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777X

Old 27th Jan 2019, 15:54
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Originally Posted by PAXboy View Post
They were running out of numbers, with only '9' left for the rest of time, so they had to reuse '7'.
I imagine that after 797 they can get clever and use 7X7 Roman Numerals are your friends.
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Old 27th Jan 2019, 16:03
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Quite a few years ago, I was flying (as a passenger) UK to Copenhagen, (I think it was an A320, but might be wrong,) for the whole flight in which starboard wing had no winglet and the port one did. The aircraft behaved quite normally as far as I could see, but my colleague was more than little concerned, and asked the pilot about it. He was told that it was quite normal and certified, and the only effect was a small fuel consumption penalty.
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Old 27th Jan 2019, 22:50
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Originally Posted by Machinbird View Post
I remember reading about it in the newspaper. Saw a picture taken from below. I was impressed.
Yes, amazing home video of that event on YT. Also another 707, TWA 42 which lost about 25 feet of wing in a collision with an Eastern Connie over CT/NY border. Never have been able to find a picture of the damage to that aircraft. Amazing piloting skills by both crews.

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Old 27th Jan 2019, 23:25
  #64 (permalink)  
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Looking at the 707-321B and the video, one must ask what part of it's survival was played by it's 'heavy metal' construction versus how such a failure would affect the modern day airliner?
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Old 28th Jan 2019, 02:22
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Originally Posted by PAXboy View Post
Looking at the 707-321B and the video, one must ask what part of it's survival was played by it's 'heavy metal' construction versus how such a failure would affect the modern day airliner?
Uhh other than a better aero shape, the wing construction methods and materials have not significantly changed. Improvements in riveting and better fit fasteners and in some casesminors changes for fatigue improvement- wing construction has not changed until the carbon fiber wings were put into service. And that was about 25 years ago ( on the B2 bomber ) . 737 wings and 767 wings and 777 wings up to 7x7, are all aluminum, similar spars and ribs, improved riveting and fastening.


And the failure point in the video was within a few inches of that predicted on the top surface ( compresion buckling ) a close match as it was for the 747 test , 767 did not quite go to failure,
So what do you consider a ' modern day ' airliner.

787 was not taken to failure- which is NOT a requirement anyhow .

And OLD B52 wings are still flying and they really do bend and bend and bend and at takeoff appear to ' flap "

All mostly aluminum with similar construction . .
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Old 28th Jan 2019, 07:43
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high capacity seating
Whih only helps, if you are able to sell all those seats. If you fill an A380, it is a very economic machine. Unfortunately you do only reliably fill it on very limited routes.
Now with all those smaller long range aircraft around (not even talking the very small ones just making it to the market), you do not have to buy size to get range, it becomes much more attractive to buy two smaller aircraft instead of one large, it gives you much more flexibility with only minor efficiency losses.
Time will tell, and I might stand corrected. But I am sceptical whether size still matters and big is still beautiful...

planes equipped with winglets able to complete flights while missing a winglet?
Following according procedures. If you lose a winglet just after rotation without adapted speed, you will barely be able to correct the wing drop.
See the crash of N652GD as an example for selecting the wrong speed in a failure case scenario (in this case one engine out, not one winglet missing).
So noticing that your folded wing is not properly locked at rotation with low margings (which today is the norm, due to flex power), may put you in a very undesirable situation.
If you always plan with enough margin, you lose the efficiency you just gained with the additional wingspan that your folding wing allowed...

787 was not taken to failure- which is NOT a requirement anyhow .
This has been under debate for quite some time... Actually if you demonstrate compliance by "calculation supported by test" (which is possible and done), you need to demonstrate that you identified the right failure mode (as mentioned above, for example compression buckling). So somehow you need to take real or representative structure to failure, to demonstrate that not only the load level, but also the mode of failure has been correctly predicted. For the 777X Boeing may take credit for the 787 Wing test.
With composites it is a bit more complex anyway, as you have to consider an "environmental knockdown factor" for the test not done under the worst environmental conditions (hot and wet). So you do expect a higher failure load under test hangar conditions anyway, above nominal ultimate load.

the wing construction methods and materials have not significantly changed.
Actually the materials have changed much more than the construction methods. Which is why some cynics state that today we build aircraft from black aluminum...
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Old 28th Jan 2019, 16:58
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Actually the materials have changed much more than the construction methods. Which is why some cynics state that today we build aircraft from black aluminum.
Uhhh how many ' ALL black aluminum " aircraft are flying since the707 -321 you referenced? ( hint count 20 B-2 bombers plus current number of 787 ) compare to ' aluminum" aircraft flying or in production since 707.

As to your comments as to taking wing test to failure being under debate for some time - please notify BA and Airbus that they obviously do not understand the risks, nor do the agencies involved, and provide a list of those aircraft that passed the ' no failure ' requirements bnut which lost wings in service absent a bomb or similar and crashed. To prove your point you need not lilst over 100 such.

And at what altitude do you claim the temperature is significantlty hotter than near sea level absent speeds over mach 1 for commercial aircraft.

SR71- is/was not black aluminum - it was predominately titanium ...
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Old 29th Jan 2019, 08:03
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at what altitude do you claim the temperature is significantlty hotter than near sea level
For example at 60 ft altitude, on the apron of DXB airport... This is when your composite structure is above 60°C just when you perform a takreoff at MTOW.

Uhhh how many ' ALL black aluminum " aircraft are flying since the707 -321 you referenced?
Compare a composite glider with a metal glider, and then compare the 707-321 stabilizer with a 787 stabilizer. Still the same rib and stringer stiffened shell, connected by fasteners.
Yes, we learned our lessons about sandwich structure in rough commercial air transport environment. Yes, we had issues with bonded struchture. Yes, we need a design which is quick and easily repaired. And yes, some composite design today is really innovative (e.g. the CSeries/A220 wing produced with vaccum assisted RTM), or the wound barrel design of the 787 fuselage sections.
But a majority is still a metal design using composites material. We are still far from using the potential of those materials in an adapted design.
For example we use multiple load path design in metal structures for damage tolerance reasons. Composites material however is inherently damage tolerant, there are already millions of load paths (fibres) which fail individually, so the complete design concept could be completely different. We can embed structures health monitoring devices in composites layup (impossible in metal) to detect damage in service without the need for dedicated inspections. This also means we can design with significantly less access provisions.
There is still a lot of future ahead with respect to composites aircraft...

However, the hybrid 77X may tell whether it performs better in the end, compared with the all composites 787. There probably is a reason why Boeing did not change the fuselage to carbon, maybe the same reason why the A350 fuselage design is completely different from the 787 fuselage design (panels vs. seamless barrels), and why Mitsubishi switched back the MRJ wing to aluminum.
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Old 29th Jan 2019, 13:16
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Excellant set of pictures. Sadly, XV431 @ Bruggen 1974 wasn't so lucky. Witnessed the whole event on the way to the Mess for a spot of lunch.
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Old 29th Jan 2019, 16:02
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https://boeing.mediaroom.com/2010-03...20295_1138-117
As to body - how many large autoclaves with several hours cycle times plus layup and bagging tooling would it take to maintain a high production rate- and then there is the making of carbon fiber,etc. probably an overall cost versus rate issue compared to possible improvements.

As to wet conditions- A6 REwings of composite have been around for over a decade..
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Old 31st Jan 2019, 07:53
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A310 composite vertical tails have been around for some 34 years...
However, structural design of A380 and A350 vertical tails is completely different, so there are lessons learned as well.

Composites gliders are around for some 63 years now and CFRP gliders for 46 years. Lessons with respect to hot and wet have been learned.
This however is covered today by cupon testing in the laboratory, full scale tests are done in "as procduced" (= fully dry after curing above 100°C) and room temperatur, hence an "environmental knockdown factor" is applied. Epoxy resin absorbs a few percent moisture in service.

It would be interesting to know, how many design changes are between the 787 and the 777X wing, I assume Boeing has meanwhile learned something about the 787 design as well...
It is amazing how the aviation world has changed, aircraft like the A380 and 787 were developed "on the internet", both manufacturers published an awful lot on the web, you could follow the complete design and testing period. Topics like GLARE or would fibre barrels were discussed in scientific conferences and publications. For A350 and 777X there is almost total silence, you just see some high level marketing publications and that is it.
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Old 5th Jul 2019, 13:29
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Originally Posted by DaveReidUK View Post
The proof of the pudding will be whether the 777X is grandfathered onto the current 777 Type Certificate. If it's essentially a new aircraft it won't and can't be.
It is. And I won't be suprized if we hear more about that this year.
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Old 11th Feb 2020, 22:28
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I'm no aircraft designer, but the direction of the folding wing puzzles me. Wouldn't it be better for the wing to fold down so airflow in flight can keep it securely locked?
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Old 11th Feb 2020, 23:10
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Originally Posted by CogSim View Post
I'm no aircraft designer, but the direction of the folding wing puzzles me. Wouldn't it be better for the wing to fold down so airflow in flight can keep it securely locked?
If it required airflow to keep it securely locked, it wouldn't be.
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Old 12th Feb 2020, 00:01
  #75 (permalink)  
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Originally Posted by tdracer View Post
Depends on the flight characteristics and procedures - the 757 and 767 are very obviously different aircraft, yet they have a common type rating.
Yet the 787 and 777 do not have common FAA type ratings. Type ratings have nothing to do with type certificates. https://registry.faa.gov/TypeRatings/

Originally Posted by DaveReidUK View Post
No. you're wrong, I'm afraid. The Fokker 50 (alias F27 Mark 050) was most certainly added 30 years later to the original 1957 F27 Type Certificate.
There is no F50 type rating on a FAA licence https://registry.faa.gov/TypeRatings/
Originally Posted by tdracer View Post
Simply not true - prior to first flight, the original 777 had a little over 110 orders. The 777X currently has over 300 orders and is still months away from first flight. The original 777 didn't top 300 orders until it had been in-service for over two years.
How many of those orders have been cancelled cancelled ..... 50 ?
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Old 12th Feb 2020, 07:26
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Originally Posted by swh View Post
There is no F50 type rating on a FAA licence https://registry.faa.gov/TypeRatings/
No argument there.

But, as I'm sure you're aware, a type rating and a Type Certificate are two completely different things. The discussion was about the latter.
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Old 12th Feb 2020, 12:53
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Originally Posted by reverserunlocked View Post
Interestingly the wing fold occurs automatically on the landing roll out below 50kts, with the idea being that by the time you vacate they have folded. Smart idea.
Would the wing tips automatically fold up from a rejected take off at a speed above 50 kts?
If not, would there be a "warning" to fold them?
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