B747F, Pressure test, BANG!!!...:-(

[Nige321]

I'd liked to have been a fly on the wall when this one went off....:} :eek: :ouch: :(

This from Flight International...

"Boeing is investigating the causes and the costs of a botched pressurisation test that resulted in severe damage to a new 747-400F destined for an unidentified Asian operator. The manufacturer, which says the mishap occurred during a routine pre-delivery pressurisation test inside the Everett final-assembly building on 3 March, says “two teams have been set up, one to investigate the causes and the other to assess the repairs that will be needed”. Reports say the build-up in internal pressure caused the aircraft’s hinged nose cargo door to suddenly release from its locking mechanism. The door pivoted so rapidly around the upper hinges that it reportedly broke the flightdeck windows and caused structural damage to the fuselage skin. The radome is also thought to have been dislodged during the incident, which Boeing says did not result in any injuries."

© Flight international

[Rainboe]

Wow- anything up to 8 psi over that area of opening, which is enormous- it must have gone with a wallop! Deformation of the nose area- I would think a complete change of everything in front of the forward passenger door area. With all the electronics bay area around the nose gear well......probably easier to use as spares and build a new one! (that is a joke if anybody takes it too seriously)

[Flightmech]

Wow- anything up to 8 psi over that area of opening, which is enormous- it must have gone with a wallop! Deformation of the nose area- I would think a complete change of everything in front of the forward passenger door area. With all the electronics bay area around the nose gear well......probably easier to use as spares and build a new one! (that is a joke if anybody takes it too seriously)
But is it really a joke?. Would you want to pay for a brand new aircraft that must have suffered secondary, tertiary damage after a pressure failure? Repairs like this can cause the aircraft to become a regular "Hangar Queen" for it's entire life:\

[surely not]

So should Boeing now carry out a full re certification of the 747F? This sort of failure would be catastrophic in flight and similar to an A380 wing breaking?

[clicker]

If I was the airline that was due to get this aircraft I would want a new aeroplane and compensation for the delayed delivery.

[gas path]

Boeing routinely carry out a pressure test up to (IIRC)12psi on new build and also after extensive major repairs. Called the 'blowtest' it is used to improve the fatigue life of the structure and skins. We have carried out this test after a major repair and it is impressive to watch.......from a distance:ooh: with the skins looking like a quilt, especially noticeable around the cargo doors.

[Airbus340FO]

This doesn´t sound good at all.
I still believe those 3 747´s from Air India, over the Atlantic, the TWA off the U.S. Atlantic coast and the 747 from Lockerbie where also hull damages and not a fuel pump, nor a bomb.
Just imagine BOEING would have said:
Yes our planes fall apart. No one would have a bought a Boeing jet from this day on. I still believe in a cover up for economic reason. But this was the old 100series.
The hull design of the 747 is just not ideal. it should be a tube and round and not assymetrical, this oval design brings a lot of problems.
But I also take seat in 747´s and I am not afraid :D
to "surely not" : By the way, read the thread about the A380 wing, it didn´t break, but had a crack at 150% and this at a test assembly. That is something a little different then at a plane, ready for sale !

[punkalouver]

[QUOTE=Airbus340FO]This doesn´t sound good at all.
I still believe those 3 747´s from Air India, over the Atlantic, the TWA off the U.S. Atlantic coast and the 747 from Lockerbie where also hull damages and not a fuel pump, nor a bomb.


I have deleted what you said after your first sentence in this reply. After all you have completely destroyed your own credibility in that sentence. Suggest you don't tell your employer about your reluctance to believe reality and logic. Otherwise you may keep your "handle" for the rest of your career as common sense should be a requirement for an upgrade. However as an alternative, the Egyptian accident investigating agency may be interested in your help. Guess I just don't think much of conspiracy theorists.

[Taildragger67]

This doesn´t sound good at all.
I still believe those 3 747´s from Air India, over the Atlantic, the TWA off the U.S. Atlantic coast and the 747 from Lockerbie where also hull damages and not a fuel pump, nor a bomb.
Just imagine BOEING would have said:
Yes our planes fall apart. No one would have a bought a Boeing jet from this day on. I still believe in a cover up for economic reason. But this was the old 100series.
The hull design of the 747 is just not ideal. it should be a tube and round and not assymetrical, this oval design brings a lot of problems.
But I also take seat in 747´s and I am not afraid :D
to "surely not" : By the way, read the thread about the A380 wing, it didn´t break, but had a crack at 150% and this at a test assembly. That is something a little different then at a plane, ready for sale !

Isn't a monocoque (egg/oval) cross-section the one which imparts the greatest inbuilt strength, expecially over a pure circle?

I thought that's why all Boeing jets have been oval. I can't recall what cross-section Airbus aircraft have but I'd be surprised if it's perfectly circular.

[Charles Darwin]

Where are the pictures? :E

[Rainboe]

Well funnily enough, Airbus seem to think the A380 is OK with an ovalised cross section (as it's a 2 decker....in fact 3 decker)!

[Max Revs]

I think Airbus340FO has left us all hoping we don't meet him / her professionally? Mind you, I'm sure the nurse will keep the tranquillisers coming just as fast as they are needed in order to keep 340 safe from reality!:uhoh:

[barit1]

Isn't a monocoque (egg/oval) cross-section the one which imparts the greatest inbuilt strength, expecially over a pure circle?
I thought that's why all Boeing jets have been oval. I can't recall what cross-section Airbus aircraft have but I'd be surprised if it's perfectly circular.

The fact is that Boeing aircraft since the Stratocruiser (and BTW the Curtiss C-46 before that) have a dual-lobe cross-section. The upper lobe and lower lobe are each circular, and joined at the cabin floor. All elements (skin & floor beams) are thus in pure tension under pressurization loads. Very efficient structural design! :ok: (Blow up a balloon if you don't believe me)

The departure from this practice is in the nose section (e.g. 747), where the fuselage becomes more slab-sided. Here the formers must be heavier to withstand the bending loads in the non-circular area.

[3PARA]

Just because it blew it's nose doesn't mean it's terminally ill :p

[banana head]

Well the article states it was being prepared for delivery to an undisclosed 'Asian' operator....
.... Bird Flu perhaps?:) :)

[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.

[Diatryma]

Hey Banana Head - is this it???


http://pip.rubberfeet.org/05/plane.gif

Di

[HotDog]

This doesn´t sound good at all.
I still believe those 3 747´s from Air India, over the Atlantic, the TWA off the U.S. Atlantic coast and the 747 from Lockerbie where also hull damages and not a fuel pump, nor a bomb.


You must be a disciple of that nutcase John Barry Smith.:yuk:

[chornedsnorkack]

I think that double-bubble cross-section is rather popular. The upper and lower frames as well as deck beams in pure tension (with cabin and underbelly equally pressurized), no bending forces anywhere.

There are perfectly circular planes, sure. Airbus 300 series as well as Boeing 777 series.

The advantage of double-bubble is that thanks to pure tension, it is the cheapest way to deviate from circle. Boeing 767 is strongly double-bubble while 777 is not. Reason? The underbelly bulge ensures that 767 underbelly has about as much headroom as 777 underbelly, even though it is narrower. 777 is wide enough that there is adequate headroom for both cabin and underbelly in perfect circle, so a perfect circle it is.

The narrowbodies again are double bubbles in order to get extra underbelly space. Airbus 320 is wider than 737, and very slightly double bubble compared to 737 - but it is not a perfect circle.

380 is triple bubble - again, so as to get the headroom in underbelly and main deck and upper deck.

But the ends are problematic. As are doors.

I think Boeing has had one disaster uncontroversially because a cargo door failed... it was in underbelly - and when it failed, the pressure in cabin broke the cabin floor above, blowing 9 passengers with their seats out of the plane! The rest of the B747 kept flying, though, and eventually landed.

Douglas has had a rather similar disaster - cargo door on a DC-10 failed, 6 passengers above blown out with seats... but the rest of the plane crashed as well with over 300 fatalities.

Well, passenger B747 do not have nose door to blow... but if a B747 nose door slams into the cockpit on climb, what are the chances the plane crashes with those aboard and a lot of people on ground?

[PAXboy]

banana head Bird Flu perhaps? Actually, this Bird is still in production and has not yet flown, so cannot be said to have flew ... :=

[barit1]

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.

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! :ok:

[chornedsnorkack]

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! :ok:
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...

[FlyVMO]

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?

[barit1]

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...

Not so stupid - structurally that idea makes sense, IMHO.

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.

[411A]

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...:ooh:

[Grunf]

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.

[SaturnV]

You must be a disciple of that nutcase John Barry Smith.:yuk:
HotDog, indeed. And John Barry Smith did not stop at those three. The China Airlines 747 in-flight breakup off Taiwan in May 2002 was the occasion of his latest sleuthing.

[Mike Rudder]

Malaysia Airlines is due to take delivery one of two new freighter at the end of March. It could be one of theirs

[Mr @ Spotty M]

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.:uhoh:

[gas path]

If it was only at 3psi it was waaaay short of the 'high blow' figure:eek:

Anyway, dead easy to fix, just graft on a complete section 41:ok:

[chornedsnorkack]

If it was only at 3psi it was waaaay short of the 'high blow' figure:eek:

Indeed. 200 mb differential? The pressure in cruise is what, 750 mb? This meant that the door would blow at 550 mb outside, meaning below 5000 metres... unless the pressurization is started gradually after takeoff instead of at 2400 metres, in which case 200 mb differential would be reached lower than 5000 metres! A cargo plane exploding on climbout...

[barit1]

...

Some of the upper chords do see compression for the pressure case.

Sure, these are beams after all, and the pax/cargo loading creates bending stress (compression in the top chord, tensile in botton) whether pressurized or not. These stresses add algebraically to the pressurization (tensile) stresses. Whether the summation of compression & tension in the top chord of the floor beam is ultimately positive or negative must depend on the individual design.

[Flight Safety]

Perhaps there was a nose latching error prior to the test, or incorrect installation of the nose latches, or manufacturing defect in the nose latches.

[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.

[Grunf]

Barit1:

Right on the spot.

Mr @ Spotty M:

High blow test is at 1.5xdelta_Pi = 13 psi (app)

[Founder]

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.

I agree with you, there must be a reason why they carry out the test in the first place...

Do other aircraft manufacturers carry out similar tests? anyone who knows?

[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,

[Founder]

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,

Okey, didn't know about that... Thanx =)