UPDATE on the LHR (Heathrow) 777 incident

All Greg really knows is how to push all the buttons in response to all the pretty lights. ;)
 
AWACSEng said:
Greg, do you know if the 777 has an auto fuel heat feature? I.e. if a restricted fuel flow is detected, the fuel heat is automaticaly activated.
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I am going to have to go look in the book, but IIRC, the fuel heat is on all the time.

And as far as the fuel blockage theory, ice isn't the only contaminate in fuel that causes unexplained flameouts.
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Well, yeah. But at the END of a 4400 mile, 9 hour flight?
 
I have never worked a 777 nor a RR Trent engine. All other jet engines route the fuel through a fuel oil cooler to heat the fuel and cool the oil. On the early jet engines you also hadadditional fuel heat that you could manually select to add heat to prevent ice from blocking the fuel filter. On the newer engines on ETOPS aircraft even that manual fuel heat function was made automatic to reduce pilot work load. If that is basically how the 777 and Trent engines work than that would mean the icing would have to be someplace upstream. Again don't know how the 777 fuel tanks are plumbed or how the sumps are set up. Are the sump drains actually in the low part of the tank? Has maintenace actually been sumping the tanks? I guess we'll just have to wait until they finish their investigation.
Ron
 
I understand the skepticism about it happening when it did, unless the cause is something that's unique to that part of the flight.
 
Oh, oh, [raising hand]... They forgot the Prist! ;)











<jk> Prist is an anti-icing additive for jets which do not have fuel heat.
 
Thanks, I appreciate the insight.

SCCutler said:
All Greg really knows is how to push all the buttons in response to all the pretty lights. ;)
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Greg Bockelman said:
That is cold, Spike. :D True, but cold.
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I thought that was kinda funny. :)

Not to hijack the thread too much, but a fellow who flies the A-330 mentioned to me that he was sad about the way flying is going - something about the automization (sp? is that even a word?) taking the flying out of the equation. He seemed genuinely sad about it.
 
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Obi Heed Kenobi said:
Not to hijack the thread too much, but a fellow who flies the A-330 mentioned to me that he was sad about the way flying is going - something about the automization (sp? is that even a word?) taking the flying out of the equation. He seemed genuinely sad about it.
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Well there is a component to that, but you CAN turn it all off. At least as far as the yank and bank goes.

But the reality is that is why I stay connected to GA. Especially the antique/classic end of it. I have owned 5 airplanes, the newest of which is my 1950 Cessna 195.
 
Greg Bockelman said:
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But the reality is that is why I stay connected to GA. Especially the antique/classic end of it. I have owned 5 airplanes, the newest of which is my 1950 Cessna 195.
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That is also what this pilot said - he had two planes, one of which, if I remember correctly, was an old J-3.
 
I just read an interesting article about the fuel icing theory. Keep in mind this is a journal published by an aviation law firm so keep that tucked away in your head but the theory is quite interesting. As will all accidents it states that the blockage if there was any could have been caused by outrageously low temps and cold airmasses in the region the plane was flying as well as a new type of decent that Heathrow was using that kept the engines at a lower temp thus not producing sufficient temps to warm up the fuel enough through a heat exchager. Of course this is just a theory but its is facinating.

http://www.aviation-safety-security...om-sustained-exposure-to-extreme-cold-we.html
 
Aero-news today reported that the British authorities have ruled out icing, fuel contanimation, and water, as well as bird strikes.

Elsewhere I saw a rumour about pump cavitation (where a mass of air interferes with the smooth flow of fuel through the pump).
 
Attached is the latest "public" document. I've confirmed that this information is okay to post (those of you "in the know" know what I'm referring to... this means you, Spike), along with the following comments from a 777 pilot friend of mine .

777 captain said:
In case you were wondering, the normal configuration for approach and landing is for each engine to be feeding off it's respective tank (left engine off the left fuel tank, etc.) and for the crossfeeds to be closed. It would not be unusual to open a crossfeed in a situation where one could not figure out why one or both engines was not responding, but this would be done after a problem was noticed.

The autothrottle would command both engines to the same thrust setting and would never command one engine to a different setting than the other. Each throttle is driving an independent engine controller which is driving independent fuel valves. Fuel moves to each engine from it's respective tank using independent tank fuel pumps, isolated plumbing and independent fuel filters. For something to affect both engines independently and simultaneously, one is left with the only thing common to both engines: the fuel.

This one may end up as a pure mystery with lots of speculation as to cause.
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wsuffa said:
Speaking of the 777 LHR incident, there's been another case of throttle failure to respond on a 777. This time on an AA plane going into LAX:

http://www.flightglobal.com/article...-777-engine-fails-to-respond-to-throttle.html
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Actually, Bill (and thankfully), the investigation team has pretty much concluded the FO was accidentally blocking the No. 1 throttle from moving under autothrottle control, while guarding the speedbrake handle.

http://www.pprune.org/forums/showpost.php?p=3958188&postcount=41


Nothing to see here, move along...
 
BA038 CRASH EXPLANATION

Is anyone asking the right questions? You're really going to have to want the answer, to read all of this.

The fuel being used on this Boeing 777-ER was Jet A-1 spec. confirmed by AAIB.

JET A-1 Fuel is:

Jet A-1 is a kerosene grade of fuel suitable for most turbine engined aircraft. It should, have a flash point above 38°C (100°F) and a freeze point of -47°C

Occidental Jet A1-Fuel normally contains, but is not required to contain:

Antioxidants to prevent gumming, (alkylated phenols)
Antistatic agents, to dissipate static electricity and prevent sparking;
Corrosion inhibitors, e.g. DCI-4A
Fuel System Icing Inhibitor (FSII) agents
Bacteriocidal "Biocide" agents


The fuel in BA038 wouldn't contain:
Biocide (Unlikely in the first place, in case of doubt, the fuel system was checked for water etc. Jan 15th, and it would have been added to the outbound fuel if necessary) [AAIB]

May have contained: (these are beneficial to the ground crew)
Antioxidants
Antistatic agents
FSSI-type Agents (we'll come back to this)

May have contained some types of these:
Corrosion inhibitors, e.g. DCI-4A (but, not the types needed!)

The AAIB pointed out the freezing point for the specific batch of fuel found in the plane's tanks was -57 C.

The fuel estimation system deduced, that the expected fuel needed to arrive at London Heathrow with 6,900 kg remaining would be 79,000 kg. Weight of the aircraft, contents, and weather, should already be factored in here. The aircraft left with 79,000 kg and the flight conditions were cold but not exceptional.

The plane arrived with an estimated 10,500 kg.

- At the high speeds that jet engines operate, the engine performance decreases with decreases of engine altitude and so, with increases of atmosphere pressure. - (to a point - "cruising altitude")

AAIB confirms that the plane flew higher than planned. We don't as yet have any specific information about the Thrust Specific Fuel Consumption (TSFC) [TSFC = FF/Thrust]; the TSFC, was obviously much lower than planned.

But Why?

Jet A-1 standards are not strict at all, read "Standards Requirements for Domestic and Foreign Jet Fuels for Civil Aviation" in the Journal of Chemistry and Technology of Fuels and Oils. What they discuss, are quality indices, for Jet Fuel. But isn't the Jet A-1 "strict" standard enough? Well these professors didn't think so.

NOW THIS GETS COMPLICATED IF YOU DON'T HAVE A CHEM BKGND DON'T GIVE UP:

Jet fuel much like gasoline, is a mix of hydrocarbon chains (hydrogen bonded with carbon -- we use the hydrogen, and expel the carbon as waste gas); these chains vary in length. Notice that you pay by the octane level in the gasoline? Oct = 8 for 8 carbons. Octane is the best fuel for high performance cars, unfortunately in the gasoline (PRODUCT NAME) you have longer or shorter carbon chains (+ or - Octane) to a very high degree, in fact petrol or gasoline is a combination of septane, octane, nonane, decane, and, well you see; there are a lot of ways to cheat, when a fuel is not branded by the exact chemicals it contains.

So what happens as these carbon numbers rise? Well methane, I think everyone knows is a gas, and it has 1 carbon and 4 hydrogens (C1 H4), and octane (C8 H18), I think everyone knows by now, is a liquid. The higher the number of carbons, the more hydrogen (energy) the fuel possesses, but the thicker, more dense, and harder to burn, the fuel becomes. It also raises the freezing point. So we need to find a balance between a long chain hydrocarbon so that we can get more thrust per litre or gallon and not make it solid at -47 C. Right!!

Jet fuel is based on kerosene, and should have hydrocarbons in it that vary in length from 10-16 carbons. Something like cetane C16 H34 (16 carbons 34 hydrogens) has immense energy per molecule and is barely liquid at room temperature, it freezes at around 17 C; decane freezes around (C10 H22) around -28 C.

Jet A-1 is partially made by changing the distillation cut points or component blending to produce a jet/aviation fuel having an acceptable freeze point. The desired freeze point being -47 C for Jet A-1. But decane still freezes around -28 C. How do we make it freeze at a lower temperature? Well, there are a lot of ways. There are thousands of fuel additives most ending in -ene that have very low freezing points, various polymers, are useful as "middle distillate pour point depressants" and are prepared from ethylene etc.

These pour depressants include copolymers of ethylene and vinyl esters of lower fatty acids such as vinyl acetate (U.S. Pat. No. 3,048,479); copolymers of ethylene and alkyl acrylate (Canadian Patent No. 676,875); terpolymers of ethylene with vinyl esters and alkyl fumarates (U.S. Pat. Nos. 3,304,261 and 3,341,309); polymers of ethylene (British Patent Nos. 848,777 and 993,744); chlorinated polyethylene (Belgian Patent No. 707,371 and U.S. Pat. No. 3,337,313.

Wait, wait, polymers and patents? That sounds expensive. It is.

-57 C degrees is pretty low even for a long haul in winter, that's more like Jet B fuel, except that we have extra fuel to think of. Oh, and don't forget that because jet fuel is a mixture of so many different fractions of hydrocarbons, and other chemicals, it remains pumpable for about ten degrees below the temperature where it starts to freeze.

Now what has a freezing point of -57 C? Wait for it...

Octane does!

Basically, they tried to run the plane on something much closer to petrol/gasoline than kerosene?

Yes, Jet fuel and Gasoline have about the same API Gravity. What does that mean? It means that one gallon of jet A fuel, and one gallon of gasoline weigh about the same, 6.76lbs per gallon and 6.73lbs per gallon respectively; well to me or you they do, but on a plane, those differences would be greatly magnified. Someone would have noticed the extra volume.

Oh wait but, there is no "basically", or anything basic, about a catastrophic failure like BA038.

And even if they were running on gasoline, they would not have had fuel left over. Extra fuel would suggest the opposite of everything we've been saying.

It gets much more complicated.

Oh that's right, we never talked about isomers of hydrocarbons. Oh, I hear your pain. C10 H8, ten carbons, shouldn't that be decane? Wait, why are there only eight carbons? Because the carbon molecules are holding on to each other differently, now there is less room for hydrogen to attach. Picture carbon with four arms, so one carbon can hold on to four molecules of hydrogen, hydrogen only has one arm. (C1 H4 Methane) So put two carbons next to each other, and one arm of each goes to the other carbon to keep them together, and the two of them now have 6 other free arms to grab a hydrogen (C2 H6 Ethane). Couldn't it just be that simple. No, God has a sense of humour. The carbons can hold on to other carbons with two or three arms and make funny shapes instead of neat rows. C10 H8 is the empirical formula for NAPHTHALENE check out this picture:

200px-Naphthalene-3D-balls.png


Ok, what the hell are you talking about now?

Remember I talked about "other chemicals" in fuel. Well, turns out China isn't as rich in oil as it is in coal. You can use coal to make gasoline, or kerosene, with one clue, unusual amounts of NAPHTHALENE residue or "Moth Balls" and if you've checked, coal is much cheaper than petroleum right now.

So what?

Well the properties of that fuel are going to be pretty different because of the "other chemicals" that are by-products of the fractional distillation of coal. It's not the same as the fractional distillation of petroleum; your going to have all these nasty crazy things called isomers, like napthalene, that make the jet fuel poor quality.

And the engine damage? Well diesel fuel, like gasoline and jet fuel, is rated as well, except not by octane number but, by cetane number (C16 H34). Cetane having a rating of 100 and Napthalene having a rating of 0.

Napthalene and other isomers of hydrocarbons cause engine damage by screwing with the fuel's ignition delay (the time period between the start of injection and start of combustion). But cause Cavitation, are you sure? Wait for it.

And the extra fuel? Well that is a question.

I'm in China, oil is at $100 a barrel but, I can make jet fuel from coal for almost nothing but, I'll have to add a few things to it to spruce it up. It doesn't matter how expensive they are, I'm still making a tonne of money.

What shall I add? What about the same stuff we add to diesel fuel on land, alkyl nitrates. Nitrogen products are part of the "other chemicals" that get produced when you distill oil or coal anyway, and we have all the right chemicals. Plus we'll add all the normal stuff for jet fuel, a dish of Xylene, and dash of Toulene, etc. but the fuel quality is still too low because we started with coal. Damn it.

Wait a second, I've got it, the key to our riches, I'll even add some of those high tech polymers. The money will roll in, and no one will be the wiser. Wish I knew more about polymers though.

What happens when you use high tech polymers as a fuel additives? Well it reduces the freezing temperature of the fuel quite a bit. Could i reduce cetane from freezing at 17 C to freezing at -57 C? Well not quite, but combined with more additives like xylene and toulene, sure, with out issue but, you have to handle polymers with care.

Why? because fuel is moved and pumped all over the plane. So? Movement causes foaming, that's where the antifreeze agents (the polymers), and the fuel separate especially in very cold weather. What happens when the polymers foam? It causes fuel pump cavitation.

Well that's a coincidence, G-YMMM had pump cavitation. Hmmm.... isn't it just.

Ok, so the fuel's hydrocarbon chain was longer than normal, but it met with A-1 Spec freezing temperature of -47 C in fact it exceeded by 10 C. That explains the fuel economy, the polymers explain the temperature rating, the absence of sufficient de-foaming agent explains the cavitation but, why did the fuel pumps fail?

They had simply had enough of pumping around this sludge, and they were not designed to do it either.

Wouldn't it be happening to other planes on other airlines. Not necessarily, the route of BA038 is unusual, the plane's fuel system is highly automated, this plane G-YMMM was a frequent Beijing visitor, each airline makes it's own fuel arrangements and, it may just not have happened yet. There are many, many, things that all have to go wrong for a failure like this to occur.

How do you know all this? Well nothing here is written in stone but, it's all in the science, my friend. Empirical evidence doesn't lie.

**Someone should pass this on to AAIB. They're probably going crazy trying to figure it out, it has been awhile**
 
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Too... much... chemistry...!! Head... going... to... explode...!!!

Seriously though, from what I understood of the above (not much, by the way), this explanation sounds plausible.
 
t0r0nad0 said:
Too... much... chemistry...!! Head... going... to... explode...!!!

Seriously though, from what I understood of the above (not much, by the way), this explanation sounds plausible.
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Same here. FWIW, the normal Cetane rating of #2 diesel is 40, and it does turn to sludge (gel, really) if it gets too cold. Lots of additives used in winter.

This begs the question: Doesn't the AAIB have any chemists or petroleum engineers???

Speedbird, have you tried to bring this up to the AAIB?
 
SkyCaptainSpeedBird, When you say that Jet-A and Gasoline have the same weight, what sort of gasoline are you talking about? 100LL, 93UL, what?

I've always been taught that 100 LL is 6 pounds per gallon and is lighter than Jet-A.
 
Aside from what Tim said (Jet A is heavier than gasoline), remember that there are a lot of isomers in gasoline or Jet-A. For example, the "octane" that provides the 100 point on the octane rating scale is really 2,2,4-trimethylpentane. 8 carbons, but the long chain is only 5 carbons long. There are about 18 different ways to have a saturated 8 carbon chain, not including chiral isomers. As you get to larger hydrocarbons (such as those in kerosene or Jet A), there are more opportunities for branching. This creates a very complex mixture of hydrocarbons which include the aromatic compounds (like napthalene shown by SkycaptainSpeedBird).

Each different compound in the mix (and there may a fairly large number of them) lowers the freezing point in the same way salty water has a lower freezing point than fresh water.

Freezing point depression becomes complex since there is such a mixture of compounds. Hydrocarbons (such as cyclohexane) show more sensitivities WRT freezing point depression than other compounds such as water or alcohol. They show a 10 to 20 fold depression compared to water for a 1 molal addition of an "impurity"

An interesting premise, but more research needed. Also remember that the USAF tested a B-52 on a jet fuel derived from coal and didn't seem to have trouble.
 

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