Ask the pilot

Avoiding speculation, the pilot weighs in on the Madrid plane crash.

Published August 21, 2008 11:00AM (EDT)

At least 150 people were killed on Wednesday when the Spanair MD-80 veered off a runway during takeoff at Madrid's Barajas Airport. Spanair is a low-cost carrier headquartered on the Spanish resort island of Mallorca. Founded in 1987, the company is today owned by Scandinavian Airlines System (SAS) and is a member of the Star Alliance. It has been dealing with an ongoing financial crisis and possible pilots' strike.

Details from the scene are sketchy, and it's probably best, with the investigation barely out of the blocks, to go easy on the speculation.

That being said, it is extremely unlikely that last winter's widely reported wiring problems with some MD-80 series planes has anything to do with the accident. Several media reports are already bringing up the wiring issues, implying a possible link. (For what it's worth, I have flown MD-80s, and although anything is possible, and at the risk of violating my own anti-speculation rule, it would be very difficult for a wiring malfunction to lead to a catastrophic takeoff crash.)

According to one report, the flight had returned to the gate for an unspecified maintenance issue, then departed again, which, if true, may or may not have anything to do with the accident. At least one person claims to have seen fire in the plane's left engine seconds before the crash, as the jet was accelerating down the runway. The crew then attempted to abort the takeoff, careening off the runway and bursting into flames. One newspaper describes as follows:

"Spanair flight JK 5022 was accelerating on the runway of the Madrid airport, the left engine of the MD-82 plane caught fire, the pilot pulled the jet up, however the wing touched the ground, the plane crashed into a ravine to the right of the runway -- and exploded in a huge ball of fire."

Assuming the engine fire erupted past the so-called takeoff decision speed, or "V1" in aircrew parlance, the pilot would indeed have been expected to continue the departure, as single-engine climb performance is guaranteed beyond that point. That assumes the crew maintaining proper control, of course. That a wing may have hit the tarmac suggests that control may have been compromised, either due to improper execution of the single-engine takeoff maneuver, or some unknown complication that we are not yet aware of, and which could have been beyond the crew's control. It's possible that a catastrophic failure of a power plant (i.e., explosion or fragmentation of internal parts) could have affected hydraulics, flight controls, etc.

Or, another possibility: one or more tire failures together with loss of an engine (ingestion of tire debris?), making directional control more challenging.

Bear in mind, however, that eyewitness reports are notoriously unreliable. Remember also that reported "engine fires" are often misconstrued compressor stalls. Compressor stalls, which by themselves are fairly innocuous, can manifest themselves through loud bangs and, sometimes, rather dramatic tongues of flame. They are caused by, among other things, overanxious application of reverse thrust, such as when a crew is attempting to stop as quickly as possible during an emergency. In other words, they are often a symptom, not the cause. Additionally, per regulation there must always be adequate stopping distance should an engine succumb to failure or fire prior to that aforementioned decision speed (V-1). The ill-fated flight was departing on runway 36L at Barajas, which at more than 14,000 feet is one of the longest runways in Europe. Stopping distance should not have been a factor.

Whatever happened, it was something more serious than failure or fire alone.

I would also remind people that despite occasional accidents like this one, global aviation safety has made tremendous strides over the past two decades. Worldwide, air travel is an estimated five times safer than it was a quarter-century ago, despite a doubling in the number of daily flights.

On the one hand it seems that in recent years we've been seeing more and more incidents similar to this one -- that is, crashes occurring on or very close to the ground, such as runway excursions after landing (Air France, TAM, Southwest), or takeoffs gone badly awry (Comair, Hewa-Bora, Spanair). Without having any official stats on hand, this is possibly a false perception: The number of such crashes appears to be rising only because most other types of accident have been falling. Around the world, better training and technology have greatly reduced the number of weather-related crashes, midair collisions, in-flight fires and other, more "traditional" disasters.

Incidents like the one in Madrid can result from a multitude of causes, and are maybe the hardest type of accident to address. Here the airplane is making the transition from ground to flight, traveling at high speeds, on or near the ground. It's by no means a dangerous time, but it's arguably the most precarious portion of flight. Anything from tire blowouts to engine failure to impact with birds can potentially affect safety.

Although nominally a Boeing, the MD-80 aircraft is a later-generation variant of the McDonnell Douglas DC-9. Boeing acquired McDonnell Douglas several years ago and the "Boeing" tag was applied to each of the types it inherited. There are several MD-80 subvariants, including the MD-83, MD-87 and MD-88. The Spanair plane was an MD-82. Though neither remains in production, approximately 1,000 MD-80 and 400 DC-9 aircraft are in service worldwide. Spanair flies roughly three dozen of the MD-80 series, along with several Airbus A320s.

UPDATE, 13:00 EDT: A reader posted a comment to the letters section saying, in part, the following:

"I read on the BBC news page a factoid that surprised me. They reported that Spanair has a very high safety/maintenance record. I fly the Barcelona-Malaga Spanair route fairly often and frequently find that large sections of the passenger compartment on their ancient MD80 fleet literally are held together with duct tape! I guess this goes to show that you can be perfectly safe in the air in an old shoe box if the parts that make it stay in the air and take off and land safely are in good order."

A few things here. First and foremost, virtually all commercial carriers have outstanding safety and maintenance records. With the frequency of accidents so rare to begin with, it's usually an academic exercise when you start comparing airline to airline. On some minuscule statistical level, perhaps it's fair to judge one company "safer" than another, but on a practical level, the distinctions aren't so meaningful.

This is also true when comparing aircraft type to aircraft type. Since yesterday I've received e-mails expressing concern over the safety of the MD-80 family of aircraft. As part of their coverage from Madrid, several media reports have included lists of past MD-80 accidents, suggesting a pathology of disaster particular to that type. In practice, the MD-80 is no more safe or unsafe than any other jetliner. It is not the newest, most advanced or, quite frankly, the most forgiving plane in the sky, but in no way is it unsafe to travel in.

And finally, equating the condition of cabin fixtures and other superficial equipment with overall safety is, however tempting, a bad idea. I agree that the use of duct tape in the passenger cabin is not only unprofessional, but sets a bad example, encouraging people to wonder if more serious problems lurk unseen. But believe me, it is in no airline's best interest, financial or otherwise, to play fast and loose with critical components. Any accident, whether caused by negligence or a proverbial act of God, can be devastating to a carrier's reputation and bottom line. Airlines occasionally screw up; we remember last winter's infractions at Southwest and American Airlines. In 1996, procedural lapses were partly to blame for the horrible crash of a ValuJet DC-9 in the Everglades (in the aftermath, ValuJet was forced to cease operations until reinventing itself as AirTran). Mistakes are not always excusable, and sometimes tragic; but they are neither as widespread nor as underhanded as many people assume.

For what it's worth, Spanair's MD-80 fleet is primarily of late 1980s, early 1990s vintage, which is not terribly "ancient" by commercial aircraft standards. Planes are built to last more or less indefinitely, and with regular upkeep and overhaul can remain in service for several decades. Retirement of a particular model is driven more by efficiency than age itself.

UPDATE, 15:00 EDT: As of this morning, at least, press coverage of the crash had been reasonably calm and accurate. Then came this from the London Times.

Never underestimate the U.K. media's capacity to sensationalize. "Passenger 'Forced to Stay on Madrid Crash Flight,'" blares the headline. "Cabin crew aboard the ill-fated Spanair flight which crashed on take-off at Madrid airport yesterday refused to let a passenger off despite earlier technical problems with the aircraft, the man's family said today."

This "chilling accusation" refers to an earlier maintenance issue that forced the MD-80 to return to the gate. The issue reportedly involved an overheating of one of several air data sensors found near the jet's nose. The sensors relay information to computers and instruments. Anything is possible, but this malfunction was, in all likelihood, totally unrelated to the accident.

The story also contains this:

"There were reports that pilots had complained of strong winds on the runway. Experts suggested that a powerful gust could have forced the pilot to put too much pressure on the engine during take-off, making it burst into flames."

That's one of the wilder and weirder paragraphs I've seen in a crash story. I think what they are getting at is that an overzealous application of thrust, in response to a sudden loss of speed, may have caused a compressor stall. Compressor stalls, referenced earlier in this column, are a sudden disruption of the airflow within a jet engine, often resulting in temporary loss of power, loud bangs and sometimes a burst of flame. Strong gusts or crosswinds can increase the likelihood of compressor stalls, and it's possible that one occurred on the runway while the plane was traveling at high speed. But that alone should not have caused a crash. Here is a rather dramatic photo of an actual compressor stall on an MD-11 just after takeoff.

By Patrick Smith

Patrick Smith is an airline pilot.

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