http://enplaned.blogspot.com/2005/11/a380-wake-turbulence-hog.html
Tuesday, November 22, 2005
A380: Wake Turbulence Hog?
A Wall St Journal report (summarized here, for instance) reports this AM that initial ICAO (International Civil Aviation Organization) wake turbulence rules for the A380 require double the safety margin for current aircraft at low altitudes, and 50% more at high altitudes.
The WSJ emphasizes that these rules are preliminary and almost certainly more conservative than the final rule. But it's a matter that Airbus will be sweating over.
Wings generate lift, and in the process generate vortices from the ends of wing (there are some great photos of this effect available on the web--do a google search on "lift" and "vortices"--for instance here and here). These "mini tornados" take time to dissipate and can be destructive (wake turbulence has been implicated as a cause of various crashes--see here for instance). A smaller aircraft can be flipped or worse by the wake turbulence coming off a big aircraft (it's not all that surprising: consider the force that a wing is required to generate to keep an 800,000 lb 747 aloft, for instance).
So it's not all that surprising that an A380 might generate more severe wake turbulence than, say, a 747. After all, the A380 is bigger. What is surprising is the magnitude of the initial ICAO separation recommendations.
If these recommendations stick, or if something similar to them sticks, Airbus is going to be in real trouble. One of the primary rationales for A380 purchases is to jam more passengers through slot-constrained airports (airports that have reached saturation in terms of the number of flights). If the A380 requires significantly bigger slots (because of more powerful wake turbulence) then buying an A380 isn't a solution to this problem.
Shouldn't this problem have been picked up in the design phase? Well, turns out we're not very good at modeling wing vortices yet.
Tuesday, November 22, 2005
A380: Wake Turbulence Hog?
A Wall St Journal report (summarized here, for instance) reports this AM that initial ICAO (International Civil Aviation Organization) wake turbulence rules for the A380 require double the safety margin for current aircraft at low altitudes, and 50% more at high altitudes.
The WSJ emphasizes that these rules are preliminary and almost certainly more conservative than the final rule. But it's a matter that Airbus will be sweating over.
Wings generate lift, and in the process generate vortices from the ends of wing (there are some great photos of this effect available on the web--do a google search on "lift" and "vortices"--for instance here and here). These "mini tornados" take time to dissipate and can be destructive (wake turbulence has been implicated as a cause of various crashes--see here for instance). A smaller aircraft can be flipped or worse by the wake turbulence coming off a big aircraft (it's not all that surprising: consider the force that a wing is required to generate to keep an 800,000 lb 747 aloft, for instance).
So it's not all that surprising that an A380 might generate more severe wake turbulence than, say, a 747. After all, the A380 is bigger. What is surprising is the magnitude of the initial ICAO separation recommendations.
If these recommendations stick, or if something similar to them sticks, Airbus is going to be in real trouble. One of the primary rationales for A380 purchases is to jam more passengers through slot-constrained airports (airports that have reached saturation in terms of the number of flights). If the A380 requires significantly bigger slots (because of more powerful wake turbulence) then buying an A380 isn't a solution to this problem.
Shouldn't this problem have been picked up in the design phase? Well, turns out we're not very good at modeling wing vortices yet.
