For now, it is not known if the floating plastic tail fin or its rudder may have been complicit in the crash.

Airbus has now delivered 3,893 A320s, which have now been involved in 10 fatal accidents, killing 565 people, and at least one famous nonfatal crash – that of US Airways Flight 1549 in the Hudson River on January 15, 2009. 

May 31, 2009 - Aboard Air France Flight 447 Over the Atlantic Ocean 400 Miles Off the Coast of Brazil

Two of three pilots aboard an Airbus A330 were monitoring the autopilot controls on a flight carrying 216 passengers from Rio de Janeiro as it cruised at 550 mph at an altitude of 35,000 feet.  It was just before midnight and the captain may have been asleep in preparation to landing the plane in Paris the next morning. 

The pilot reported that the plane was flying through a towering thunderstorm containing black, electrically charged clouds confirmed by satellite data to be charging upwards to 41,000 feet at 100 mph.

Due to the frequency of equatorial storms in the area, it is likely that the flight crew and Air France management were aware of the impending storm before it was encountered, and a decision was made to fly through the storm, rather than to turn back or to navigate around it. 

Ten minutes later, the autopilot switched off and a four-minute series of automatic failure and warning messages from the plane’s Aircraft Communication Addressing and Reporting System were relayed by satellite to Air France headquarters.

It is difficult to imagine the scene within the cockpit of the plane being thrown about by a raging hail storm in the middle of the night, but the automatic messages provide some clues.

With the autopilot disengaged, the pilots had to manually contend with an ever-escalating series of failures in the flight control systems.  All of this had to be done with alarms sounding, in absolute darkness, with no natural horizon to observe and with aerodynamic forces erasing all sense of up or down.  The pilots were entirely dependent upon the plane’s instruments and the sensors that provided electronic data.

Then, there was a cascading series of failures within the flight control computer and systems to monitor air speed, altitude and direction.

The pilots were flying blind

The wing spoilers failed, the rudder limiter became inoperative and the rudder may have locked into place.  At this point, it is likely that the plastic stabilizer was ripped from the plane.

There is little or no likelihood that we will ever know whether the tail fin was blown off by the storm, as a result of the pilot’s attempt to control the plane, or by uncontrolled movements of the rudder.

What then happened, aerodynamically, is that without the vertical stabilizer and engine control, the airplane was like a giant Frisbee spinning through the storm until it fell apart.

The last automatic message confirmed a complete electrical failure and a loss of cabin pressure, as the plane plunged down almost seven miles in less than a minute to the ocean surface. 

We can try to imagine the scene on the flight deck and in the passenger compartment; however, we cannot possibly feel the terror experienced by everyone aboard, including seven children and one baby.

During the long 14 minutes, as the pilots fought to control the aircraft, everything trusted by those who boarded the aircraft failed – catastrophically.  In addition to their terror, they must have felt terribly betrayed.

To date, several large pieces of the aircraft fuselage, and the virtually intact vertical stabilizer, have been recovered from the ocean.  All indications are that the plane broke up in midair.  There is no evidence of fire.

50 bodies have been recovered, and almost all had multiple fractures, but no burns.  Water was not found in the lungs of any victims.  They were spread up to 53 miles apart, further confirming that the plane undoubtedly broke apart at high altitude.

A concentrated, multi-national effort, including nuclear submarines, is being made to locate the flight data and voice recorders from ocean depths of more than 15,000 feet and very rugged underwater terrain, before the attached “pingers” become silent after approximately 30 days.

There are early indications that speed sensors may have iced up in the storm and provided inconsistent speed readings, which may have initially caused the cascading failures of flight control systems aboard the plane.  We may never know for sure exactly what initiated the collapse of systems unless the “black boxes” are found, which is increasingly unlikely with each passing day.

All we know for sure is that the plastic tail fin separated from the fuselage under conditions that should have been expected to occur at some time during the life of the airplane.

Would metal stabilizers, rudders and couplers have failed under the same or similar circumstances?  They never have.

What Are the Lessons Learned and What Questions Do They Give Rise To?

At the cost of 500 lives and millions of dollars in lost aircraft, what can be learned from the crash of Air France Flight 447 and the series of emergency incidents and other similar airplane crashes that led up to it?

Is Composite Structural Design and Manufacturing Technology Sufficiently Mature To Be Used in Critical Structures on Passenger Aircraft?  In cooperation with NASA’s Aircraft Energy Efficiency (ACEE) Program to improve the fuel economy of commercial aircraft, Boeing commenced an experimental carbon/epoxy flight service program in the early 1970s and included a limited number of experimental elevators on 727s and horizontal stabilizers and spoilers on 737s.

“The experience gained from the ACEE programs provided the confidence needed by Boeing to select CFRP [carbon fiber reinforced polymer] for the Boeing 757, 767 and 737-300 control surfaces in the late 1970's”

Although some Boeing 737s have experienced rudder problems, including two fatal crashes; none involved aircraft with plastic stabilizers.  Rather, the problem with unexpected rudder movements was traced to a faulty hydraulic servo valve, and the metal tail fins did not separate from the fuselage during flight.

While Boeing was still experimenting with the use of composite materials in commercial aircraft, Airbus began to extensively install plastic materials in the construction of its first A300 series as early as 1974, introduced a composite tail fin box in its A310 series in 1978, and began delivery of the A320 series with an all composite tail fin in 1988.

NASA’s efforts to explore the effective use of composites in aircraft design and manufacture in the U.S. was transparent, papers were presented, and information and experience was openly shared.  European research and experience in the design and use of composites was more closely held, and it is less clear what kind of foundation work Airbus did in developing its use of composites.

In 2001, NASA assessed the state-of-the-art in the design and manufacturing of large composite structures in a paper by Charles E. Harris and Mark J. Shuart, which concluded that:

According to Mr. Shuart, there are places where it may be inappropriate to use composite materials instead of metal such as where there is a “banging around” or “excessive wear,” as in joints, hinges, or bearings.

Mr. Shuart believes it may be useful and prudent to do a “hard scrub,” or thorough review, of the design loads used by Airbus in the design of critical structures in its aircraft.  He is of the opinion that “failures are more likely a design, rather than a composite problem.”

Regarding Airbus’ use of composites in rudders, couplers and vertical stabilizers, Mr. Shuart said, “What you’re asking is a good question.”

In the Use of Composite Materials, Should Aircraft Designers Anticipate the Unexpected in Recognizing That Composite Materials Used in All Critical Structures Will Experience Extreme Stress At Some Point?  As we have seen, a variety of causes have been found in the various emergency in-flight incidents and crashes involving the damage or loss of composite rudders and tail fins on Airbus aircraft.

In the case of American Airlines Flight 587, the primary cause was attributed to pilot error in the “unnecessary and excessive rudder pedal inputs” that caused the rudder to move beyond “design limitations” and cause the plastic tail fin to be broken off the airplane.  However, it must be expected that, at some time during the lifetime of an aircraft that a pilot may accidentally push a little too hard on the rudder or that the rudder actuator mechanisms may fail.

If the expectation is that the composite tail fin may be torn off when that happens, then perhaps composites should not be used in that structure.  Although aluminum vertical stabilizers may be heavier and accordingly provide less fuel economy, the fact is that there is no history of metal tail fins being torn from fuselages in commercial passenger aircraft in the past half century.  This is true even though there has been a history of rudder problems, which necessarily caused the same stress on metal stabilizers as was caused to the composite tail of AA587.

While the crash of Air France Flight 447 is still under investigation, a variety of likely suspects, including lightning, severe thunderstorm, and clogged speed sensors are being advanced as possible causes.  However, passenger airplanes have been flying through storms for the past 50 years and there is no history of metal vertical stabilizers being torn off.

In fact, the National Oceanic and Atmospheric Administration makes a practice of flying through the most severe hurricanes to collect forecast data using ordinary Gulfsteam and Orion turboprop aircraft.  There is no history of any of them being blown apart.

Critical structures on aircraft, particularly those intended to carry passengers, cannot be constructed of materials that fail to anticipate that they will be exposed to extreme stress at some point during their lifetime.  It is true that, ultimately, all materials can be made to fail, why should passenger’s lives be included in the equation or the experiment to determine the breaking point?

Should the Use of Composite Materials Be Prohibited in Critical Structures in Commercial Passenger Aircraft?  The use of composite materials in commercial aircraft is for one reason only – to save operating costs.  The bottom line in this discussion is not how much money can be saved by composites.  The true bottom line is the physical fact that composites fracture when they reach their limit, while metal usually bends before breaking.

Boeing and Airbus are the only two viable commercial manufacturing companies designing and delivering passenger aircraft, and they are competing in every market and with every product line.  They are in a race to develop the least heavy aircraft to carry the greatest weight the greatest distance for the least amount of fuel possible.

If the Federal Aviation Administration and the National Transportation Safety Board should decide that, until such time as the composite structural design and manufacturing technology becomes sufficiently mature for all applications, composite materials could be prohibited for a common set of structures, including those most critical to flight operations.

That way, the playing field will be equal, and competition will still favor innovation in all other areas.

Should Commercial Passenger Aircraft Using Composite Materials in Critical Structures Be Regularly Inspected by Technology That Reaches Below the Surface to Identify Hidden Defects?  The experience of the Federal Express rudder (see above) illustrates completely why ultrasound and other technologically advanced devices that can look below the surface are essential to the prevention of catastrophic crashes.

The rudder was taken out of service because of visible damage, and upon ultrasound inspection was found to have internal disbonding damage that could spread further during flight.  Fortunately, we will never know if or when the rudder would have failed, or if its failure would have brought down the aircraft.

The current European Aviation Safety Agency ordered testing on Airbus composite rudders only applies to the A300/310 series, with only about 20 wide-body A330 and A340 planes included in the order.

The order does not include any of the almost 4,000 A320 series aircraft or the remaining A330, A340 or the new A380 aircraft.  Nor does it include the composite vertical stabilizers, or any composite couplers used to connect these structures.

Consideration should also be given to including Boeing aircraft, such as the 777 that operates with a composite tail fin, in the inspection order.

Other than for the time and expense of conducting the test, it is far more likely that opposition from manufacturers and operators will be based on the fear that internal defects will be found and that replacement could cost up to a million dollars per plane.  What value can be placed upon a baby’s life, or the life of any passenger?

Should All Aircraft Manufactured with Composite Materials in Critical Structures Be Grounded Until They Can Be Inspected For Hidden Defects?  The most deadly crash in U.S. aviation history occurred on May 25, 1979 when an American Airlines DC10 crashed on takeoff from Chicago’s O’Hare Airport, as a wing pylon failed and an engine fell off.  All 273 people aboard were killed.

The entire DC10 fleet was immediately grounded until it could be determined that the pylon bolts were at fault.

Following the fatal crashes of several Comet airliners in the 1950s, with a total loss of less than 200 lives, the entire fleet was grounded by English Prime Minister, Winston Churchill.  He said  “The cost of solving the Comet mystery must be reckoned neither in money nor in manpower.”

The Airbus is not manufactured in the United States; however, they are being operated by a number of American carriers and U.S. citizens fly on them every day all over the world.

Under the Bush administration, the last FAA administrator, Marion Blakey, “was a fervent free marketeer and opponent of increased government regulation.”

President Obama appointed Randy Babbitt to administer the agency, and he was confirmed last month by the Senate.  Mr. Babbitt is the former head of the Airline Pilot’s Association.  What will he decide?

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