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Old 8th Jul 2009, 03:26
  #3261 (permalink)  
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I've remarked in the past that the Inmarsat satellites and protocols are designed to work well within a deluge. I dug into references (the ITT handbook) and looked at the charts. Rain attenuation at Inmarsat frequencies is a bit under 2dB per km in a 25mm/hour rain storm at sea level. So in the very middle of a storm at low altitude the Inmarsat communications probably can become lost, at sea level. At FL350 there is less rain and less distance through it. For rain attenuation to be a factor the plane would have had to have already descended well down into the storm.

That's another useful data point. I am guessing the point where a loss due to rain becomes feasible to consider is maybe 15,000 feet give or take some.

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Old 8th Jul 2009, 03:38
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Will Fraser, physicists and engineers seldom employ the word deceleration in my experience, as an engineer, unless talking to lay persons. A deceleration is simply a negative acceleration. Hitting the water imparts a (very) high negative rate of acceleration.

Please give it a rest. You can't seem to tell the difference between facts that can be checked against evidence made available and rumors leaked by unauthorized people wanting their moment of fame. If you can PROVE your contentions about the Brazilian leaks being facts, then do so. Otherwise, please drop it. The facts so far pulled from reports suggests that the plane did not magically transport itself backwards tens of kilometers along its path and then fall apart in the air. And no other scenario of break up in the air seems to fit where the plane could possibly have been and breakup in the air as you insist. It must have been coming down very fast with a pull up attempt right at the bitter end to support takata's data, the timing data derivable from the ACARS, and the apparent condition of the plane.

It would be nice to know the condition of the passengers, too. A cultural and communications snafu got in the way of BEA getting the autopsy reports. And it had a deadline by law for issuing the report while they were still in the field trying to collect what evidence they could. They were too busy to sit down a please everybody with a very complete report. And they were not required to present any conclusions at all. That they did vouchsafe us with an opinion is stepping beyond the minimum requirements of their charter.

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Old 8th Jul 2009, 03:50
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unless flat spin includes considerable motion in a constant direction after the spin is entered.
Translation along the earth axis coordinate system would have been at the wind velocity.

Not claiming a flat spin from altitude, or a flat spin at all, as there are other scenarios. One item to note, if someone can line up the ACARS pieces, is that pitot's are only good for small alphas. On the order of 15 degrees. A flat spin would produce alphas much higher, with rotation, generating a split among all three pitots. If a flat spin is suspected as producing the ASI splits, then it would be left to determine the chances an experienced crew would need to enter the spin in CB turbulence at altitude. Keep in mind that an aircraft at high alpha translates AOA to sideslip with wing rolloff. Two things are needed for spin entry, stall and sideslip.
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Old 8th Jul 2009, 04:02
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I have not once used the word deceleration. There is nothing to desist from. I have experience with the FAA and deliberative investigative authorities. I have no agenda, I believe everything I write. My lament is for a truly objective investigation. What started my displeasure was the inability of the French and the Brazilians to put any concerted effort together to collaborate. If I'm wrong, and there was free and active teamwork between the two, I will be the first to acknowledge it.

I am at this moment reading and translating the report from the French.
Please don't tutor me in Physics.

You are putting so many words on my plate that I never wrote. For one, I didn't say the a/c wasn't intact at impact, I criticised the BEA for concluding that it was, there is a difference. I am not pushing any theory, I continue to say there is virtually no evidence at all. My only surmise is I think consistent with prior history and reasonable interpretation of conditions based on my knowledge of them.
I think it may be you who is ahead of himself.

Regards JDEE


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Old 8th Jul 2009, 04:04
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Originally Posted by singpilot
The concept of the descent of AF447 troubles me.

Anyone who has brought a 208 ton aircraft from altitude (normal, normal, normal) knows how 'difficult' it is to do when heavy. The aircraft will VERY happily accel to MMax with very slight pitchover. From FL350 to surface is 'normally' 25 minutes (powered), clean, and with unrestricted clearance. Gliding, under control as described, 15-ish minutes. Emergency dive, spoilers, (loss of pressurization) maybe 10 minutes (Regs) to 10000, then who knows to surface.

Throw in CB activity, mod to extreme turbulence, nightime, surprise, inattention, one or more failed engines, reversion to some unknown control law, and how long will that take?

Who knows. After a high altitude upset. Geez, maybe speed of a rock from 7 miles up.

My point is that a LOT of attention needs to normally be paid to keep the speed under control in a descent.

These modern designs are so clean, they accel going downhill at the drop of a hat.
I believe there is evidence (and its been posted fairly recently too) that a transport category aircraft in departed flight (stalled condition or similar) descends at a very high rate. While the modern airliner is indeed a slick, low-drag design in normal flight, with a stalled wing the drag is very much higher - perhaps orders of magnitude higher, in fact. IF AF447 had departed controlled flight at altitude into a stall (or spin as some have suggested) then a substantial rate of descent is entirely reasonable.
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Old 8th Jul 2009, 04:12
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Yes, but is not the acars satcom based, and if so, how is is going to stay stabilized during said flat spin, or any departure from controlled flight for that matter?
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Old 8th Jul 2009, 04:36
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Translation issues

"normal flight attitude" smells to me like the best equivalent for "ligne de vol" in the BEA report.

In addition, one translation of "accélération" is "G"; thus "avec forte accélération" becomes "with high G forces". Source for this is Dassault's house dictionary: Lexique bilingue. Members may want to rummage through other equivalents for the term.

Nonetheless, Harry Mann is convincing with:

Airplane is travelling down. It makes contact with the water which stops the fall. This causes upward acceleration (possibly to a zero vertical speed).

Strong vertical acceleration means a strong CHANGE in the vertical component of the velocity. It doesn't necessarily mean anything beyond that.

Hope this helps.

Last edited by ArthurBorges; 8th Jul 2009 at 05:05.
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Old 8th Jul 2009, 04:37
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flyingchanges asked, "And how is the acars still transmitting in a flat spin?"

I contend that as long as the plane was not on emergency power ACARS had the capability to transmit and reach the satellite unless it was really in the middle of a Biblical deluge.

If you are worried about antenna aiming draw an airplane, any old outline sketch will do. The antenna is a 6dB gain model relative to an antenna that radiates identically in all directions. A gentleman named Poynting observed that if you draw a sphere around a transmitter antenna you cannot get more power out of that sphere than you put into it. With that in mind you get gain by sacrificing portions of the sphere to enhance other portions. The first thing most antennas in practical installations sacrifice is "the other hemisphere". If they are to look up they lose down. If they are to look down they lose up. That gives a cool 100% power boost, 3dB. If they cut the angle down further, say from being a section of a sphere from 0 to 90 degrees from vertical and it becomes oh maybe 60 degrees from vertical to pure vertical the gain boosts another (very) roughly 3dB. If I require less than 1 to 2 dB of loss from peak performance I've been figuring on 40 degrees and the Atlantic satellite in use was 10 degrees to the East.

Thus if the plane's attitude was within 20 to 30 degrees of horizontal and it had power for ACARS then ACARS messages could be sent.

There is question of whether or not there really were. Although to my untutored eyes they seem to cut off almost mid-sentence, so to speak. There looks like there should have been more story to tell.

Rain has been mentioned for the short signal loss that happened. That might, also, have been the plane coming down to a level where there was enough air bite to execute a turn or other attitude changing maneuver to recover from uncontrolled flight. That might also explain the loss.

The ACARS signal does give us some data to estimate, only estimate, the condition of the plane through 0215 as being roughly horizontal and with power. After that it was controlled or uncontrolled flight without power, most likely. We don't know for sure. But, this limits the range of guesses for what might have happened.

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Old 8th Jul 2009, 04:42
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The Show Must Go On

What started my displeasure was the inability of the French and the Brazilians to put any concerted effort together to collaborate.
PARIS, July 7 (Xinhua) -- French President Nicolas Sarkozy and his Brazilian counterpart Luiz Inacio Lula da Silva discussed hereon Tuesday the cooperation between the two countries on the search operation and investigation following the June 1 air crash of Air France Flight 447 en route from Rio de Janeiro to Paris. "There is a black hole. This is not normal," Sarkozy said at a joint news conference with Lula.
Sarkozy said Foreign Minister Bernard Kouchner and Cooperation Minister Alain Joyandet were headed to Senegal to see "how we can avoid this black hole, this void in communications."

You can see the rest of the article at

France, Brazil discuss cooperation following plane crash_English_Xinhua

Dare I anticipate exasperation among members here who read all the way to the end where it says:

Lula rejected French claims that they were denied access to the autopsies. "There is nothing to hide," he said. Sarkozy and Lula also called for "a more democratic world order, one founded in greater solidarity and justice," to give emerging economies more say in international finance and justice.
Lula insisted that now be the right time for a South American country to host its first Olympics.

With a gold, silver and bronze for the first three passengers out the emergency exits?
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Old 8th Jul 2009, 04:51
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Just a point of interest from NASA:-

July 7, 2009

RELEASE : 09-154

NASA Research to Help Aircraft Avoid Ocean Storms, Turbulence

WASHINGTON -- NASA is funding the development of a prototype system to provide aircraft with updates about severe storms and turbulence as they fly across remote ocean regions.

Scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., in partnership with colleagues at the University of Wisconsin, are developing a system that combines satellite data and computer weather models with cutting-edge artificial intelligence techniques. The goal is to identify and predict rapidly evolving storms and other potential areas of turbulence.

"Turbulence is the leading cause of injuries in commercial aviation," said John Haynes, program manager in the Earth Science Division's Applied Sciences Program at NASA Headquarters in Washington. "This new work to detect the likelihood of turbulence associated with oceanic storms using key space-based indicators is of crucial importance to pilots."

The system is designed to help guide pilots away from intense weather. A variety of NASA spacecraft observations are being used in the project, including data from NASA's Terra, Aqua, Tropical Rainfall Measuring Mission, CloudSat and CALIPSO satellites.

The prototype system will identify areas of turbulence in clear regions of the atmosphere as well as within storms. It is on track for testing next year. Pilots on selected transoceanic routes will receive real-time turbulence updates and provide feedback. When the system is finalized, it will provide pilots and ground-based controllers with text-based maps and graphical displays showing regions of likely turbulence and storms.

"Pilots currently have little weather information as they fly over remote stretches of the ocean, which is where some of the worst turbulence occurs," said scientist John Williams, one of the project leads at NCAR. "Providing pilots with at least an approximate picture of developing storms could help guide them safely around areas of potentially severe turbulence."

NCAR currently provides real-time maps of turbulence at various altitudes over the continental United States. Williams and his colleagues are building on this expertise to identify turbulence over oceans. The team has created global maps of clear air turbulence based on global computer weather models that include winds and other instabilities in the atmosphere. Drawing on satellite images of storms, the scientists also have created global views of the tops of storm clouds. Higher cloud tops often are associated with more intense storms, although not necessarily with turbulence.

The next step is to pinpoint areas of possible turbulence within and around intense storms. The team will study correlations between storms and turbulence over the continental United States, where weather is closely observed, and then infer patterns of turbulence for storms over oceans.

In addition to providing aircraft and ground controllers with up-to-the-minute maps of turbulence, the NCAR team is turning to an artificial intelligence technique, known as "random forests," to provide short-term forecasts.

Random forests, which have proven useful for forecasting thunderstorms over land, consist of many decision trees that each cast a yes-or-no "vote" on crucial elements of the storm at future points in time and space. This enables scientists to forecast the movement and strength of the storm during the next few hours.

"Our goal is to give pilots a regularly updated picture of the likely storms ahead as they fly over the ocean, so they can take action to minimize turbulence and keep their aircraft out of danger," explained NCAR scientist Cathy Kessinger, a project team member.

The NCAR project is funded by NASA's Applied Sciences Program, which seeks to translate NASA's investment in Earth observations into applications that address real problems. The program and its partners are working to bridge the gap between research results and operational aviation weather products in such areas as in-flight icing, convective weather, turbulence, volcanic ash and space weather.

For images related to this turbulence prototype system, visit:

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Old 8th Jul 2009, 05:36
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Conditions for a spin

Two things are needed for spin entry, stall and sideslip.
Just to review, 3 1/2 other things can possibly replace the sideslip.
1) When close to the critical AOA, dropping an aileron (say in rapid response to the start of roll-off on one side) effectively increases the AOA in the region of the aileron and could stall that region.
2)When close to the critical AOA, having a some upward gust applied to the outer wing section on one side, causing it to exceed critical AOA.
3)When close to the critical AOA, making a smaller radius turn so that the inside wingtip is flying more slowly that the outer wingtip and effectively causing a greater AOA on the inside wingtip (same vertical vector amount, less horizontal). More an issue with long-winged aircraft.

and 1/2) The typical spin entry we're all aware of, when close to the AOA kicking in rudder for some reason. With the A330 you can substitute differential engine thrust for the rudder. While it may or not slip sideways overall, that's not the problem. It's the yawing so that the inside wingtip flies more slowly or even backwards relative to the other tip. Due to vertical vs horizontal flight vectors of the tips, the inside tip goes critical and the other away from critical.

I'm sure you knew this.

Last edited by ttcse; 8th Jul 2009 at 11:21.
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Old 8th Jul 2009, 06:24
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There are a few statements in the BEA report that are questionable to say the least. No matter. I would like to better understand your posit that the aircraft's engines were not turning and burning?
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Old 8th Jul 2009, 06:42
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vapilot2004 said, "There are a few statements in the BEA report that are questionable to say the least. No matter. I would like to better understand your posit that the aircraft's engines were not turning and burning?"

As far as can be determined nothing that was not supposed to have flame active in, on, or near it had flame in, on or near it.

A recent message raised doubts about which busses have to go down to kill ACARS. I'd had the understanding that if the engines were turning, properly, that ACARS had power. The plane was sufficiently "together" for ACARS to work through the last ACARS transaction and acknowledgement cycle. That puts the plane in one piece, approximately horizontal, and with power at that time. Loss of power, a relatively large attitude abberation, loss of source of ACARS messages, or simply there were no more ACARS messages to send are the only things that come to mind that would stop them. That latter option sounds like a lower probability than the other three for any long term interruption of ACARS messages while the plane was still under power, horizontal, and in one piece.

My contention is that takata's work coupled with "where could the plane have gotten to before signals ceased" will tell is something important about what the plane did subsequent to the end of the ACARS messages. We can test the flat spin scenario, the dive to try to restart scenario, and all the other scenarios against it. That trims out a lot of bad ones, does it not? The current data very strongly suggests the plane did not stop in mid air and start falling at any of the times of the ACARS messages, for example. The currents would have carried the bodies and debris to completely different positions in those scenarios.

Once we have a class of scenarios that fit these two data sets we add a third and start eliminating what does not fit. We keep adding data sets as they appear and eliminating the scenarios that don't fit. In the end, if we have new data fed in, we may arrive at a solution without the suspected political biases. For fact checking the final report, whether or not it reaches any conclusions, the only original data we cannot get for ourselves is the on site visual impressions from the condition of the debris.

Peel away what is impossible. Whatever is left becomes probable.

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Old 8th Jul 2009, 06:45
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NASA Research to Help Aircraft Avoid Ocean Storms, Turbulence
Ironically .. seem's all the scientifics and people linked to aviation safety discovered suddenly ocean storms and turbulences existence after the AF447 event ...
Sure it's some bussines and some bucks to make there.

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Old 8th Jul 2009, 07:05
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Ironically .. seem's all the scientifics and people linked to aviation safety discovered suddenly ocean storms and turbulences existence after the AF447 event ...
Sure it's some bussines and some bucks to make there.
In the U.S. it has been a common political tactic to dismiss as wasteful almost any spending for what appears to our political leaders as abstract scientific research. When a large number of people suddenly die without apparent reason, the political figures hold hearing to deflect the blame and sometimes even authorize spending to find a cause. If it then happens again they can blame the scientific community for not having come up with the answer.

Is this not how it would be handled in Spain?
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Old 8th Jul 2009, 07:08
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Ironically .. seem's all the scientifics and people linked to aviation safety discovered suddenly ocean storms and turbulences existence after the AF447 event ...
Sure it's some bussines and some bucks to make there.
I'm sure there is some of that going on. But most of that sort of thing would be people proposing new ideas they will happily research if they are provided with lots of money.

I think this is the other side of that coin.
The evidence is they have been slogging away at this for years and probably spending half their time trying to avoid getting their funding cut because implementation takes more than 3 months. They see people suddenly worried about thunder storms and flying things, and quickly send out a press release saying 'Hey! We're working on fixing that!" They can then use the press clippings when the question of funding again comes up in another 2 months. Now, whether they will ever come up with anything useful is another quesiton.
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Old 8th Jul 2009, 08:42
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Radius of turn

Re: #3243 (JD-EE)

Thanks for replying.

Please note that my post gives turning parameters as a function of angle of bank (angle of roll if you like) - not angle of attack.

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Old 8th Jul 2009, 09:16
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And how is the acars still transmitting in a flat spin?

Good question. The Antenna used for the ACARS transmission is a low profile electronically steerable array.
On system power up, the antenna sweeps through 360o looking for a syncronisation signal and locks to this at the acquisition bearing. The system is then able to track this sycronisation signal on ground and in-flight and If looses lock,which can inevitably happens for a number of reasons, it then enters the re-acquisition mode and re-starts the sweep. This however would not be fast enough, or designed to be able to obtain and re-acquire lock if the aircraft was in a flat spin - therefore would loose the sycronisation path with the Satellite and loss of ACARS transmission.
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Old 8th Jul 2009, 09:21
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PJ (& others) I have a couple of supplementary Q’s

- If one engine (either one) failed, at what shaft (% RPM) would the associated GEN trip out? And;
- Notwithstanding the above, following a single engine (either one) failure, would AC1 remain energized by the other power plant? If yes;
- Following the inevitable ECAM/s, would ACARS output message/s?

On a similar but different subject, at FL350 & M.82:-

- Following an asymmetric failure (whilst in ALTN 2), how promptly would the PF need to get rudder in to avoid yaw induced roll?

Last edited by ARFOR; 8th Jul 2009 at 09:46. Reason: typo
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Old 8th Jul 2009, 09:26
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BEA report - what it is saying in french

Will Frazer/Willy B. I'm afraid there might be a gross misunderstanding of the warning foreword (Avertissement p.1)

"This document has been prepared on the basis of the the first elements gathered during the investigation, without any analysis and even - given the continuing absence of wreckage, the flight recorders, radar tracks and direct testimony - without any description of the circumstances of the accident."

This means the report is made ONLY with the information gathered during the investigation.
- There was no analysis of the data coming from FDR/VCR (available to the investigation team) as they have not even been found
- There was no direct testimony (available to the investigation team) as nobody was there to tell what they have seen.
- There was even no wreckage and no radar track available.

This is clearly stating (to a french speaking person):
This report is not the final one (because it is using only the first elements found, other might be found at a later stage) and, we have nothing available to help us understand, only what was found, with only our eyes to see it and our brains to try to understand what could have caused what we see (= we are the first ones to try to figure out what happened and we know nothing of the major facts: no wreckage to see, no analysis of the FR done by experts because there is no FR available yet, and nobody has seen the crash...).
It is a very humble statement, they know -and they are writing it without any ambiguity- the finding of the wreckage, the finding and analysis of the FR data might completely change the picture.
Again I hope this helps...
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