AVIATION MYSTERIES

12.29.14 5:52 PM ET

Did Bad Weather Bring Down AirAsia 8501?

As officials speculate the missing plane is at the “bottom of the sea,” experts question whether the Airbus 320 ran into similar problems as a doomed Air France flight in 2009.

As the second day of searching for AirAsia flight 8501 ended without finding any trace of the Airbus A320, Bambang Soelisto, the chief of Indonesia’s National Search and Rescue Agency, said the airplane “was likely to be at the bottom of the sea.”

This was very blunt and surprising to hear from any official in charge of an aviation disaster. It leaves the impression that the airplane hit the water and sank whole. That never happens. Experience shows that whatever the force of the impact of an airplane as it hits the ocean, some of the most fragile parts will break off and, as the airframe shatters, the lighter and more buoyant parts will float free. At the same time, the heaviest parts—the main fuselage, the engines and wings—sink to the bottom.

Soelisto’s statement was frustratingly ambiguous in other ways. He said: “Based on the co-ordinates given to us and the evaluation that the estimated crash position is in the sea, the hypothesis is the plane is at the bottom of the sea.”

Specifically, “the co-ordinates given to us” touches on an essential and, so far, missing detail about how accurately the flight was being tracked by radar. The flight path remained close to the Indonesian archipelago, well within what is the normal reach of air traffic control radar. There should be a retrievable record of exactly when the Airbus disappeared from radar. And this could be combined with the automatic position reporting sent from the airplane’s transponder to compute its position.

However, given the broad sweep of the search area, it is clear that the Search and Rescue Agency had no data that would lead to a more pinpointed search. One reason could be that radar coverage is a combination of civilian and military stations, as well as overlapping coverage by Indonesia and Malaysia. In the case of Malaysian Airlines Flight 370, overlapping jurisdictions and confusion between military and civilian stations led to long delays in getting a radar track that was reliable.

Another detail is emerging about a request from the pilot to climb to an altitude of 38,000 feet because of high storm clouds ahead. In the short time before the controllers were able to give him clearance to do this (or not do it), the airplane had already lost contact. This suggests that the pilots were overtaken very rapidly by an emergency.

Before clearing a request like this, controllers would normally check to see what other traffic was in the area—this is a busy route between Indonesia and Singapore. We have no information yet on what other flights were in the air then, and what they encountered. This will be crucial.

There are some very strong similarities between this flight and the doomed Air France Flight 447 in 2009—but also some key differences.

In the Air France disaster, the pilots had been flying a larger airplane—an Airbus A330—and, like the AirAsia pilots, they had spotted a large storm system ahead of them, towering over their flight path. Knowing that storm systems of this kind contain strong updrafts and downdrafts—one following another—the Air France pilots made a course change but the thunderheads were far too high to avoid.

Yet it wasn’t actually the weather that triggered the sequence of events that led to the loss of the Air France airplane. Because of a design flaw, airspeed instruments iced up, fed false readings to the computers controlling the flight, and the computers shut down. Left to fly the Airbus manually, the pilots mishandled the controls and instead of stabilizing the airplane, destabilized it and never regained control until it hit the Atlantic—in one piece—at the huge velocity of 11,000 feet per minute.

But a key—and potentially positive—difference between the two flights is that the main wreckage of the Air France A330, including its flight data and cockpit voice recorders, sank to the extreme depths of 14,000 feet, whereas the ocean area where the search for the AirAsia A320 is taking place is far less deep—apparently, with depths accessible to divers.  

In view of Soelisto’s statement implying that the whole airplane sank, it’s important to note that within three days, a significant piece of the Air France A330—its vertical stabilizer, conspicuous with the airline’s logo—was found floating among other debris.

Also like the Air France disaster, the pilots of AirAsia had no time to issue a mayday call. In emergencies the mantra is, ‘aviate, navigate and communicate’—and communication comes last when the pilots are fighting to save an airplane.

The automated flight deck on the Air France A330 and the AirAsia A320 are basically the same, operated by so-called “laws” written into the flight management system. When the autopilot is engaged (as it was not, in the case of the Air France plane) the computers prohibit pilots from making control commands that take the airplane beyond its safety “envelope.”

There has been an animated debate among pilots, recharged by this new incident, about whether automation has produced a generation of pilots with insufficient “seat of the pants” proficiency, with the quick reflexes and acute situational awareness necessary to sense when an airplane is in danger and instantly take corrective action.

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These skills are particularly needed when, as in the case of the AirAsia flight, the airplane is at cruise altitude. Because of the thinness of the air, there is a very tight margin between the correct and incorrect airspeeds, as little as 50 mph. If an airplane is destabilized by, say, a sudden updraft in a storm, it is prone to either a high-speed or low-speed stall, in which the control surfaces lose their grip. One report has the AirAsia Airbus flying at a speed very close to what would trigger a low speed stall.

Airline pilots are now slowly, too slowly, being given access to flight simulators able to reproduce sudden and unexpected upsets. The idea is that they will be able to learn to equal the legendary skills of the generation of pilots who never sat in a cockpit where computers ran everything, rendering humans by and large monitors of the systems rather than masters of them.

That being said, there is no record of an airplane as well-built and sophisticated as the AirAsia A320, and with such a fine safety record, ever being broken apart in a storm. Only last week there was a scary case of severe turbulence hitting an American Airlines Boeing 777 over Japan and shaking up and injuring passengers and crew, an ordeal that lasted for 45 minutes—but the airplane itself was never at risk.

Nor should we ever assume that weather alone, however extreme, should be fatal to a commercial flight. Bad weather is a feature of hundreds of flights across the world every day. Air traffic controllers and pilots together take great care not to fly in conditions that can jeopardize an airplane. The weather on the route of AirAsia Flight 8501 was not unusual for the region and the season.

As for the search, which will soon resume, Soelisto confessed that “the capability of our equipment is not optimum.” Planes have been sent from other countries to help —notably from Australia, which is already deeply engaged in the search for Malaysian Airlines Flight 370, which went missing last year in the southern Indian Ocean.

If there are 162 confirmed deaths from Flight 8501, this would make 2014 the worst year for accident deaths since 2005. However, this distorts an overall picture in which, given the ever increasing volume of flights and the spread of air travel across the globe, the safety record is actually astonishing. This year’s numbers include a truly anomalous and freakish statistic—699 deaths on the airlines of one country, Malaysia. That includes Malaysia Flight 17, brought down in a war zone, and Flight 370, which is still not officially admitted to be missing.