how safe is 737 NG
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Sure. The first place I would turn to to learn completely factual information about complex technical issues related to a highly proven aviation system would be something put together by general news journalists and a personal injury lawyer. Sorry for the sarcasm, but this story is old news.
Can anyone give a right / wrong on the following;
The NG's additional MTOW & service ceiling over the NG were approved on the basis of high accuracy automated production techniques being used for key structural components, which assured finer tolerances?
Ducommun were found to be hand crafting the critical structural parts?
Several hundred NG's had rolled from the production line before Ducommun's practices were highlighted?
The NG's additional MTOW & service ceiling over the NG were approved on the basis of high accuracy automated production techniques being used for key structural components, which assured finer tolerances?
Ducommun were found to be hand crafting the critical structural parts?
Several hundred NG's had rolled from the production line before Ducommun's practices were highlighted?
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Can anyone give a right / wrong on the following;
The NG's additional MTOW & service ceiling over the NG were approved on the basis of high accuracy automated production techniques being used for key structural components, which assured finer tolerances?
Ducommun were found to be hand crafting the critical structural parts?
Several hundred NG's had rolled from the production line before Ducommun's practices were highlighted?
The NG's additional MTOW & service ceiling over the NG were approved on the basis of high accuracy automated production techniques being used for key structural components, which assured finer tolerances?
Ducommun were found to be hand crafting the critical structural parts?
Several hundred NG's had rolled from the production line before Ducommun's practices were highlighted?
A simplistic answer to your question, is by asking more questions:
How many B737 NGs suffered structural failure and fell out of the sky? None.
How many B737 NGs were flown into the ground by various accidents? Several.
A list of all accidents on Wikipedia provides some context: https://en.wikipedia.org/wiki/List_of_accidents_and_incidents_involving_the_Boeing_737#737 _Next_Generation_(737-600/-700/-800/-900)_aircraft
For most passengers, structural failure inflight should be the least of their concerns, with takeoff and landings being far more risky. This is nothing like the Comet airliner, where they really did fall out of the sky, due to a design flaw and metal fatigue...
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Topic Going Back Nearly 2 Decades.
[QUOTE=Arydberg;10453267]I happened on this video and think it deserves a look.
Was this what you were after?
https://www.washingtonpost.com/archi...=.e6a1d78c4c55
Was this what you were after?
https://www.washingtonpost.com/archi...=.e6a1d78c4c55
Thank you GRC;
True, but it's still a pretty fresh aircraft
Completely not what or why I'm asking.
I'm not trying to suggest for a second that NG's are going to start falling out of the sky, but if approval was granted on the basis of parts tolerances that weren't acheived, I'm puzzled.
I'm not trying to suggest for a second that NG's are going to start falling out of the sky, but if approval was granted on the basis of parts tolerances that weren't acheived, I'm puzzled.
"Mildly" Eccentric Stardriver
True, but it's still a pretty fresh aircraft.
Senility must be setting in. I could have sworn I was flying the NG in 2003. I make that coming up 16 years.
Senility must be setting in. I could have sworn I was flying the NG in 2003. I make that coming up 16 years.
Sorry to let facts interfere with a good story, but:
Hull loss rate (through 2017).
737NG (-600, -700, -800, -900): 0.17
A320 (A318, A319, A320, A321): 0.21
Fatal Accident rate (again through 2017)
737NG (-600, -700, -800, -900): 0.08
A320 (A318, A319, A320, A321): 0.10
Yep, those 737NGs sure are deathtraps...
BTW, 737NG EIS was 1997 - so not exactly a spring chicken.
Hull loss rate (through 2017).
737NG (-600, -700, -800, -900): 0.17
A320 (A318, A319, A320, A321): 0.21
Fatal Accident rate (again through 2017)
737NG (-600, -700, -800, -900): 0.08
A320 (A318, A319, A320, A321): 0.10
Yep, those 737NGs sure are deathtraps...
BTW, 737NG EIS was 1997 - so not exactly a spring chicken.
Psychophysiological entity
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I posted on this having picked up the Tube video from another recent poster. I watched it in full and have just read the Washington Post link above. I feel the latter substantiates the old fears.
Not falling out of the sky? Okay, but what about the photo shots of airframes broken into three parts after survivable crashes? They make the point the breaks are reasonably clean around the circumference at the break points.
But be this as it may. If Boeing were setting out to make every part within three thou' tolerance, and hand-building them failed to come close to this, how could the Henry Ford philosophy be so readily abandoned when the parts turn up off-pattern?
What made me take an initial look was the Rosemont vane builds and rebuilds. In short, I'm starting to be spooked on the macro scale.
https://www.pprune.org/archive/index.php/t-616624.html
Not falling out of the sky? Okay, but what about the photo shots of airframes broken into three parts after survivable crashes? They make the point the breaks are reasonably clean around the circumference at the break points.
But be this as it may. If Boeing were setting out to make every part within three thou' tolerance, and hand-building them failed to come close to this, how could the Henry Ford philosophy be so readily abandoned when the parts turn up off-pattern?
What made me take an initial look was the Rosemont vane builds and rebuilds. In short, I'm starting to be spooked on the macro scale.
https://www.pprune.org/archive/index.php/t-616624.html
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http://rgl.faa.gov/Regulatory_and_Gu..._Emergency.pdf
Cirrus and Aerosonic (manufacturer of the technical standard order AOA sensor) have identified the probable root cause as an AOA sensor malfunction due to a quality escape in the assembly of the AOA sensor at Aerosonic. Two set screws that secure the potentiometer shaft to the AOA vane shaft may have improper torqueing and no application of thread locker (Loctite) to secure the two set screws. The AOA sensor with this quality escape is labeled with part number 4677-03
Not the first time that a shaft set screw backing off has caused an AoA sensor to fail.
http://www.smartcockpit.com/docs/Boe...On_Takeoff.pdf
Examination of the main gear revealed that the set screw that secured it to the shaft was not fully tightened: the overhaul manual specifies an assembly torque of 4.0 - 4.5 inch-pounds for this item. This was established as the reason for the random readings of the resolver outputs with respect to vane displacement, which thus resulted in the right ADC receiving erroneous angle of attack data.
Maybe not the best design choice? I've pretty much never seen a set screw installed in a self-locking threadform, they typically rely on anaerobic sealants to prevent them from loosening. A more permanent type of fastener might be a better choice.
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I've seen analyses by many people with impressive credentials that seem very impressive but amount to, a quote I remember, pseudoscientific sheep dip. tdracer cites the most relevant statistics - fatal accident rates. Even these are skewed but that is nit-picking. Pilot suicides are a hit on the airframe. Airframes lost to bombs are in the statistics. Pilot training - several hull losses have been followed by shutting down an airline due to safety deficiencies.
I've lived the life of engineering through manufacturing to failure analysis and accident investigations. Do out of tolerance parts get used in production? Yes. In fact at one company we engineers needed to analyze parts and determine if they had Critical or Major characteristics, mark those characteristics, and indicate on the part number if it had a Critical or Major characteristic. Referring to W Edward Deming's quality philosophy, I remember him stating in the first of his video series that quality started to go downhill with the hiring of the first inspector. Relying on an inspector to check whether or not you did your job correctly was an insult to workmanship.
In 1974 I had the opportunity to take a course Applied Fracture Analysis by Dr David Hoeppner who had worked for the Skunk Works but wanted to move on to a place where his research could be taught outside the confines of a small part of Lockheed. Our first class would have made those with weak stomachs leave as he brought in failed components that had resulted in fatal crashes. Our class following the crash of TK901 found Dr. Hoeppner bringing in a cargo door latch from a DC-10 and telling us we stupid engineers created this disaster - that was before knowing which part of the design caused the failure. One class, unnerved by his thoughts of engineers, I asked him if he were flying a transcontinental flight and could chose any plane, he selected a Convair 990 (remember, this is 1974). I asked him why not a Boeing? He said in his opinion they got burned early in the company's life and overdesigned everything. Boeing's carry a lot of extra weight due to overdesign. That was back in the days when the 737 was an infant. Dr. Heoppner was upset because he could not get TWA to send their engineers to his class as this was near their overhaul base. One day he entered the classroom particularly elated jumping on top of his desk and dancing. Seems the day before an axle had failed on one of TWA's L1011s. Being a Lockheed product, Dr. Heoppner was asked to investigate and diagnosed stress corrosion cracking. "Those idiots don't know how to identify a simple failure mode and they won't spend the money to send a group of engineers to my class." Unfortunately we engineers learn the most from failures - oh crap, well, I won't do that again." When we reach our peak we retire and let the new people repeat our errors.
I've lived the life of engineering through manufacturing to failure analysis and accident investigations. Do out of tolerance parts get used in production? Yes. In fact at one company we engineers needed to analyze parts and determine if they had Critical or Major characteristics, mark those characteristics, and indicate on the part number if it had a Critical or Major characteristic. Referring to W Edward Deming's quality philosophy, I remember him stating in the first of his video series that quality started to go downhill with the hiring of the first inspector. Relying on an inspector to check whether or not you did your job correctly was an insult to workmanship.
In 1974 I had the opportunity to take a course Applied Fracture Analysis by Dr David Hoeppner who had worked for the Skunk Works but wanted to move on to a place where his research could be taught outside the confines of a small part of Lockheed. Our first class would have made those with weak stomachs leave as he brought in failed components that had resulted in fatal crashes. Our class following the crash of TK901 found Dr. Hoeppner bringing in a cargo door latch from a DC-10 and telling us we stupid engineers created this disaster - that was before knowing which part of the design caused the failure. One class, unnerved by his thoughts of engineers, I asked him if he were flying a transcontinental flight and could chose any plane, he selected a Convair 990 (remember, this is 1974). I asked him why not a Boeing? He said in his opinion they got burned early in the company's life and overdesigned everything. Boeing's carry a lot of extra weight due to overdesign. That was back in the days when the 737 was an infant. Dr. Heoppner was upset because he could not get TWA to send their engineers to his class as this was near their overhaul base. One day he entered the classroom particularly elated jumping on top of his desk and dancing. Seems the day before an axle had failed on one of TWA's L1011s. Being a Lockheed product, Dr. Heoppner was asked to investigate and diagnosed stress corrosion cracking. "Those idiots don't know how to identify a simple failure mode and they won't spend the money to send a group of engineers to my class." Unfortunately we engineers learn the most from failures - oh crap, well, I won't do that again." When we reach our peak we retire and let the new people repeat our errors.
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As for the MAX, you might want to check the title of the thread
BTW - NWA SLF, terrorism and 'acts of war' are normally excluded from the Hull Loss and Fatal Accident rates. I'm not sure about pilot suicide.
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The thread title asks if the 737NG is safe. That's what I was responding to. There seem to be several other current threads available to you if you want to discuss the MAX.
