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AF447

Old 5th Jul 2009, 00:57
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Within 30 meters, repeatable is " normal GPS" accuracy. This is not WAAS accuracy.
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Old 5th Jul 2009, 01:03
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vovachan

What seemed immediately incongruous to me about ACARS was that a/p tripped out (as it is programmed to do), because of exceeded limits reached by the a/c in auto flight. Nothing particularly dramatic about that, but even in turbulence, the a/p has generous +/- parameters, and it seems odd the pilot(s) would let the a/c get that rambunctious so as to require auto disconnect rather than manual disconnect sometime prior.

The a/c appears to have transited the wx when ACARS transmits a/p disc, A/THR drop, again why wait, if it appears inevitable hand flying will be necessary, being in turbulence, why hesitate?? One risks the instability of turbulence of course, but adjusting to minor out of trim state could be done earlier with a manual disconnect. Another question might be, is their record of aircrew briefings on the pitot unreliable a/s, and how often is it briefed especially prior to an ETOPS over water, night, wx impacted flight?

Last edited by Will Fraser; 5th Jul 2009 at 02:14.
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Old 5th Jul 2009, 01:47
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The absence of communication from the flight deck, or any known attempt at communication, from 0136 onward does not necessarily correlate to there being “no problems”. IMO there is merit in the suggestion by some that given the known circumstances in this case, the lack of comms could in fact be an indicator of problems.

If anyone wishes to discuss / debate the above I'd be happy to do so on JB.

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Old 5th Jul 2009, 01:57
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Flight Crew Incapacitation

I am really struck by the absence of signs of life in the cockpit after 1:36
Are we inferring a Helios 737 replay here? If the flight crew was insensible then it's likely that all on board were. If the aircraft then flew on into a CB, suffered an upset and nobody was conscious to manually intervene, it could be just a variation on that theme. Time of useful consciousness at a cabin of FL350 is a mere few seconds. However ACARS recorded no loss of pressurization, so what other form of subtle incapacitation is there, other than poison? Both crew fell asleep perhaps and woke with a start at autopilot disconnect - after entering a large cu-bubbly?
.
Not sure whether or not there's any other evidence to deny flightcrew disinvolvement as a theory (or for that matter, any viable scenario - short of an MS990 replay - in which it could play out). However it could also explain why no significant diversions around heavy weather along track were carried out.
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Old 5th Jul 2009, 02:01
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Originally Posted by grizzled
The absence of communication from the flight deck, or any known attempt at communication, from 0136 onward does not necessarily correlate to there being “no problems”. IMO there is merit in the suggestion by some that given the known circumstances in this case, the lack of comms could in fact be an indicator of problems.
Whilst I agree with you to some extent, HF comms are notoriously inconsistent, especially in a storm situation (Possibly).
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Old 5th Jul 2009, 02:06
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Are there programmed alerts and mx transmissions that would in any way suggest that the crew was attempting 'recovery' eg overloading, rapid and multiple control limit excursions? Additional over limit/rate excursions beyond a/p limits? Anything? Or would all those be in the CVR/FDR?? I simply get the notion that for some time, the pilots were out of the loop in every way. I haven't seen this addressed, but with the last post of grizzled, It just seems things for four minutes just got worse and worse.

I've asked before, but can a 330 Captain characterize for us what the 'transition'/ reversion process a/p to pilot involves? Seems that so much confidence is placed in the a/c, the possibility of letting slip the in and out of transfer training may be a bit out of balance. Are there displays that cue the pilot 'what's left'? Not just 'what's gone'?
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Old 5th Jul 2009, 02:12
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Lightning6 -- Agreed. Your comments about HF are of course correct. Having said that there were other aircraft on the same assigned HF frequencies, some of which would likely have heard any attempts at HF contact by AF447. And some of those same aricraft were well within VHF range of AF447.
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Old 5th Jul 2009, 02:29
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Originally Posted by grizzled
Lightning6 -- Agreed. Your comments about HF are of course correct. Having said that there were other aircraft on the same assigned HF frequencies, some of which would likely have heard any attempts at HF contact by AF447. And some of those same aricraft were well within VHF range of AF447.
I take your point grizzled, the supposition that they had just had a selcal check previous to apparent loss of HF comms leads one to believe that HF comms was probably not a problem, even if they had gone onto standby, they would probobly have got the selcal, presuming the controller tried contacting them on selcal. Selcal being more unreliable as vocal HF transmissions.
I would imagine whatever was going on up there, comms would be the last thing they would have considered. No 1 consideration is to fly the a/c.

Last edited by Lightning6; 5th Jul 2009 at 02:50.
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Old 5th Jul 2009, 02:51
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From the BEA report (and confirming what has been posted here before in many ACARS analyses):

F/CTL PRIM 1 FAULT (2 h 13)
Meaning: This message indicates that FCPC1 (PRIM 1) has stopped functioning.
This shutdown could be the result of a command or of a failure.

F/CTL SEC 1 FAULT (2 h 13)
Meaning: This message indicates that FCSC1 (SEC 1) has stopped functioning.
This shutdown could be the result of a command or of a failure.
So this is a possible indication of the crew alive and functioning as things go bad.

Last edited by WhyIsThereAir; 5th Jul 2009 at 03:56. Reason: A more reasonable font size
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Old 5th Jul 2009, 03:09
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Flight crew incapacitation?

When is anyone going to use the phrase "false sense of security" to help understand the lack of communication from AF447's cockpit after it flew beyond ATC radar range?
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Old 5th Jul 2009, 03:10
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Graybeard - thank you, sir, for the pointer.

The antenna has greater than 6dBiC gain. So those who who declare steered and those who declare omnidirectional both have something on their side.

If I may riff on this a little, the dBiC specification basically refers to gain over a hypothetical purely isotropic circularly polarized antenna. Circular polarization avoids the Polaroid (tm) Sun glasses effect. Isotropic means the reference antenna pattern is a sphere. A pure hemisphere pattern would give exactly 3dBiC gain. So the antenna is somewhere betwen 60 degrees and 45 degrees beamwidth and aims itself roughly at the satellite. If they were using classical service they were sitting close to directly under the satellite per this link. Classic services coverage - Support - Inmarsat If they were using SwiftBroadband service they were off at an angle of about 55 degrees from vertical relative to the satellite. SwiftBroadband Coverage - Support - Inmarsat

So if they were using the classical Inmarsat modes they would not lose coverage in a flat spin until the equipment ceased to function. If they were on either the bird over Africa or the one South of Mexico then they'd have intermittent coverage that would depend on their spin rate.

Now can we determine which mode they used? If they support the Internet service I suspect it would be the SwiftBroadband service the antenna would be setup to support. Although being electronically steered it might be able to track the satellite adequately for communications through some pretty awesome gyrations if they were slow enough. If it was GPS aided tracking would be a slam dunk. If the integrated SatCom equipment that steers it is dumb enough then it'd lose track fairly easily with a high rate of spin.

I must admit that I was thinking "aimed" in terms of the antenna I was used to which had a much narrower beamwidth and tracked relatively reliably down to at least 7 degrees from the horizon. It used operator input for approximate position and aimed itself from there with a tracking algorithm that would uncomfortable once the gyros providing basic antenna stabilization became upset. But then, ships don't generally go into aircraft type spins. It was perfectly adequate for a ship in a pretty heavy storm.

If I had to put money on it I'd say that pretty close to 0214 and before 0215 the plane had met its fate.

Again, thanks for the pointer. It answered a lot of questions.

JD-EE
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Old 5th Jul 2009, 03:19
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grizzled. in a single acro-breviation, 'SelCal'. Visit its page on Wakipoodle for a quick upgrade on the concept.

JD-EE
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Old 5th Jul 2009, 03:35
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Why did the VS, as reported, appear to have broken away on impact from aft. Also other sections appear to have been ripped away from reverse forces. Is this consistent with the aircraft having been in a flat spin and, as chance would have it on the day, hitting the water tail first?

Just a question to the better informed.
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Old 5th Jul 2009, 04:15
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I have reservations about a flat spin with no forward motion; but with the information publicly available it may be impossible to rule it out. Some mode where the plane spiraled in, nose up, seems a bit more consistent with what the BEA is really describing. At a rough guess (very rough, but the best possible with the public data) the plane probably needed about equal forward and vertical speed, say 100-150 MPH each way. And a small bit of leftward force at impact.

The BEA analysis of the tail separation and the "vertical acceration" they describe for the other damage seems to be at odds. The VS needs a strong force to the front of the hull, yet everything else is described as having a force downwards. But this might not be a contradiction if the plane came in at 45 degrees forward and down, and hit somewhat tail first. (Flight angle 45 degrees downward; pitch maybe 5-20 degrees nose up.)

Breaking the tailcone from HS impact with the water could pull loose the VS. This could also account for the damage to the bottom of the rudder. The remainder of the body slapping into the water and being arrested by the wings, combined with the forward motion, would provide the moment to pull loose the VS in a forward direction. Spiraling or turning moment to the right will throw the VS over the left side, as described. Slapping the body into the water will provide the "vertical acceleration" for the other damaged items, but there should also be evidence of some forward acceleration as the forward motion is arrested.

And possibly there is. If you carefully examine the picture of the galley tray rack, you will see that many of the right rails are bent down, but not the corresponding left rails. This implies that the trays were thrown to the right side and not straight down, or both rails would be damaged equally. (The bottom two rails are damaged on both sides, but that is understandable as things piled up.)

Question: where was this galley unit located? Is there any indication that the right of the tray rack would have been forward?
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Old 5th Jul 2009, 05:59
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JD-EE

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.
I apologize for not being more precise in my previous post.

My experience with satellite communications goes back the the OSCAR 1 and later series of experimental satellites. However without getting into the nitty gritty detail of antenna design, phased array gain / isotropic dipole and linear / circular polarization, my intention was to state that the A/C was still was in comms with an INMARSAT-3 geostationary satellite at 2014z. We are informed by BEA that for a short period between 0211z and 0212z that the satellite lost contact with AF447. That is the important point, as if the antenna in use was an omni-directional with a nominal gain of 6 dBi the beam width would have been about 70 degrees - quite large for a L Band antenna (nominal 1.6GHz).

One can only imagine what was happening during this loss of signal.

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Old 5th Jul 2009, 06:48
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JD-EE

I'm quite sure I have more experience with SelCal than you could possibly imagine. You've missed my point.

I've read the whole thread (and the previous incarnation); I've participated ocassionally over the past month; I've read the prelim report; and I am familiar with the reported comms and attempted comms (in all their various forms).

Your post is exactly the type of post that I had in mind when I invited discussion on JB, rather than here. If you and I debate the issue of comms over the Atlantic (including SelCal) on this thread, we will quickly and correctly be scolded or deleted by the mods.

Feel free to meet me on JB or PM me. Or perhaps I should start a new thread.

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Old 5th Jul 2009, 07:30
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If we assume that the VS separated on impact, does it follow that:

1. From the time/date and location of VS recovery, and

2. the known or estimated drift patterns

3. the impact site can be (generally) determined?
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Old 5th Jul 2009, 07:43
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In theory. The main problem is that the surface currents are not known exactly for the early June time period, so you can only take the current currents and make guesses about the previous currents. The guesses will not be 100% accurate, because the currents change.

This excercise was carried out here a week or so ago using the marked location of the bodies that were located, as these were marked on the Braszilian charts, and the other items were not uniquely marked. Since then at least one chart shows the found location of the VS, and it would be interesting to correlate that to the previous work.

As best I recall the maps, the estimated zero point was about 1 degree (60nm) almost due south of the June 6 cluster of recovery items. That would be near the bottom and a little left of center of the search area shown in the BEA report, so we can assume that the searchers know something about the currents that hasn't been made public. Note this is also about 30nm back from the 0210 position report, indicating (if the true location) that AF447 covered at least 30nm before hitting the water, rather than going "straight down".

Last edited by WhyIsThereAir; 5th Jul 2009 at 07:53.
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Old 5th Jul 2009, 07:45
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As a PPL and SLF, the thing that most worries me from the report is that an airliner went missing and nobody looked for it or even showed any concern for many hours.

If I understand the situation from the report (sorry I've been away for 2 days and trying to catch up on the report + about 6 pages), at 3 minutes after 02.20 Senegal should have kicked off to Brazil that they had no contact (which they should have had 5 mins before 02.20 Z). It seems that hours later they almost thought AF447 had just flown past them without contact and reported next to Cape Verde.

If the ACARS should send out a routine position report every 15 mins, should AF not have noticed within 30 - 45 mins that AF447 was not reporting and kicked off ?

Whilst in the AF447 case this may have been entirely academic, in another case it may not be at all.
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Old 5th Jul 2009, 07:49
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mm33

On page 46 of the English language version they state:

The messages received on 1st June after 2 h 10 all transited via the same satellite (Atlantic Ocean West, operated by the Inmarsat Company) and SITA’s ACARS network.
So they do specifically state which satellite was in use and that basically puts them almost dead center under it. It would take something fairly dramatic for them to lose the satellite. A 30 degree or so change in attitude that was not corrected by the antenna steering logic could do it. That would suggest they were in something other than a purely "flat" spin at least some of the time but not a large percentage of the time. So if I were a person who bet often I'd bet the plane broke up very shortly after the ACARS last message and was basically in one major piece and out of control in but relatively constant attitudes until them.

We basically agree. (And I go back a few years from you for satellite work. I have one assembly on the GPS satellites, a whole not of kibbitzing in other assemblies, and both hardware and software involved in two aspects of the pre-launch testing of the puppies. I'm the bad person who provided the hardware for doing the dithering. I mitigated that by noting to the right person this also allowed for improving the precision of the signal by using the frequency dithering capability to correct for oscillator drifts. Heh, I also provided a throw away statement that led to the major cosmic ray and nuclear event upset recovery - reboot the silly thing periodically on a separate watchdog timer whether it needs it or not.)

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