Posted on 04/09/2019 12:49:46 PM PDT by CondoleezzaProtege
This Boeing 737 Max 8 problem, again, just to reset this, traces back to 2011. I’ll tell you what this is about. It’s about the bloodletting that is competition in capitalism...I think the competition in capitalism is one of the great things in the design of our country, but it can lead to some things as well. But it’s far better than anything else.
What happened was in 2011, Airbus (which really doesn’t fairly compete because they’re a government entity. The Airbus plane is the result of a coalition of governments in Europe.)
But the Airbus A320 was able to be upgraded and outfitted with new engines, more powerful and more efficient engines without redesigning or rebuilding the airplane. The competition that Boeing has for the A320 was the Boeing 737-500, -600, -700 series. The Boeing 737 design would not accommodate simply upgrading engines.
If they had just put new engines — larger but more efficient engines on those wings, because it’s so low to the ground, it would totally upset the center of gravity. It would change the angle of attack. So they had to modify certain aspects of the Boeing 737, rather than go to the expense of redesigning it, retooling the manufacturing equipment and process. And they created software to handle how the airplane would behave differently during takeoff and at flight. And that’s what the MCAS system is.
...The nose gear was actually eight inches longer to accommodate the bigger engines. So it changes the elevation of the nose of the airplane as it’s flying through the air, creating the aerodynamics that are called “lift.” So because it tended to elevate the nose, these new engines and new angle of attack, they needed software on the rear horizontal stabilizer to keep the nose down.
(Excerpt) Read more at rushlimbaugh.com ...
How wrong?
The Edsel was regarded as a good solid car, noted mostly for being “ugly”.
I MEANT specifically this particular 737 here, the “Max 8”, not the 737 in general which is probably one of the most successful jets ever (even perhaps without the Southwest deal).
Thank you for your reasoned response to those with minimum technical knowledge and maximum opinion. I wish I could do as well. Then again, maybe I wouldn’t, there is some egregious options flying around.
The Handling Characteristics of Swept-wing Commercial Airplanes
FTA: "Since download on the tail is negative lift, effectively increasing the weight of the airplane, the location of the CG affects the cruise performance of any airplane. Flying at an aft CG will reduce the download on the tail and improve cruise performance."
"When airplanes are operated near the aft CG limit, download on the tail is minimized and angles of attack and drag are reduced. However, moving the CG aft reduces the longitudinal static stability of the airplane, something that all flight crews should be aware of"
"As airspeed varies from a trimmed condition, the column force required to maintain a new speed (without re-trimming) is a measure of static longitudinal stability. For any conventional airplane, the location of the CG has the strongest influence on static longitudinal stability. For a statically stable airplane the required column force, as speed varies from the trimmed condition, is less at an aft CG than it is at a forward CG. The minimum average gradient allowed by U.S. Federal Aviation Administration FAR Part 25 is one pound for each six knots. As the CG moves aft, it reaches a point where the stick force per knot drops to zero, then reverses. This location is called the neutral point. The difference between the actual CG location and the neutral point is called the static margin. With a CG forward of the neutral point, an airplane has a positive static margin and positive static longitudinal stability. At a CG aft of the neutral point, an airplane has a negative static margin, is statically unstable, and requires some form of augmentation to be flown with an acceptable workload."
My guess is that Boeing designed the MAX with a CG further aft than earlier versions of the 737. This was done to improve cruise performance and compete against the Airbus 320. During flight test the test pilots discovered that the aft CG causes adverse stall characteristics, necessitating the MCAS (stall prevention) system.
MeganC...kudos to you for bringing up Longitudinal Static Stability. I believe this will be a contributing factor in the accident reports. My hope is that the accident reports get published for all to read.
Also, best wishes on your upcoming solo...an event you will always remember.
“The Edsel was regarded as a good solid car, noted mostly for being “ugly”.’
The Edsel was delivered to showrooms with lists of missing parts.
Early models were on Mercury chassis. Later models on Ford.
Look up Tele-Touch.
You just did.
“My guess …”
Why not research. Details have been available for several months.
Please provide me one link where CG as a percent of MAC is discussed. I have not been able to find one.
I didn’t say it was discussed.
What us MAC?
Mean Aerodynamic Chord. It is defined primarily by the wing of the aircraft and is used to determine Center of Lift.
Here’s a link that explains it:
https://www.skybrary.aero/index.php/Mean_Aerodynamic_Chord_(MAC)
Typical CG for an aircraft with positive longitudinal static stability is 32% to 33% MAC. I would be interested to see what CG limits are for the King Air.
The point I am making is that the reporting on 737 MAX issues has been horrible, even to the point of being misleading. In all of the reading I have done, I have not seen any mention of CG as % of MAC which impacts longitudinal stability. In all comments by Freepers, I have not seen longitudinal stability mentioned, except by MeganC...and I will say again, kudos to MeganC.
I am a pilot, not an aero engineer. If there are any Freepers that can expand (agree or disagree) please do so.
You're joking right? Boeing makes the most technologically advanced commercial airliner available. It has changed how the world flies now. Boeing bet on long and thin, making the ultra-efficient 787. Airbus bet on hub and spoke, making the ultra-large A380. The 787 is selling remarkably well. The A380 program has been cancelled and was a commercial failure. Boeing and its technology is not falling behind.
“The point I am making is that the reporting on 737 MAX issues has been horrible, even to the point of being misleading. “
Issues were clearly laid out last year, designs discussed and problems verified based on FDR analysis.
“and I will say again, kudos to MeganC.”
ROTFLMAO!
“In all of the reading I have done, I have not seen any mention of CG as % of MAC which impacts longitudinal stability.”
You sound like you have no idea what caused the crashes even though cause has been documented and reported.
The 737 Max would become a lawn dart without considerable constant input from a pilot or a control system. And that’s in good weather, no turbulence, and without any mechanical problems.
That’s the difference.
Comparing the flight characteristics of a tiny general aviation prop plane to a modern turbofan commercial airliner is bizarre. You may as well throw in an F-16 to the discussion.
That said, it seems to me that you are implying that the 737 Max would drive itself into the ground without input from a pilot or control system, and that the previous 737 NG (and perhaps A320 Neo?) would not. Is that what you are implying? That all older 737s and A320s would fly along just fine without any inputs until they run out of fuel like your King Air?
What makes your assessment a particularly interesting statement is that from what we know so far, both 737 Max crashes were due to input from a (faulty) control system, not a result of any aerodynamic deficiencies.
Regarding airline deaths, I quoted and linked the source in the post you replied to.
This stat is for commercial passenger aircraft above some number of passengers so the Amazon cargo crash wouldn't count.
It isn't that one company is necessarily "better" than the other - it's that both are in essence state-controlled enterprises and Airbus has been scoring some big wins lately in the commercial marketplace. In the Air Force tanker marketplace too, until Boeing's government operatives managed to get the winning Airbus bid squashed and force the Air Force to take their 767 variant, instead.
The A380 failed - so did Boeing's newer 747-8 (the cargo variant is still seling). Both are great planes, but the age of the four-engine airliner has passed - regrettably.
It isn't that one company is necessarily "better" than the other - it's that both are in essence state-controlled enterprises and Airbus has been scoring some big wins lately in the commercial marketplace. In the Air Force tanker marketplace too, until Boeing's government operatives managed to get the winning Airbus bid squashed and force the Air Force to take their 767 variant, instead.
The A380 failed - so did Boeing's newer 747-8 (the cargo variant is still seling). Both are great planes, but the age of the four-engine airliner has passed - regrettably.
The A380 is a failure because Airbus incorrectly bet on the hub and spoke model, while at the same time Boeing concluded long and thin routes were the future. Your comment was that Boeing was falling behind. Does this not sound more like Airbus fell behind?
It's odd that you'd say that the A320 NEO is a big step over the 737 NG and call the 737 MAX rushed, yet not say anything about the 787 being an order of magnitude larger step up over the A330 and the A350 truly being the plane rushed to market.
NEO is "New Engine Option" of an older generation of plane.
The 787 is a ground up brand new plane which is the most technologically most advanced airliner ever built. The only way the rushed A350 can complete is through price discounts and availability. Still, it hasn't sold as well as the 787 or 777. It is just not as efficient as a 787. Nothing is.
Now as far as the 737 MAX being rushed, maybe it was, maybe it wasn't. I can't believe Boeing would allow a system which can drive the plane into the ground rely on a single AOA sensor. That blows my mind. The redundant sensor was optional, and I believe already installed in all aircraft, jut not connected to the MCAS system. That's damn near criminal in my mind.
But then again, there was an A320 which crashed due to a stall when two of it's triple redundant AOA sensors failed. The computers ignored the single properly working sensor. All perished.
There was also an A330 that stalled and crashed over the Atlantic due to mismatched pitot tube readings. If there was a system like the 737 MAX's MCAS on that aircraft, it likely would not have stalled and crashed. MCAS is independent of the auto pilot mode from what I've read.
So while I agree that neither Airbus nor Boeing are necessarily better than the other as you've stated in your response to me, I do take exception to your statement that Boeing's technology is falling behind in your earlier post.
“The redundant sensor was optional, and I believe already installed in all aircraft, jut not connected to the MCAS system. “
As I understand their are two FCS, each supplied by one AOA sensor. The option was to have an alarm if the sensors were deviated from one another. Part of the fix was to make the sensor comparison mandatory.
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