Q: I’ve been reading about the Airbus A380. My question is, assuming there is a runway long enough, is there a limit to how big an aircraft can be and still fly?
—Ray Prior, Newnan
A: Planes potentially could continue to be built bigger as long as there is "infinite" runway space and engines can be built large enough to power the aircraft, John-Paul Clarke, an associate professor at Georgia Tech's Daniel Guggenheim School of Aeronautical Engineering, told Q&A on the News in an email. "… One would think that at some point, you could not build a feasible aircraft, although that would occur at a very large size." Clarke wrote that the climb gradient requirement would have to be met. "Basically, you have to have enough thrust after the loss of one engine to still be able to climb a certain minimum gradient (climb angle)," he wrote. "So, if you have an aircraft with two engines, you need to be able to continue to climb with only one engine if the other engine fails at, or just after, takeoff. If you have an aircraft with three engines, you need to be able to climb with only two engines." Clarke wrote it's easier to meet that requirement with more engines, but that would increase drag and "reduce the overall efficiency" of the aircraft. "It is a real challenge to build really big engines, and because they are so heavy, the structure required to hold them up increases."
Andy Johnston wrote this column. Do you have a question about the news? We’ll try to get the answer. Call 404-222-2002 or email q&a@ajc.com (include name, phone and city).
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