Readers with longer attention spans than ‘Puter will remember the Czar’s suspicion that the truth about the May 2009 crash of Air France Flight 447 would not come from the French government, because the truth would expose a problem in Air France’s Airbus A330-200 planes.

And, well yeah.

A combination of the French airline pilots union, an aerospace manufacturer named Thales who suspected a piece of their equipment was involved, and Germany’s BFU (similar to the US NTSB)* were brought together in a report in Der Spiegel found by the Volgi and forwarded to the Czar for analysis.

Basically, for those who wish not to read the article, Thales manufactures, among other things, pitot tubes for aircraft. Pitot tubes measure the speed of air or fluid moving through a small tube: they are used on aircraft for measuring the speed of the aircraft. Thales was concerned that under certain conditions, their pitot tubes could ice up. If this happens, the pilots are given a false reading: the plane appears to be moving much slower than it is. The pilots could accelerate the plane to compensate. Of course, this fails to clear the problem because the tube is clogged with chunks of ice. Seeing the plane failing to increase speed, the pilots assume there is a massive headwind, and get concerned that the plane is about to stall. Standard practice is to counter the headwinds by adjusting the flaps. The pilots change the flaps, not realizing the plane is in fact traveling at tremendous speed, and the plane immediately loses control and lift, crashing.

This has happened many times already (about three dozen times). And it is not Thales’ design or device: this has happened with pitot tubes of different manufacturers and on a variety of equipment, not just Airbus planes. But Thales was concerned that Airbus was over-relying on their design, and notified Airbus of their concerns. Airbus responded by putting heaters in the pitot tube.

However, ongoing incidents indicated that this was not enough: Airbus identified several incidents on their own planes showing the heaters are insufficient to melt ice at the absurdly cold temperatures of the upper troposphere during a thunderstorm. So they made a €300,000-per-aircraft software patch available for the flight control computers that would guide pilots to correcting the situation by using GPS to pinpoint the plane’s speed and altitude and linking this data to the plane’s angle of attack (AOA) sensors that measure lift under the wings. The result is that the software tells the pilots where to position the thrust to maintain perfect lift without knowing the speed of the aircraft. This software package, shown here as it appears to the pilot in a crisis, is called the Back-Up Speed Scale, or BUSS. A330 pilots say it works.

Air France opted not to pay for the software upgrade on AF447.

They did not realize the plane was falling out of the sky in a stall, until it landed nearly flat on its belly so hard that the tail fin ripped off and cartwheeled forward.What appears to have happened, as near as we can tell without full data, is that AF 447 was flying through turbulent thunderstorm weather, with an extremely cold exterior temperature. The pitot tubes froze, and the pilots began to suspect their plane was losing speed fast. They increased the throttle to no avail, not realizing the plane was now accelerating into turbulence. They adjusted the flaps, and still saw the plane was losing speed. With no BUSS system to help them, the two back up pilots (there is evidence to suggest the captain was in the cabin, not the cockpit), suddenly realized the plane was dropping out of the sky. With the turbulence, they probably could not viscerally tell what the plane was doing. Alarms began to light up, but nothing seemed to work. In a frantic effort, the pilots rebooted the primary and beckup flight control systems. We know this because Brazilian air control did receive automated warning transmissions from the plane before losing contact. The Czar’s theory? They knew something was wrong with the instrumentation because the information did not jive. In the panic and turbulence, they may not have realized their air speed indicators were non-functional.

And so then what? Without the BUSS package, the pilot must watch the altimeter and adjust the flaps manually to hold a steady altitude. The co-pilot needs to cross reference a complex table to determine where the plane’s controls should be positioned to maintain steady flight. This assumes, of course, that the pilots correctly guess the pitot tubes are frozen over.

If they are used to the fly-by-wire computer systems of the Airbus cockpit, they may trust the computer more than their own instinct—rather like the famous calculator experiments where kids were given rigged calculators on a simple math test, and students dutifully wrote down answers that were blatantly incorrect. When the plane’s flight computers began showing seemingly bizarre data—we are at full throttle but losing speed but not altitude—the pilots may have assumed the primary computer was screwed up. When the backup computer agreed, they elected to attempt a manual reboot of the entire flight control system.

And did not realize the plane was falling out of the sky in a stall, until it landed nearly flat on its belly so hard that the tail fin ripped off and cartwheeled forward. The only weirdly comforting news was that the turbulence was so severe that passengers were evidently also unaware of the plane’s drop out of the sky. Gruesome evidence shows oxygen masks were up, flight attendents were not strapped in, and passengers were not in crash or panicked positions. Let us hope their last four minutes on earth were only bumpy and rocky.

So why, you ask, if the turbulence was so bad, did the pilots not divert their course around the weather pattern? We rely on badly one-sided viewpoints here, but pilots familiar with the route claim that the plane was heavy with passengers, and to meet take off weight requirements, fuel was kept to a minimum. This meant the pilots needed to fly as direct a path as possible between Rio and Paris. This was a pretty common practice, evidently, with Air France.

So here is what we have. Air France routinely flew planes with limited fuel through an area plagued with weather convergence—turbulence and thunderstorms—which required pilots to fly through bad weather rather than around it. The equipment they used lacked a software package that could save the plane in the event this bad weather froze the pitot tubes. Instead, they relied on the pilots’ ability to recognize this situation and refer to a manual lookup of a table in a flight emergency book, but allowed two pilots with less experience to handle the crisis.

And the French government, which owns both part of Airbus and all of Air France, was aware that the one advised the other on what to do to prevent the tragedy years before it happened. When Brazil began to suspect the causes of the accident, the French government demanded they cease and desist rescue operations. When the Americans offered to send in the NTSB, the French government refused. And now the truth is starting to come out.

The truth looks like it will be horribly painful for the families of the dead.

* The Spiegel article mentions that the German BFU recognized a near-similar situation occurred over Frankfurt in 1998, when a Lufthansa Airbus suffered a near catastrophic pitot freeze and control system glitch. The Czar cannot substantiate this ever happened, as all references point back to der Spiegel article. The article later references a March 1, 2008, near-crash at Hamburg, which appears to be the correct one discussed above.

Update: The Frankfurt incident of 5 April 1998 is described at the BFA’s website. [PDF] —
ŒV—how the hell did you find that? The Czar looked there, too.

The Czar of Muscovy

Божію Поспѣшествующею Милостію Мы, Дима Грозный Императоръ и Самодержецъ Всероссiйскiй, цѣсарь Московскiй. The Czar was born in the steppes of Russia in 1267, and was cheated out of total control of all Russia upon the death of Boris Mikhailovich, who replaced Alexander Yaroslav Nevsky in 1263. However, in 1283, our Czar was passed over due to a clerical error and the rule of all Russia went to his second cousin Daniil (Даниил Александрович), whom Czar still resents. As a half-hearted apology, the Czar was awarded control over Muscovy, inconveniently located 5,000 miles away just outside Chicago. He now spends his time seething about this and writing about other stuff that bothers him.