Cockpit Chronicles: There’s more behind the Air France 447 crash than pilot error

Recently a couple of pilots found themselves in a situation that was foreign and perplexing to them; a scenario the designers of the airplane hadn’t fully expected. They fought their way for 3 minutes and 30 seconds while trying to understand what was happening after a failure of one of the pitot static systems on their Airbus A330. At times the flying pilot’s inputs exacerbated the problem when he assumed they were flying too fast rather than too slow.

Because they hadn’t seen anything like this in the simulator, and the airplane was giving conflicting information, the recovery would have been all the more difficult.

Pilots are taught that an erroneous airspeed indicator can be countered by paying close attention to their pitch and power. It sounds so simple that many pilots wonder aloud, just how anyone in the situation could mess it up.

In the early morning hours of June 1st, 2009, the pilots of Air France flight 447 were working their way around thunderstorms while flying from Rio de Janeiro to Paris in the widebody Airbus A330.

A faulty pitot tube created a situation where any changes in pressure resulted in fluctuations in the airspeed indicator. To understand how difficult it is to recognize this problem and then correct for it, let me use the following analogy:

Imagine you’re driving a car at night. You come down a hill and you feel the cruise control back off on the gas to prevent the car from going too fast. Just as you look down at your speed noticing that it is, in fact increasing, a siren and lights go off behind you. A police car has woken you up from your late night drive.

Instinctively you kick off the cruise control and apply the brakes. The speedometer indicates you’re still accelerating, so you press harder on the brakes. Your car has now decided that because you’re trying to slow so quickly, it will shut off the anti-skid braking system and allow you to use manual brakes. You then skid off the road and into a ditch.

Based on the released information about one of the most mysterious accidents in recent history, it appears the pilots of Air France 447 faced a set of circumstances similar to our driving example.When flying in turbulence, it’s important to watch your airspeed. Flying too fast will result in a situation called mach tuck, where the nose can slowly pitch over and the controls lose their effectiveness.

Flying too slow can result in a stall. Not an engine ‘stall’ as might be incorrectly reported by the press, but an aerodynamic stall where the wings aren’t developing enough lift, and an immediate increase in the airspeed is needed to recover. Here’s a tip for reporters. In aviation, the term ‘stall’ will never be used to describe engines that fail. Ever.

Up at altitude, the difference between flying too slow and too fast can be as little as 20 knots. It’s called the ‘coffin corner,’ a morbid term used to describe narrow band of airspeed that we need to maintain.

In this 767 example above, the airplane has a very safe margin between
too slow and too fast, as shown on the airspeed indicator on the left.

While working their way around clusters of cumulonimbus clouds in the inter-tropical convergence zone that night, our two first officers (the captain was in the back on his planned rest break) did their best to stay away from the weather.

A side note: whoever takes the second break is usually the pilot who made the takeoff and who will also make the landing. So the relief pilot (who’s a type-rated copilot) took over the flying related duties while the captain slept.

Back to the flight: During turbulence, maintaining that speed can be more difficult, much in the way it’s tough to hold the speed in a car going over hills. You may look down after studying the weather only to notice that the auto throttles aren’t holding the .80 mach speed you have selected and the airplane is now at mach .83 and accelerating. In a moment, the clacker goes off, indicating you’re now exceeding the normal cruise speed of the airplane, which certainly gets your attention, much like the sirens of the police car in our example.

In the case of Air France 447, the autopilot kicked off in response to the overspeed, and was followed by a warning Airbus calls a ‘cavalry charge’ sound which is designed to get your attention quickly. About 30 seconds later the auto throttles were turned off manually and the throttles were pulled back, but it takes an eternity to slow down such a slippery airplane, and it may have seemed to the flying pilot that he was still accelerating anyway. So he pulled the nose up, an effective way to slow down in a critical situation like this. (See last week’s post on the eight ways to slow a jet.)

Amazingly, as the airplane climbed from 35,000 feet to 38,000 feet the airspeed continued to increase, at least that’s what it looked like on the flying pilot’s side of the airplane. He must have been surprised then to hear the stall warning activate moments later, indicating that they were flying too slow.

The other pilot likely noticed the airspeed on his side was decreasing, and perhaps because he saw the difference between both airspeed indicators, he’s heard to say on the recording that “we’ve lost the speeds.”

They had slowed from 275 knots indicated to 60 knots, at which point the airplane went into a mode called ‘alternate law’ which meant the automatic protections that kept the airplane from stalling were removed.

To make matters worse, the stabilizer trim moved from 3 degrees to 13 degrees nose up, which meant the airplane may have needed almost full nose down inputs on the stick just to fly level.

And to further confuse and confound the pilots, it’s recently been reported that as the airplane slowed further, the stall warning stopped. When max power was applied and the nose was lowered at one point, the stall warning came back. This is opposite of what the pilots were looking for in a recovery.

The airplane ‘mushed’ in a 15 degree nose up attitude all the way to the water, at a rate of 11,000 feet per minute.

We occasionally train for unreliable airspeed indications, but it isn’t covered during every recurrent training period. Stall training is often limited to the low altitude variety, which is far less critical than one occurring at 35,000 feet. I’m certain training departments all over the world will soon be required to train for high altitude stall recoveries.

Since this will take some time to become a requirement, on a recent simulator session, I asked my instructor to give me a loss of airspeed scenario at altitude. I told him I’d prefer to have the failure at any random point during our four hours of simulator time that day.

When he eventually failed it, causing the airspeed to slowly increase, I immediately pulled the throttles back and raised the nose a bit. The non-flying pilot simply said ‘airspeed’ which I thought was obvious, as it appeared to me that the airplane was accelerating rapidly and I was doing my best to get it back under control.

But on his side, the airspeed was dropping rapidly. When he said “airspeed” he actually meant that the airspeed was slowing and that I needed to do something about it. I finally looked over at his side, and saw that his speed was actually decreasing while mine increased. This all occurred within ten to twenty seconds.

I immediately lowered the nose and told him that I suspected my airspeed indicator had malfunctioned. Since my indicator was useless, I offered the airplane to him.

It’s easy for pilots to harp that “pitch and power equals performance” but it’s not easy to ignore the instruments you’ve trusted for thousands of hours. For the pilots of Air France 447, the incorrect airspeed indications and confusing stall warning sounds that were caused by a failure of the pitot static system proved to be too much to handle.

Furthermore, the Airbus design reinforced ideas that counter everything a pilot is taught, Specifically, these pilots learned that pulling the stick full aft would not result in a stall when the airplane was operating under a condition known as “normal law.” Much of their careers had been flown in airplanes with this feature. That night, after the initial climb, they were operating under “alternate law” which allowed far greater changes to the flight envelope, and removed that protection.

I wouldn’t have wanted to be in their shoes.

Much of the focus of the accident in the press has been to blame the pilots for clearly stalling the plane. One strange headline read “Baby pilot at the controls of AF 447.

The ‘baby pilot’ was actually 32 years-old and had previously flown an A320 for 4 years and the A330/340 for just over a year. He had 2,936 hours of flight time with 807 hours in the A330/340.

The other copilot, at age 37 had 6,547 hours with 4,479 of them in the A330/340. Sadly, his wife was also on board the aircraft as a passenger.

And the 58 year-old captain, who came to the cockpit from his break halfway through the event had 11,000 hours of which 1,747 were in the A330/340.

I’ve said it before; in the eyes of the media, pilots are either heroes or villains depending on the outcome of the flight. These pilots faced challenges few of us have ever come across. Given the mechanical failures that started the chain of events, there’s certainly plenty of blame to go around. Events like these have a profound impact on our training and help prevent future accidents. And at least that is something we can be thankful for.

In case you’re interested in even more details, AvHerald has an excellent summary of the BEA preliminary Air France 447 accident report.

Cockpit Chronicles takes you along on some of Kent’s trips as an international co-pilot on the Boeing 757 and 767 based in New York. Have any questions for Kent? Check out the Cockpit Chronicles Facebook page or follow Kent on Twitter @veryjr.

Cockpit Chronicles: Take your kid to work day!

Cockpit Chronicles takes you along on each of Kent’s trips as a co-pilot on the Boeing 757 and 767 out of Boston.

“We’re going to try a new place to eat,” Doug, the captain said as I walked into operations.

While he waited for the dot matrix printer to spit out the twenty feet of paperwork needed for our flight, he filled me in on what was the plan was for Paris.

“Mike (the co-pilot) and I read a review on a New York Times blog about a really small restaurant up near the Arc de Triumph called Le Hide. I figured we’d give it a try.”

Crew members tend to have their own favorite places that they frequent. Sometimes it’s easy to get into a rut and not venture out very far to experience anything different. Not so for Doug. He’s on a quest to try a new restaurant almost every layover.

“This is my step-son, Mack. He’s coming with us tonight,” Doug said, as Mack stepped forward to shake my hand. “Mack has just turned 21 this week, so what better way to celebrate the occasion than to bring him along.”

I was starting to get flashbacks of Michelle’s daughter almost getting bumped from the last trip.

“Are we weight restricted?” I asked.
“Not at all. It’s wide open there and back.” Doug explained.

Doug gave Mack a tour of the cockpit while I did my FB duties, since I was again the relief pilot. I went outside and looked over the nose, landing gear areas including the tire pressures and worked my way clockwise around the airplane. Wings, engines, lights, wheel wells, tail skid, rudder, elevator–it looked like everything was all there, with no leaks or damage.

It’s easy to get complacent after looking at hundreds of airplanes that have nothing wrong with them. I try to challenge myself to catch something out of place, but everything looked fine.

After the obligatory pictures of Mack in the cockpit, I showed him how we set our airspeed bugs manually on the airspeed indicator. Each ‘bug’ represents the point where we can retract our flaps to the next lower level.

So after takeoff and above 1000 feet we nose the airplane over slightly and select climb power, which is a bit less than our takeoff power setting. As the speed accelerates we can then move the flaps, which change the shape of the wing. This allows us to go from a wing that’s optimized for the slow speeds needed at takeoff to a shape that would allow for a cruise speed at MACH .80 or 80% the speed of sound.

Departing at flaps fifteen, we’d then ask for flaps five, then flaps one and finally flaps up. At around 2500 feet above the ground, we’re all ‘cleaned up’ and ready to accelerate to 250 knots, which is the maximum speed the FAA allows below 10,000 feet.

Passing through 10,000 feet we can then accelerate to our climb speed, which would be around 320 knots tonight.

Since Mack already has a few hours under his belt, and he’s even soloed a small airplane, he quickly understood the concept and he even helped me to reach over and set Doug’s bugs. May as well make him useful.

The departure was uneventful, and I did my relief-pilot duty of dividing the flight into three parts of about an hour and fifty minutes each to divide up the breaks.

I was fortunate to be back in the cockpit during Mike, the copilot’s break, when we passed just south of Ireland as the sun was rising. I couldn’t help thinking how Lindbergh may have hit this exact part of Ireland, near the Dingle Peninsula, on his solo flight across the Atlantic.

I also thought of Ruthann,, who lives in a tiny village in Western Ireland. She’s been reading my blog almost since the beginning and she’s the one responsible for editing and proofreading everything I’ve written since coming over to Gadling.

Since the age of eleven, Ruthann has gone to sleep while listening on a VHF radio to Shanwick Air Traffic Control give out clearances to airplanes passing just above her house.

She still catches our flight every now and then, using a VHF or HF radio. I suppose you could say she’s an aviation nut–just take one look at her flickr pictures to get an idea. She plans to start flight training this fall in Florida.

After arriving in Paris, we went down the stairs near the top of the jetbridge and down to the waiting bus. After swinging around to pick up Doug’s step-son at the front of the terminal, we were on our way to the hotel.

The Saturday morning van ride took only 35 minutes–a far shorter ride than the hour and forty-five minute ride that’s common on weekdays.

Since this was the first trip of three 3-day Paris trips in a row, I figured I’d catch up on some sleep, so I arranged to meet Doug and Mack at a pub after a nice five hour ‘nap.’

Doug and Mack toured all over Paris, going all the way up to Montmartre, north of the city and finally ending up at a wine tasting event that’s held at the Dernier Goute, a wine store in the Latin Quarter.

I worked my way toward the pub where we’d meet up, stopping at my favorite creperie for a crepe Nutella. For me, it’s not an official Paris trip without a crepe Nutella.

Doug found a nice Irish pub right off the Seine called “Le Galway.” Since we both have GSM cell phones that work in Europe, he was able to send me text messages to let me know exactly how to find this pub.

Mike managed to find the meeting point as well, so we worked our way to the metro station where we’d eventually come out in front of the Arc de Triumph.

Doug had read some great reviews about a restaurant that was moderately priced, especially considering the quality. Le Hide is described by Alexander Lobrano of Gourmet magazine as “a fantastic new bistro run by genial Japanese chef Hide Kobayashi. I left looking forward to my next meal here, and since I’m not alone, make sure to reserve, since word is getting around on this one.

We chose our appetizers and entrées, and left the desert choice for later. The prix fix meal was 29 Euros, which was great for such a prime location. As I’ve mentioned before, a pr
ix fix menu is made up of your choice of one of the starters, one main course and often a dessert.

I played it safe and ordered the Lyonnaise sausage over mashed potatoes, while Mike and Mack went for the escargot. Doug’s appetizer was the pan fried foie gras.

Doug and Mike insisted that I try their appetizers. I may have made a mistake in playing it safe, since I sampled a bit of Mike’s escargot and Doug’s foie gras, which were both out of this world.

For the main course, I had the pan-fried fillet of sole, and the others had either saute of chicken or veal chops in a butter sauce. That was all I needed to officially crown the French as having the best food in the world.

And we hadn’t even had desert by then.

Unfortunately, the battery in my camera died during our time in the city. Luckily Mack came to the rescue with some nice shots along the way. Thanks, Mack.

The next day, Mack came up to the cockpit once again during boarding to pose with Doug and Mike. I was busy doing the preflight, of course. I think he had a great time on his second trip to Paris with Doug.

Doug bought enough supplies to have a Parisian picnic in the cockpit on the way home, sans wine of course. We enjoyed some baguette and cheese, and some deli meat that had to be eaten before we arrived in Boston since the U.S. agricultural department doesn’t allow these kind of food items into the country.

We usually end up racing Air France flight 332 into Boston at the end of the leg. We generally beat them into Logan, which is important because U.S. customs occasionally prevents our passengers from deplaning until the crowd of people from other flights has cleared the customs area.

But this time, AF332, was just passing 2000 feet overhead as we prepared for our descent. Even though they managed to get a few miles ahead of us, Boston center decided that they’d give the Air France flight a 30 degree heading change to properly space the arrivals. That meant we’d be in the lead.

As I went to get my camera and take a picture of the second-place Air France jet, it slipped into the melted bucket of water that was once full of ice. I immediately yanked out the battery to prevent anything from shorting out.

Perhaps it’s just payback for taking the lead away from the faster Air France flight. But I’m happy to report that after drying out for 24 hours, the camera works fine.

Anytime you can take a family member or close friend on one of your trips, it hardly feels like work. I’m sure Doug was excited to bring Mack along. It was fun for all of us to experience the city through his eyes. I’m hoping that Mack continues flying, as I’d love to have him as my co-pilot someday.

Cockpit Chronicles takes you along on each of Kent’s trips as a co-pilot on the Boeing 757 and 767 out of Boston. For the months of May through July, he’ll focus on Paris almost exclusively. If you have any good suggestions for Parisian activities, feel free to leave your tips in the comments.