Does this really deserve sensible comment?

A plane can only glide a limited distance. Larger wings will not necessarily increase this. Increasing the wings can increase lift, but will also increase drag. This will slow the plane faster and reduce its range.

It would be theoretically possible to shut down the engines at some point in the flight and glide in the rest of the way to save fuel. However, landing without thrust is far more dangerous.

What if we first go higher by certain thousand ft. and then glide down towards destination? Like from London to Singapore, we glide down on -2 degrees, to New delhi -3.

The idea is to use the height to glide down to the destination which is on the ground, thousands of ft. below, just by gaining a little more height in the take off process and then adjusting its nose to be able to glide down within a set number of hours.

A loaded airliner starting at maximum altitude (~45,000 ft) can glide about 150 miles. London to Singapore is about 6,750 miles. So an airliner would only be able to glide a small percentage of the trip. Modifying the plane to improve its glide distance might help some, but it would likely reduce its efficiency during the powered part of the flight, which is most of it. Keep in mind that airliners throttle back their engines during decent anyway, so they already use a lot less fuel coming down.

I forgot to mention that it takes a lot more fuel to climb to a higher altitude than to cruise at a lower altitude. On a short flight, climbing higher to increase glide distance would actually use more fuel. The reason they fly as high as they do is because the air is thinner at high altitude so there is less drag.

BTW, maximum altitude is limited by available oxygen. Above ~50,000 feet the air is so thin that it's hard for the engines to get enough oxygen to run.

This is an excellent idea for saving fuel and achieving greater velocities. By having the wing extended during takeoff, the plane can loft at slower speeds and with greater payloads on shorter runways. Then when aloft the wing is slowly withdrawn into itself to become a shorter wing. The reduced frontal area allows the same engine to accelerate the aircraft to higher airspeeds on the same power; a savings of fuel. Once near the destination, the aircraft speed is reduced to near stall speed for the short wing and the wing is extended with decreases the stall speed of the aircraft and allows it to again land at slower airspeeds. This is an excellent idea if it is given a small twist. You won't get something for nothing, but it does provide desireable performance characteristics.

The SCRAM jet in design at NASA flys into low orbit where the air is extremely thin and glides to near its destination with almost no power used. This doesn't use any moveable flight surfaces for maneuvering at those altitudes, but I suppose control over surfaces might be manipulated to maintain specific attitudes during re-entry. Also, the wing or flying body shape might dynamically be changed inflight to transition from subsonic to supersonic to hypersonic flight speeds. What the needed shapes would need to be I have only some idea. Also, the cross-sectional area of the aircraft must remain the same from bow to stern of the aircraft to allow for good aerodynamic flight at supersonic speeds. Dynamic surfaces may need to be available to maneuver the aircraft instead of using vectoring tail surfaces related to overall aircraft stability and attitude during re-entry.
No idea is a bad idea ! It is up to the rest of us to find the strengths and applications for those ideas.

Thanx for encouraging again.

You have a positive attitude which is a sad scarcity on this site.

People are just not prepared to dive in the depths and would rather like to remain on the surface of the idea and exhibit their critical talents.

Naresh, I'm sorry that you don't like the way I respond to your ideas. I am trying to to teach you about the science that is relevent to your posts. The ideas mentioned here by junkstopshere are actually different ideas than the one you posted. Expanding the wings for takeoff and landing is not what you had suggested. Actually, airliners already do that, that's what flaps and slats are for. Of course flaps and slats increase the width of the wing instead of the length, but the effect is the same. This doesn't increase glide range any, it allows the plane to land and takeoff at slower speeds and cruise at higher speeds as junk explained. Swing wings, as used on the F14 and F111, accomplish the same thing.

The scramjet doesn't glide at altitude by using wings. The air at that altitude is so thin that it really can't provide much lift. It basically is in a ballistic trajectory, like a bullet fired from a gun. The very thin air at very high altitude produces little drag, which enables a long flight. Control surfaces aren't used because the air is too thin for them to have much effect. After it reenters the atmosphere, it glides down with wings.

I can understand your preference for having someone tell you how great your ideas are. I like getting my ego stroked too. I just think it is more important for people to get honest feedback on their ideas. The more you understand about the topics you think about, the better equipped you'll be to generate truly great ideas.

Modern jet engines are extremely heavy. Jets are designed as little more than rockets that can land. Once they lose propulsion, they lose almost all of their control. For a short time, they are able to maintain some flight control, but not for long.

Junk is wrong, however, there will be a performance boost, but not an efficiency boost, as he described. Modern jet liners coast on their turbo-props as much as possible with a nice long wing span. That does cut down on speed, but it also maximizes fuel efficiency. Think for a moment about your car, if you go faster, the fuel efficiency will get better to a point, then it will begin to roll off. Same ballpark here. The plan will go faster with smaller wings, but the engines will need to burn more fuel in order to keep it aloft. Look at the F-14 Tomcat, (A 35 year old fighter) it used the same design with some success. The wings folded back in order to gain speed, and then folded out to gain flight performance. Swing-wings on airliners will do nothing for fuel efficiency.

Dwayne is right, and Junk knows some nice things, but it's obvious to those that have at least a basic understanding of these concepts that they won't be implemented. They're simply not practical, and you're thinking in much too small of a world.

Regarding EmeraldFalcon's comment about efficiency not being improved by reducing the frontal area of a wing for a given air speed, I believe he is mistaken.

An airplane with a Vne of 150 knots (never exceed velocity in knots, guessing a factor of about 0.8 of mph) is usually based upon the wing of the aircraft causing lifting forces that exceed the structural strengths of the wing itself. Given a fuel useage of 7 gallons per hour for a small aircraft like a Cessna 152 at 120 knots. The fuel useage will increase to about 10 gallons per hour at 150 knots due to exponential increases in drag. Reducing the wing area can significantly reduce the structural forces depending upon the locations of the structural weaknesses. This could concievably increase the Vne by some amount. Because the exponential increases in drag were due to aerodynamic configuration, reducing the cross-sectional area of the wing allows for the same power produced by the engine and propellor to cruise at higher airspeeds on the same or conceivably less fuel useage.

EmeraldFalcon applied your proposal to strictly one case of aircraft, heavy high flying turbine engine aircraft, and I'm not sure there would not be benefits there as well. But certainly, in experimental and small commercial aircraft there would be tremendous benefits.

Currently, experimental aircraft are configured for special characteristics. The Rutan Varieze uses 100 hp to fly at 200 mph but it can only land on paved runways and can only carry a light payload. The bush type aircraft carry large payloads and can land without runways, but tend to cruise at only 85 mph. Having a variable geometry wing for experimental aircraft would make aircraft much more versatile for the common person.

Look at all the problems including a lot of crashes and deaths the military had just getting the swing wing to work--A passanger or even a 2 or 4 seat aircraft is not designed as a glider and never will be in the near future--just think about it--you are in a 747 at 38,000 feet you extend the wings and cut power slowly coming down--now John doe is on another 747 traveling the other direction at 36,000 feet--here you are coming down and then a great big splat as you and John collide--Please read about aircraft, how they work, assigned altitudes they must maintain, A.T.C. before making more stupid suggestions!!

Wait a minute--that will help out with the over population problem and the aircraft plants will add more people to build more planes because of all the midair crashes--You got a darn good idea!!!!!!!!!!!

Nope

Naresh is right in that a wing becomes more efficient when it has a higher aspect-ratio (longer than it is wide), so the vehicle can fly on less fuel. Unfortunatly, they also have more drag, so they will fly on less fuel at a slower speed. Great for planes that don't need to get somewhere, but bad for travel. Also, a high aspect ratio wing would be much simpler if it didn't have to 'transform' to be that shape. This sounds heavy and failure-prone to me.

The U2 flies very efficiently for as long as 12 hours, but it's much slower than an airliner and it would make a really poor passenger plane, as would any glider.

Also, Dwayne, at 45K ft, (8.5 miles) I would expect a maximum glide ratio of an airliner to be something like 6:1, so 150 miles is not do-able, but 51 miles is. Max glide for a performance sailplane can be 20:1--workable for Naresh's idea at 170 miles, but again, gliders fly slow. People right now don't want to pay for airline travel at 150mph.

Anyway, I can see the impetus for Naresh's idea and it has some basis in fact. It's just that the other factors required of travel make it not-workable. If we all just traveled in our own motor-gliders, it might actually save some money over the fat heavy airliners.

As for Junk's points about wings expanding for landing, you all need to take into account that this occurs for a completely different purpose--to slow the plane down. A high-aspect plane can already fly slow without flaps.

Maybe Naresh has a point here--maybe in fifty years, airliners will look like U2's to allow them to fly more efficiently. Since we won't have to work because robots do our jobs, we won't need to be places quickly. I doubt it.