Old 03-06-2010, 08:00 PM   #1
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Default Air France 447 - On topic only!

I can't imagine why, except due to a mistake or reaching some bytes limit, why a thread in the Aviation Safety forum that is discussing a fatal accident of a plane made by one of the big manufactures and flown by one of the big airlines, a thread where discussion is being taken mainly on-topic, with respect, constructivelly, with technically sound discussion, where everybody is learning, and a thread that is BY FAR the most popular ever in terms of post and views, bringing people to this site to participate or just to lurk (and some times to click on the advertisements), would be closed by the moderators.

EDIT: I've just thought I'd add a link to the original thread:

http://forums.jetphotos.net/showthread.php?t=47442
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Old 03-06-2010, 08:52 PM   #2
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It may be because of a perceived challenge to the professionals who we appreciate and need input from.
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Old 03-06-2010, 09:00 PM   #3
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Well - let's assume an innocent reason Maybe after 167 pages in the old thread it was time to start a new one
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Old 03-06-2010, 09:01 PM   #4
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It may be because of a perceived challenge to the professionals who we appreciate and need input from.
That's nonsense, Deadstick.
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Old 03-06-2010, 09:04 PM   #5
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Would have been better to call this thread "Air France AF447 accident", though
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Old 03-06-2010, 10:01 PM   #6
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That's nonsense, Deadstick.

OK. Glad to be wrong if that's the case.
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Old 03-06-2010, 10:44 PM   #7
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Well - let's assume an innocent reason Maybe after 167 pages in the old thread it was time to start a new one
Spot on Peter. No conspiracy, the other one was betting too hard to moderate.
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Old 03-07-2010, 12:34 AM   #8
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Alright people, can someone make for us in this new topic, a brief and constructive summary about what was discussed previously. Thank you.

It was a bit hard for me to read the whole 167 pages from the beggining!!
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Old 03-07-2010, 01:12 AM   #9
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Yeh, a summary of months of discussion would be very useful to someone new. Actually, I think it could be extremely brief, too, since almost nothing is known for sure.
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Old 03-07-2010, 06:57 AM   #10
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Actually, the thread basically revolved around general aviation safety issues sparked by speculation on what might have happened to AF447. The latest round was caused by a totally crappy article in Germany's "Der Spiegel" magazine, which claimed to know what happened but ended up with a lot of sensationalist speculation and nothing concrete. The last issue discussed here was the fuel policy for AF447 but that issue has pretty much been resolved here, so I think we are ready for a new one to spar about
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Old 03-07-2010, 07:20 AM   #11
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A link to the BEA report might suffice for people to know what is actually known. Though, admittedly, the speculation was very addictive to those who had theories.

http://www.bea.aero/docspa/2009/f-cp...90601e1.en.pdf

Read thru the whole thing. Really helps to have to glossary memorized, but still lots wasn't in code, so I got some big chunk of it.

One question: The interviews with other crews with routes similar to AF447 were told to divert and resume course as soon as past the weather. The report has transcripts of radio communications. Nowhere did I see the topic of course diversion raised. I wonder why this discrepancy. Sure would love to see Air France address it. The meterological discussion in the interim report said the cumulonimbus cluster was not only quite tall but like quite turbulent with powerful downdrafts. If only for the passengers' comfort, making a diversion would have seemed advisable.

Second point: Dakar apparently had a lot of communication trouble. There were multiple mentions of Dakar not responding or transmitting at points defined by agreements. They reported they didn't get called by the aircraft, but maybe the aircraft was trying and not getting through.
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Old 03-07-2010, 11:38 AM   #12
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Thank you all for helping!
Economyclass, superb report.
But i got a feeling that those black boxes will never be found, and the crash cause will remain a mistery. Let's hope it isn't the case...
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Old 03-07-2010, 07:19 PM   #13
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The last issue discussed here was the fuel policy for AF447 but that issue has pretty much been resolved here, so I think we are ready for a new one to spar about
While I don't see any clear evidence to suggest any influence of fuel policy of the decision of AF447 to fly directly into weather, I don't agree that the question is quite resolved either. But hear me out:

To begin with, let me state that I'm making the assumption that Prof. Huettig is a legitimate professor and knows far more than I. Yet I immediately see conflicts between his logic and the BEA report.

First of all, I don't follow his reasoning about how a FL change could have any effect on a decision to divert in this case, because the decision to divert or proceed must have happened by the time they reached SALPU. SALPU is only about 215 nm from the storm cell and any reasonable vector is going to be taken by that point (I assume the multiscan wxr is painting the weather system at this point, correct me if I'm mistaken). I imagine by SALPU they have made their decision to traverse the storm rather than divert, but according to the flight plan, the FL change to FL37 doesn't even happen until SALPU; they are planned for FL35 up to this point.

Secondly, I'm not following his math. By the above reasoning, climbing out of FL35 for FL37 at SALPU, there would be 2.4t of route reserve providing 20 minutes of diversion available without a fuel stopover (with seems adequate to me). That works out to an average burn rate at cruise of 120kg/min: 2,400/20=120. Then he states that if the flight maintained FL35 after SALPU instead of climbing as planned, the route reserve would only allow for an 8 minute diversion after SALPU. The average burn rate at cruise is now 112.5kg/min: 900/8=112.5. That doesn't add up in my head. Why is the burn rate lower at the lower FL, when it should be higher?

I wish I could see how he reached these figures.

Thirdly, If these figures are correct, and AF447 had instead opted for the DCT flight plan as filed (37.5t load and 69.5t of fuel), and if they had been pinned down to FL35 beyond SALPU, they would have been carrying .9t less fuel than the actual flight and therefore would have both a remaining route reserve for 0 minutes diversion time and no RIF option. And that assumes the same burn rate at Mach .82; but the actual flight had a 243kg lighter TOW, so I would expect, all else being equal, an even higher burn rate in the DCT scenario and even less remaining fuel reserves. Yet, the BEA report confirms that 69.5t was the regulatory fuel requirment for this flight. So, if Huettig is right in his calculations, where is the route reserve in the DCT flight plan assuming the flight is held to FL35 for a few extra waypoints?

Ok, math isn't my strong suit, and I'm no Professor of Aeronautics, but I'm pretty good with logic, so either I must be missing something, Prof Huettig is a quack, or the FAA regulatory fuel requirements are mighty thin. Anyone care to resolve this for me?
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Old 03-07-2010, 07:53 PM   #14
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Why is the burn rate lower at the lower FL, when it should be higher?
Well - the burn rate IS higher at lower flight levels. I read these numbers like this: The same fuel will give you an extra flight time of 20min (for diversions) at FL370, but only 8min at FL350.

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Ok, math isn't my strong suit, and I'm no Professor of Aeronautics, but I'm pretty good with logic, so either I must be missing something, Prof Huettig is a quack, or the FAA regulatory fuel requirements are mighty thin. Anyone care to resolve this for me?
I googled Prof. Huettig and it seems he is a professor at TU Berlin which is one of the best technical universities in Germany. So he appears to be legit and should know what he is talking about. Also, on a flight from Brazil to France, the FAA wouldn't have any jurisdiction over the flight and I assume that AF447 would have been required to comply with French and Brazilian regulations (not that I think they would differ significantly from US regulations).

But, Evan, rather than discussing the regulatory fuel, i.e. what AF447 was legally required to carry, we should stick to what they DID have on board and that was 0.9t OVER the legal requirements, so I really do think that we have put the "the crew was under pressure to save fuel and avoid diversions"-discussion behind us.
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Old 03-07-2010, 08:53 PM   #15
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Well - the burn rate IS higher at lower flight levels. I read these numbers like this: The same fuel will give you an extra flight time of 20min (for diversions) at FL370, but only 8min at FL350.
So, let me try this. Huettig's premise is that, when approaching this weather, they had already been experiencing heavy turbulence and doubted their ability to climb above FL350 throughout the duration of the flight? And therefore if AF447 continued for the duration of the flight at FL350, the burn rate would use up all but 8 mins of the route fuel (after deducting the fixed reserve requirement), and those 8 minutes of reserve would be insufficient to divert without the required fuel stopover. In this hypothetical scenario, from the moment they deviated from the flight plan altitude assignments, the would be spending the reserves, and course deviations under these conditions would spend them faster than at the higher flight level.

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Also, on a flight from Brazil to France, the FAA wouldn't have any jurisdiction over the flight and I assume that AF447 would have been required to comply with French and Brazilian regulations (not that I think they would differ significantly from US regulations).
Sorry, insert whatever regulatory agency applies.

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But, Evan, rather than discussing the regulatory fuel, i.e. what AF447 was legally required to carry, we should stick to what they DID have on board and that was 0.9t OVER the legal requirements, so I really do think that we have put the "the crew was under pressure to save fuel and avoid diversions"-discussion behind us.
One thing I have considered is that the captain had a lighter load than expected and could have taken advantage of that by taking less fuel and getting off at a lower TOW, but instead he ordered the different in extra fuel. That tells me that he placed a premium of safety over profits. The flip-side is that he was apparently in the crew rest when AF447 made the decision to continue and might not have had a part in that decision. Is that a reasonable conclusion?

Earlier I agreed with you that there was more than enough reserves on hand, but now we have Prof. Huettig's revelation that, due to turbulence restricting flight level, even these may not have been enough to make a clear diversion without requiring a fuel stop. If so, this makes it hard to put the possibility of external pressure behind us.

The fact is, they flew directly into this weather system, and from the very beginning I've been wondering if this was because they saw no threat, because they had no choice, or because their choice was weighted by external pressures. Heuttig's findings do support the possibility of the third motivation, and I don't think we can rule it out unless we can rule it out by the numbers.
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Old 03-08-2010, 04:46 AM   #16
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Evan, I just read the Spiegel article (talk about disaster porn!) It reasons from debris that the least-experienced pilot was in the captain's seat when they lost the autopilot. Maybe if the captain had not been resting (assuming he was), he would have chosen to divert. Maybe the junior pilot felt uncomfortable with a decision like that and hoped to be relieved before it became impossible. I still am scratching my head why none of the ATC's radioed about the decision of the other captains with regard to the weather.

I'm also wondering if any flight plan across the ITCZ wouldn't plan for diversion to avoid violent storms. It has been said repeatedly that "there was nothing unusual in the weather that day". So if flying a zigzag path is to be expected, fuel loads should comfortably cover that. If luck is with them and they get to fly straight, then they land with fuel to spare.

The Spiegel article said there was some sort of 300,000 euro/plane upgrade that Air France hasn't chosen to add. OK, maybe I can understand that, but to also trust to luck that diversion is unnecessary is something only an executive who hates passengers would do.
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Old 03-08-2010, 08:32 AM   #17
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Secondly, I'm not following his math. By the above reasoning, climbing out of FL35 for FL37 at SALPU, there would be 2.4t of route reserve providing 20 minutes of diversion available without a fuel stopover (with seems adequate to me). That works out to an average burn rate at cruise of 120kg/min: 2,400/20=120. Then he states that if the flight maintained FL35 after SALPU instead of climbing as planned, the route reserve would only allow for an 8 minute diversion after SALPU. The average burn rate at cruise is now 112.5kg/min: 900/8=112.5. That doesn't add up in my head. Why is the burn rate lower at the lower FL, when it should be higher?
Urks, I'm guilty on this one. the 8 minutes were calculated by me, not by Huettig.... In Hüttig's mail, he makes the remark that 2.4t is good for "over 20 minutes of flight at most", and I used this number to turn the 900 remaining kilograms into *roughly* 8 minutes... so nothing really wrong here with the professor's math.


Maybe I'll with him a second time, or better point him to the forum directly, but to me the last remark in his mail - that a B747 or A340 wouldn't have had the problem - seems to point out that the A320 on this route will always be tight on fuel. Can anyone post the full fuel capacity of the A320 - maybe compared to the other types mentioned? How much more than the rather close numbers in the three flight plans can the aircraft actually take?

m.
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Old 03-08-2010, 12:02 PM   #18
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Urks, I'm guilty on this one. the 8 minutes were calculated by me, not by Huettig.... In Hüttig's mail, he makes the remark that 2.4t is good for "over 20 minutes of flight at most", and I used this number to turn the 900 remaining kilograms into *roughly* 8 minutes... so nothing really wrong here with the professor's math.


Maybe I'll with him a second time, or better point him to the forum directly, but to me the last remark in his mail - that a B747 or A340 wouldn't have had the problem - seems to point out that the A320 on this route will always be tight on fuel. Can anyone post the full fuel capacity of the A320 - maybe compared to the other types mentioned? How much more than the rather close numbers in the three flight plans can the aircraft actually take?

m.
The A330 (not A320) is advertised by Airbus as having the effective range to service the Paris to Buenos Aires route nonstop in a typical configuration. I assume that means taking a full passenger load + luggage and then fueled to MTOW. I assume this claim excludes non-passenger related cargo. I'm almost certain the A330 used by AF447 was at or below the typical configuration, and if it was not carrying freight, it would have been able to take on more fuel. Therefore, it is not the limitations of the aircraft, it is the limitations of the aircraft combined with the load. What Huettig is saying is that, given the load they chose to carry, a longer range aircraft would have more margin in the MTOW for additional fuel. The alternative to using longer range aircraft is to file a Reclearance-in-Flight (RIF) option with the flight plan, as they did here. The RIF allows them to legally fly more load with less fuel reserve. Obviously, this option is more appealing to the operator, since the A330 is capable of making the flight without a stopover in most cases.

If you contact Prof. Huettig again, ask him to expand on how he calculates the route fuel requirement for the two different flight levels. I'm curious to know how that is done.
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Old 03-10-2010, 12:18 PM   #19
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The fact is, they flew directly into this weather system, and from the very beginning I've been wondering if this was because they saw no threat, because they had no choice, or because their choice was weighted by external pressures. Heuttig's findings do support the possibility of the third motivation, and I don't think we can rule it out unless we can rule it out by the numbers.
Well, Evan, I don't think you will ever be able to rule that out by the numbers. I might be coming at you all with hpyerbole again, but if you think the "maximum fuel" thing through you might end up at asigning a fully fueled 747-400 for a CRJ flight because if they discovered one of their wheel lights was inop they would have a maximum flight time to sort out the problem. (Hyperbole off)

For me the AF447 issue still doesn't seem so difficult. The flight carried 0.9t more fuel than was legally required. Pilots have a natural instinct of self-preservation. All pilots were fully qualified (nicluding the most junior pilot on the flight deck) to operate an A330. The weather in the path of AF447 was not unsual for this area or route. Bearing all this in mind I don't see anything dangerous looming for AF447 from these aspects of the flight.
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Old 03-10-2010, 12:55 PM   #20
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Well, Evan, I don't think you will ever be able to rule that out by the numbers. I might be coming at you all with hpyerbole again, but if you think the "maximum fuel" thing through you might end up at asigning a fully fueled 747-400 for a CRJ flight because if they discovered one of their wheel lights was inop they would have a maximum flight time to sort out the problem. (Hyperbole off)
You know Peter, with all due respect, admitting that you are using hyperbole does not make it any more relevant or any less useless here. I'm not sure why you keep doing it.

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Pilots have a natural instinct of self-preservation.
I realize this. They also have a natural instinct for completing tasks as assigned, and for calm practicality in the face of danger. The mind of the pilot is influenced by complex instincts. The less clearly situations are defined, the more these instincts can contradict one another, and this complexity makes their grey-area decisions harder to predict.
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