French air accident investigators today gave an update on their progress-or lack of it-into the disappearance of Air France Flight 447 over the Atlantic on June 1. They say: “…on the basis of available information, it is still not possible to understand the causes and circumstances of the accident.”
Nonetheless there are some significant clues buried in the opacity of the report. They relate to the prime suspect in the case, faulty readings from the Airbus A330’s speed gauges, the effect of those readings on the computers that were flying the airplane, and the influence of the storm system through which Flight 447 was passing at its cruise altitude of 36,000 feet.
Most startling is a revelation that the investigators have been trying
to establish how many incidents there have been involving faulty speed
readings on the Airbus airplanes. They seem to have found at least 53 instances in which flight crews have faced control problems directly caused by flaws in the three exterior gauges, called pitot tubes,
which tell the computers the speed the airplane is flying at-a measure
crucial to all the behavior of all the control systems in flight.
These included what the investigators say were “13 significant events involving 5 airlines operating A330/A340 airplanes.” And they add “Around forty other reported events could not be analyzed completely due to missing data.”
From these incidents it became obvious that there were common features:
In other words, both the Airbus A330, as involved in this disaster, and the A340, which shares the same computerized flight controls, are prone to unpredictable failures of these automated systems triggered by faulty speed readings but…here’s the astonishing conclusion…these are not considered exceptional enough to require special action, which would be either a warning to flight crews of what procedures to follow if this happens or, more extreme, a grounding of the airplanes until a fix is found.
This is akin to a car manufacturer saying that there have been more than fifty instances of a model becoming uncontrollable but not to worry, we’re working on it and when we understand what is going on we’ll fix it.
Things are plainly different for airplane manufacturers and accident investigators.
Two other details jump out from this new report. The first is that the effects of the kind of turbulent storm that straddled the flight path of Flight 447 have not been replicated when the speed gauges are passed by certification-in the words of the report, these tests “do not cover all the situations that modern long-range airplanes can encounter…the composition of the cloud mass is not taken into account precisely.” And second, there are clues from the autopsies carried out on bodies recovered from the Atlantic that the Airbus had fallen from 35,000 very rapidly but had not broken up before hitting the water. “The majority of injuries was,” says the report, “compatible with a violent shock upwards from below.”
Given what can be divined from these new inferences and the characteristic evasions of the investigators, I think I can sense where this is going. On more than fifty occasions flight crews faced with circumstances similar to those confronted on the flight deck of Flight 447 managed to re-boot their systems and carry on. The pilots of 447 did not. The weather itself was not unusual on that route. QED, they must have been overpowered by the speed of the events and thus were in some way inattentive and to blame.
If this is what the combination of the air crash investigators, Air France and Airbus are thinking should be the conclusion, I don’t buy it.
BLACK BOX CHANGES
In the meantime, at least the French investigators have turned their attention to another serious problem exposed by this disaster - that in circumstances like this when it is impossible to retrieve the “black box” flight recorders there should be an alternative way of getting significant data for investigators.
Back in the summer I recommended this. The black box idea dates back to the 1960s, way before the digital age. It was based on the principle that no matter how severe the impact of a crash the flight data recorder (which is not black and is not a box but about the shape and size of a carry-on duffle) should be able to survive it. In other words, to use a nautical term, the data goes down with the ship but can remain intact.
These days you can get data out of an airplane in real time. In fact, the only really salient data retrieved from Flight 447 came from 24 fault messages transmitted from the A330 via satellite to the Air France base in Paris. These were fortuitously part of a system designed to speed maintenance when an airplane arrives at its destination. Indeed, today’s report makes it clear that it was possible for the A330 to send these data bursts to the satellite right up until it hit the ocean.
The problem is that the data needed for maintenance needs to be supplemented by a constant, real-time stream that describes the behavior of every key function of flight. Thus the French investigators now recommend that study should urgently begin into “the possibility of making it mandatory for airplanes…to regularly transmit basic flight parameters (for example position, altitude, speed, heading)."
There are a few technical questions about the bandwidth this would need. But when you consider just how much digital entertainment is playing in the cabin of any modern airplane as it crosses the oceans, adding bandwidth for this purpose is a no-brainer.
Related stories
Timeline: The Long Night of Air France Flight 447
Another Airbus Alarm
These included what the investigators say were “13 significant events involving 5 airlines operating A330/A340 airplanes.” And they add “Around forty other reported events could not be analyzed completely due to missing data.”
From these incidents it became obvious that there were common features:
- They happened in weather conditions that were highly unstable
- The autopilot-which together with the computerized flight management system was actually flying the airplanes at the time-disengaged in all cases
- The faulty speed readings lasted for more than three minutes
- Changes
in the airplanes’ altitude during these events did not exceed a
thousand feet. “The airplane always remained within its flight
envelope” says the report.
In other words, both the Airbus A330, as involved in this disaster, and the A340, which shares the same computerized flight controls, are prone to unpredictable failures of these automated systems triggered by faulty speed readings but…here’s the astonishing conclusion…these are not considered exceptional enough to require special action, which would be either a warning to flight crews of what procedures to follow if this happens or, more extreme, a grounding of the airplanes until a fix is found.
This is akin to a car manufacturer saying that there have been more than fifty instances of a model becoming uncontrollable but not to worry, we’re working on it and when we understand what is going on we’ll fix it.
Things are plainly different for airplane manufacturers and accident investigators.
Two other details jump out from this new report. The first is that the effects of the kind of turbulent storm that straddled the flight path of Flight 447 have not been replicated when the speed gauges are passed by certification-in the words of the report, these tests “do not cover all the situations that modern long-range airplanes can encounter…the composition of the cloud mass is not taken into account precisely.” And second, there are clues from the autopsies carried out on bodies recovered from the Atlantic that the Airbus had fallen from 35,000 very rapidly but had not broken up before hitting the water. “The majority of injuries was,” says the report, “compatible with a violent shock upwards from below.”
Given what can be divined from these new inferences and the characteristic evasions of the investigators, I think I can sense where this is going. On more than fifty occasions flight crews faced with circumstances similar to those confronted on the flight deck of Flight 447 managed to re-boot their systems and carry on. The pilots of 447 did not. The weather itself was not unusual on that route. QED, they must have been overpowered by the speed of the events and thus were in some way inattentive and to blame.
If this is what the combination of the air crash investigators, Air France and Airbus are thinking should be the conclusion, I don’t buy it.
BLACK BOX CHANGES
In the meantime, at least the French investigators have turned their attention to another serious problem exposed by this disaster - that in circumstances like this when it is impossible to retrieve the “black box” flight recorders there should be an alternative way of getting significant data for investigators.
Back in the summer I recommended this. The black box idea dates back to the 1960s, way before the digital age. It was based on the principle that no matter how severe the impact of a crash the flight data recorder (which is not black and is not a box but about the shape and size of a carry-on duffle) should be able to survive it. In other words, to use a nautical term, the data goes down with the ship but can remain intact.
These days you can get data out of an airplane in real time. In fact, the only really salient data retrieved from Flight 447 came from 24 fault messages transmitted from the A330 via satellite to the Air France base in Paris. These were fortuitously part of a system designed to speed maintenance when an airplane arrives at its destination. Indeed, today’s report makes it clear that it was possible for the A330 to send these data bursts to the satellite right up until it hit the ocean.
The problem is that the data needed for maintenance needs to be supplemented by a constant, real-time stream that describes the behavior of every key function of flight. Thus the French investigators now recommend that study should urgently begin into “the possibility of making it mandatory for airplanes…to regularly transmit basic flight parameters (for example position, altitude, speed, heading)."
There are a few technical questions about the bandwidth this would need. But when you consider just how much digital entertainment is playing in the cabin of any modern airplane as it crosses the oceans, adding bandwidth for this purpose is a no-brainer.
Related stories
Timeline: The Long Night of Air France Flight 447
Another Airbus Alarm
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