AF447の事故調査が進む。
ACARSが公開された後、現在はカンタス機事故原因だったIRUを調査して
いるようだ。
ACARSでは、
1.洗面所の一つに故障発生
2.自動操縦解除
3.操縦不能
とのことらしい。
ピトー管異常による速度(高度含む?)の警告があるが、IRUの誤動作の
可能性もあるとのこと。
センサーの誤動作で、自動操縦が解除される誤動作を起こした可能性が
高い。
エアバスCEOが主張していた落雷による原因は少ないようだ。
---AF477 investigators switch focus to computer bug---
Friday, 19 June 2009
http://www.impactpub.com.au/aircargo/index.php?option=com_content&task=view&id=3915&Itemid=60
Investigators seeking the cause of the Air France crash that killed all 228 passengers and crew are now looking at the Airbus’s computer system.
Paul-Louis Arslanian of the French accident investigation bureau said: “I think we may be getting closer to our goal”, referring to a suspicion that a bug in the computerised flight system could be the key.
Arslanian described the speed readings reported in the alerts that the stricken aircraft transmitted automatically to Paris during its final four minutes as “incoherent”.
The follow-on alerts “appear to be linked to this loss of validity of speed information”, he said, adding that the faulty speed data affected other systems that relied on them.
Air France replaced all external speed sensors - the Pitot tubes - on its A330 fleet last week, after acknowledging a “significant” number of failures in recent months, but experts say blocked Pitots alone would not have caused the disaster.
They suspect a flaw in the behaviour of the three independent air data 'inertial reference units' which collect raw flight parameters such as speed and altitude.
One such faulty unit was blamed for a near accident on a Qantas Airbus A330 over Western Australia last October.
---エールフランスＣＥＯ、事故と速度計の関連を疑問視---
2009.06.12 Web posted at: 13:36 JST Updated - CNN
http://www.cnn.co.jp/world/CNN200906120008.html
パリ（ＣＮＮ） リオデジャネイロ発パリ行きのエールフランス機が大西洋上に墜落した事故で、同航空のグルジョンＣＥＯ（最高経営責任者）は１１日の記者会見で、同機に搭載された速度計の不具合が事故につながったとされる説には「確信が持てない」と述べた。
グルジョン氏はフランス国内での記者会見で、「一部メディアによる仮説は、単なる憶測にすぎない」と強調した。
同氏は一方で、事故直前から墜落機と同じＡ３３０などを対象に実施している速度計の交換は、今後も続行すると述べた。この速度計は高い高度で悪天候に遭うと結氷しやすいなどの問題が指摘されている。墜落機の速度計は未交換だった。
事故原因の解明で重要な手掛かりとなるブラックボックスは、現場付近の海底に沈んでいるとみられる。ブラックボックスが発する信号音を求め、仏軍の原子力潜水艦などが捜索を進めている。米海軍は、海底からの信号を探知する特殊な装置を提供している。
一方、仏誌レクスプレスは１０日、同機の搭乗者の中に、イスラム系テロリストに関連する氏名の乗客２人が含まれていたと伝えた。これに対し、米連邦捜査局（ＦＢＩ）のテロリスト監視センター（ＴＳＣ）は、「われわれの監視対象となっている人物が墜落機に乗っていたことを確認する情報はなにもない」と述べている。
---AF477 ACARS--
http://www.eurocockpit.com/images/acars447.php
---Error Messages From Air France Jet Offer Details but Little Insight---
By MATTHEW L. WALD
Published: June 12, 2009
http://www.nytimes.com/2009/06/13/world/13plane.html?ref=world
WASHINGTON - A transcript of the error messages sent by Air France Flight 447 makes clear how many details the investigators have about the last minutes of its flight - and how little it tells them.
A routine message about a malfunction in one of the plane’s lavatories is followed by a worrisome one that says that the speed sensor has a problem, but the cascade that follows is hard to parse.
The plane, an Airbus A330, crashed June 1 on a flight from Rio de Janeiro to Paris, with 228 passengers and crew members. Searchers have recovered 44 bodies, including three on Friday. The plane was approaching a line of huge thunderstorms, but these were not unusual for the location and season, experts said.
The transcript was posted on www.eurocockpit.com, and its authenticity was confirmed by industry officials. The error messages were received by an Air France maintenance base.
The messages begin with a routine one, a problem in one of the lavatories. But an hour and 47 minutes later, another message indicates that the autopilot has switched itself off, an event that can be caused by a variety of problems.
Soon after, the plane reports it has lost a computer protection that overrides any commands from the cockpit that would threaten the flight’s stability. The Airbus has a computer that accepts commands to change various settings and transmits them to the rudder, flaps, ailerons and other parts, but only if such commands do not threaten stability. For example, the computer would not let the pilot pitch the nose so high that airflow over the wings would be disrupted and lift would be lost.
But the computer switched to a mode in which the protections either disappeared or could be overridden. Experts said that could happen if turbulence was so severe that the plane was thrown into an unusual attitude, but it might also be caused by the breakdown in the speed-sensing system.
The messages also indicate that warning flags appeared on the displays of the captain and the first officer indicating a problem with the speed sensing.
Jets sense their speed with a system that includes a part called a Pitot tube, an open-ended, forward-facing tube. Pressure in the tube varies with speed and is compared with the pressure in an opening facing the side of the plane.
The plane that crashed had a model of Pitot tube that Airbus had recommended be replaced because it had a tendency to collect moisture, giving inaccurate readings. Air France was in the process of replacing the tubes on its A330s, but it had not gotten to that one.
The problem was not perceived as urgent - and, in fact, it has not yet been proven so. Regulators in Europe and the United States have not made the replacement mandatory.
Another message indicates a problem with the rudder travel limiter, a system that prevents the pilot from turning the rudder too hard when the plane is flying fast.
The functioning of the rudder travel limiter was an issue in a previous Airbus crash, an A300 in New York in November 2001, but in this case the message might simply indicate that the computers, confused about the speed at which the plane was flying, decided to lock the rudder into the narrow range of motion allowed at high speed.
A later message indicates a disagreement among navigation devices that receive information from the speed-sensing system. And another shows problems with one of the three primary computers that control the flight, and one of the two secondary computers, possibly for the same reason.
Then a flight management computer, which keeps track of the required course and altitude, shows a fault.
The last transmission shows that air pressure in the cabin was dropping rapidly. Cabin pressure, which is ordinarily maintained at a level equivalent to 10,000 feet above sea level, was changing at a rate equivalent to more than 1,800 feet per minute. That advisory may mean the plane has depressurized or broken up in the air.
Aviation experts caution that the error transcript has two main weaknesses: the messages are sent in batches, and within a batch, their order is not meaningful. And some were probably caused by the cockpit crew trying to reset components that were acting up, like a person trying to reboot a computer, rather than by new failures.
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