Thrust From United States of America, joined Sep 2003, 2691 posts, RR: 9 Posted (3 years 2 months 3 weeks 11 hours ago) and read 3209 times:
Hi. I was wondering about the wings of the 747 classics, as well as its ability to climb fully loaded. I was told that the wings of the 747 classic by comparison to the -400 were much heavier and that a longer takeoff roll was required as a result. What I don't know about the 747 at all for any of its models is how well it climbs...I know that in terms of cruise speed it is among the best performers in that area. Did the classics climb like the A340, or was it better?
I'm also curious as to why the first giant jetliners had such narrow wingspans compared to today's. The L-1011, DC-10, and 747 all featured sharply swept wings whose spans were not any greater than the 777. In fact, the 747 classic wingspan was a bit shorter than the 772!
It's just as bad. The A340 has a reputation for being a bad climber but it's not really deserved...the A340 just shows up on really long-haul trips (where it's highly loaded) more often than the 747. At equivalent payloads (as a percentage of MTOW) they're both terrible climbers, as is any quad.
Quoting Thrust (Thread starter): I'm also curious as to why the first giant jetliners had such narrow wingspans compared to today's. The L-1011, DC-10, and 747 all featured sharply swept wings whose spans were not any greater than the 777.
In the days of the early widebodies, they hadn't discovered supercritical airfoils and fuel was cheap so they wanted to cruise fast. High sweep was the easiest way to push up the cruise Mach and, with a particular area requirement and a high sweep you end up with a smaller wingspan. Once they figured out supercritical airfoils and brought the cruise speeds down in the mid 80's to combat rising fuel costs, wingspans went up as the sweep angles came down. Today you see really high wingspans as they go to higher aspect ratio wings (enabled by CFRP) in order to try to minimize induced drag.