I’ve always wondered why airliners are not built with delta-style wings. Delta wings have some neat advantages:
-for a given lift, they can be shorter than a conventional wing
-they are considerably stronger, since they attach to the whole fusilage
-they can handle larger, heavier engines
I don’t see any prototypes or actual models , though. As far as I know, the only really big delta=wing plane was the English DeHavvilland “VULCAN” long-range bomber. That was a sexy plane-too bad they are all out of service!
Delta wings are great for supersonic flight, which is why the Concorde had them. However, they lack control and stability at subsonic speecds, which is why most airliners do not have them.
They also lack lift at low speeds, hence Concorde’s unusully fast takeoff speed.
Au contraire, **Q.E.D., ** NASA is currently testing a prototype for a blended wing body aircraft. They forsee a 450 passenger subsonic airliner with a range of 7,000 miles.
Nice. But that’s not a delta wing, strictly speaking. Besides, it’s my understanding that planes such as this are inherently unstable in flight, and require computer control to maintain the appearance of stability. That article isn’t detailed enough, however:
This part sort of hints at that.
It isn’t just the long runways required by the high takeoff and landing speeds that **gorillaman ** mentioned, which creates a severe limitation on operating flexibility. The delta or blended-wing approaches are also inflexible. They cannot be easily stretched or shortened to optimize a model for particular routes or airliners, and those whom that one size doesn’t fit will shop elsewhere. Further, they are very difficult to make freighter variants of - any place the loading equipment could readily go is impeded or blocked by the wing. That eliminates another huge part of a potential market. (The same cause creates a similar problem in connecting passenger jetways). Those factors combined to kill the Boeing Sonic Cruiser, for instance.
Even though the fuel burn might be less, the manufacturing and operating economics just aren’t competitive with the straight-tube-with-caps-on-the-ends architecture.
The Vulcan was designed by Avro.
You should also remember the B-58 Hustler.
Not to start a GD but you might define “planes such as this.” Do you mean flying wings? Of so there is no reason to think that they are inherently unstable, they’ve been flown for years with no computer controls from Northrop’s various wings to RC aircraft (arguably harder to fly since the pilot has no feel). They certainly have characteristics that might be different than conventional aircraft such as yaw damping and pitch sensitivity but that doesn’t imply inherent instability.
If you want to see a big delta wing aircraft take a gander at the XB-70 at the USAF museum in Dayton, OH.
Actually, a variant of the Avro Vulcan was proposed as a passenger plane; it didn´t really advanced much, I recall a picture of a maquette showing the interior were the seats faced backwards!
Yes, I mean flying wing aircraft. And the reason to think they are inherently unstable is because the are inherently unstable:
I have to go with Padeye on this one, QED. I used to fly balsa wood flying wing gliders that were inherently stable. They flew quite well in defiance of your cited reference.
Just 'cause you can find it on the web don’t make it true, in spite of the bona fides of the quoting source.
The XB-70 Valkyrie was a big delta wing plane. They only ever made a couple of them, but they rank right up there on my list of cool looking planes.
Whoops. Padeye already mentioned it.
Thanks MM.
That points out one of the problems with web references; just cause it says it’s so doesn’t mean it is.
The same site says the F-16 is inherently unstable and there is little unconventional about it. Pretty normal wing and tail layout. All that means is that virtually any design can be made to be unstable if extra manueverability is desired. Design a plane with an aft CG and it will be squirrely to the point you may need fly by wire and computer control to maintain normal flight. The original Wright flyer was extremely unstable and any one who has done any flying can see the pitch instability in the movies. That doesn’t mean that canard designs are unstable but that the distance from CG to the canards was much too short. The wrights figured this out too and lengthened the foward frame on the model B flyer.
The YB-49 did have a yaw stability issue but only as far as making the guy peering through the Norden bombsight wanna hurl chunks. It wasn’t a flight safety issue and according to what I’ve read might have been solved with a Sperry gyro yaw damper coupled to the autopilot.
I noticed the website said that the B-2 is a fine example of modern, swept wing design. Gee, exactly like the B-35/YB-49 half a century earlier. :rolleyes:
Here’s a few shots of the single remaining XB-70. The hangar is so crammed with experimental planes that it’s virtually impossible to see the whole thing in one shot from ground level.
http://www.padeye.net/XB-70_1.jpg
http://www.padeye.net/XB-70_2.jpg
I read somewhere that that’s actually safer than having them pointing forwards, but paying customers prefer to look where they’re going. Anyone know if there’s any truth to that?
Well, yes, flying wings can be built to be inherently stable, however such designs are much less efficient than a wing with neutral or negative stability. And probaly marginaly more efficient than a conventional airplane design.
The stability is obtained either by a reflex airfoil (or S airfoil, the trailing edge bends slighty up) or by using swept wings and wash-out (the wingtips have negative incidence compared to the center section) Both methods work as a traditional elevator for obtaining positive stability, pitches the nose up when speed increases (the wing climbs and loses speed) or pitches down when the speed decreases.
For lateral stability either a conventional rudder can be used (as in the Vulcan) or just the wing swept as in most of the Gotha brothers designs.
I guess so, planes usually crash nose first, so a backwards facing seat would support and protect the passenger better, in normal seatings the passenger is hold on the seat by the thin seat-belt at the hip and a sudden deceleration puts the upper and lower body into whip mode.
In any case a backwards facing seat would feel really weird at take-off, the Vulcan climbed quite steeply, and passengers would have ended up hanging from their seats facing down the fuselage. 
Facing backwards can also increase the effect of motion sickness.
Hmmm, motion sikness + people facing down the fuselage… talk about the vomit-comet. 
Watch out down there!
As others have said, flying wings can be inherently stable. The U.S. military flew a prototype flying wing bomber. It had an unfortunate tendency to dutch roll, which made it impossible to drop bombs accurately.
Delta wings are useful in supersonic airccraft because they keep the wingss in the cone of the shock wave. But they aren’t all that efficient. For high altitude subsonic cruise, I would think a long, high aspect ratio wing would be better.
There are other problems with blended wing and flying wing airliners - lack of windows. I think researchers have discovered psychological issues with putting people deep inside the hold of an aircraft with no view out. Also, emergency egress would tend to be a probem, wouldn’t it?