When the French found the black boxes from Air France flight 447 nearly two years after the A330 airplane crashed in the Atlantic off Brazil, it was an incredible feat. But now, the French probably are wishing those black boxes remained on the floor of the ocean, because its national airline is about to face some tough questions regarding the actions of its pilots on that flight. No airplane accident happens because of just one problem, and this is no exception, but so far pilot error is really sticking out as the single largest contributor here.
Photo of Sister Ship to Crashed Airplane via Flickr user Tab59|CC 2.0
The French accident investigation group, the BEA, has put out an update on its investigation around what caused Air France 447 to crash (pdf) in the Atlantic back in 2009. Flightglobal has a good minute-by-minute breakdown of what all of the technical verbiage means, but let’s focus here on a few key points.
Pilots Were Not Inexperienced
One thing that has been picked up on elsewhere is that the Captain was not in the cockpit when this all started happening. That’s true, and it’s not a surprise. That’s why there are three pilots on longer flights like these. They rotate taking rest and this was the Captain’s turn. Does that mean that there were two inexperienced fools manning the controls? No. The co-pilots were highly trained and should have been able to handle this situation without needing the Captain. As Flight notes, one of the co-pilots had more time on the A330 than the Captain himself (just not in command). Experience shouldn’t have been the issue.
Turbulence Was Not a Factor
The aircraft went down in an area near strong equatorial storms, so many people assumed that the storms and the likely associated turbulence played a role. That no longer appears to be the case. The pilots were actively working their way around the storms, and while there was turbulence around, it doesn’t appear to have been anything severe. The storm likely did play a role in that it caused the pitot tubes to freeze over. Let’s talk about that . . .
Frozen Pitot Tubes Are the Likely Trigger
I don’t believe this has been officially confirmed, but the belief remains that the pitot tubes froze and that kicked off the problems on the airplane. Pitot tubes are little pokey-looking things that stick off the side of the airplane and measure airspeed. If the pitot tubes froze as expected, then speed readings would have been erratic and incorrect. That would have caused the airplane to shut off the autopilot as happened here. While it is a serious issue, it shouldn’t have cause and accident on its own.
Ultimately, the Pilots Screwed Up
Regardless of what happened with the pitot tubes, what happened next seems just unbelievable and certainly casts a great deal of blame on the pilots even though we won’t have the final report until next year. About 10 minutes before the autopilot shut off, the pilots noted that they couldn’t climb any higher than the 35,000 feet they were at because of their weight and the relatively warm air outside. In other words, if they climbed higher, they wouldn’t be able to generate enough lift. That makes what happens next even more strange.
When the autopilot shut off, the pilots should have worked to keep the plane flying as it was. After all, there wasn’t an actual speed problem but just a speed measurement issue. The engines worked just fine, so it should have been quite possible to keep the airplane on its path. That’s not what happened. Over the next four minutes, the pilots pulled the airplane into a climb and right into a stall and that led to the crash into the ocean. This goes against one of the most basic rules of flight.
When an airplane stalls, that means its angle of attack (the angle of the wing as compared to the direction of the air) is too great. Fixing it is pretty straightforward and it’s something that gets trained at very basic levels. As the FAA says in its Airplane Flying Handbook:
Reducing the angle of attack is the only way of recovering from a stall regardless of the amount of power used.
That means pushing the airplane’s nose down until the air once again runs smoothly over the wings. If you’re at 35,000 feet, don’t worry about losing altitude. Just get the airplane back into normal flight. How do you know if you’re in a stall? This is where the Boeing vs Airbus people will start their “mine is better than yours” fight.
On Boeing airplanes, the control column actually shakes to warn the pilot. (It’s known, unsurprisingly, as a stick shaker.) But most Airbus types, including the A330 that crashed here, operate with little joysticks on the side and these don’t have stick shakers. Instead, there is a very loud verbal warning repeated multiple times. Either way, it shouldn’t be missed. But don’t Airbus airplanes have greater automation to prevent these things anyway? Not in this case.
Airbus normally has automation protection that prevents pilots from doing something stupid like going into a steep climb in a situation like this, but those protections weren’t in effect because of the inaccurate airspeed readings. That pushed the airplane into Alternate Law which shuts down many of the protections that are in place during Normal Law.
When the Captain got back into the cockpit, the airplane had an angle of attack at an incredibly high 40 degrees and it was losing 10,000 feet per minute in altitude. Despite his best efforts to recover, it was a failed effort. The airplane hit the water with its nose up 16 degrees but still losing more than 10,000 feet per minute in altitude. I can’t imagine how awful those few minutes were for the passengers.
But the Pilots Aren’t To Be Blamed Completely
The final report hasn’t been issued and won’t be until next year, but it’s easy to see from this that the pilots and the pitot tubes were the two biggest contributors. Why did the pilots continue to apply nose-up pressure when that was the exact opposite of what would have happened? We’ll never know what was running through their heads, but it’s easy to see that they could have been distracted.
Remember, the pilots were already working to pick their way through the worst of the storms. Add to that the loss of the autopilot, dozens of failure messages, and inconsistent speed readings and it seems like the answer might be simple. The pilots may have been so distracted that they forgot to do the one thing they needed to do to survive: fly the airplane. Once the final report is issued, look for training changes to come out of this and possibly even some changes in the way Airbus puts its airplane logic together.