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.

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

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.

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.

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.

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

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.

http://3.bp.blogspot.com/-cq5D-npsCo...GE90%2Bjtr.jpg

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

http://aviationandaccessories.tpub.c...21-10_71_1.jpg

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.

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

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...

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.

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.

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

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?

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.

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.

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.

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... :)

Yes, people are blabbermouths, but it took a long time for the story to come out that fighter pilots were cleared to shoot down flight 93. And nobody has yet revealed the location of Jimmy Hoffa's body. So you cannot count on the blabbermouths to leak in a timely fashion.

^^lol!^^

All 6 would need to happen or it can't go boom. I am NOT on the conspiracy theory of a missile. But the internal tank going boom requires a lot of things all lined up to happen.

Again, if there is a breaker on the fuel pump and the pump is over loaded, it will trip. That trip should occur well before you reach the point of wire damage. But we are also have to be running a pump on an EMPTY TANK. And whatever has to have done what it needed to cause a spark. And the tank had to be above 160F for the vapors to occur that will cause an explosion.

If any one of those things didn't happen. No boom.

One theory was that the pumps were running on an empty tank. This damaged the pumps such that they drew more current and heated up more. Therefore, #1, #3, and #5 would follow if #2 happened. It doesn't take too much imagination to see #6 then following from that. So, basically, #2 needs to be done to excess and #4 needs to happen. Not like 6 unrelated things all going wrong at once.

Where are you getting the flash point from? The few sources I see say it is 100F for Jet-A or kerosene.

Plus, the aircondtioner packs were directly under the center wing tank.

They get very, very hot while on the ground and taxiing.

And it was a hot summer evening.

>140F or 60C

Here is a link to the JP-5 MSDS

http://www.hess.com/ehs/msds/9942JetFuelJP5.pdf

Interesting. Does JP-5 have additives to raise that from the normal kerosene or is JP-5 not based on kerosene like Jet A?

Take a look at the top of the wiki

Jet fuel - Wikipedia, the free encyclopedia

100F was the old standard. Look at the upper right hand side in the yellow box.

JP-5 is fairly standard stuff, but Mil-Spec.

Lets say the "damaged wiring" was a breakdown of the insulation that allowed a spark.

Measuring the performance of wiring insulation in situ is actually fairly easy. All you need is a hi-pot tester. This applies several thousand volts to a conductor with a very low current. The current is so low that no damage is done, certainly not to big honking fuel pumps. When the high voltage is applied you can then measure leakage current with is a direct indicator of the health of the insulation.

So why wouldn't the investigators go and measure a sample of the many aircraft of similar age, type etc and report back.

e.g. 1 in 10 of the aircraft have questionable wiring and will be grounded until they can be repaired.

Just requiring pilots to leave a min level of fuel in the tank seems a bit weak for a corrective action.

I believe the fuel minimums were before the accident because they knew the fuel pumps would get damaged by running dry. I thought that after the accident the FAA said that they couldn't route wires through the fuel tank anymore on new planes. Not sure what they did about the existing fleet.

To continue my thought further...

with all the aircraft out there with this fuel supply configuration,

and all the delays on hot days

and allowing for human error managing the pumps

and the possibility of faulty switches and sensors exacerbating the situation

surely another a/c would have experienced similar conditions and suffered the same fate.

Faulty wiring that was not repaired but simply mitigated by changing an SOP seems a little too convenient and a little too successful.

If the minimum fuel requirement was in place *before* then don't we have operator error? Assuming the residue was less that the required min.

That would be the case. I was just going by what the tanker pilot posted in post #90.

This incident led to a lot more than a simple fuel minimum. This was the event that triggered an airworthiness directive requiring grounding the fleet and verification of the wiring prior to dispatch. That was the immediate action, the long term action was removal from service of that style of wiring for that application, and a complete revamp of the disign requirements of fuel tank wiring for all aircraft. Many years later I routinely do testing on aircraft fuel systems that are driven directly by this incident, on many types of aircraft.

Lessons in aviation tend to be expensive, and are rarely disregarded.

A interesting recent change in direction regarding fuel tank wiring safeguards according to the FAA:

"On July 17, 2008, the Secretary of Transportation visited the facility and announced a final rule designed to prevent more accidents caused by explosions in fuel tanks. The NTSB first recommended such a rule just five months after the Flight 800 accident and thirty-three years after a similar recommendation issued by the Civil Aeronautics Board Bureau of Safety on December 17, 1963, nine days after the crash of Pan Am Flight 214.[135]
In 2009, Boeing advised the FAA that its new Boeing 787 Dreamliner could not meet the new safety standards. The FAA proposed to relax the safeguards for preventing sparks inside the fuel tank, calling them "impractical".[136]"

Tonight on C2C-AM for anyone who's interested:

Investigating TWA 800 - Shows - Coast to Coast AM

Former police officer specializing in accident investigation, James Sanders was married to a TWA flight attendant when TWA flight 800 went down in 1996. He started his own investigation and later was indicted for the crime of receiving residue from the accident and having it tested. He'll discuss his journey looking for the truth behind what happened.

Find a local station carrying the show here... some have streaming audio:

Radio Stations - Coast to Coast AM

C to C AM?

Those nuts all believe in 'Chemtrails', rusty 'tools and gears' lying around on the surface of Mars, and other nonesense.

That show is for entertainment only.

Zero facts.

Except for the the weekend guys sometimes, but never on weeknights.

So, you're not among the interested, thereby not whom I was addressing. No problem.

"Zero facts"...not true. I'm guessing you haven't listened all that much.

Sure, they sometimes have some fruit loops on there who talk to their houseplants, and I tune out when they're on, but there's plenty of guests (weeknights and weekends) that are credible.

Tonight's guest... I kinda doubt he's in the fruit loop category, so I'm gonna check it out.

There was a second missile ?

This just keeps getting better (worse).