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AF447

Old 4th Jul 2009, 21:55
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DJ77 said:
Precise calculations using the last ACARS position message coordinates (as reported by BEA) show that the crosstrack error (XTK) was 2.95 nm left of UN873 centerline.
At further risk of being a pedant here I note from the BEA report's ACARS transcripts that the report was in 100ths of a degree latitude and lognitude.

That is a six tenths to 12 tenths of a mile possible error from the truncation or round off process that took place. You quoted an unjustified level of precision there. However, even with that error band it was very slightly to the left of track when you'd expect any pilots even minimally weather aware to be somewhere else.

I also note that altitude, which would be nice to know at this time, was left off the report.

Further I did not see in the report a definitive statement whether the ACARS antenna was an omnidirectional component of the SatCom antenna or whether it had to be precisely aimed at the satellite. That would give an important resolution to the 4 minute give or take a little ambiguity about when the problems started that exists.

If the antenna is omnidirectional or in an omnidirectional mode for ACARS then for transmissions to cease at 0214 one might hazard to guess they were already in trouble at 0210. If the ACARS antenna requires accurate aiming then they were not in trouble until 0214 when they'd have been nearly out of the storm unless they'd become disoriented and turned sharply.

I've been yelled at on this list for presuming both of these antenna propositions. With what I know about SatCom I am inclined to suggest ACARS transmissions would not need a directional antenna to work.

JD-EE
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Old 4th Jul 2009, 22:10
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Squawk Indent

If my calculation is correct It would mean that crew would have drastically reduced its speed after INTOL.
INTOL to TASIL is 364NM and irrespective of the SALPU ORARO intermediate reporting waypoints, the ETA TASIL was 0220z based on M0.82 FL350 OAT 45°C. This gives a GS of 477NM -10KT headwind = 467KT.

BEA have previously published the auto SATCOM 10 min reports transmitted from departure Rio de Janerio up to and including 0210z. Checking the A/C positions would tend to suggest that there was an easterly component in the headwind and the A/C had drifted nearly 3NM left of track by 0200z. Reference to the MET data published by BEA would also confirm an increasing east component in the wind closer to TASIL.

ATLANTICO requested ETA TASIL from AF447 following the by INTOL SELCAL check (01:35:43). There has been no evidence presented by BEA to suggest that ATLANTICO actually tried to SELCAL the aircraft when not receiving an answer to the requested time at TASIL.

The requested time for TASIL would suggest that ATLANTICO did not require reports at either SALPU or ORARO - probably due to no known conflicting traffic.

Other than ACARS messages that indicate the SATCOM ANT was still locked to the satellite at 0214z, and the rejected attempts by AF447 to log on to DAKAR ATC, the only other recorded contact with the A/C was the last squawk received at 0148z when approx 250NM from SBFN secondary radar.

0201z was the last rejected log on to DAKAR ATC, and it is reasonable to assume that FLT OPS were normal at that time, and there is no evidence to suggest that speed had drastically been reduced after INTOL.

mm43
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Old 4th Jul 2009, 22:15
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BEA x search

I understand Air France should be on "alert" or "high concern" mode after receiving all those ACARS (all Ambar and one RED?).

But Air France, along with French government and coordinated with Brazilian authorities, only launched the "a/c missing" alarm after AF 447 had no fuel to continue flying. I know this is SOP, but after all those ACARS, shouldn't AF have jumped on all the radios, SATCOMs, phones and tried to have any info about AF 447 with various ATCs? Maybe they did...

Maybe if Brazil, Senegal and Cabo Verde had received from AF info about those ACARS, the search effort maybe would have started earlier.

But the world only knew about those ACARS on the next day, when it leaked to the press.

I don't think it is fair to "imply" Brazil was "late" in launching the rescue efforts.

The search a/c were flying with 300 ft ceiling before sunrise, all ships in the area were alerted, to include fishing boats...

I believe that if Brazilian Air Force and Navy had known about those ACARS earlier, the search would have been directed to a more specific and smaller area.

I don't understand BEA's attitude towards Brazil, but in the FAB (Brazilian Air Force) web site it is very clear that all the procedures related to flight coordination with AF 447 were conducted as usual with all flights on that same route, day after day, week after week...

Someone can be so kind and tell me what am I missing here?

Thanks
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Old 4th Jul 2009, 22:16
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Pitot Static

Safetypee: IMHO your analytical logic fails with the assumption that the pitot systems would see different air masses on each side of the aircraft. From experience of tests and often due to the architecture of the pitot systems (cross balance pipes) this occurrence is most unlikely.

There are pitot-static systems, but I've never seen cross-connected pitot systems, or (cross balance pipes). If you remember from the prior diagrams, Pitot tubes 1 and 3 are on the left side of the lower nose, while #2 is on the right side. Each feeds only its own pneumatic to digital converter.

There is a cross-connected static port on each side of the fuselage that feeds each of the above converters.

Three pitot tubes; six static ports, unless I've lost count..

GB
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Old 4th Jul 2009, 22:42
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Amdar reports

Is the flight number 0046 also masked; i.e., 0046 is not the actual flight number?
Correct, it is not a flight but an aircraft designator

From the little information available it is very likely it belongs to a LH 744
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Old 4th Jul 2009, 22:43
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Surplus1 your comment below got uneducated little me thinking:
I would suggest that a ‘near vertical trajectory’ (descent) – in a level or flat attitude - is not possible unless both wings are fully stalled – the aircraft isn’t flying, it is falling and there is very little ‘forward motion’. I would postulate further that in such a prolonged “stall” condition a spin of some type, would almost certainly develop. If there was a “spin” there would also be rotation. If there was a conventional spin, the nose would be down – unless the ‘spin’ was a “flat spin” – in which the tail could be down and the nose up with reference to the horizon. The BEA made no mention of “rotation” on impact.
You also mentioned the T-tail shadowing. I know enough to be dangerous so I immediately flashed on T-tail shadowing when reading the above paragraph. In a nose high attitude with the wings stalled creating a lot of turbulence might that provide some degree of shadowing that would prevent the VS from doing its job and straightening the plane out?

I'm wondering more than thinking I've solved anything. It might explain why the VS stayed attached until contact with the water, as the BEA report suggests.

JD-EE
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Old 4th Jul 2009, 22:43
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Transcription of AF447-related radio communications

Squawk_ident and others,

For some some reason, the transcription of the AF447-related radio communications was not included in the English translation of the BEA interim report (maybe another cause for misunderstanding).
For full access to these transcriptions (most are in English, a few are in Portuguese), please check annex 3 of the native version of the BEA interim report here.
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Old 4th Jul 2009, 22:46
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Graybeard, (#3028), thanks for the reminder. I was probably being carried away by the ‘logic’ of the argument.
However, even if my thoughts on pitot systems are corrupted by my experience in developing another type (it most probably was a static error in a sideslip), the magnitude of the differing inputs required by the ‘digital’ comparators in the A330 might be more than is feasible in turbulence. Relatively a lot of dynamic pressure for the reduced static pressure at altitude?
Also, depending on the system architecture and input mechanism, and the way in which the ADC uses static pressure, the resultant airspeed should still be a function of the difference in total (pitot+static) and static pressures; thus there could be some ‘logic’ in this area.

JD-EE, if you consider a stalled situation or any other low speed scenario, then the aerodynamic forces on the fin would be quite low anyway, and thus it would not require any protection from the low-set horizontal tail.

Last edited by safetypee; 5th Jul 2009 at 13:00. Reason: clarification
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Old 4th Jul 2009, 23:15
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AstraMike

Why all the violence? Surely there is enough in the turbulance to satisfy your worst nightmare? In a spin the bigger the airplane the less violently it behaves - to a point and, by the way, centrifugal force builds in a flat spin with both wingtips pulling towards the horizon, which is why it is a spin and not a continuing roll.

If you think about what you wrote there is little difference between what you say and what might be found in severe turbulance - I might submit that you could stall an airliner and enter a spin, in conditions of severe turbulance, without even noticing any change to your discomfort and the real point is that there is little, if anything, that will tell you something else has happened - except, perhaps, systems will start shutting down.... including engines, at the high angles of attack associated with the situation. So it is not impossible that some of this might be passed along via ACARS and much of it... not.

Referring to an accident report I have read, conditions of a large airplane in a flat spin can be violent. The following involves such an airplane roughly in the weight class of the A330 (but with a different planform).

In this accident one crew member of a crew of two survived because he was able to eject, the second crew member did not eject. The violence during the flat spin was the likely cause of the failure to eject.

Quoting the report:

"The airplane started to roll slightly, and when the pilot put in a little aileron to correct the roll. it yawed violently to the right. The pilot pulled the left throttles to idle, and was trying to advance the right-hand throttles to stop the yaw, but the airplane was out of control. The airplane rolled rapidly to the right and during the second rotation, the left wing separated at the manufacturing splice.

The pilot remembers:

"At some time during those violent maneuvers, I encapsulated, which was the first step in the bail out procedure, I expected the co-pilot would have done the same. The airplane settled into a flat spin and the forces became strong and almost constant, pushing us forward and to the side. I was having a hard time trying to keep my feet back against the heel kickers."

The pilot reported that he seemed for a period to be unable to move in the capsule due to loads throwing him forward and to the left. Finally he pulled the right handle of his escape capsule and encapsulated ballistically and was able to complete his ejection. In statement and testimony, the pilot indicates extreme forces were holding him forward and to the left during the period after loss of control of the airplane and until his own ejection was completed. The following three quotes from his statement indicate the severity of these forces:

"For the next few seconds I seemed unable to move in the capsule; the loads being somewhat oscillatory, throwing us forward and to the left. During this period of time I tried to talk, thinking that I had a hot mike; but I could only hear myself grunting under the excitement and extreme forces that seemed to be excerted on us and throwing us forward and to the left. Since it is mandatory for succesful completion of ballistic encapsulation and ejection from the airplane that the seat be moved to the full aft position, the gas pressure must overcome any forward forces. (Manual encapsulation under these conditions would be extremely difficult, if not impossible.)

Post crash capsule analysis (of the co-pilot) indicated that the relief diaphragm which releases the gas overpressure when the seat reaches a full aft position had been ruptured. This could have occurred as the result of gas pressure building to the limit when the system attempted to move the seat back against extreme forward forces. Had the latter occurred, no further opportunity for ballistic encapsulation would have existed. Even though moments of lowered force levels may have allowed successful ejection by one crew member, an unfortunate timing for actuation of the ballistic cycle during this forward force by the other may have resulted in the seat failing to retract precluding further possibility of escape.

It should be noted that the airplane remained in a flat spin, which would impose forward forces on the crew, from shortly after loss of control until ground impact. It is concluded that this was a likely cause for the co-pilot's failure to escape."

End of quote.

It took 76 seconds from the beginning of the event at 25,000 ft until the moment of impact on the ground. These 76 seconds included 16 seconds of level flight.

Because this was a test aircraft it carried an instrumentation package and its associated data recorders and telemetry equipment. Therefore, lots of data was available to the investigators.

http://www.pprune.org/5010930-post2070.html

Last edited by Green-dot; 4th Jul 2009 at 23:34. Reason: Correction, typo
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Old 4th Jul 2009, 23:17
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mm43 noted:

Other than ACARS messages that indicate the SATCOM ANT was still locked to the satellite at 0214z, and the rejected attempts by AF447 to log on to DAKAR ATC, the only other recorded contact with the A/C was the last squawk received at 0148z when approx 250NM from SBFN secondary radar.
ACARS is a VERY low bandwidth operation. It does not need any appreciable power. Nor does it need an aimed antenna to transmit data to a satellite, even in a Clarke orbit. It needs a little more than the 5 watt hand held equipment used by some ham radio operators in coordinated demonstrations with ham radio operators on the ISS for voice communication demonstrations.

The distance is greater. That would require more power. The data bandwidth is much smaller than the FM voice. That would require less power. It's not quite a wash. An omnidirectional antenna is not necessarily needed. Several ACARS-like systems exist in the Maritime service that use virtually handheld sized equipment with omnidirectional antennas to talk to geosynchronous satellite with a data rate running below a couple hundred bits per second.

Therefore requiring the antenna to be "aimed at the satellite" is pushing my credibility limits. Even if there is only one satcom antenna I more than one or two people here know whether the ACARS transmissions use the SAME satellite. And if not it's as easy to shift a steered phased array antenna to omnidirectional to reach the ACARS bird as it is to try to aim at it.

This list is full of people asserting the SatCom antenna is fully aimed with a narrow beamwidth to reach the satellite for ACARS transmissions AND people who assert equally strongly that ACARS uses an omnidirectional antenna, which apparently must be part of the one antenna labeled SatCom aboard the aircraft.

So I simply contend that if thei aircraft entered an out of control spin we do not know when within at least 4 minutes since we do not know beyond a doubt whether the antenna is omnidirectional or not.

The one or two people here who DO know must be terribly frustrated with those asserting otherwise. Hopefully this clears up why some people are still asserting both positions as of the last time I presumed the antenna was directional after getting screamed at for presuming it was omnidirectional.

I do know, beyond any doubt, that I can communicate with a satellite with a device smaller than an iPod at a sufficiently low data rate. I designed the famn dool thing in 1978 for an unnamed agency through a cutout agency.

JD-EE (We all knew who. And it had a TLA in the US.)
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Old 4th Jul 2009, 23:23
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Wow

This thread has now digressed to T Tail deep stall concerns. I do have a few questions I feel are valid to be answered by those in the know ans Airbus drivers.

For the record, I am a Boeing/Douglas/Learjet/Embraer pilot and other assorted airframes with over 17K hours in jets worldwide.

My question involves control by the flight crew in the cockpit. I have had the privilege of the famous "Hoot" Gibson on my jumpseat and have discussed the departure from controlled flight over Lake Michigan, in the US, in the late 1970s. He alluded to the fact that that he lost over 20K feet in altitude, broke out of the bottom of the clouds, saw the Moon and pulled "hard". Hard being about 6 Gs. He told me they bottomed out at about 2700 feet. The airplane and passengers all survived, although well shaken up.

My question now to the Airbus gurus here is does the airplane allow you to exercise your piloting skills to maximimun advantage in an untrained and or unplanned situation? Remember, I am a Boeing/Douglas guy. Can you pull as hard as may be required? The difference between hitting the ground/ocean and recovery may well be pull hard on the horizion.

I will leave this open for discussion. Obviously the TWA aircraft under Capt. Gibson's command survived a 6 g recovery. The B-727 was never designed for this load factor, and the airframe in question was retired.

I do not want to hear BS about airframe certifiaction standards, comparrison in G loadings, etc. I will supply a link soon to the TWA incident, but I would hope that all professional aviators on this thread are aware.''

Over
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Old 4th Jul 2009, 23:44
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JD-EE about my crosstrack error calculation:

You quoted an unjustified level of precision there. However, even with that error band it was very slightly to the left of track when you'd expect any pilots even minimally weather aware to be somewhere else.
You are right, I should have given a range, about 2.6 to 3.2 nm, to my XTK result. The intention was to give those willing to check it what I found using all the available digits. Not a good idea, I admit.

My point is not to throw a judgment on the position relative to the weather. It is that the a/c was not riding on the airway centerline with the AP in NAV mode straight into the storm, as have been suggested earlier. The pilots almost certainly attempted deviations. I don't pretend this is a big piece of information either.
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Old 4th Jul 2009, 23:50
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BEA x search

I understand Air France should be on "alert" or "high concern" mode after receiving all those ACARS (all Ambar and one RED?).
What we know yet is even more intriguing than that. From an article published in "Le Canard Enchainé" (French investigative newspaper) on June 24, it seems that when they received the ACARS messages, the AF maintenance center sent a maintenance team to wait for the plane. If I got it right, this was no emergency measure (at the time, they didn't know the plane was missing yet), but rather regular maintenance routine for loss-of-airspeed problems.

I don't understand BEA's attitude towards Brazil, but in the FAB (Brazilian Air Force) web site it is very clear that all the procedures related to flight coordination with AF 447 were conducted as usual with all flights on that same route, day after day, week after week...
I can't speak for the BEA, but I tend to believe their attitude is due more to clumsiness and lack of diplomatic skills than to anything else. Be assured that a lot of people here in France are fully aware that Brazil did A LOT for the search and rescue operation, for the subsequent retrieval of bodies and debris, and for public information too.

There is one point, though where I strongly agree with the BEA: at some point, a plane with 228 souls aboard went missing, and because of a mix of various reasons (including the fact that ACARS messages are apparently not used for this purpose), nobody even noticed it
I am not accusing anyone, as this is not and should not be the point: I just think that what happened should be examined from a standpoint of flight safety, so that one may try to fill up the d***ed Swiss cheese holes.
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Old 5th Jul 2009, 00:07
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JD-EE

Relative to 'rotation'. The BEA's conclusion that the VS was with the a/c until impact, and that it failed 'forward', with a 'left torsional component' implies a rotation of the airframe to the right before impact. As the a/c went in, its velocity in all vectors subsided, the abrupt halt to a rotation to the right would have provided the 'left torsion', IMO. I still believe the VS failed at altitude, but from the statements of BEA, there's your rotation. Obviously not in Pitch, though, sorry if you knew that.

Will
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Old 5th Jul 2009, 00:27
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ADS-C msgs

It is mentioned in the BEA report that AF447 tried three times to log on to Dakar ATC using ADS-C messages. Does it necessarily require human intervention to send those msgs, or, like ACARS, this is something automatically generated?

I am wondering if the fact those msgs were sent really proves there was someone alive\conscious in the cockpit at the controls at that time, or it proves nothing at all? I am really struck by the absense of signs of life in the cockpit after 1:36
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Old 5th Jul 2009, 00:30
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Another crash that began with a departure from controlled flight in IMC, a low-tailed, heavy jet, that never regained control, and crashed intact, was N827AX: DC-8 Mishap on 12 Dec 1996 N827AX -Stall Recovery in Mountainous Terrain ASN Aircraft accident McDonnell Douglas DC-8-63F N827AX Narrows, VA
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Old 5th Jul 2009, 00:39
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Pictures of a/c freefalling in a flat aspect are intimidating, the XB-70 and the 707 over Fuji aren't what comes to mind when entertaining the concept. What is surprising is that the airframe reaches a relatively reasonable 'stability' though certainly not what the designers had in mind. I think given those pics (and others) it suggests that larger a/c have a more inherent integrity of flight envelope. In my experience, the larger the a/c, the more 'benign' the recovery from 'unusual' attitudes. I think given the short time since the accident, BEA had a lot more they could have written, but for many reasons, held off. One assumes they didn't have all the pertinent recovery and pathologies data as well.

Will
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Old 5th Jul 2009, 00:45
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Super GPS position accuracy

From the English version of the BEA report:

The first position message (AOC type message) was transmitted on 31 May at 22 h 39. On 1st June at 2 h 10 min 34, the last position received was latitude +2.98° (North) and longitude -030.59° (West). The position transmitted was the aircraft’s FM position which, in normal conditions, is close to the GPS position.
(Emphasis added)

Note here that the ACARS positions are presumably NOT gps positions. They are CLOSE TO gps positions.

What is "close"? Within an inch? Within 5 feet? Within a mile? Within 10 miles?

Unless that can be answered I'm not sure that the position being 2.71284635 miles to the left of the theoretical track means anything.

Last edited by WhyIsThereAir; 5th Jul 2009 at 00:46. Reason: Fix bad formatting that only showed up after posting
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Old 5th Jul 2009, 00:46
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Satcom Info

For JD-EE and others: look at Product Lines

The CMU-900 and the IGA-2100B - SATCOM Intermediate Gain Antenna would be the items of interest.

These may not be the units fitted to the AF fleet, but would be representative of the technology.

GB
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Old 5th Jul 2009, 00:55
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Has there been any ifo published anywhere that indicates if there has been any positive results in the search for wreckage on the sea floor? I saw a report in the newspapers here in Oz on friday that the search for the pingers would only continue for another 11 days (now 9 days) Would the search for other wreckage continue? Without being able to examine a large amount of wreckage and preferably the FDR and CVR, then it would seem to me that we are not realy going to learn much from the loss of this aircraft.
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