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Walter Watts
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Hopes dim for 228 aboard missing French jet
« on: 2009-06-02 00:25:15 » |
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Hopes dim for 228 aboard missing French jet
http://www.msnbc.msn.com/id/31040692/
Hermit.
You're a pilot.
Do commercial pilots really tango with horse-latitudes squall lines of indeterminate machismo?
Seems very sterile statistics to me....
Walter
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Walter Watts
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Re:Hopes dim for 228 aboard missing French jet
« Reply #1 on: 2009-06-02 00:41:49 » |
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I hate to speculate, but I'm thinking 200+ passengers got about 14 minutes of really, really hard pounding by turbulence as the last 14 minutes of their lives.
That really, really sucks.
Walter
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Re:Hopes dim for 228 aboard missing French jet
« Reply #2 on: 2009-06-02 01:25:59 » |
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[Walter Watts] Do commercial pilots really tango with horse-latitudes squall lines of indeterminate machismo?
[Hermit] They do indeed. Modern aircraft (and this was a very safe and relatively new airframe with under 20,000 hours on it) have very good instruments (including weather radar and strike sensors) and reasonably good forecasts and modern transport aircraft are pretty immune to normal weather. Weather radar allows you to fly around nasty squalls. Due to the cost of fuel, nobody routes aircraft around storms unless they really are exceptional. Even then, operators prefer pilots to thread the needle, and as is shown by the fact that other planes preceded and followed the lost French flight without any trouble, this isn't very tricky when your instruments and judgement are working correctly.
[Hermit] For what it is worth, it takes an awful lot to down a modern aircraft accidentally, which is why most "accidents" we get to hear about are caused by a lengthy sequence of failures, usually involving both technical failures and failures of judgement. My working hypothesis is that this case is no different, that the Captain (who had immense experience (11,000+ hours, over 1,100 hours in type)) tootled off to his hammock after the take-off, leaving one of the two first officers managing the cockpit; that they then lost the weather radar somehow (technical glitch, lightning, operator error, whatever) while flying into storms with tops exceeding 41,000 feet - and then wasted valuable time trying to solve the problem; or tried calling the Captain; rather than simply turning the plane around and scooting back towards the largest lump of concrete capable of supporting a landing. While flying blind they encountered a vertical draft, massive turbulence or large hailstones which then caused sufficient damage (it is a twin engine aircraft with a somewhat greater statistical susceptibility to FOD than a quad engine, but of course a lower probability of an engine failure) to result in a loss of command and communication capabilities with the sad but almost inevitable consequences.
[Hermit] This hypothesis has the virtue of matching all the known data, explains how poor judgement might have crept into the mix (an fo with a massive service differential, as was the case here, would prefer to solve a problem himself or wait to gather all needed information before calling the Captain), and not contradicting anything we know about modern aircraft and their pilots.
[Hermit] The black boxes will likely be recovered, and ought to be able to confirm or invalidate this.
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Re:Hopes dim for 228 aboard missing French jet
« Reply #3 on: 2009-06-02 04:49:05 » |
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I have a private license (haven't used for some time), but from what little I know about severe thunderstorms, sticking a fly-by-wire aircraft into known lightning would just tend to grate on my sense of due caution.
Walter
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Re:Hopes dim for 228 aboard missing French jet
« Reply #4 on: 2009-06-02 13:45:33 » |
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[Walter Watts] I have a private license (haven't used for some time), but from what little I know about severe thunderstorms, sticking a fly-by-wire aircraft into known lightning would just tend to grate on my sense of due caution.
[Hermit] You can't avoid all lightening strikes, though a strike detector allows you to fly-around many of them (and it is a good idea as strikes usually mean fast moving air currents). Still strikes are often triggered by the passage of modern high-speed aircraft raising local energy levels above the dielectric breakdown point.
[Hermit] This means that modern aircraft have to be, and are, very carefully designed to ensure that physics protects them. Refer http://en.wikipedia.org/wiki/Faraday_Cage. And it does. So it is pointless to try to avoid lightning except to avoid flying into turbulence, hail or water at a level where it can affect the engines, particularly as trying to fly around lightning would dramatically increase the duration of lights, waste fuel, increase pollution and statistically increase the probability of accidents.
[Hermit] All in all, I would not expect the fly-by-wire controls to be implicated in the event sequence except peripherally after so many vital systems had been lost that it did not matter.
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Re:Hopes dim for 228 aboard missing French jet
« Reply #5 on: 2009-06-02 19:23:30 » |
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Here's a take on it....
decent enough video is on this page:
http://www.nytimes.com/2009/06/03/world/europe/03plane.html?pagewanted=1
--excerpted from below
"The new Airbus 330 was a “fly-by-wire” plane, in which flight controls operate electrically rather than by cables or hydraulics. Fly-by-wire systems can automatically conduct maneuvers to prevent an impending crash, but some Airbus jets will not allow a pilot to override the self-protection mechanism.
On both Qantas flights, the planes’ inertia sensors sent faulty information into the flight computers, making them take emergency measures to correct problems that did not exist, sending the planes into sudden dives.
If the inertia sensor told a computer that a plane was stalling, forcing it to drop the nose and dive to pick up airspeed, and there was simultaneously a severe downdraft in the storm turbulence, “that would be hard to recover from,” Mr. Weber said."
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The New York Times
June 3, 2009
Wreckage Is From Jet, Brazilian Official Says
By DONALD G. McNEIL Jr. and CHRISTINE NEGRONI
Wreckage spotted by Brazilian military planes in the Atlantic Ocean is that of the missing Air France Flight 447, the Brazilian minister of defense said at a news conference on Tuesday afternoon, confirming that the passenger jet had crashed, several news agencies reported. The jet, bound for Paris from Rio de Janeiro with 228 aboard, disappeared Sunday night without any distress call.
Nelson Jobim, Brazil’s defense minister said “without a doubt” that the debris was that of Air France Flight 447, according to Reuters. Military planes located the wreckage, which included metallic and non-metallic pieces in a three-mile swath in the ocean, ashope of finding survivors all but vanished.
The debris included an “an orange life vest, an aircraft seat, a drum, kerosene and oil,” according to an earlier statement from the Brazilian military. The flotsam was sighted about 600 miles off Brazil’s northeastern coast and about 400 miles northeast of the Brazilian island of Fernando do Noronha, the military said, roughly along the plane’s scheduled flight path.
The French Prime Minister François Fillon said earlier in the day that the confirmation of the debris would “allow us to better determine the search zone."
"We are in a race against the clock in extremely difficult weather conditions and in a zone where depths reach up to 7,000 meters," he told lawmakers in the lower house of French parliament Tuesday, The A.P. reported.
Working throughout the day on =Tuesday, 10 airplanes and a number of ships from Brazil, as well as aircraft from France, Spain, and other nations hunted for signs of the jetliner. The United States Navy sent a P-3C Orion maritime surveillance airplane to aid in recovery operations. The aircraft, with a crew of 21, was scheduled to take off from an airfield in Natal, Brazil, at 11 p.m. local time, according to Jose Ruiz, a spokesman for the United States Southern Command.
At the same time, investigators grappled with the mystery of how a well-maintained modern Airbus 330, built to withstand electrical and physical buffeting, could have gone down so silently.
Brazil’s Air Force said the first sighting of the debris came at around 1 a.m. Tuesday from a R-99 reconnaissance plane searching close to the plane’s last reported position. Based on that report, a C-130 returned to the area shortly after dawn and spotted debris 37 miles from the original sighting.
The military said it would try to collect the debris and analyze it, although Brazilian Navy ships are not expected to arrive at the area until Wednesday. Brazil’s Navy said in a statement on Tuesday that three commercial ships in the vicinity were helping with the search, The Associated Press said.
The sighted wreckage is “very little material in relation to the size” of the Air France plane, Air Force Col. Jorge Amaral told reporters at a news conference on Tuesday morning. He added that there was no sign of life amid the debris.
Air France said the passenger list included 61 French citizens, 58 Brazilians and 26 Germans. There were 12 crew members, 11 of them French and one Brazilian. While the airline did not release a passenger list Tuesday, news of who was aboard began to trickle in from friends, family, and employers. .
Two Americans were also on board, Air France said, and a spokesman for Devon Energy, based in Oklahoma City, identified them as Michael Harris, 60, a geologist with the company living in Brazil, and his wife, Anne, 54.
Air France Flight 447 encountered bad weather and turbulence about four hours after takeoff from Rio, and the company said an automated warning system on the four-year-old plane beamed out a message about electrical problems 15 minutes later. The signals were not sent as distress calls, and they were not read for hours, until air traffic controllers notified the airline that the plane’s crew had not radioed in on schedule. As is common with transoceanic flights, the plane was too far out over the sea to be tracked on land-based radar from Brazil or the first point across the Atlantic, Senegal. Whether its location was captured by satellite or other planes’ radar was not immediately known.
The flight took off from Rio de Janeiro at 7:30 p.m. local time (6:30 p.m. Eastern time), and its last verbal communication with air traffic control was three hours later, according to a statement from Brazil’s civil aviation agency. At that time, the flight was at 35,000 feet and traveling at 520 miles per hour.
The last communication from it came 40 minutes after that — a series of automatic messages indicating it had suffered an electrical-system malfunction. The Associated Press reported that it also suffered a loss of cabin pressure.
Brazilian officials said the plane disappeared over the Atlantic somewhere between a point 186 miles northeast of their coastal city Natal and the Cape Verde islands off Africa. The tropics of the Northern and Southern Hemispheres mix there, sometimes creating violent and unpredictable thunderstorms that can rise to 55,000 feet, higher than commercial jetliners can go.
Experts were at a loss to explain fatal damage from lightning or a tropical storm, both of which jetliners occasionally encouter, despite efforts to avoid them. Pilots are trained to go over or around thunderstorms rather than through them — as much out of concern for passengers’ nerves as for the planes’ safety. Brigitte Barrand, an Air France spokeswoman, said the highly experienced pilot, a 58-year-old Frenchman, had clocked 11,000 flying hours, including 1,100 hours on Airbus 330 jets.
The two co-pilots, also French, were 37 and 32 years old, and both had thousands of flight hours in Airbus A330s, the company said.
“A completely unexpected situation occurred on board the aircraft,” Mr. Gourgeon, the Air France CEO, told France’s LCI television.
Julien Gourguechon, who has been an Air France pilot for a decade, said: “Lightning alone is not enough to explain the loss of this plane, and turbulence alone is not enough. It is always a combination of factors.”
By some estimates, jetliners are typically hit by lightning at least once a year. But the strike normally travels across the plane’s aluminum skin and out the tail or a wingtip. Passengers are insulated in the nonconductive, largely plastic interior, and vital electronic equipment is shielded.
Large hailstones created by some thunderstorms have been known to break windshields or turbine blades, though pilots would be likely to rapidly report something like that.
The missing aircraft was relatively new, having gone into service in April 2005. Its last hangar maintenance check was on April 16, Air France said. No Airbus A330-200 passenger flight ever had a fatal crash, according to the Aviation Safety Network.
Hans Weber, head of the Tecop aviation consulting firm in San Diego, offered a hypothesis about the episode, based on his knowledge of severe losses of altitude by two Qantas jets last year.
The new Airbus 330 was a “fly-by-wire” plane, in which flight controls operate electrically rather than by cables or hydraulics. Fly-by-wire systems can automatically conduct maneuvers to prevent an impending crash, but some Airbus jets will not allow a pilot to override the self-protection mechanism.
On both Qantas flights, the planes’ inertia sensors sent faulty information into the flight computers, making them take emergency measures to correct problems that did not exist, sending the planes into sudden dives.
If the inertia sensor told a computer that a plane was stalling, forcing it to drop the nose and dive to pick up airspeed, and there was simultaneously a severe downdraft in the storm turbulence, “that would be hard to recover from,” Mr. Weber said.
Donald G. McNeil Jr. reported from New York, and Christine Negroni from Greenwich, Conn. Reporting was contributed by Mark McDonald from Hong Kong, Alan Cowell from London, Sharon Otterman, Liz Robbins and Micheline Maynard from New York, Caroline Brothers from Paris, Alexei Barrionuevo from Buenos Aires, Brian Knowlton from Washington, and Andrew Downie from São Paulo, Brazil.
Copyright 2009 The New York Times Company
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Walter Watts
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Re:Hopes dim for 228 aboard missing French jet
« Reply #6 on: 2009-06-02 19:34:47 » |
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So, you want moi to relenquish control of a real jumbo-jet full of meatpuppets to a running computer sim in early summer equatorial waters that are blossoming 50, 000 ft. + tops?
Oh, and don't forget. Those roiling skies are coming straight at you.
No fucking way I'm going to play footsies with that weather in front of me, so yes we seem to agree, NOT turning tail and running was the major causal on this one.
Walter
<who's obviously having a hard time with the adoption of such lax attitudes in the commercial aviation industry>
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Re:Hopes dim for 228 aboard missing French jet
« Reply #7 on: 2009-06-02 20:26:18 » |
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Re:Hopes dim for 228 aboard missing French jet
« Reply #8 on: 2009-06-03 17:23:00 » |
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Was Air France flight brought down by turbulence or hail?
100 m.p.h. winds, hail, and rain might have brought Flight 447 down, says a former Air Force meteorologist.
[ Hermit : Your list is strange. I could understand the omission of Libyan Arab Airlines, shot down by Israel in 1973 with a loss of 108 lives on the grounds that the list may have only looked at events subsequent to that, but I cant understand why it omits Korean Air Lines 007, shot down by the USSR in 1983 with a loss of 289 lives, and Iran Air 655, shot down by the USA in 1988 with a loss of 290 lives (and after which the crew of the vessel responsible Vincennes were awarded Combat Ribbons and the CO a Legion of Merit), representing the 7th and 8th worst airline disasters in terms of fatalities. I recommend http://en.wikipedia.org/wiki/List_of_notable_accidents_and_incidents_on_commercial_aircraft for a more comprehensive list.
Please note that while everything was operating normally, a 300 mile storm with tops above the airframe ceiling (41,000 feet) simply meant that two pilots paying careful attention to the instruments were needed on deck to fly around the worst of the storm. This is standard procedure and no reason to make serious deviations from the flight plan or to cut & run. If the weather radar or strike sensor or both were lost, that would change things and I still suspect that this is a likely component in the failure sequence, as with the aid of those instruments it is quite easy to avoid the nastier patches. Unfortunately, if, as it now appears, they were lost after 12 minutes of transiting part of a severe storm, the crew might well have decided to face the unknown rather than go eye to eye with something particularly unpleasant they knew was squatting behind them.
Below is the best article on flight 447 I have found to date. Not unsurprisingly I see it as saying more or less the same things as I did. I'd add to the article something that might not be completely clear, and that is that pilot training emphasizes that altitude is life - and unless there is a fire on board, it usually is. The lower you fly in a storm, the more likely you are to be hit by really large ice or to ingest flame quenching amounts of water. Compared to this, lightening isn't a major concern. In anycase, given the reported airframe altitude, apparent storm energy and temperature, ice and water can be next to eliminated from the analysis, leaving extreme turbulence as the most likely culprit. From the combination of pressure loss and major electrical malfunctions, I'm thinking that they lost most or all of the empennage quite early in the failure sequence.]
Source: Christian Science Monitor
Authors: David Clark Scott
Dated: 2009-06-02
Was Air France flight 447 brought down by a 100 m.p.h. updraft?
Or were its two jet engines snuffed out by hail or heavy rains?
In the absence of a black box, the leading theory now is that the Airbus 330-200 was brought down by a 300-mile-wide band of tropical thunderstorms that it could fly neither around nor over.
Brazil’s defense minister confirmed Tuesday afternoon that military planes found a three-mile path of wreckage in the Atlantic, hundreds of miles from Fernando de Noronha, a Brazilian archipelago.
Professional pilots and meteorologists are digging through the available data – flight routes, satellite images, aircraft specifications, and weather reports – and spinning out several likely causes.
One of the most detailed and cogent pieces of analysis of Flight 447’s last minutes – winning the praise of pilots around the world – is a blog by Tim Vasquez. [ Hermit : Walter you really want to read this. ]
Mr. Vasquez is a former US Air Force meteorologist. He now consults and publishes weather forecasting texts and software.
Vasquez plots the likely flight path of Air France 447 and overlays it on satellite imagery and weather reports in the area at the time:It appears AF447 crossed through three key thunderstorm clusters: a small one around 0151Z, a new rapidly growing one at about 0159Z, and finally a large multicell convective system (MCS) around 0205-0216Z. Temperature trends suggested that the entire system was at peak intensity … Air France says that it received an automated message from Flight 447 reporting electrical faults and loss of pressurization. Vasquez says that message was sent just as the jet was nearing the final edge of the storm cells, but after being battered by turbulent updrafts as high as 100 mph for about 12 minutes (or 75 miles).
Several pilots, in comments on his site, agree that turbulence was probably a factor.
AccuWeather.com, a private forecasting firm, issued a statement Tuesday, offering a similar theory based on its own data:The plane appears to have flown into or near a large cluster thunderstorms that were in the development stages northeast of Fernando De Noronha, which is located off Brazil’s northern coast, and along the Intertropical Convergence Zone (ITCZ), the belt of low pressure that surrounds the Earth at the equator.
Based on weather information from Fernando De Noronha, the updrafts associated with the thunderstorms may have reached up to 100 m.p.h. Such an updraft would lead to severe turbulence for any aircraft. In addition, the storms were towering up to 50,000 feet and would have been producing lightning. At its last check-in time, the Air France aircraft was flying at 35,000 feet. A check of the Airbus 330-200 specifications shows that the aircraft has a ceiling of 41,000 feet.
It couldn’t fly above a thunderstorm with a 50,000-ft. top. It would have been using its onboard radar to try to pick a path through the storm cells.
Vasquez also makes note of another possible cause: The jet engines were shutdown by rain or hail.A dual engine flameout due to precipitation or ice ingestion is a noteworthy possibility as has been discussed on other sites (specific to the A330 type too). The precipitable water content in any tropical weather system can run very high. [ Hermit : I disagree with this reading of Vasquez. He is of the opinion (as am I) that there cannot have been any water involved as the temperature was too low, and that the storm had insufficient energy to have cycled large ice to FL 350, although graupel as well as clear and rime ice may have been present. ] Vazquez says that lightning may also have been a factor. And Accuweather raises the same point:Tropical thunderstorms and the lightning patterns generated by them are different from storms that typically occur over the United States. Studies have shown that the top region of tropical thunderstorms is highly charged and more conducive to lightning, which indicates that an airplane flying near the top of a tropical thunderstorm could be more susceptible to a lightning strike. Tropical thunderstorms are also notorious for producing frequent cloud-to-cloud, as well as cloud-to-air lightning. But commercial pilots and aviation safety experts say that such jets are designed to take lightning strikes without significant damage. Still, the fact that this was a fly-by-wire aircraft (where the control surfaces are moved by electrically signaled controls, rather than cables, chains, and pulleys) raises doubts among some pilots. [ Hermit : Only those not familiar with these sorts of systems and how they have been tested. Yes, it is possible that lightning was implicated, but it is also more possible that something went wrong in the cargo hold as a result of extreme turbulence - or that the entire empennage fell off. Based on my knowledge of what can and has been tested and how, I would put the relative probabilities of these as 1:1000, 10:1000 and 100:1000 respectively. ]
Most pilots, in the absence of more information, are leaning toward turbulence or engine flameout as the most likely causes of AF447’s demise. [ Hermit : As do I, though with the current level level of knowledge I am tending to strongly suspect turbulence. A flameout at 35,000 feet would not in and of itself caused a depressurization or loss of multiple electrical systems. ]
But there is at least one faction within the meterological community that disagrees with the theory that the Air France jet was brought down by a storm.
The World Meteorological Organisation (WMO) says that two Lufthansa jets – heading from South America to Europe – flew through the same area where the thunderstorms were reported, about half an hour before the AF447.
The two aircraft collected wind and temperature information during their flight as part of a WMO program.On Monday, a source with access to the data transmitted to WMO told Reuters in Paris that the two jets passed through turbulence before and after the plane without incident…. More than 5,000 aircraft collect data under WMO’s Aircraft Meteorological Data Relay Programme (AMDAR). The two Lufthansa jets participated in the system, but not the Air France flight, according to the Geneva-based United Nations agency.
But Herbert Puempel, chief of the WMO’s aeronautical meteorology division, also told Reuters that thunderstorms tend to be very localized. If one plane reports turbulence, another one passing through the same area even shortly afterward is unlikely to experience it. [ Hermit : And I have to agree. Even instruments dropped simultaneously into tropical storms often show completely different pictures to one another, and multiople flights through the same formation often give radically different sets of data. ]
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Re:Hopes dim for 228 aboard missing French jet
« Reply #9 on: 2009-06-03 20:33:10 » |
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I also found it interesting that the last act of the Droid: Class "Airbus A330", with flight number 447, was to transmit back to its overlords in its last frenetic 15 minutes of existence data that essentially translates to "This aircraft is completely and totally fucked. Goodbye."
Walter
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Re:Hopes dim for 228 aboard missing French jet
« Reply #10 on: 2009-06-03 20:36:23 » |
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[Hermit]
But commercial pilots and aviation safety experts say that such jets are designed to take lightning strikes without significant damage. Still, the fact that this was a fly-by-wire aircraft (where the control surfaces are moved by electrically signaled controls, rather than cables, chains, and pulleys) raises doubts among some pilots. [ Hermit : Only those not familiar with these sorts of systems and how they have been tested. Yes, it is possible that lightning was implicated, but it is also more possible that something went wrong in the cargo hold as a result of extreme turbulence - or that the entire empennage fell off. Based on my knowledge of what can and has been tested and how, I would put the relative probabilities of these as 1:1000, 10:1000 and 100:1000 respectively. ]
[I'll buy that.]
good to type at ya,
Walter
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Re:Hopes dim for 228 aboard missing French jet
« Reply #11 on: 2009-06-03 20:46:39 » |
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Here's my latest theory Hermit....
They ran across a severely strong outflow boundary (updraft), were pulled above the turbofan engines's service ceilings, flamed out, then rudely dumped into the inflow boundary (downdraft) that usually accompany outflows.
Then they were all on the express elevator to the basement, which, as you point out, would have the aircraft broken apart long before reaching the mezzanine.
Walter
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Re:Hopes dim for 228 aboard missing French jet
« Reply #12 on: 2009-06-03 23:07:01 » |
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The trouble with this theory is that all of the engine packs fitted to the A330 have FADEC including automatic reigniters. Unless there was significant structural damage during the postulated altitude excursion the control system would bring the fans back on-line in very short short order, irrespective of attitude, unless deliberately countermanded by the flight-crew. Also the A330 has a 4 way segmented bus - which again means that even the simultaneous loss of alternator power from both engines would not result in loss of critical circuits (unless you regard the weather radar as critical, but after an excursion such as you have suggested, nobody would be looking at anything but the critical aviation and engineering screens until the airframe was stabilized anyway).
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Re:Hopes dim for 228 aboard missing French jet
« Reply #13 on: 2009-06-05 01:18:50 » |
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In an otherwise unexceptional article, more in support of structural damage:
Two officials told The Associated Press that investigators are looking at the possibility an external probe that measures air pressure may have iced over. The probe feeds data used to calculate air speed and altitude to onboard computers. Another possibility is that sensors inside the aircraft reading the data malfunctioned.
If the instruments were not reporting accurate information, the jet could have been traveling too fast or too slow as it entered turbulence from towering bands of thunderstorms, according to the officials.
"There is increasing attention being paid to the external probes and the possibility they iced over in the unusual atmospheric conditions experienced by the Air France flight," one of the industry officials explained to the AP, speaking on condition of anonymity because he isn't authorized to discuss the investigation publicly.
Meteorologists said the Air France jet entered an unusual storm with 100 mph updrafts that acted as a vacuum, sucking water up from the ocean. The incredibly moist air rushed up to the plane's high altitude, where it quickly froze in minus-40 degree temperatures. The updrafts also would have created dangerous turbulence.
The jetliner's computer systems ultimately failed, and the plane broke apart likely in midair as it crashed into the Atlantic on a flight from Rio de Janeiro to Paris Sunday night.
Independent aviation experts said it is plausible that a problem with the external probe — called a "pitot tube" — or sensors that analyze data collected by the tube could have contributed to the disaster.
The tubes have heating systems to prevent icing. But if those systems somehow malfunctioned, the tubes could quickly freeze at high altitude in storm conditions, said the other industry official, who also was not authorized to discuss the investigation.
Other experts outside the investigation said it is more likely that the sensors reading information from the tubes failed.
"When you have multiple system failures, sensors are one of the first things you want to look at," said John Cox, a Washington-based aviation safety consultant and former crash investigator for the Air Line Pilots Association.
Jetliners need to be flying at just the right speed when encountering violent weather, experts say — too fast and they run the risk of breaking apart. Too slow, and they could lose control.
"It's critical when dealing with these conditions of turbulence to maintain an appropriate speed to maintain control of the aircraft, while at the same time not over-stressing the aircraft," said Bill Voss, president and CEO of the Flight Safety Foundation in Alexandria, Va.
France's accident investigation agency has established that the series of automatic messages gave conflicting signals about the plane's speed, and that the flight path went through dangerously stormy weather. The agency warned against any "hasty interpretation or speculation" after the French newspaper Le Monde reported, without naming sources, that the Air France plane was flying at the wrong speed.
<snip>
With the crucial flight recorders still missing, investigators were relying heavily on the plane's automated messages to help reconstruct what happened as the jet flew through thunderstorms.
The last message from the pilot was a manual signal at 11 p.m. local time Sunday saying he was flying through an area of black, electrically charged cumulonimbus clouds that come with violent winds and lightning.
At 11:10 p.m., a cascade of problems began: the autopilot had disengaged, a key computer system switched to alternative power, and controls needed to keep the plane stable had been damaged. An alarm sounded indicating the deterioration of flight systems. Then, systems for monitoring air speed, altitude and direction failed. Controls over the main flight computer and wing spoilers failed as well. At 11:14 p.m., a final automatic message signaled loss of cabin pressure and complete electrical failure as the plane was breaking apart.
The pilot of a Spanish airliner flying nearby at the time reported seeing a bright flash of white light plunging to the ocean, said Angel del Rio, spokesman for the Spanish airline Air Comet.
The pilot of the Spanish plane, en route from Lima, Peru to Madrid, said he heard no emergency calls.
I agree that if the airspeed was too high on entry to turbulence that it could lead to an immediate breakup, and that too slow an airspeed could lead to a rapid loss of control. This could of course happen to any plane under manual or autopilot control if the pitot tubes or interface was non functional. From the early automated bus transfer message, which points to damage in the sub-cockpit through centre hull area, in the absence of more details about "controls needed to keep the plane stable had been damaged," I am now inclined to think that the structural trouble began near the wing, even though this is usually the strongest part of an aircraft (and why empennage damage is much more likely).
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Walter Watts
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Re:Hopes dim for 228 aboard missing French jet
« Reply #14 on: 2009-06-05 02:15:55 » |
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a touch more on the story.....
--Walter
PS--Another possibility is they may very well have been flying too leisurely, ie. too slow for wind conditions, improper trim, or both.
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latimes.com
http://www.latimes.com/news/nationworld/world/la-fg-brazil-crash5-2009jun05,0,6741218.story
From the Los Angeles Times
Air France jet's flight-control system under scrutiny
Automated messages before the crash point to a failure of the system that flies the plane most of the time, experts say. Weather looks like less of a factor.
By Ralph Vartabedian
June 5, 2009
A sophisticated flight-control system that relies on electronic instruments and computers came under growing scrutiny Thursday as investigators tried to unravel the mysterious crash of an Air France Airbus 330 into the Atlantic.
A series of messages sent automatically by the jet moments before it plunged into the ocean late Sunday with 228 passengers and crew members aboard has raised speculation that the crash might have involved a malfunction of the automated system that flies the plane most of the time.
One of the messages reported that one of the plane's navigational control units had failed and that, almost simultaneously, the autopilot system had disengaged.
The sequence of events forced the crew of Flight 447 to fly the jet manually, a difficult task on an Airbus traveling at high altitude near its maximum speed, aviation experts said. Any significant change in airspeed could have caused the plane to lose lift or stability, both potentially deadly conditions.
Meanwhile, new analysis of the weather in the vicinity at the time of the crash appears to cast doubt on earlier reports that the plane encountered severe thunderstorms, lightning and wind gusts. Though there were storms, they were almost certainly less intense than those sometimes encountered above the United States, and lightning was at least 150 miles away, said Greg Forbes, severe-weather expert for the Weather Channel.
Forbes said an examination of weather data for Sunday, including satellite images, indicated updrafts of perhaps 20 mph, far from the initial reports of 100 mph.
"I wouldn't expect it to be enough to break apart the plane," Forbes said.
Though experts generally agreed Thursday that weather alone did not explain the crash, USC aviation safety expert Michael Barr said the investigation was still wide open.
"You can never disregard any possibility until you can prove what happened," Barr said. "The key here is to determine what the crew could have done after the initial event. Or was there nothing they could have done and they were just along for the ride?"
Air France executives said the plane had sent out a series of messages indicating technical failures, confirming news reports in Brazil and data that U.S. aviation experts had already gained access to.
A series of serious electronic breakdowns occurred on the Airbus over a four-minute period before the jet plunged into the sea, said Robert Ditchey, an aeronautical engineer, pilot and former airline executive.
The sequence started with an autopilot failure and a loss of the air data inertial reference unit, a system of gyroscopes and electronics that provides information on speed, direction and position. That system has been involved in two previous incidents that caused Airbus jetliners to plunge out of control, though the pilots were able to recover.
The automated messages then indicate that a fault occurred in one of the computers for the major control surfaces on the rear of the plane. Such a failure would have compounded the problems, particularly if the pilots were flying through even moderate turbulence.
The last message indicates that multiple failures were occurring, including pressurization of the cabin. Such a message would have reflected either a loss of the plane's pressurization equipment or a breach of the fuselage, resulting in rapid decompression.
All of these issues would have made the plane difficult to control.
When cruising at high altitude, a plane must fly within a fairly small window of speed, said Robert Breiling, an aviation safety expert in Florida. If speed drops even slightly, the plane can lose lift. If the speed is too high, it causes instability over the control surfaces.
"Flying a big jetliner at high altitude without autopilot, you have your hands full," Breiling said.
Ditchey said the Airbus software would have left the crew with a very small margin of error, where even minor buffeting could have boosted the risk of losing control.
"As they got into a degraded regime, they probably got into a bigger and bigger pickle," Ditchey said.
ralph.vartabedian @latimes.com
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