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kmh1956
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Swept-wing Passenger Aircraft..possible?

Mon Nov 05, 2007 2:55 pm

Ok, gang, don't laugh at me for what seems to me to be a perfectly reasonable question....I'm no aircraft expert by any means (I CAN tell the difference between a 737 and a 747!!) but I was wondering...how practical or possible would it be for a passenger aircraft to be built with sweep-wing technology? (A la the F-14) Would it help to increase speed, reduce flight times etc?

Reasonable replies only, if you don't mind.
'Somebody tell me why I'm on my own if there's a soulmate for everyone' :Natasha Bedingfield
 
mirrodie
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RE: Swept-wing Passenger Aircraft..possible?

Mon Nov 05, 2007 3:04 pm

Search for the Boeing 2707.

IIRC that was sweep wing technology. Unfortunately, like today, fuel was a huge issue and thus speed was killed off in exchange for efficiency.
Forum moderator 2001-2010; He's a pedantic, pontificating, pretentious bastard, a belligerent old fart, a worthless st
 
kmh1956
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RE: Swept-wing Passenger Aircraft..possible?

Mon Nov 05, 2007 3:10 pm

So, if I am to read between the lines of your response, sweep-wing technology uses much more fuel than fixed wing? The Boeing 2707 looked to be more of a delta wing than a sweep wing.....ok, never mind...just saw another article which descibes the possible sweep technology of the 2707 and possible stats: (from unrealaircraft.com) That puppy was going to be huge!!
POWERPLANT:
Four General Electric GE4/J5P turbojets,
each of 63,200 lb. st (28677 kgp) each,
with augmentation.

EMPTY OPERATING WEIGHT
(International model):
287,500 lb (130308 kg)

MAX. RAMP WEIGHT:
675,000 lb (306175 kg)

MAX. LANDING WEIGHT:
430,000 lb (195045 kg)

MAX. PAYLOAD:
75,000 lb (34020 kg)

NORMAL CRUISING SPEED:
Mach 2.7 1,800 mph (2900 km/h)
at 64,000 ft / 21000m

RANGE:
4,250 mls (6840 km)
with 277 passengers TAKEOFF LENGTH:
5,700 ft (1870 m)

LANDING LENGTH:
6,500 ft (2133 m)

SPAN:
180 ft 4 in (54.97 m) spread,
105 ft 9 in (32.23 m) swept.

LENGTH:
306 ft 0 in (93.27 m)

HEIGHT:
46 ft 3 in (14.1 m)

FUSELAGE MAX. EXTERNAL DIMENSIONS:
Width 16 ft 8 in (5.08 m),
depth 15 ft 7 in (4.75 m)

[Edited 2007-11-05 07:14:25]
'Somebody tell me why I'm on my own if there's a soulmate for everyone' :Natasha Bedingfield
 
speedracer1407
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RE: Swept-wing Passenger Aircraft..possible?

Mon Nov 05, 2007 3:56 pm

Quoting Kmh1956 (Reply 2):
So, if I am to read between the lines of your response, sweep-wing technology uses much more fuel than fixed wing?

Yes and no.

-Swing wings were a relatively popular solution for military jets that needed to be able to perform at a wide range of speeds, including supersonic, in the 60s and 70s. But swing wings add weight, complexity, and maintenance costs to any design. Advances in wing design have made the swing wing unnecessary, which is why nobody uses it anymore in newer designs, even military jets that don't have the same efficiency and low-cost maintenance requirements as airliners. And a commercial airliner can't afford to get any heavier, complex, or high-maintenance.

And anyway, what problem would a swing wing solve? Super sonic transport isn't yet economical enough for any manufacturer to begin developing, and a swing wing won't add much performance capability to a subsonic airliner, and certainly not enough to justify the weight, complexity, and maintenance of such a system.
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474218
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RE: Swept-wing Passenger Aircraft..possible?

Mon Nov 05, 2007 4:00 pm

What you are calling sweep wing is actually called "swing wing". A couple of reasons a passenger aircraft has not been built using a "swing wing".

The complexity of the "swing wing" would make it very costly.

The complexity of the "swing wing" would make it very heavy.

And while there are may more reasons, the benefits of a "swing wing" would not be enough to overcome just these two.
 
kmh1956
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RE: Swept-wing Passenger Aircraft..possible?

Mon Nov 05, 2007 4:58 pm

Thanks for the responses, gang, without the flaming that I can sometimes anticipate from some questions I have asked.
'Somebody tell me why I'm on my own if there's a soulmate for everyone' :Natasha Bedingfield
 
prebennorholm
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RE: Swept-wing Passenger Aircraft..possible?

Mon Nov 05, 2007 8:46 pm

All military swing wing planes have (or had) this feature to be able to fly very fast at low altitude. And "low altitude" means just that - ground skimming below the radar.

No transport plane has that need. In fact practically all over, below 10,000 feet a speed limit of 250 kts is imposed on them.

Even if they could fly quite fast at low altitude, then they are not certified for that - they are not structurally made for fast flight in the dense part of the atmosphere. The Concorde was limited to something like Mach 0.5 at low altitude. The Concorde wouldn't even be able to keep pace with a straight wing DH Vampire or Lockheed P-80 at low altitude. Not even a Spitfire or Mustang.

Airliner wings are optimized for cruise at Mach 0.8 to 0.85 at 30,000 to 40,000 feet altitude. Fuel economy in that regime dictates long and narrow wings.

They could benefit a little having straight wings for take-off and landing. Just a little. But with the long wings it wouldn't be practical, even if we ignore the weight penalty. Such a swing of the wings would impose a dramatic center of gravity shift which would be impossible to handle.
Always keep your number of landings equal to your number of take-offs
 
LMP737
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RE: Swept-wing Passenger Aircraft..possible?

Mon Nov 05, 2007 9:26 pm

Having worked on a swing wing aircraft, the F-14, I can tell you from personal experience that along with the added weight you will be adding a great deal of mechanical complexity to an aircraft. With the added weight the number of passengers and amount of cargo that can be carried will be reduced. With the added complexity the chances of delays/cancellations due to maintenance will be increased. Mirrodie mentions the Boeing 2707. I'll mention the folding wingtips option on the 777. The reason no airline has ever ordered a 777 with this option is it would have added a couple thousand pounds of weight to the aircraft, not to mention the added maintenance.

Possible from an engineering standpoint, yes. Practical, no.
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Starlionblue
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RE: Swept-wing Passenger Aircraft..possible?

Tue Nov 06, 2007 3:47 am

Expanding a little on the subject: Swing wings fall into variable geometry planforms. Strictly speaking, high lift devices such as flaps and slats fall into variable geometry. In the future, we might also see wing warping such as used by the Wright Brothers and recently tested by NASA on an F/A-18.

As for pure swing wings, perhaps these will appear with future supersonics, but there are also other solutions, for example Tu-144 style retractable canards.

The problem of how to design a wing both for cruise and for take off/approach/landing is a complex one, currently pretty much taken care of by high lift devices. However, said devices are mechanically complex, meaning they add weight and maintenance. Making them simpler is a desirable goal.

If the desired performance envelope is expanded to a supersonic regime, we will definitely see some development in the area. Concorde solve the low speed problem by simply raising the nose and thus increasing angle of attack. However, this resulted in a lot of drag, meaning higher engine power levels were required. The subsequent engine noise and aerodynamic noise, never mind the added fuel consumption, were a big problem. Concorde-B would have introduced slats, significantly improving fuel burn at low speed.
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2H4
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RE: Swept-wing Passenger Aircraft..possible?

Tue Nov 06, 2007 4:28 am

Quoting LMP737 (Reply 7):
Having worked on a swing wing aircraft, the F-14

How frequently did the swing mechanism fail in flight?

2H4
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LMP737
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RE: Swept-wing Passenger Aircraft..possible?

Tue Nov 06, 2007 4:52 pm

Quoting 2H4 (Reply 9):
How frequently did the swing mechanism fail in flight?

I never saw one that failed in flight. In case one hydraulic system failed there was a crossover shaft that connected one side to the other so that both wings would still move together. However I did see a wing sweep motor fail on the ground, tiny parts everywhere. I also saw flgihts scrubed becasue of hydraulic leaks associtaed with the system. Then there's the fact that the wing sweep system makes the whole flight control system that much more complex. Saw more than my fair share of flap/slat lockouts. Why, becasue all that stuff has to move on a swing wing aircraft.
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