TWA Flight 800 - Revisited

[kach22i]

Originally Posted by Seahawk

As I watched the unfolding events of the Flight 800 accident investigation it was clear to me that the protocol was being ignored.

Maybe I missed it, what specific protocols did they abandon?

There was a lot in that website link you posted earlier, somehow I missed the synopsis.

[aston@ultrasw.c]

I am not an expert but I also believe that getting kerosene to burn is difficult, let alone explode.

On the TV the other night there was a flight 800 documentary where they did the same experiment: mostly empty fuel tank, heat, spark.

First small spark nothing, a couple more tries with slightly larger sparks (but still very small) and then kaboom, the whole thing blows apart.

Any insight on why ostensibly the same experiment yielded such different results?

Thanks

Originally Posted by IROC

This is exactly right. I worked for Boeing at the time (and had nothing to do with any of the investigation) but paid attention to this Flt 800 stuff. At one point early in the investigation, Boeing engineers went on record as saying that there was no way fuel vapor in the center fuel tank could be made to explode.

They even did a test where they took a spare tank, added the approximate amount of fuel in the tank and then added an ignition source and they couldn't get it to ignite.

That was the last we ever heard about that. In the end, the official report said that the center fuel tank exploded.

I'm not jumping on the conspiracy theory bandwagon, but I trust the engineers more than I trust the politicians.

[red-beard]

The issue is flash point. Jet A has a flash point of 140 F (60 C). For the fuel tank to have explosive vapors, the fuel and tank would need to be 140 F or higher.

Jet fuel - Wikipedia, the free encyclopedia

Did the show you were watching mention what fuel they used? If it wasn't JET A, then it wasn't a good experiment.

[aston@ultrasw.c]

I think they mentioned it was JET fuel: they showed a 55 gal drum being handled.

They also heated the tank to simulate the temps incurred while waiting on the runway for 2 hours.

I don't think they quoted what the internal temp was.

[fingpilot]

The theory was that the air conditioning packs (2 of them), being mounted immediately in front of the center fuel tanks were radiating their heat to the forward wall of the fuel tank.

An air conditioning 'pack' is a turbocharger that takes very hot bleed air as motive energy, spins a compressor turbine, and then uses a condenser and pressure drop to chill ambient air. It works so well that hot bleed air is even introduced in the cool air flow to keep it from freezing and blocking the condenser.

A LOT of ambient heat is generated. Normal normal, the center tank has enough fuel in it that is cooled by the temperatures at altitude. The route that FLT800 was flying (JFK to Europe) was so short, no fuel was needed in the center tank. The long time on the ground with the packs running was assumed to have heated the empty tank, and it's vapors to flash point. The ignition source was one of the three A/C electric submersed pumps in that tank. Each of those breakers are 100 amp, three phase, A/C. More than enough to arc. They are also fairly high on the likely fail list, especially uncovered/uncooled.

Ever since that accident, we have been required to carry a minimum fuel amount in that tank.

[aston@ultrasw.c]

wow

now we have a sufficient heat source and a significant ignition source

that key info makes the fuel tank explosion entirely plausible

thanks for the explanation

[red-beard]

Originally Posted by fingpilot

The theory was that the air conditioning packs (2 of them), being mounted immediately in front of the center fuel tanks were radiating their heat to the forward wall of the fuel tank.

An air conditioning 'pack' is a turbocharger that takes very hot bleed air as motive energy, spins a compressor turbine, and then uses a condenser and pressure drop to chill ambient air. It works so well that hot bleed air is even introduced in the cool air flow to keep it from freezing and blocking the condenser.

A LOT of ambient heat is generated. Normal normal, the center tank has enough fuel in it that is cooled by the temperatures at altitude. The route that FLT800 was flying (JFK to Europe) was so short, no fuel was needed in the center tank. The long time on the ground with the packs running was assumed to have heated the empty tank, and it's vapors to flash point. The ignition source was one of the three A/C electric submersed pumps in that tank. Each of those breakers are 100 amp, three phase, A/C. More than enough to arc. They are also fairly high on the likely fail list, especially uncovered/uncooled.

Ever since that accident, we have been required to carry a minimum fuel amount in that tank.

Except, the turbines are at idle. The bleed air off the compressor will not be at full temp. Back in the cabin, the air conditioning isn't very good while sitting on the ground and taxiing. You're not getting 24 to 1 CPR at idle. On the industrial machines, you have almost a 5 to 1 variation in CPR from FSNL to Full Load. And with the 2 shaft machines, like jet engines, it is wider.

I'd need to look at the 747 bleed stage. I can't find a CF6 diagram. Here is the 777's GE90.



From here, it looks like the intermediate bleed is used for the cooling system.



I'd like to see the data of the bleed pressure/temp and the heat rejection to that compartment. If at idle, it truly is enough to get the empty fuel tank above the flash point, that is a serious design flaw.

[rick-l]

On the ground would the high pressure (hot) air come from the APU?

[red-beard]

I don't think the APU is used for operating the cooling system. I think you have power for Electrical systems and starting air. I passed that question to my sister who worked for an APU company until about 2 weeks ago...

[BE911SC]

So with damaged/worn fuel tank pumps, as 800 had, and they then start galling (metal on metal) from lack of fuel to lubricate the pumps (fuel in the tank but not enough to submerge and cool the pumps) and thus heat up, way more than normal, and finally after prolonged "abuse" they get hot faster and get so damn hot that they can ignite even "hard to ignite" fuel and vapor then what's the issue?

I flew Boeing KC-135Rs in the USAF (1988-94) and now 737s in commercial service I've always had to abide by very, very strict fuel pump limits--when I can turn them on and when I have to turn them off--imposed directly by Boeing. Run a KC-135 pump 100 pounds (of fuel) below a limit (3500 or 5500 pounds in a body tank) and they'd bust you on the spot. Unqualified. Need to take a re-check and your name was mud. If the TWA guys inadvertently ran those pumps dry too many times (on the ground in Rome for several hours, if memory serves) and thus incurred pump damage over time, isn't it possible that the pumps finally wore to a point that they got hot enough, finally, on climb-out from Kennedy, to ignite the fuel/vapor in the tank?

This missile theory is like the grassy knoll. It sounds really good but it just cannot be proven beyond a reasonable doubt. I'd call it damaged pumps that wore so much that the friction built up and made enough heat to finally blow her up.

[red-beard]

If the tank was empty, why would the fuel pump be running?

[BE911SC]

Originally Posted by red-beard

If the tank was empty, why would the fuel pump be running?

IIRC, the TWA 800 airplane, an older 747, had sat on the ramp at Rome, that particular tank empty, and the fuel pumps left on for several hours. Happened a day or two before the accident I think. On the departure from Kennedy they may have not have had that much fuel in that tank (called "slosh fuel") and with the likely existing pump damage the scenario I described above occurred.

New Boeing 737s have fuel pump shutoff systems that automatically switch pumps off when fuel is at a certain level. In the old days the pilot or flight engineer simply monitored the quantity and switched the pump(s) off at the specified level. If the pump(s) get left running without fuel then that's when damage can occur. Cumulatively that repeated damage, over time, can result in a pump making excessive heat and possibly causing an explosion.

[kach22i]

So if it was the fuel pump, why did they say it was the wiring harness?

Or did they?

EDIT: found this

Safety investigators stand by cause of TWA Flight 800 crash
http://news.yahoo.com/safety-investigators-stand-cause-twa-flight-800-crash-003054024.html
Susan Cornwell July 2, 2013

ASHBURN, Virginia (Reuters) - U.S. government safety investigators on Tuesday stood by their report on the 1996 crash of TWA Flight 800 that said faulty wiring likely caused the plane to explode, ahead of the airing of a documentary that suggests a missile may have brought down the plane.

[Flieger]

There is wiring that goes to the fuel pumps and passes through the tank. If the fuel pumps were damaged they would draw more current due to the increased frictional load and less fuel flow to cool them. More current means hotter wires, which could damage their insulation and result in a spark.

[red-beard]

Originally Posted by Flieger

There is wiring that goes to the fuel pumps and passes through the tank. If the fuel pumps were damaged they would draw more current due to the increased frictional load and less fuel flow to cool them. More current means hotter wires, which could damage their insulation and result in a spark.

It takes a lot of overcurrent to damage the insulation.

So lets play the game. To get this to happen:

#1. The tank is above the flash point
#2. The fuel pump in the center tank is running without fuel
#3. The fuel pump is damaged and causing an overload
#4. The overload does not trip a breaker on the circuit
#5. The overload causes the wiring to be damaged
#6. A spark occurs from the damaged wiring which ignites the air/fuel mixture in the fuel tank

Do I have this correct?

[Flieger]

Some of those things are inter-related, so I would say it is not 6 individual things having to line up, but I still think it is more plausible than a missile.

[Cajundaddy]

Originally Posted by red-beard

It takes a lot of overcurrent to damage the insulation.

So lets play the game. To get this to happen:

#1. The tank is above the flash point
#2. The fuel pump in the center tank is running without fuel
#3. The fuel pump is damaged and causing an overload
#4. The overload does not trip a breaker on the circuit
#5. The overload causes the wiring to be damaged
#6. A spark occurs from the damaged wiring which ignites the air/fuel mixture in the fuel tank

Do I have this correct?

Yep, either that or a highly experienced combat veteran flying a P-3 with the sun on his 6 and a birds eye view of the 747 sees two vertical streaks followed by ordinance flashes just prior to the plane coming apart and going down. This view was corroborated by scores of witnesses on the ground. Definitely no SAMs involved. He was clearly delusional.

[BE911SC]

Originally Posted by Cajundaddy

Yep, either that or a highly experienced combat veteran flying a P-3 with the sun on his 6 and a birds eye view of the 747 sees two vertical streaks followed by ordinance flashes just prior to the plane coming apart and going down. This view was corroborated by scores of witnesses on the ground. Definitely no SAMs involved. He was clearly delusional.

Several people saw a shooter on the grassy knoll too. I'm not saying the P-3 guy is a liar or an idiot but sometimes the explanation is simple. One shooter in Dallas, faulty fuel pump and/or wiring in the 747.

Besides, "the government can't do anything right" right? If that's the conventional wisdom with everything else then how come the government is, conversely, so highly skilled at covering up presidential murder conspiracies and airliner explosions inflight?

People are blabbermouths. (Yes, here I am blabbering on the Internet. Point taken.) If TWA 800 had been shot-down by a military missile firing error it would have come out right away. The news media would have feasted on that. Talk about a great story--the national media would have absolutely eaten that up, especially with a Democrat in the White House. (The media is only as "liberal" as its corporate suits allow it to be.) Someone would have uncovered that fact right away. Pierre Salinger, an early proponent of the missile theory, was treated as a wacko by the media. Yeah, they put him on the air, but it was not as a credible commentator but as a sideshow nutcase. It basically ruined his reputation IMO.

Maybe there is a conspiracy. It would have to include all levels of government and all levels of the media. Any one person who tried to shed light on the conspiracy would have to be dealt with. How? Threaten to ruin their career? Or worse, have the "black ops guys" deal with that person? Sounds like that could spin out of control pretty fast and then the rest of the news media swims in fast and starts feasting.

Sometimes the real explanation is the simplest one.

[BE911SC]

Originally Posted by Cajundaddy

Yep, either that or a highly experienced combat veteran flying a P-3 with the sun on his 6 and a birds eye view of the 747 sees two vertical streaks followed by ordinance flashes just prior to the plane coming apart and going down. This view was corroborated by scores of witnesses on the ground. Definitely no SAMs involved. He was clearly delusional.

Second night of the 1991 Gulf War. There I was in the right seat of a KC-135R climbing northwest out of Riyadh for the second night's mission, a bunch of F-111s, and we were lead of an 8-ship tanker cell (formation). As we drew near the border with Iraq, where we would meet the 111s (approximately 40 of them) we began seeing flashes on the horizon. WTF? Looked like flashes from bombing raids. Holy crap the poop's in the fan out there. We take the cell into its big oval orbit while realizing the 111s aren't coming. Most of the guys in the formation think we're seeing Baghdad getting pounded and the flashes are big enough to see from the border. But the radios were silent. The special "war" frequency, where we could listen in to various missions as they happened, was silent. Finally AWACS informs all airborne tankers that there is a line of severe thunderstorms south of Baghdad and the missions are cancelled. Boy did we laugh at that! We swore it was "the war" but it was just lightning over the horizon. Still makes me laugh.

[Cajundaddy]

Originally Posted by BE911SC

Several people saw a shooter on the grassy knoll too. I'm not saying the P-3 guy is a liar or an idiot but sometimes the explanation is simple. One shooter in Dallas, faulty fuel pump and/or wiring in the 747.

Besides, "the government can't do anything right" right? If that's the conventional wisdom with everything else then how come the government is, conversely, so highly skilled at covering up presidential murder conspiracies and airliner explosions inflight?

People are blabbermouths. (Yes, here I am blabbering on the Internet. Point taken.) If TWA 800 had been shot-down by a military missile firing error it would have come out right away. The news media would have feasted on that. Talk about a great story--the national media would have absolutely eaten that up, especially with a Democrat in the White House. (The media is only as "liberal" as its corporate suits allow it to be.) Someone would have uncovered that fact right away. Pierre Salinger, an early proponent of the missile theory, was treated as a wacko by the media. Yeah, they put him on the air, but it was not as a credible commentator but as a sideshow nutcase. It basically ruined his reputation IMO.

Maybe there is a conspiracy. It would have to include all levels of government and all levels of the media. Any one person who tried to shed light on the conspiracy would have to be dealt with. How? Threaten to ruin their career? Or worse, have the "black ops guys" deal with that person? Sounds like that could spin out of control pretty fast and then the rest of the news media swims in fast and starts feasting.

Sometimes the real explanation is the simplest one.

Over 150 witnesses reported a "streak of light". 38 reported "streak of light originating from the ocean surface" including several trained observers with unobstructed visibility (pilots at altitude). I have a hard time ignoring this. I am not suggesting any conspiracy or friendly fire incident. It just seems improbable to rule out such overwhelming observational evidence. Once you have seen missile streak and ordinance flash in combat, you don't easily forget it.

http://forms.house.gov/israel/issues/shoulderfiredmissiles.pdf

In general I think the NTSB is right on the mark and doesn't miss much in accident investigations. They got it exactly right when my dad's Glassair went down in April 1996. Everyone overlooks something sometimes and the Flt 800 investigation does not ring true to me... but I could be wrong...