Friday, May 31, 2019

Air France 447: 10 Years After

It's been 10 years tonight since Air France 447, an Airbus A330-200, flew into a thunderstorm en route from Rio de Janeiro to Paris, France on the night of May 31st, 2009. The crew flew into a line of thunderstorms north or Brazil and the airspeed-measuring Pitot tubes clogged up. Without airspeed information, the sophisticated fly-by-wire flight control system could no longer operate in its highest mode: Normal law. The flight control law degraded to Alternate law, causing the autopilot, flight directors and autothrust to disengage. Multiple alerts sounded, alerting the crew that they must now manually control the airplane. Within five minutes all lives were lost. This accident is classified as a "loss of control in flight."
Similar circumstances had occurred on over a dozen other flights in various parts of the globe.  Those pilots were able to manually control the airplane for the minute or so that it took their Pitot tubes to clear before resuming normal operation. 
Airbus and Air France had issued bulletins of how to handle the occurrence and Pitot tubes were being replaced with a different design as fast as they could be produced. 
After several hours it was clear the flight had been lost, the location of the crash unknown. It took a week to find the floating debris and some of those lost. That provided about a 50 square mile area where the wreckage most likely was. It took another two years to find the remains of the aircraft 12,000 feet below the surface of the Atlantic Ocean not far from its last known position. 
How could this happen? That was the question on everyone's mind. Why were some flight crews able to handle a similar situation with nothing more to show for it than a logbook writeup while AF447 lost 228 precious lives?
My assessment can be summed up in two words: Training and Practice. 
There is no doubt that the situation the crew experienced that night was unexpected and stressful. The unexpected aspect contributed an element known as "startle factor," which degrades our cognitive abilities where we instinctively revert to training and habit patterns. Add the additional factors of a dark night with no outside visual references, turbulence, lightning, and multiple alarms and alerts, both aural and displayed on the A330's aircraft monitor displays, and the stress level is sure to be turned up. Training and solid skills can overcome this, but training takes time and practice to form habits and skills that can be relied on in a crunch. Skills, degrade over time without practice, ask any athlete or musician.

Of course, it's a little more complicated than that. A complete understanding of all of the elements involved includes a study of the weather, aerodynamics, aircraft systems, communications, and the human element. In 2012 the BEA (French transportation investigation authority) issued its final report on the accident. In 2013, I published Understanding Air France 447, which takes the findings a step further, allowing the reader to connect the dots and understand all of the underlying factors.
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Not quite four months earlier, (Feb 12, 2009) another loss of control in flight accident occurred on approach to Buffalo, New York.  
These two accidents spurred increased action and emphasis on training for upset recovery including stalls (including those at high altitude like AF447). In addition to training pilots, the flight simulators were required to have their operational envelopes extended as well and operational scenarios built in. This allowed more realistic training in stall recovery, unusual attitudes, bounced landings. Additionally, several aviation safety businesses around the world specialized in upset recovery training using a variety of aircraft to take the experience beyond what a ground-based simulator can provide. 
Airbus also did not ignore the accident. While no official statement from the manufacturer says so, the design of the A350, a 300+ passenger widebody two-engine jet, seems to clearly address many areas that were factors in the loss of AF447. 
It has an enhanced weather radar that automatically turns itself on and warns the crew when approaching too close to weather (even if it has not been selected for display). To prevent a loss of airspeed indications the A350's air data system automatically switches between available Pitot tubes. If all of those are affected the air data system can derive airspeed from pressure sensors within the engine cowlings.  A degradation from Normal law to Alternate law results in no degradation of handling characteristics or protections (assuming no structural damage). The A350's autopilot is extremely robust and remains operational. Saving the crew from having to hand fly the airplane immediately upon an abnormal event.  It attempts to recover the airplane to a normal attitude itself until such time as the crew can take over. The autopilot can remain engaged up to 120° of bank and other extremes in pitch, and speed. It can operate in situations like no other aircraft such as during a dual engine failure, complete hydraulic failure, and loss of all generators. The A350 can also automatically make climb and descent (TCAS) maneuvers to avoid a collision with other air traffic and automatically descend the airplane to a safe altitude in case of depressurization with crew incapacitation (A  Payne Stewart scenario).

Following the loss and extensive search for Malaysia 370 in the Indian Ocean, in March 2014, with only a few pieces of aircraft debris ever found, extensive efforts sought a solution to locating aircraft worldwide. Previously, aircraft operating over the oceans had little to offer in tracking between reporting points. Now, a constellation of Iridium satellites carries ADS-B receivers to be able to track aircraft worldwide down to the second. Other schemes to automatically detect distress situations and transmit position and critical flight data or to eject flight recorders prior to a crash have also been proposed. The ADS-B solution, while still dependent on the system on the aircraft operating (and it's not clear that this would have actually been the case in MH370), requires no specialized equipment beyond what will otherwise already be required as of 2020.
So, while the loss of Air France 447 was a terrible tragedy that took 228 lives, the aviation industry has taken the causal and other factors to heart to improve pilot training, training devices and aircraft and surveillance systems to prevent a reoccurrence.
Aviation is amazingly safe. It is the safest form of transportation ever invented. But it is not inherently so. It is that way because a lot of people work very hard every day to make it that way. Let us never rest from that endeavor. 

A Brazilian TV show did a 14 1/2 minute production for this anniversary. I am interviewed in the show. It is available here:

Bill Palmer

Friday, February 1, 2019

A unique take on AF 447 by Flying Magazine

The January 2019 issue of Flying magazine has a unique take on the June 2012 AF 447 accident. It is one that I don't think I've ever seen taken on an accident before. It is how it should have turned out. It is a reminder that despite all the "magic" in our cockpits today, sometimes you still have to be a pilot, an aviator, stick and rudder guy, what the passengers think they're getting when they climb on board, a person of the sky who understands the air and the machine. One who uses his superior knowledge to avoid having to use his superior skill, but also one with that skill to keep everyone alive.

Inside the Saving of Air France 447 | Flying Magazine
air france 447