B747F, Pressure test, BANG!!!...:-(
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Originally Posted by Grunf
Barit1,
Small correction:
Not all floor beams/frames in tension since the cargo compartment is pressurized and therefore there are some floor beams and parts of some frames that are compression critical for pressurized loads.
Small correction:
Not all floor beams/frames in tension since the cargo compartment is pressurized and therefore there are some floor beams and parts of some frames that are compression critical for pressurized loads.
By maintaining near-zero delta P on the floor -
o Upper lobe skin is in pure tension
o Lower lobe skin is in pure tension
o Floor is in pure tension, preventing the "kink" between the two from bulging out!
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Originally Posted by barit1
OF COURSE the cargo (lower lobe) is pressurized. Otherwise there would be a pressure differential across the flat floor, tending to circularize it (as we saw 33 years ago in the DC-10 cargo door blowouts!)
By maintaining near-zero delta P on the floor -
o Upper lobe skin is in pure tension
o Lower lobe skin is in pure tension
o Floor is in pure tension, preventing the "kink" between the two from bulging out!
By maintaining near-zero delta P on the floor -
o Upper lobe skin is in pure tension
o Lower lobe skin is in pure tension
o Floor is in pure tension, preventing the "kink" between the two from bulging out!
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This accident may be completely irrelevant to normal operations. Wait and see what they find. I believe overpressure safety devices must be disabled for this test, and with that someone may have screwed up and gone well above the design pressure diff. Human error is the more common cause of accidents in the air compared to mechanical failure, why should it be any different on the ground?
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Originally Posted by chornedsnorkack
OK, a stupid question - why shouldn´t the lower lobe be pressurized to a higher pressure? It has to carry bending loads due to its own weight and the weight of passengers, seats, galleys/lavatories and cargo placed on it... pressurizing the underbelly to a higher pressure would help with that...
But the added systems complexity (trying to compensate for zero g, +2 g, full pax, unloaded etc.) seems to make the cure worse than the disease.
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Quite a long time ago a Lockheed JetStar (owned by Mobil Oil) was undergoing a hull pressure test, wherein the ultimate pressure reached 21psi, before failure.
The fuselage was quite a sight, and the aeroplane was sent back to Lockheed, where the wing was demated, and attached to a brand new fuselage.
A not inexpensive project, to say the least.
Lockheed paid, IIRC.
A tough 'ole bird, the JetStar...
The fuselage was quite a sight, and the aeroplane was sent back to Lockheed, where the wing was demated, and attached to a brand new fuselage.
A not inexpensive project, to say the least.
Lockheed paid, IIRC.
A tough 'ole bird, the JetStar...
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Barit,
agree for the skin, not for the floor. Some portions of the floor are in compression (for the XX delta PSI load case). I am toalikng aobut floor as floor beams havin the upper chord, lower chord and the web.
Some of the upper chords do see compression for the pressure case.
agree for the skin, not for the floor. Some portions of the floor are in compression (for the XX delta PSI load case). I am toalikng aobut floor as floor beams havin the upper chord, lower chord and the web.
Some of the upper chords do see compression for the pressure case.
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Originally Posted by HotDog
You must be a disciple of that nutcase John Barry Smith.
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Mike Rudder
I have seen a photo of the first B747-400F for MASkargo flying at Seattle PAE, so it is not that one. The pressure test l am sure will be done before it reaches the flight line.
This is what was printed in a Seattle newspaper.
The worker said the plane is being built for a customer in China.
The 747-400 was undergoing what's called a "high blow" pressurization test when the accident occurred, the worker said.
The pressure inside the plane was about 3 pounds per square inch, he said.
I have seen a photo of the first B747-400F for MASkargo flying at Seattle PAE, so it is not that one. The pressure test l am sure will be done before it reaches the flight line.
This is what was printed in a Seattle newspaper.
The worker said the plane is being built for a customer in China.
The 747-400 was undergoing what's called a "high blow" pressurization test when the accident occurred, the worker said.
The pressure inside the plane was about 3 pounds per square inch, he said.
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Originally Posted by gas path
If it was only at 3psi it was waaaay short of the 'high blow' figure
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Originally Posted by Grunf
...
Some of the upper chords do see compression for the pressure case.
Some of the upper chords do see compression for the pressure case.
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From what i can see this is a test Boeing make on all aircraft out of production. So it failed the test - surely thats the reason for the test in the first place. All this does is prove the test was worth doing.
Boeing far exceed Airbus at speed and quality of structrual repairs and hopefully the operator will get an aircraft as good as they expected without too long a delay.
Boeing far exceed Airbus at speed and quality of structrual repairs and hopefully the operator will get an aircraft as good as they expected without too long a delay.
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Originally Posted by swedish
From what i can see this is a test Boeing make on all aircraft out of production. So it failed the test - surely thats the reason for the test in the first place. All this does is prove the test was worth doing.
Boeing far exceed Airbus at speed and quality of structrual repairs and hopefully the operator will get an aircraft as good as they expected without too long a delay.
Boeing far exceed Airbus at speed and quality of structrual repairs and hopefully the operator will get an aircraft as good as they expected without too long a delay.
Do other aircraft manufacturers carry out similar tests? anyone who knows?
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Founder and Swedish:
Main reason is to see if everything "fits" fine (MCD including!).
Second, maybe more important thing, is to reinforce the structure by preloading it. This procedure should give better fatigue life. Sadly, this was discovered on the Commet's accident.
Cheers,
Main reason is to see if everything "fits" fine (MCD including!).
Second, maybe more important thing, is to reinforce the structure by preloading it. This procedure should give better fatigue life. Sadly, this was discovered on the Commet's accident.
Cheers,
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Originally Posted by Grunf
Founder and Swedish:
Main reason is to see if everything "fits" fine (MCD including!).
Second, maybe more important thing, is to reinforce the structure by preloading it. This procedure should give better fatigue life. Sadly, this was discovered on the Commet's accident.
Cheers,
Main reason is to see if everything "fits" fine (MCD including!).
Second, maybe more important thing, is to reinforce the structure by preloading it. This procedure should give better fatigue life. Sadly, this was discovered on the Commet's accident.
Cheers,
