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Apparently, wake damage is a pretty serious thing; it happens more than you'd think - even on the ground.
First up: a brief description from this article (which admittedly is for the light-plane pilot, but is useful anyway. quote:So what exactly is wake turbulence, or wake vortex? All aircraft generate vortices at the wingtips as a result of producing lift. The heavier the aircraft and the slower it is flying, the stronger the vortex. Vortex size also increases with wingspan, and some aircraft - eg the Boeing 757 - are known to produce particularly vicious wake turbulence. The vortices descend relatively slowly until they decay or reach the ground. Typically, for each mile behind the generating aircraft the vortices will have descended between 100 and 200ft. These vortices generally persist for up to 80 seconds, but in light or calm air this period can extend up to two and a half minutes.
An encounter with wake turbulence can result in severe upset to the equilibrium of the aircraft, with rapid uncommanded movements in roll, pitch or both. Generally, the lighter the aircraft the greater the degree of upset. A Cessna 172, for example, is vulnerable to the vortices generated by a similar size of aircraft, although such an encounter will usually be uncomfortable rather than life threatening. An encounter with the vortices generated by a jet transport is, however, another matter. It could've been something as simple as this advice (from a Wake Turbulence publication, google-cached version as I can't seem to get FAA documents on it at the moment.) quote:When departing behind a larger aircraft: Note larger aircraft's rotation point -- rotate prior to larger aircraft's rotation point -- continue climb above the larger aircraft's climb path until turning clear of his wake (Figure 16). Avoid subsequent headings which will cross below and behind aircraft (figure 17). Be alert for any critical takeoff situation which could lead to a vortex encounter. As I understand it, an A300 is smaller than a B747 - he might've left the ground that fraction too late.
Coincidentally, there was footage on the news (night before last) of a manufacturer's test video of wake effect on an airliner: I think it might've been a Boeing one - as the plane (looked like a 767) moved, intentionally, into the jetstream of another jet, there was massive wing flex and aircraft movement - it was being tossed around, pretty much.
Another thing to consider: it could've happened as a result of damage from the preceding plane on the ground. This is from this page on engine thrust hazards.
quote:Exhaust Hazard Accident
The following is the abstract of Aircraft Accident Report NTSB-AAR-71-12 written by the U.S. National Transportation Safety Board. It summarizes a fatal commercial airplane accident near New York City that was later determined to be caused by exhaust hazard. The report concluded that the introduction of new large jet aircraft "...caused considerable erosion along most taxiways and runways. According to New York Port Authority personnel, the products of this erosion, pieces of asphaltic material, rocks, etc., were being blown onto taxiways, ramps, and runways, making it difficult to keep these areas clean."
A Trans International Airlines DC-8-63F, N4863T, Ferry Flight 863, crashed during takeoff at John F. Kennedy International Airport at 1606 e.s.t., September 8, 1970.
Approximately 1,500 ft after starting takeoff, the aircraft rotated to a nose-high attitude. After 2,800 ft of takeoff roll, the aircraft became airborne and continued to rotate slowly to an attitude of approximately 60° to 90° above the horizontal at an altitude estimated to have been between 300 and 500 ft above the ground. The aircraft rolled about 20° to the right, rolled back to the left to an approximate vertical angle of bank, and fell to the ground in that attitude. The aircraft was destroyed by impact and postimpact fire. Eleven crew members, the only occupants of the aircraft, died in the accident.
The (National Transportation Safety) Board determines that the probable cause of this accident was a loss of pitch control caused by the entrapment of a pointed, asphalt-covered object between the leading edge of the right elevator and the right horizontal spar web access door in the aft part of the stabilizer. The restriction to elevator movement, caused by a highly unusual and unknown condition, was not detected by the crew in time to reject the takeoff successfully. However, an apparent lack of crew responsiveness to a highly unusual emergency situation, coupled with the captain's failure to monitor adequately the takeoff, contributed to the failure to reject the takeoff.This, however, happened during a test run - what if the preceding jet had caused a similar level of damage? quote:An airplane experienced damage to the horizontal stabilizer during a maintenance engine run. The airplane was positioned for the run with asphalt extending from close to the wing trailing edges to beyond the empennage. During the high-power part of the run, asphalt lifted from behind the left engine and broke into pieces, sending large fragments into the aft fuselage and outboard horizontal stabilizer. The outboard 4 ft (1.2 m), including the elevator, was sheared off, and the entire stabilizer required replacing. The initial section of asphalt that lifted was a sheet about 20 ft2 (1.9 m2) and 4 to 5 in (10.2 to 12.7 cm) thick before breaking into pieces. There were no injuries. Seems wake damage is a concern, especially to airliners. It could well be that that's responsible.
More info, including airliner reports. |
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