777X fails stress test

FlyingAccountant

Well-Known Member
I'm thinking it did as well, but it was so long ago I can't remember. is it the same test? Did they change the passing requirements?
I think it's the same test. The original 777 did 1.54, while this one did 1.46. My understanding is that's 54% or 46% over what the max loading rating for the airplane is - so there seems to be a pretty healthy safety margin there even if it technically "failed".
 

SeanD

Well-Known Member
Didn’t the 787 fail numerous stress test on its fuselage also? So is Boeing rehashing the 777? I didn’t know that. Why can’t they just buck up and make something completely new that customers want and need?
 

z987k

Well-Known Member
Maybe you should give them a call, what if they haven't thought of that? ;)
Have you not been following along with the 737 saga? Boeing seems not to be a company of engineers in innovators anymore. Just a bunch of bean counters worried about the next quarter. And we've seen the FAA doesn't really do oversight in certification anymore. They just defer to the manufacturer and take them at their word.

I’m sure the engineers have thought about it, it’s the managers not giving a crap so long as it passes that I’d be worried about.
This.
 
Didn’t the 787 fail numerous stress test on its fuselage also? So is Boeing rehashing the 777? I didn’t know that. Why can’t they just buck up and make something completely new that customers want and need?
777-8X & 777-9X. Basically a newish carbon fiber wing and updated engines. Bigger and trying to be a 747 replacement, with two engines.
 

z987k

Well-Known Member
777-8X & 777-9X. Basically a newish carbon fiber wing and updated engines. Bigger and trying to be a 747 replacement, with two engines.
It'll kill the 744 eventually. When the cost to maintain and fuel the 744 outpaces what a new 777 costs. Could be awhile still. I think FedEx is planning on a bunch of them though.
 

Zapphod Beblebrox

Well-Known Member
If you want something to read and ponder than I would suggest the NTSB saga or TWA flt 841. On April 4, 1979, TWA 841, a B727-100 was enroute from JFK to MSP, a night flight. The flight was commanded by TWA captain Harvey "Hoot" Gibson. The aircraft, "fell out of the sky" from FL390, recovering at about 5000ft. Here is an excerpt from the NTSB report page 19.


https://libraryonline.erau.edu/onlin...s/AAR81-08.pdf

From 2148:04 to 2148:28, the heading trace moved to 360°, the altitude decreased to about 19,500 ft, the airspeed increased to about 390 knots and the g-trace increased to 4.0 g's. During the next 17 seconds, the airpseed increased to its maximum value of 470 knots and the heading trace moved to about 310". Also, the g-trace increased to 5.5 g's , the altitude trace decreased to its minimum value of about 5,000 feet.

At 21148:51, after having decreased to about 4.5 g's, the g-trace increased to about 6.0g's. 2148:58, the airspeed was 280 knots and the altitude was 8,500 feet. During the following 27 seconds, the g-trace varied between 1.0 and 0.3 g, the heading trace moved to about 240", the altitude increased to about 11,300 feet, and the airspeed decreased to about 160 knots

5,000 feet were converted to mach numbers by applying position error, compressibility, The FDR airspeeds recorded during Flight 841's descent from 39,000 to about and density altitude corrections. As the aircraft descended, the initial cruise mach number increased to a maximum of 0.96 mach at 31,800 feet and then decreased to 0.78 mach at 10,000 feet and about 0.70 mach near 5,000 feet

Survival Aspects
This was a survivable accident. The injury causing mechanism was thevariable but comparatively high in-flight load factor -- maximum of about 6.0 g's -- and its duration. The high g's forced the occupants' heads and upper extremities toward the floor of the cabin and caused the muscle strains of the neck and back. Passengers who contacted objects that caused bruises and cuts.were standing when the maneuver began were forced to the floor and, in
the process.


All passengers and crew survived the inflight accident. The airplane almost went Mach1 (indicated 470Kts at one point) and took 6 g's. The flight landed in Saginaw Michigan. The airframe was wrinkled and the gear doors and been torn off. There has been great speculation about pulling circuit breakers and extending trailing edge flaps to 2 degrees to increase performance. That's not the point of this post. Boeing's new 777 failed at almost exactly 1.5 times the load limit. The Seattle Times reported; " The relatively good news for Boeing is that because the test failed so explosively at just 1% shy of meeting federal requirements, it will almost certainly not have to do a retest. Regulators will likely allow it to prove by analysis that it’s enough to reinforce the fuselage in the localized area where it failed." The same article later stated; " All this simulated the loads in a flight maneuver where a pilot would experience a force of 3.75 G, compared to the maximum of 1.3 G in normal flight."

In the old days Boeing engineers, and McDonald Douglas types, sat in big rooms at drafting desks with slide rules, nerdy glasses, skinny ties crew cuts and flat tops, but they were very conservative. The flight load limit graphs were like ancient mariner maps. Outside of the required 1.5 factor was an area labeled' "Here be dragons.." Every guy calculated load limits on each part to the best of his ability, but they generally ended up adding a little bit more to be sure. Just a little stronger, wider, thicker, larger rivets, whatever to be sure. Because computer design was not really that great in 1960, the edge of the flight load limits could not be calculated that well and no engineer wanted to be the guy who designed the part that failed the load limit test. The end result was a heavy but "hell for stout airframe."

Current computer aided design and manufacturing techniques allow designers to build to just the certificated limits and not much beyond. Instead of a very fuzzy edge of the load limit envelope there is a hard line. The airplane is only as strong as the Feds require it to be. (2.5g limit with a 1.5 safety factor = 3.75). The Airbus load limiting FBW design will not let you pull more than 2.5g The takeaway from all of this is don't ever think you can pull a "Hoot Gibson" in a newer designed Boeing or Airbus and think you will survive it. The newer airplanes may very well come apart.
 

trafficinsight

Well-Known Member
If that's a problem then your problem is with 14 CFR, not with the manufacturer working to design an efficient airframe. Those ultimate limit loads haven't changed and added lightness has always been a thing, it's just a thing we're getting better at.
 

trafficinsight

Well-Known Member
Have you not been following along with the 737 saga? Boeing seems not to be a company of engineers in innovators anymore. Just a bunch of bean counters worried about the next quarter. And we've seen the FAA doesn't really do oversight in certification anymore. They just defer to the manufacturer and take them at their word.


This.
I've been following it with great interest, and have had several long discussions with an engineer friend who retired from Boeing and hasn't sugarcoated the systemic warts that exist there and, lets face it, probably exist at every manufacturer... Read the G-650 prototype accident report sometime.

I'm not afraid of engineering though, and missing the target by 1% is not unprecedented nor is it particularly troublesome at all.

But don't let me get in the way of a good dogpile ;)
 

z987k

Well-Known Member
If you want something to read and ponder than I would suggest the NTSB saga or TWA flt 841. On April 4, 1979, TWA 841, a B727-100 was enroute from JFK to MSP, a night flight. The flight was commanded by TWA captain Harvey "Hoot" Gibson. The aircraft, "fell out of the sky" from FL390, recovering at about 5000ft. Here is an excerpt from the NTSB report page 19.


https://libraryonline.erau.edu/onlin...s/AAR81-08.pdf

From 2148:04 to 2148:28, the heading trace moved to 360°, the altitude decreased to about 19,500 ft, the airspeed increased to about 390 knots and the g-trace increased to 4.0 g's. During the next 17 seconds, the airpseed increased to its maximum value of 470 knots and the heading trace moved to about 310". Also, the g-trace increased to 5.5 g's , the altitude trace decreased to its minimum value of about 5,000 feet.

At 21148:51, after having decreased to about 4.5 g's, the g-trace increased to about 6.0g's. 2148:58, the airspeed was 280 knots and the altitude was 8,500 feet. During the following 27 seconds, the g-trace varied between 1.0 and 0.3 g, the heading trace moved to about 240", the altitude increased to about 11,300 feet, and the airspeed decreased to about 160 knots

5,000 feet were converted to mach numbers by applying position error, compressibility, The FDR airspeeds recorded during Flight 841's descent from 39,000 to about and density altitude corrections. As the aircraft descended, the initial cruise mach number increased to a maximum of 0.96 mach at 31,800 feet and then decreased to 0.78 mach at 10,000 feet and about 0.70 mach near 5,000 feet

Survival Aspects
This was a survivable accident. The injury causing mechanism was thevariable but comparatively high in-flight load factor -- maximum of about 6.0 g's -- and its duration. The high g's forced the occupants' heads and upper extremities toward the floor of the cabin and caused the muscle strains of the neck and back. Passengers who contacted objects that caused bruises and cuts.were standing when the maneuver began were forced to the floor and, in
the process.


All passengers and crew survived the inflight accident. The airplane almost went Mach1 (indicated 470Kts at one point) and took 6 g's. The flight landed in Saginaw Michigan. The airframe was wrinkled and the gear doors and been torn off. There has been great speculation about pulling circuit breakers and extending trailing edge flaps to 2 degrees to increase performance. That's not the point of this post. Boeing's new 777 failed at almost exactly 1.5 times the load limit. The Seattle Times reported; " The relatively good news for Boeing is that because the test failed so explosively at just 1% shy of meeting federal requirements, it will almost certainly not have to do a retest. Regulators will likely allow it to prove by analysis that it’s enough to reinforce the fuselage in the localized area where it failed." The same article later stated; " All this simulated the loads in a flight maneuver where a pilot would experience a force of 3.75 G, compared to the maximum of 1.3 G in normal flight."

In the old days Boeing engineers, and McDonald Douglas types, sat in big rooms at drafting desks with slide rules, nerdy glasses, skinny ties crew cuts and flat tops, but they were very conservative. The flight load limit graphs were like ancient mariner maps. Outside of the required 1.5 factor was an area labeled' "Here be dragons.." Every guy calculated load limits on each part to the best of his ability, but they generally ended up adding a little bit more to be sure. Just a little stronger, wider, thicker, larger rivets, whatever to be sure. Because computer design was not really that great in 1960, the edge of the flight load limits could not be calculated that well and no engineer wanted to be the guy who designed the part that failed the load limit test. The end result was a heavy but "hell for stout airframe."

Current computer aided design and manufacturing techniques allow designers to build to just the certificated limits and not much beyond. Instead of a very fuzzy edge of the load limit envelope there is a hard line. The airplane is only as strong as the Feds require it to be. (2.5g limit with a 1.5 safety factor = 3.75). The Airbus load limiting FBW design will not let you pull more than 2.5g The takeaway from all of this is don't ever think you can pull a "Hoot Gibson" in a newer designed Boeing or Airbus and think you will survive it. The newer airplanes may very well come apart.
Ya, but you lose an aweful lot of payload when you build them that strong. I don't think I could be in favor of it unless we show that we'd regularly kill a bunch of people without doing so. And to that I say, we need to make part 25 airplanes higher than 2.5G, not just expect Boeing to build them like a tank.
My current airplane is rated for 4.5G at mgtow. Why the designed did that I have no idea, it's not aerobatic. Given the choice, I'd much rather have the empty weight lower and at 3.8G like standard category for part 23 requires. I can't help but wonder how much dead weight I'm carrying due to that design choice.
There's no way you can get away with crap like that on a commercial scale.
If Boeing said we can build these more stout, but you guys are going to lose 10% of your useful load, not a single airline would buy that version.
 
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