Nitrogen in Fuel Tanks

[Cusco]

I posted this on another Forum, but on reflection I figure I'm more likely to get a response here: Any help gratefully received

I was watching on Sky last night a spin-off to those awful 'Air Crash Investigation' programmes entitled something like 'Crashes that changed flying'

One section related to a 747 which was delayed fully loaded on the stand on a hot day for over 4 hours while a misplaced piece of baggage was found.

Shortly after takeoff it exploded killing all on board.

Turned out that while on the ground, the airconditioning plants, situated directly under the main fuselage fuel tank had quielty cooked up the (virtually empty) main fuselage tank and resultant vapour was ignited by faulty insulation in a fuel gauge sender circuit.

Now this is the bit I need help with: As a result of this a gismo was developed which has subsequently fitted to all passenger jets which filters oxygen out of the air via fine filtersso that the resultant remaining nitrogen can be fed into the fuel tank airspace, reducing explosion risk.

Filters out the oxygen? How does that work? I guess yer average coffee filter paper wouldn't work?

Any Commercial Jet engineers here could explain this to me/ tell me what this gismo is called? I've tried googleing without success and am fascinated to know how air can be broken down by filtration alone in a gadget small enough to shove in all airliners.

Thanks in advance.

Cusco

[MLT]

Google OBIGGS (On Board Inert Gas Generation Systems):

Honeywell's version:

On-Board Inert Gas Generation System (OBIGGS) - Honeywell Aerospace Engineering

Parker's version:

http://www.parker.com/literature/Air...k.inerting.pdf

NASA OBIGGS Test:

http://www.fire.tc.faa.gov/pdf/04-41.pdf

In short, they work a bit like your cars catalytic converter.

[Cusco]

MLT:

Just what I wanted.

Thanks a million.

Cusco.

[hawker man]

Google SFAR88 this is what come out after the TWA 800 crash.
The Nitrogen system even has its own ATA chapter 47

[SNS3Guppy]

Presumably the original poster is talking about TWA 800.

Turned out that while on the ground, the airconditioning plants, situated directly under the main fuselage fuel tank had quielty cooked up the (virtually empty) main fuselage tank and resultant vapour was ignited by faulty insulation in a fuel gauge sender circuit.

No 747's have simply taken off and exploded.

"Air conditioning plants" don't cook up the fuel tank, or fuel for that matter.

In the B747, the center wing tank presently has minimum fuel quantities when fuel is to be placed in the tank, based on speculation from the TWA 800 investigation. These AD's only apply when fuel is to be used from the CWT, and even then they're only applicable to certain segments of flight.

TWA 800 was shot down. It did not simply "blow up."

Further, the fuel gauges in the 747 CWT and wings are capacitance gauges, passive, ant not implicated and not accused of being the culprit. The current "fix" Airworthiness Directive addressing the matter requires minimum quantities of fuel in the tank when the tank is used, and that's all...never any suggestion, inference, or hinting at a need to inert anything, address "fuel sender gauge circuits," or anything of the sort.

Nitrogen systems, such as those used in the C-17, can be troublesome. The system on the C-17 in particular was originally conceived not with the concept of daily routine operation, but the prevention of a flash or explosion following a weapons strike. It's intended to make the aircraft more survivable in combat.

This is not generally a necessity for the B747 in passenger or freight service, save for TWA-800, of course. Even then, whereas the heat source for the target was the packs, which are located beneath the center wing tank, filling the tank with nitrogen wouldn't have helped them.

In most flight operations, the CWT seldom gets used.

In 1976 an Iranian 747 crashed following wing failure, the result of an explosion caused by a lightening strike. The lightening has been determined a likely contributing factor, although other ignition points have also been cited, including a fuel pump. A key issue for the aircraft, however isn't just the lightening or fuel pump issues, but that the aircraft wasn't using straight kerosine fuels; it was using a cut fuel, JP4, which is both kerosine and gasoline combined. This is considerably more volatile than straight jet fuel. The incident is sometimes used as a reference in a call for inert gas in fuel tanks, but those using it as an example seldom remember to note that there's never been an explosion from lightening based on JetA (kerosine-only).

Now this is the bit I need help with: As a result of this a gismo was developed which has subsequently fitted to all passenger jets which filters oxygen out of the air via fine filtersso that the resultant remaining nitrogen can be fed into the fuel tank airspace, reducing explosion risk.

This is untrue, and there is no such device fitted to the B747, nor mofidication used which would accomplish such a thing.

SFAR 88 has nothing to do with inerting tanks. It was a special federal aviation regulation citing a requirement to inspect existing and future fuel tanks and systems for potential ignition sources, and to ensure that no such sources were available in the tanks.

[galaxy flyer]

TWA 800 was shot down. It did not simply "blow up."

Guppy

Any proof on that? Like an accident report or criminal investigation? That story is as realistic as the US Government causing 9/11.

Two Lockheed products had nitrogen inerting systems-the SR-71 and the C-5. The C-5 system removed dissolved oxygen in the fuel as it was boarded and used nitrogen to inert the ullage in the tanks. Two 750 pound nitrogen containers held liquid nitrogen for inerting and for fire protection in the pylons and dry bays.

GF

[SNS3Guppy]

I don't think there's any question that TWA 800 was shot down. I can tell you my personal beliefs, and I can't tell you certain things that I do know, given personal connections to the incident itself. I know very few who believe it was a fuel tank explosion, particularly among the Classic 747 crews and mechanics out there. I happen to be one of the 747 crewmembers which does not believe it was a fuel tank failure, and who does believe it was shot down. I also believe that asked candidly, you'll find that my point of view represents the majority of those with experience on type, and in particular among those with any association to the incident itself.

I can certainly point you to web sites which will address the situation...which you'll be quick to discredit, no doubt. You can certainly ignore the hundreds of witnesses who reported seeing a streak of light leave the surface and head skyward, then saw the explosion, and you can ignore the radar plots of a boat rapidly exiting the area, or the fact that commercial salvage and rescue was excluded by the US Navy...or the fact that recovery and investigation was handled not by the usual commercial and government sources but by the FBI and military.

You'll hear the nutcase conspiracy theories about a military coverup because of a military shootdown...which never held any water to begin with. You won't have to look far to see the truth, however, that TWA 800 was indeed shot down.

[GlueBall]

SNS3Guppy

". . . TWA 800 was shot down. . . you'll find that my point of view represents the majority of those with experience on type."

I am an experienced nonmember of that "majority."

Notwithstanding that distant cousins of the 747 family, namely the 737 models have had dramatic center tank explosions right on the ramps at MNL & BKK. There is no "cover up" because the TWA800 entire center section fuselage is still well preserved [used by the NTSB for training purposes] and is available for re-inspections by missle theorists as you, SNS3Guppy.

The ignition source originated from inside the CWT, and there is no external penetration evidence.

NTSB - TWA800 exhibits on the web

http://www.ntsb.gov/Events/twa800/ex...leanalysis.pdf

[Fargoo]

I don't think there's any question that TWA 800 was shot down. I can tell you my personal beliefs, and I can't tell you certain things that I do know, given personal connections to the incident itself

Tinfoil hats on lads, they're coming for us

[SNS3Guppy]

Interestingly, early in the investigation, officials at China Lake verified evidence of a missile attack. That the Navy was as heavily involved to the normal exclusion of all other recovery available has never been properly addressed; simply put, many were kept away for a very long time, evidence that others had was reclaimed and disappeared, and the matter conveniently was sewn up to show a center wing tank explosion.

Despite this, the "fix" has been to have a minimum of 17,000 gallons of fuel in the CWT if the fuel pumps are to be used. That's it. The big threat, and the fix is business is usual, with a little bit of fuel.

Smoke and mirrors. The US government simply didn't want to admit at the time that an aircraft had been shot down, and went to great pains to show the world that folks were safe within her borders.

The night it happened I remember seeing witness after eye witness interviewing on television, all telling chillingly identical tales of watching a streak of light go from the surface upward, and seeing the aircraft explode. All of a sudden those reports terminated, and were never discussed again. Go figure.

TWA 800 was shot down, and it was shot down in error when an El Al flight didn't get off the ground. Not a coincidence.

When the Clinton Administration undertook to cover the problem and show it as a mechanical failure, the terrorists found that they had to strike back with something that couldn't be covered up...and there was born the impetus that lead to the WTC attacks.

You're no different than many who are content to have the wool pulled over their eyes, but the truth is, TWA 800 was shot down.

[Fargoo]

Quote:
Now this is the bit I need help with: As a result of this a gismo was developed which has subsequently fitted to all passenger jets which filters oxygen out of the air via fine filtersso that the resultant remaining nitrogen can be fed into the fuel tank airspace, reducing explosion risk.
This is untrue, and there is no such device fitted to the B747, nor mofidication used which would accomplish such a thing.

As nitrogen inerting is soon to be mandated on new aircraft in the US, i'd say that statement isn't entirely true.
The nitrogen generation system (as fitted to the 777) is in fact an oxygen reducing system. It lowers the amount of oxygen in the centre tank to an "acceptable" level.

[Cusco]

Blimey!

The words 'opening ' 'of' worms' ' can' spring to mind.

I'll leave you conspiracy theorists to scrap amongst yourselves while I study the links on the Nitrogen gadget you all so helpfully provided.

Thanks and 'Bye

Cusco.

[leewan]

I remember watching a Discovery Channel programme on the TWA 800 crash a few years ago and all signs pointed to a cover up. Here are some reasons that i remember.
1. There was a mysterious radar blip heading towards the a/c seconds before the a/c disappeared from the radar screen.
2.A beach-goer at Long beach happened to take an innocent photo of someone and when looking closely at the photo after the film was developed, noticed a missile-like object with a smoke plume heading towards the sky around the same time the a/c crashed.( It was shown on the documentary) He gave it to the FBI and after a few weeks, their reply was, " It was not heading towards the a/c" or some dismissal like that.
3. There were traces of missile-launching rocket ingredients on the a/c fabrics. The official reply was they were remains from a bomb training exercise for K9s some time back.
4.Plenty of eye witnesses saw a flaming object heading towards the sky and then exploding into pieces. The NTSB's official video showed that what they saw was the a/c's aft fuselage with the wings climbing after the explosion and then disintergrating.The a/c fwd part and the aft part just after the leading edge actually managed to separate itself cleanly after an explosion ! What is even more boggling is that the aft part with the wings climbs with the fwd part missing. Aerodynamically, the drag from the missing nose will drag it down. That's what an aerodynamicist said on the interview.

I dunno what brought TWA 800 down, but I dun think it was a CWT explosion due to faulty FQIS.

[cessnapuppy]

by 'causing' what do you mean?

If by 'causing' you mean hand training operatives and telling them what to do and blocking (both bureaucratically and directly) all actions both inadvertent or direct that would lead to the interception of the terrorists?

NO -hell no

If you mean being bumbling, inept, unable to link dots because of a disjointed and incoherent intelligence structure and poor hand off procedures* and information sharing policies (WHICH CONTINUES TO THIS DAY) the answer is a resounding YES


*Like the 400 Meters relay race, a 'hand off procedure' as with the baton is necessary because the CIA is precluded from operating of US soil.

What is even more boggling is that the aft part with the wings climbs with the fwd part missing. Aerodynamically, the drag from the missing nose will drag it down. That's what an aerodynamicist said on the interview

what is even MORE boggling is the total ignorance of physics...
consider if you will that the 'aft part with the wings' is also the part with those noisy, THRUST PRODUCING hanging on things (engines). With the plane pointing up then separation or no, anything attached to those thrust producers (engines) will perhaps CONTINUE TO GO UP IRRESPECTIVE OF 'DRAG'

"aerodynamicist " my ass

If you are looking for a civilian shootdown, look at this Siberia Airlines Flight 1812 - Wikipedia, the free encyclopedia

[Blacksheep]

Who precisely is supposed to have shot down this aircraft? The Libyans perhaps? Or maybe it was Osama bin Laden? The USN or any other navy would never have been able to cover up such an accident, there would be far too many people to silence them all.

Then there is the inconvenient fact that several other Boeing aircraft have suffered fuel tank explosions - on the ground where investigation is possible. That's why we have all these inspections of the fuel tank wiring, including for chafing of the fuel pump wiring that runs through metal conduits within the tank. Wires have been found chafed through to the conductor and with signs of arcing on the conduits.

You may even be aware of the current Boeing FTRP Emerging Issue EM-09-00036 that affects Boeing B737, B747 and B767 aircraft as a result of a B737 opertor discovering chafed wires within a conduit just 21,000 flight hours after completing SB 737-28A1120?

This is an engineering forum where engineers discuss engineering matters, not conspiracy fantasies.

[leewan]

With the plane pointing up then separation or no, anything attached to those thrust producers (engines) will perhaps CONTINUE TO GO UP IRRESPECTIVE OF 'DRAG

Going by that logic, a/c will have to shut down their engines or jettison them all altogether in order to land or descend.


Basic aerodynamics states that in order for an a/c to climb, lift must be more than weight/gravity and thrust must be more than drag. I am not an expert aerodynamicist, but I'm pretty sure that an open cross section of a 747 fuselage( 3 decks) at a climbing speed will produce significant drag.

[cessnapuppy]

I'm sorry

perhaps I was a wee bit lacking in self-moderation in my remarks earlier (which perhaps causes you now to harden your position)

Going by that logic, a/c will have to shut down their engines or jettison them all altogether in order to land or descend

Actually, what the pilots do, is
a) reduce thrust - kinda like shutting down the engines, but not all the way. Thinking of it as, taking your foot of the gas/throttle -but maintaining enough speed to maintain lift.

b) use the flappy things in the tail
c) lower the wheely rubbery things
d) do some things with the wings

Things called "spoilers" are also used. Contrary to popular opinion, 'spoilers' are not a row of people in the theater who shout out during the suspenseful bits

These all encourage the plane to go down, but under control.
(Forgive me if I get too technical.....)

[leewan]

No worries

Actually, what the pilots do, is
a) reduce thrust - kinda like shutting down the engines, but not all the way. Thinking of it as, taking your foot of the gas/throttle -but maintaining enough speed to maintain lift.

b) use the flappy things in the tail
c) lower the wheely rubbery things
d) do some things with the wings

Things called "spoilers" are also used. Contrary to popular opinion, 'spoilers' are not a row of people in the theater who shout out during the suspenseful bits

Yup, I know all of the above is needed to land the plane.

(Forgive me if I get too technical.....)

Not at all ! I actually prefer it that way. I work in the aviation engineering line, so your description of the landing procedure is way too simplified for my liking. Not to mention that i know it in the first place. I wrote the "shutting down engine for landing" statement in jest for your " continue to go up irrespective of drag" statement.
The fact that flaps and spoilers are used to increase drag and allow the a/c to descend contradict your bold(no pun intended ) statement.

[TURIN]

Well if ever a thread should end up in JB this is it.

TWA 800 shot down, my arris.

No such thing as inerting systems, tosh.

BA's latest 777s have the inerting system fitted. Lots of safety awareness stuff going on regarding engineers working in the viscinity of such. Possibility of passing out due to lack of O2 and all that.

[hawker man]

All engineers now require fuel tank safety training level 2 for aircraft with a pay load above 7500lb or 30 passengers or more. Anything that can effect the fuel system is now considered cdccl = critical design control configeration limitation. This is an absoulte nightmare as far as certification is concerned.