February 20, 2013
Australian meteorologist Grant Denyer went for a joyride with Red Bull air race pilot Matt Hall the other day, jonesing for an adrenaline rush. “Eight Gs,” Denyer begged Hall, after breezing through some four-G maneuvers. A few seconds after Hall began wrenching the airplane up one wing, then the other, knife-edge to knife-edge, Denyer’s head hit the backstop, eyes closed and down for the count. G-LOC, the pros call it: G-induced loss of consciousness.
Military pilots wear G-suits and/or tense their muscles to prevent blood from draining from the torso, but civvies are on their own, and rarely make it through six Gs, let alone eight. At six Gs, your vision begins to “gray out,” narrowing to a tunnel as blood drains from your head. It can take several seconds for pilots and joyriders to wake up from their involuntary nap, and several more seconds to realize where they are, which is why G-LOC can be deadly. Even more uncomfortable is the onset of negative Gs, when you “red out” from the blood rushing to your head. Pilots and airplanes can cope with only fairly light negative-G force — maybe one half of the positive G-load they can withstand.
At least Denyer wasn’t caught drooling on camera, something I fear when I doze off on a commercial flight.
October 5, 2012
The odds of you being killed in an airplane crash, dear reader, are a million to one. But that didn’t stop the Discovery Channel from loading a 727 with a dazzling array of sensors and crashing it into the Mexican desert, all in the name of science. The results of the experiment will be aired this Sunday, October 7, as the season premiere of “Curiosity.”
Among other things, the filmmakers wanted to determine if there was anything a passenger could do to improve his or her odds of surviving. Where should you sit? Does bracing help, or is that an old wives’ tale? Crash-test dummies (which cost $150,000 each and provide 32 different types of data) were placed throughout the aircraft. Some were set in the brace position, while others were seated upright. “Low-tech dummies” were also used, either buckled into their seats, or seated without restraints.
An experiment on this scale, notes the film, has been tried only once before. In 1984, NASA spent millions crashing a Boeing 720 into Rogers Dry Lake in the California desert. But the aircraft lost control on the final approach and burst into flames after crashing—not good for collecting data. (The experiment was part of a joint research project between NASA and the FAA to test the effectiveness of a fire-suppressing fuel additive.)
Watch a clip from the show, below:
August 28, 2012
Yesterday the National Transportation Safety Board released a synopsis, subject to further review and editing, of its findings on the September 2011 crash of a modified P-51 at the Reno air races that killed 11 people. “[The] probable cause…was the reduced stiffness of the elevator trim tab system that allowed aerodynamic flutter to occur at racing speeds.”
Peter Garrison dissected the phenomenon of flutter in his 2001 article, “The Hammer.”
Seldom reported and little understood, [flutter] occupies one of those dimly lit and unsafe places that decent people prefer not to visit. The idea that an airplane could shatter—disintegrate—for no reason other than its own motion through the air—better to let sleeping horrors lie.
Garrison went on to explain that flutter is a form of resonance, or sympathetic vibration, as seen in an out-of-balance tire. However, “Out-of-balance tires seldom lead to structural failure of the car because automobile suspensions are vastly overbuilt for the loads they normally encounter. But airplanes, which must be kept as light as possible, are not superfluously stout. They are capable of failing with sudden explosiveness when flutter sets in.”
In our April 1987 article on the Dash 80 (the prototype Boeing 707), test pilot Dix Loesch recalled that the Dash 80′s tail also was prone to flutter, and that “flutter was a black science then [in the 1950s]. When the flutter guys started talking to their bosses, everybody else just sort of looked at the ceiling.”
The vibration frequency of an aircraft section in the throes of flutter is so fast that it can’t be detected by eye. It’s visible only in slow-motion videos like these: