Nobody knows exactly why Michael
Alsbury, copilot of Virgin Galactic’s SpaceShipTwo, made the fatal mistake of
unlocking a braking system too early during a rocket-powered test flight that
had reached speeds of over Mach 1 on Oct. 31. The resulting disaster tore the
wings off the futuristic space plane in mid-flight, killing Alsbury and forcing
pilot Peter Siebold to parachute to safety with a shoulder injury. But the
history of modern aviation accidents suggests that human error is rarely just
about the mistakes of a single pilot.
The fact that human error is
responsible for a majority of aviation accidents does not necessarily mean
pilots were being sloppy or unskilled. Such cases are usually less about “bad
pilots” as they are about the human brain’s common cognitive biases and
limitations in certain situations, says Ben Berman, a 737
pilot for a major U.S. airline and a principal consultant of Berman
Aviation Associates, a consulting and management firm focused on aviation
safety. Berman coauthored a book in 2007 titled “The Limits of Expertise:
Rethinking Pilot Error and the Causes of Airline Accidents,” along with two former colleagues from the Flight
Cognition Lab at the NASA Ames Research Center. By looking at recent aviation
accidents, they concluded that individual pilot errors were often the
unsurprising results of other factors at work.
“If you put 1,000 pilots in the same
situation, would you expect them to do the same thing or not?” Berman says. “In
most cases, yes, you would expect people to make the same mistake.”
The
Story Behind Human Error
This “human performance” or “human
factors” way of thinking in aviation has roots in a World War II mystery. A number of U.S. fighter and bomber pilots were making the
mistake of retracting their aircraft’s wheels instead of the wing flaps after
landing, resulting in the equivalent of belly landings. Lt. Alphonse
Chapanis, a U.S. Army Air Force psychologist at Wright Field in Dayton, Ohio,
eventually figured out that the aircraft involved in such cases — the P-47
fighter, B-17 bomber and B-25 bomber — had nearly identical wheel and flap
controls sitting side by side in the cockpit. “Human error” had turned out to
be a cockpit design error.
The U.S. Army Air Force fixed the
problem by attaching a small, rubber-tired wheel to the wheel control and a
wedge-shaped symbol to the flap control. That quick fix immediately stopped the
problem of pilots retracting their wheels after landing.
“If it’s a bad pilot, you fire them,” Berman
says. “If it’s people not being careful enough, you can send out a memo. If
it’s inadequate training, you train them better. But training can’t really
compensate for a badly-designed display or piece of equipment.”
Neither the firing nor memo options
are likely to be effective, Berman added.
It’s still far too early to say
whether a bigger issue lies beneath the human error that led to the crash of
Virgin Galactic’s SpaceShipTwo. But the U.S. National Transportation
Safety Board announced that it had assigned a
human factors expert to piece together the puzzle behind the copilot’s action that led to the destruction of Virgin Galactic’s space
plane.
That expert will likely spend time
collecting the life histories of both SpaceShipTwo pilots and understanding
what they did up to 72 hours prior to the disaster, including details such as
the nutrition in their diets and how much sleep they got at night, Berman says.
The investigation may also look at Virgin Galactic as an organization to better
understand the company’s safety culture concerning test flights.
Investigating
a Plane Crash
Berman is very familiar with the
National Transportation Safety Board (NTSB) as a former chief of the major investigations
division for the NTSB. His job included listening to the cockpit black box
recordings in a number of aviation accidents, as well as interviewing surviving
crew members. “You get a very sobering, very powerful thing that is revealed to
you as you sit there and hear what’s going on for the first time,” Berman
explains. “You learn a lot about not just the accident, but also what to be
aware of in the future.”
Federal investigations of aviation
accidents usually include an operations person in charge of looking at what
happened in the cockpit and how it relates to training and flight procedures.
The human factors expert might join the operations person in looking at the
pilots’ actions within the context of ergonomic factors such as vibration and
heat stress in the cockpit that could affect a person’s thinking or attention.
Even the lesser distractions of
cockpit operations in commercial jets can push human attention spans to their
limits and cause inattentional blindness. When sitting in the observation seat
of an airliner’s cockpit, Berman has witnessed a pilot look directly at a
lit-up indicator showing that the main cabin door for the aircraft is open and
say that the light is off.
Collecting
the Evidence
In the case of SpaceShipTwo, the
NTSB’s team looked at video footage from inside the SpaceShipTwo cockpit that
showed the fatal moment when Alsbury unlocked the vehicle’s braking mechanism
too early during the space plane’s rocket-powered climb. That action allowed
aerodynamic forces to forcibly move SpaceShipTwo’s wing booms upward into a
“feathered” configuration — designed to slow down the suborbital space
plane during reentry — without the pilot or copilot actually commanding
the vehicle to do so. The resulting stress apparently tore SpaceShipTwo apart.
NTSB officials have said that they
expect the full investigation of the SpaceShipTwo disaster to take close to a
year. During that time, they’ll examine possibilities such as whether the
cockpit display was showing the correct information to the pilots at the time
when the braking mechanism was unlocked, according to BBC News.
The NTSB also has access to Virgin
Galactic’s telemetry data and external video to show what was happening with
the space plane during the test flight. Federal investigators have been
collecting pieces of the SpaceShipTwo wreckage from the ground. There is even
the possibility of interviewing the surviving pilot, Siebold. But even all
those pieces of evidence will likely never reveal exactly what was going on in
Alsbury’s head at the fateful moment, Berman says.
Finding
a Fix
In the end, the human factors
approach allows accident investigators to go beyond simply blaming human error
and opens the possibility of fixes to prevent future errors. Sometimes the fix
might involve making a certain action part of a checklist to ensure that the
pilots devote more of their attention to the action.
NTSB investigators with the
WhiteKnightTwo in Virgin Galactic’s hangar in Mojave, CA. WhiteKnightTwo is the
mothership that carries SpaceShipTwo before midair deployment. Credit: National
Transportation Safety Board
A particularly important action
— such as making sure the landing gear of a commercial jet is down, fixed
and locked before landing — may require both pilot and copilot to confirm
the action verbally out loud. Or there might be a focus on training pilots to
react a certain way when they see a certain display light or hear an audio
alarm. There is also the possibility of taking the human pilots out of the loop
on a particularly crucial action and automating the process.
Commercial airline pilots have the
luxury of being trained on standard procedures for both normal operations and
also abnormal scenarios. By comparison, the Virgin Galactic test pilots were in
the process of testing a relatively new space plane designed for suborbital
space tourism flights in the near future; a process that can go “much more
off script,” Berman says. He added that test flights exist in part to develop
such standard operating procedures and to figure out what can go wrong.
The possibility of finding and
eliminating sources of pilot error is especially crucial for Virgin Galactic’s
plans of launching a space tourism business. The company and its founder,
Richard Branson, had intended the first SpaceShipTwo, named Enterprise, to fly
the first paying customers to the edge of space at a ticket price of $250,000
per person sometime this year. Still, the human factors approach may yet
offer some lessons for Virgin Galactic as the company presses ahead with building a second
SpaceShipTwo that could fly sometime in
2015.
Poster’s comments:
1) My father, now deceased from old age, shared
one story from World War Two with me.
2) He was
going through Naval Flight Training at Pensacola, Florida.
3) It seemed
there was a higher crash and death or injury rate on Mondays.
4) It turns
out too many trainees were just hungover from their preceding weekend.
5) So they
reverted to “ground school training” on Mondays, and the rate of injury and
death was correspondingly reduced to acceptable levels.
6) Whether
this story is true or not, it is still a good story to me.
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