Monday, June 22, 2009

Additional Details Emerge on Air France 447 Crash

As additional details about the crash of Air France 447 are released, we now know that more information than was previously reported was being transmitted in real time including speed and altitude excursions, g-forces and all system read-outs, including computer faults.

Prior to the crash, Airbus had issued a bulletin instructing all crews to be certain, by comparing to global positioning systems that their airspeeds were being properly read by the computers from the Pitot-static Tubes on the nose of the aircraft. The suggestion is that these tubes can ice up in severe weather in spite of being heated. Here’s the reality – the reason for the odd airspeed differences is that in situations of severe turbulence the airspeed variations can be large because the wind direction and velocity are rapidly changing as is the flight altitude of the aircraft. In short, severe wind shear causes rapid changes in wind direction and velocity.

The bulletin makes sense but as the information trickles in, it begins to appear that severe turbulence and a breakup is more likely the culprit – a very bad ride indeed. The aircraft must be found in order to determine just what broke first – the tail, parts of the tail or the main wing box, the wing or parts of the wing. Only then will we know if the testing to ultimate load required for transport category airplanes is both realistic and stringent enough.

This never should have happened.

Lastly, there are serious limitations on weather radar on-board, as well as on those people who must interpret it. With all of the computing power on the A-330, much weather data was available to be downloaded, not only from the on-board radar but also from ground and space-based facilities as well because the computers can make a better decision on whether and how to proceed in the face of severe weather. We need to go there.

Arthur Alan Wolk
June 5, 2009

Tuesday, June 9, 2009


There is only one level of air safety. The problem is the experience level of the people who carry out that mission and the airplanes they must carry it out in.

There is no substitute for years in the cockpit and hours in make and model to ensure safety. A pilot can’t be worried that he doesn’t make enough to eat, put gas in his car, get his uniform cleaned or pay the rent if you want him to be clear headed enough to perform optimally. The salaries are too low, the benefits non-existent, the airplanes less than fully capable for the mission and still these kids do a great job. They make more takeoffs and landings in the worst weather and work the worst hours for the worst pay. They are motivated, enthusiastic and do their best to be safe. They are however for the most part youngsters and far less experienced than their big airline brothers.

Their airplanes still have outdated deicing systems but they are expected to fly in the worst icing. They commute to work because they can’t afford to live near their base and they are expected to perform at their highest level. Their dispatch is not to big airline standards and they are expected to deliver their passengers safely no matter what the delays, no matter what the weather and no matter how many legs they have flown in the soup.

Why is there surprise when one of them crashes?

What needs to happen is closer FAA oversight…heard that one before. They need a living wage and benefits. They need airplanes that are modern and safe in every respect i.e. no turboprops. They need the authority to cancel a flight without fear of retribution, read that getting fired, for doing so.

Continental Flight 3407 is an example of what’s wrong not with just commuters but with commercial aviation. They flew an airplane with boots that everyone knows do not work safely in many icing conditions and certainly those in existence that night. They were tired. They were not fully trained to understand the limitations of their aircraft, the limitations of its certification to fly in ice and what cues they would receive that the airplane was failing them and what to do about it. Maybe they should also have been told that if anything happens their company, the manufacturer, other pilots and the Government will turn on them and blame them for something for which they were blameless.

The problem with commuters isn’t their pilots, it’s the people who regulate them, run them and build the airplanes flown by them.

Arthur Alan Wolk
June 9, 2009

Monday, June 8, 2009

Uncompleted Pitot Tube Modification is Only Part of Air France 447 Crash Story

At 35,000 feet, the Airbus A330, the Air France 447 plane that crashed, is only about 25 knots between cruise speed and aerodynamic stall. Thus, if wind shear and turbulence are sufficiently violent, the aircraft can stall and the air data computers will take the autopilot offline because the equipment senses an anomaly. The airplane will be thrown around like a feather and composite structures will fail because they have never been tested to ultimate load. That stall can also result in the aircraft becoming unrecoverable while it breaks up on its way to lower altitudes.

With all the computing power in an A330, sources outside of the aircraft should be used to supplement radar so that the computer can determine when it’s time to turn back.

It’s also time for certifying authorities to rethink how to test composite aircraft structures. It is no surprise that that the big thing found floating in the Atlantic Ocean was the composite vertical stabilizer separated from the rest of the airplane. Speculation is that the Pitot Tubes, which were unmodified as recommended for better ice resistance, permitted erroneous speed readings. I believe this is possible but unlikely. However, if the risk was so high, the modification should have been required before further flight was permissible.

Why isn’t anyone talking about the tail fuel tank modification that was designed to prevent explosions caused by lightning? Did the airline comply with that directive? There are a lot of questions…too few answers.

Arthur Alan Wolk
June 8, 2009

Watch Wolk discuss the issue on MSNBC

Wednesday, June 3, 2009


Air France Flight 447 is down. Sadly, it is expected that all 228 aboard are lost. The earmarks are all too familiar. Severe weather and a loss of radar contact usually mean in-flight break-up and rapid descent. This would, of course, explain the lack of a distress call and automatic reporting of electrical failure and significant turbulence by the onboard real time condition reporting system.

The aircraft went down in an area called the Intertropical Convergence Zone (see picture above). This is an area where the Northern and Southern hemisphere winds and weather collide to make a perfect condition for severe convective weather. That means severe thunderstorms frequently exceeding 50,000 feet with damaging turbulence, hail, intense rainfall and lightning. On the night of the crash, this area was especially hot with thousands of miles of severe weather making circumnavigation impractical.

Therefore, the only way to get from Rio to Paris was to penetrate this band of severe weather, a daunting task for even the best aircrews flying the most sophisticated airliner. There is no coincidence that shortly after entering this area of severe weather the aircraft was lost. Whether it was due to an encounter with severe turbulence or a lightning strike that exploded a fuel tank can best be determined when the wreckage is found, and surely it will be one day.

The cockpit voice and flight data recorders will also be very helpful but the automatically transmitted data already portends the turbulence, electrical anomalies and tragic end. This is why cockpit voice and flight data recorder information should be transmitted real time to home base.

Coincidentally, an Airworthiness Directive had been issued in 2005 by the French authorities requiring float valve changes in the trim fuel tanks of this aircraft model’s horizontal stabilizers. The purpose was to avoid lightning or static electricity setting off an explosion in those tanks. The compliance time was quite lengthy and, while this aircraft was built in 2005, it is not clear whether it had the benefit of the improved floats. If it didn’t, or the fix was ineffective, a lightning strike on the trim tanks could have been a catastrophe that even the best crew would have been unable to avoid.

It is, therefore, quite possible that the old problem of airliner exploding fuel tanks has reared its ugly head again. While better fuel tank standards have been published and bantered about the industry and governments since TWA 800 exploded in 1996, none of the legacy airplanes have benefited from the new standards and this Airworthiness Directive, which aimed to chip away at the problem.

Aircraft radars have come a long way, providing flight crews with far better weather avoidance information than ever before. Unfortunately, weather avoidance is not weather penetration, but the demands of airline flying and schedules often blur the difference.

Avoidance means not going there, penetration means getting into it and avoiding the damaging weather by skillful use of the radar. The letter works most of the time but not always. Aircraft and human graveyards are full of the results of severe weather penetrations because there are limits on even the best radars. Intense rainfall absorbs signal strength and confuses returns, intense cells hide others just behind and give a false sense of security that safety is just a few miles away, when the worst may be yet to come.

Last year a computer failure pitched an identical aircraft so violently, the crew thought there was a clear air turbulence encounter. The manufacturer said it was impossible and could not have occurred. Later it appeared that indeed the impossible could happen. One out of many computers could cause a dangerous and sudden pitch excursion that might have led to structural failure. That must be ruled out in this case. While turbulence may have been the initiator, computer failure may have increased its lethality.

No one wants an accident. No one deliberately tempts an accident with a planeload of families in the back and pilots who likewise want to get home alive up front. Indeed, they are the first to go. But whether this accident is the result of mechanical failure, the failure to simply remain on the ground in the face of impassable weather or the unlikely act of a saboteur, it is nonetheless the worst of nightmares come true.

Weather. Mechnical failure. Equipment malfunction. It looks like any one of these may have played a role. Whatever the ultimate cause, with today’s technology there is no reason for an airliner accident. With the prospect that this single field of human endeavor may one day be accident free, these deaths must not be in vain.

Arthur Alan Wolk
June 3, 2009

Watch Wolk discuss the crash on MSNBC