Is a wing that runs the length of an aircraft viable?

Question

I was thinking about fighter aircraft like the Harrier which have thrust vectoring and computer-controlled stabilisation nozzles. Also an anhedral angle on the (small) wings. The aircraft relies so much on the computer stabilisation, and flies like a brick if the engine fails, so why have those wings at all? Couldn't you get as much lift from wings of the same area that run parallel to the fuselage, that is much shorter (left-to-right) but deeper (front-to-back) wings? And wouldn't this create much less drag reducing the thrust requirements?

Having thought about this I realised that for fighters it's probably not a good idea as they would lose a lot of pitch-maneuverability, but for passenger jets, would a roll-stabilised approach with a short wing that runs the full length get the same lift while reducing drag? Is such a wing viable?

Answer 1

You mean very low aspect ratio (span to longitudinal length) wings?

Low aspect ratio has larger induced drag and glide very poorly.

The total drag coefficient of an aircraft can be expressed as:

$$C_d = C_{D0}+ \frac{{C_L}^2}{\pi e AR}$$

$C_D$ is is the aircraft drag coefficient
$C_{d0}$ is the aircraft zero-lift drag coefficient,
$C_L$ is the aircraft lift coefficient,
$\pi$ is pi,
$e$ is the Oswald efficiency number
$AR$ is the aspect ratio.

This means that drag is inversely proportional to the aspect ratio. So a low aspect ratio needs more thrust just to stay in the air. This means higher fuel costs.

One of the requirement for commercial aircraft is being able to recover after losing your engines. A good glide ratio (which needs high lift to drag) is essential to that.

Answer 2

Thinking about my comment above, the fuselage length side fins could be replaced with smaller stabilising fins and the technology used for cruise missiles, with the addition of thrust vectoring, adapted for passenger flying aircraft.

Flight while airborne could be achieved, as proven by cruise missiles and other missiles. Take off could be ramp assisted if needed, it's partly why the British aircraft carriers had ramps at the bow end when the Harrier jump jets were in service. Landing could be an issue but that's where the thrust vectoring would be critical.

The other option is to replace the narrow side fins with variable sweep wings that could be retracted during flight.

The thrust vectoring functions would be critical to provide manoeuvrability when unexpected events occur, such a avoiding bad weather and encroachment into flying space by other aircraft - collision avoidance.

Answer 3

Helicopters are proof you don't need wings at all.

However, short wings (left right), no matter how long (front back), are less efficient than wide wings. You can see this from basic physics without having to understand anything about how wings actually work.

Consider a plane in straight, level, and steady flight. The net force on the air is to push down on it by the weight of the plane. That force is produced by imparting momentum downwards on the air immediately surrounding the plane as the plane flys by. Momentum is mass x velocity. In this sense stubby wings and wide wings are equivalent. You can get the same momentum by pushing a little air a lot (stubby wing), or a lot of air a little (wide wing).

However, consider the power requirement. Power is proportional to the square of velocity times the mass. Therefore, pushing a little air at high speed takes more power than pushing a lot of air at low speed. Stubby wings transfer more power into the air for the same lift. This extra power shows up as higher drag, which ultimately requires more pushing from the engines to overcome.

Wide and thin wings are best for efficiency, but there are structural limits and other trade offs. Note that wings of gliders (where efficiency is very important since the power comes from altitude loss) are very wide, but thin in the other two dimensions. They also can't carry much payload, in part because the wings are too fragile to support it.

Everything is a trade off. Jet fighters have other important criteria, like maneuverability, high top speed, good cockpit visibility, small radar cross section, etc. It is often useful to give up some efficiency in return for these other features. It all depends on what the plane is supposed to do.

Take a look at the F104 as a example of stubby and thin wings. It was fast, but also very tricky to fly, with several pilots lost due to inability to control the plane.