[Please see update here.] I don't know Kevin Townsend, though I suspect I'd like him if I did. He's been fighting the good fight against the filibuster, and we have tech and other interests in common. Today he put up a riveting post about a frightening and, in his telling, extremely dangerous episode aboard a recent United flight. The headline gives you the idea:
And he has gotten a lot of pickup for his tale. Eg:
Recently I got my one-zillionth email of the day from a friend or reader asking: What with this, and the Malaysian flight, I'm getting worried. Is something going wrong with our air-safety system?
So in case you're wondering:
- The episode Kevin Townsend describes sounds as if it could have been genuinely frightening, especially to passengers who had no idea what was happening, and he describes it quite vividly.
- On the facts he presents, even though this was frightening, it was nowhere close to as dangerous as it could have seemed. There was no sense whatsoever in which he "almost died."
- Commercial air travel remains remarkable for how extremely safe it is. Even this episode illustrates that reality, since one of many overlapping parts of the air-safety system worked rather than failed.
I wrote to Kevin Townsend a few hours ago to ask some questions
but haven't yet heard back. and have just heard back. Here are the main points to bear in mind.
1) The plane got an anti-collision warning that caused it to descend suddenly, by 600 feet. This is the part that was genuinely frightening to Townsend and other passengers. While in cruise, the United flight crew got a warning from its TCAS, the Traffic Collision Avoidance System, with which airliners and other large planes are in constant automated contact with other aircraft in the vicinity.
If the paths of two airplanes seem likely to intersect, the TCAS in each plane gives each crew a warning. If they are getting too close for comfort, the TCAS gives each of them a "Resolution Advisory" to steer them out of the other's way. One plane will be told to climb, and the other to descend. In keeping with the instrument-flying maxim that you must trust your instruments rather than going by your seat-of-the-pants sense, flight crews are told to trust and follow those TCAS/RA warnings, immediately. The United plane was told to descend right now, and its crew did.
2) How far is a 600-foot descent? This is what Townsend describes as the terror-filled part of the flight:
Weightless and staring downhill at the thirty-some rows of passengers ahead of me, I had a rare and terrible reminder of the absurd improbability of human flight. We were hairless apes crowded into a thin metal tube hurtling through the sky at a speed and height beyond anything evolution prepared us to comprehend. The violence was over after a few seconds. United 1205 leveled out, having dropped at least 600 feet without warning.
Again I am sure this was appalling, especially to people who start out with a fear of being up in the sky. But how far is a 600-foot descent? It is not very far at all. For one thing, it's about equivalent to four plane-lengths of the Boeing 757 that was flying. (That plane is a little over 150 feet long.) If an airliner descended at 600 feet per minute, passengers would probably not even notice it was headed down. If it were descending at what one manual calls a normal rate of 1,800 feet per minute, covering this vertical distance would take 20 seconds. I don't know what the 757's emergency-descent rate is, but if we say it's twice the normal rate that would mean about 10 seconds for getting down 600 feet.
Townsend includes a FlightAware chart of the course of that flight. Records from that date (April 25) are now behind FlightAware's pay wall, but here is the version Townsend published:
The blue line, which is airspeed, shows a sudden reduction at the point he is describing, with the vertical red line. This could be consistent with either a sudden reduction in power or (unlikely in the circumstances) a climb. The mustard-colored line, for altitude, seems more or less steady. Flight Aware is highly fallible, but at face value this indicates the plane rock-steady at a certain altitude. (Townsend wrote to say the chart actually records the 600-foot drop. OK)
3) How close were the planes, anyway? The premise of this story was a hair's-breadth escape from death. Eg "Two jetliners six miles over the Pacific don’t come within scraping distance of each other without something going amiss." And "the FAA is in the dark on a near miss that could have taken more lives than any air accident in history."
To put this in perspective, the closest the planes appeared to have come to each other is at least 5 miles, and perhaps 8 miles (which is what CNN told Townsend when he appeared). If airplanes are headed directly head-to-head, distances can close fast. If each was going at top speed of 600 mph, or 10 miles per minute, then a head-to-head closing speed would be 20 miles per minute, or only 15 to 20 seconds of direct head-on flight. Still, the point is that the traffic systems in both planes warned both crews when detecting a danger, and sent them in diverging directions. A five-mile margin between planes is not "scraping distance."
(The simpler traffic-warning system I have in my propeller plane sends alerts when planes are within 6 miles' distance. That is far enough away that usually it is very hard even to see the plane causing the alert.)
4) How close to the brink is the whole system? The post mentions the amazing safety record of commercial aviation, and also the irrational nature of fears involving flight:
Regardless, plane crashes hold a unique place in our fears: the fiery violence, the lack of control — they have a scale and spectacle that makes them loom larger than their actual threat. Similarly, more Americans are killed by vending machines than sharks every year, but more people fear sharks than vending machines.
All that is true. But I don't agree, as the piece goes on to claim, that "the [safety] system appears broken" or that airlines are left to "self-police" for safety regulations. Anyone who has dealt with the FAA can report otherwise. And to judge by the record, when was the last time two airliners collided in the United States? Hint: it was 49 years ago, and four people of the 122 aboard died. When was the last airliner-collision large-scale catastrophe in the US? It was when Dwight Eisenhower was president, and everything about technology was different.
Again, I think I'd agree with this author on most things, and I am meaning to be respectful about the article he wrote and the scare he endured. But people who think: first MH370, now this??? should think again. Several million commercial airline flights have taken off and landed safely worldwide since that Malaysian flight disappeared. Including the one Kevin Townsend describes.
Life is full of danger, including aboard aircraft. But if other aspects of life had even half the safety-consciousness of today's commercial air travel system, we'd live in a remarkably less perilous society.
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