Blogarithms
Doug Kaye's thoughts on web services, web hosting and managed services.
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Wake Turbulence? I Doubt It. Per the cockpit voice recorder from AA 587, the crew suspected wake turbulence, and "airframe rattle" is heard at two points on the recording. I don't know what wake turbulence feels/sounds like in a large airplane, but from first-hand experience with wake turbulence in a small airplane (Piper Malibu) I can tell you that there's no "rattle." It's extremely violent and sounds/feels more like a sudden impact or even an explosion. (We were convinced we'd hit another airplane.)
Wake turbulence is generated from the wingtips of any aircraft. Lift causes the creation of horizontal vortices--little tornadoes--that trail the airplane. When viewed from behind, the left wingtip vortex rotates clockwise, the right vortex counter-clockwise. In calm winds, the vortices sink at about 500 feet per minute, so one cannot encounter wake turbulence unles one is somewhat below the flightpath of the preceeding airplane.
Using radar recordings, the FAA and NTSB can reconstruct the position of the wake turbulence vortices and their relationship to the flightpath of the following aircraft. In my case, we descended into the downward (inside) side of a wingtip vortex from 90 degrees to the flightpath of the previous airplane, a McDonnell Douglas MD-80. Radar showed that we then dropped 700' in only four seconds. That's a heck of a jolt.
I'm no accident investigator, but I think the crew's guess of wake turbulence is a red herring. The most interesting clue so far is the relatively-impact vertical stabilizer (vertical portion of the tail) that appears to have departed the airframe before other things started going wrong. Once that happened, the nose would have pitched down, and in pulling it up (particularly in a turn, where G-forces are increased), the loading on the wings and wing-mounted engines could have exceeded design limitations. The latter is pure speculation. The real issue is what caused that vertical stabilizer to come off of the airplane. Of course, that could be wake turbulence after all.
Posted Wednesday, November 14, 2001 11:49:51 PM 
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A300 Engine Mount Failures. No answers yet regarding the cause of the AA537 crash, but there is the known problem in the dog-bone link of the aft engine-mount assembly of the A300. An Airbus Industrie presentation on 24 of March 1999 declared that:
"Under a bird strike, fan blade rupture or separation, engine seizure or heavy gust conditions , there is no guarantee the engine would be retained. Although this combined probability is very low, AIRBUS does not like this possibility." [Source: AVSIG Forum]
Posted Wednesday, November 14, 2001 11:05:55 PM
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Fed Up with IIS. "We have taken steps to remove IIS servers from direct contact with the Internet." That's one line from an interesting compilation of emails received by Timothy Dyck in response to his newsletter discussing security vulnerabilities of Microsoft IIS. [Source: eWeek]
Posted Wednesday, November 14, 2001 11:54:54 AM
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High-Survivability Hosting? "In an era of growing insecurity, having your computer equipment tucked into a hole 85 feet underground has a certain appeal. That's the selling point of Underground Secure Data Center Operations (USDCO), a server farm located in an abandoned gypsum mine near Grand Rapids, Michigan." [Source: Wired News]
Posted Wednesday, November 14, 2001 11:15:15 AM
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Patent Wars II. "The United States District Court in Massachusetts has issued key rulings that could pave the way for Digital Island to prevail in its patent dispute with Akamai," according to Digital Island. [Source: Web Host Industry Review]
Posted Wednesday, November 14, 2001 11:03:25 AM
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