stick force necessary to keep pulling the nose up when approaching a stall.
If that doesn't make since to you, I give up...
If that doesn't make since to you, I give up...
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Originally Posted by Bugbear
including downward.
Originally Posted by Bugbear
I can't see anything but turbulent flow streaming over the part of the leading edge that is blanked by this novel airflow...
Tdracer
Tdracer
"..Anything with the appropriate angle to the airflow can generate a lift force. Heck, even "drag" - in an upward direction - can be considered lift..."
Virtually word for wotd my first post on this thread.
Calling drag Lift I don't like.
Let's say "push"
"..Anything with the appropriate angle to the airflow can generate a lift force. Heck, even "drag" - in an upward direction - can be considered lift..."
Virtually word for wotd my first post on this thread.
Calling drag Lift I don't like.
Let's say "push"
Sorry, but I don't even know what your point is. You complaining about 'misleading' nomenclature, but everyone one else on this thread seems to be understanding what's being said except you.
I'm not wasting anymore time...
I'm not wasting anymore time...
Sorry bugbear
Last edited by waito; 26th Jun 2024 at 18:43.
Tdracer
Out
Boeing FBW has force feedback then, right?
Does it simulate aerodynamic forces felt in a
conventional plane, or just a synthetic force layout to guide the pilot?
So in an A320, in level flight, with the AP and AT off, you can pull the Thrust levers to idle at 340kts, and get all the way down to Vls without having to put back pressure on the stick, and wont lose altitude.
Boeing's MCAS on the 737 Max may not have been needed at all - The Air Current
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MCAS: Boeing's AlphaProt
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The original failure was 30+ years ago when it became acceptable for aircraft not to have self-test on AoA sensors for range and to detect if they had become frozen or otherwise inoperable. That is where the money was saved and everyone liked it that way; depending on the pilot to detect if there were abnormal results.
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The original failure was 30+ years ago when it became acceptable for aircraft not to have self-test on AoA sensors for range and to detect if they had become frozen or otherwise inoperable. That is where the money was saved and everyone liked it that way; depending on the pilot to detect if there were abnormal results.