Wing design - an ignorant question?

Question

OK, I uderstand the basic principles of wing lift. but ...
When flying inverted how do I get a similar lift factor ?
I like "upside-down", but having asked the question, I get different answers. Is their a definitive one in terms of wing design.
I hear that Concorde was capable of inverted flight. How so ?
There must be a simple answer.
Excuse my ignorance, and thanks for any response.
Bob

Answer 1

Simply put

The way a wing generates lift is the air on the top of the wing travels faster than the air on the bottom of the wing.

With an airfoil with camber the distance along the top of the wing is longer than the distance on the bottom, thus forcing the air to travel faster on the top, hence lift.

With a symmetrical airfoil, actually found on many aircraft, the lift is generated when the airfoil is at an angle of attack greater than zero, so the air meets the wing on the lower leading edge so we have a similar situation where the air has to travel a further distance from that point if it goes over the top of the wing, hence lift. This point where the air splits in both directions is called the stagnation point. You will see on aircraft with a symmetrical airfoil the wing is mounted at a slight upward angle so when the aircraft is cruising the wing is pointing upwards but the fuselage is more or less level.

At zero angle of attack no lift is generated, and at a negative angle of attack lift is generated downwards.

Therefore for an aeroplane with a symmetrical airfoil the lift generated by the wing at a specific angle of attack will be the same whether it is right way up or inverted. Concorde has a symmetrical airfoil so yes theoretically the aircraft could fly just as well upside down, whether the engines, fuel system and passengers would like that is a different story.

This is not to say that airfoils with camber cannot fly inverted, they can but have to fly at a very significant angle of attack to counteract the camber effect, hence higher drag, more power required and less margin to the stall.

Hope this helps, I couldn't help but answer this some of the answers are so bad I hurt myself laughing.

Answer 2

An ignorant question is one left unasked.
If the basic principles you understand revolve around Bernoulli it's easy to see how inverted flight may puzzle you. His theorem requires the principle of equal transit times to be true. And it's not. The air travels considerably faster over the upper surface of the wing arriving at the trailing edge some time before the air under the wing. And due to coanda effect is also diverted down behind the aerofoil. And it is this downwards deflection of air, in accordance with Newtons third law, that creates lift. In a very summarised form. It is for this reason that aerobatic aircraft have symmetrical wings designed for inverted flight. So as coanda works on both sides of the aerofoil effectively.
However, as someone has already said, even a Cessna 172 can be flown inverted. You'll just get a massive increase in induced drag and will need full power to sustain this attitude. And with gravity feed from the fuel tanks full power doesn't last long upside down.....
But not to worry they start easily enough! So a little birdy tells me....... Although it would be a really bad idea if the engine oil wasn't full to start with..... Actually just don't do it.

Answer 3

Some really wild answers.
It is not really hard to understand if you know air wing design.
Any aircraft designed for inverted flight will have a low camber and symmetrical laminar airfoil, such as an Extra 300 or a Pitts biplane or a fighter jet.
This is to create the same lift upright or inverted, however the lift created is from the angle of attack which is dictated by the position of the aircraft to level.
Also the dihedral angle, which from the front of the plane, is the angle the wings are from level. The above aircraft have a zero angle or even negative, whereas a cessna would have a +3 degree angle for stability. This works like a pendulum.
Having said all that, and there is more, belive me, when a plane goes inverted you must put forward pressure on the stick to maintain inverted flight. Some aircraft need little forward input for inverted as they are designed this way. That makes an aircraft unstable and necessary as we aerobatic pilots love to throw the aircraft around.
Normal aircraft are designed for upright and level flight so the chance of inverted are remote because you also need inverted fuel and oil systems and normal aircraft want to maintain stable flight.
The concord was able for inverted flght due to to wing characteristics but it was not recommended beacause the stresses on the aircraft were designed for upright flight.
An aircraft stresses are defined as +3.5g and -2 g let's say as a norm for a cessna.
My Extra is designed for +/- 10 g.
So simply the design of the "total" aircraft is necessary to achieve inverted flight as well as pilot skill.
So in all what really effects inverted flight is....
Camber of wing
Laminar Air flow
Angle of Incidence
Angle of Attack
Wing dihedral
Planform (Shape of wing)
Aspect ratio
Good question actually.
There is more but in this space I hope I answered your querie.

Answer 4

All the other answers do seem to very somewhat. In terms of wing design, like previously stated, a symetrical wing flies equally the same "up-side down" or "right side up". A high speed aircraft such as a Concord or any fighter jet, the wings are very thin and a bit more symetrical than say a Cessna or very conventional aircraft. The wings are thin because it's more efficient for high speed flight.

However, a Cessna 172 theoretically could fly inverted. Newton's third law is for every action there is an equal and opposite reaction. This one theory says it should be able to do it. It wouldn't be pretty and it'd have to have enough power to overcome the excess drag.

Answer 5

Every wing has a shape which defines its camber. This is also referred to as an airfoil. NACA defines and catalogues all these shapes and each shape has unique properties.
One property is coefficient of lift. Aerodynamicists can determine wing lift based on area, sweep, aspect ratio, and coefficient of lift. Lift also depends on airspeed and air density.
Because all airfoils have a coefficient of lift (c/l), all inverted airfoils must also have a c/l. It stands to reason that a c/l for an inverted airfoil would not be as large as for an upright wing. Nevertheless, it still has a c/l and with the right airspeed, angle of attack, can produce lift.
If the wing can produce enough lift to overcome weight, you have flight.
We seem to be bogged down by the idea of wing camber. But, if you look at the NACA book of airfoils, you will see that conventional wings do not have extreme camber.
I would guess that most airplanes, in theory, could fly inverted.
There are other problems with inverted flight such as the requirement for pressurised hydraulic reservoirs to maintain constant hydraulic fluid supply and fuel systems designed to supply fuel even when inverted on half empty tanks. Fighter jets have these design features due to the fact that they are made for inverted flight.

Answer 6

It's to do with the angle of attack of the aircraft.
The aerofoil won't have the desired effect in inverted flight, so the lift must be obtained by other means.

Inverted flight isn't as stable over a prolonged distance as normal flight is, and the altitude will start to degrade if it's sustained for too long.

In effect, the nose is pointed more sky-wards in inverted flight, which means the lift is generated mostly by the engine pulling the aircraft alon forwards, and also upwards.
There is also an element of lift generated by deflected air.
If you inclrease the angle of attack, the air hitting the aircraft gets deflected downwards towards the ground, and according to Newtons principles, this in turn pushes the aircraft away from the ground.
It's the same principle that allows a plane to approach a runway at speeds below the actual stalling speed, without it actually falling out of the sky.

Eventually, of course, the plane will stall, as it's not sustainable and the forward velocity drains off very quickly.

And additional for Dan P.
Even the Wright Brothers Flyer had basic aerofoil profile wings.
A fixed wing aircraft will not fly without a rudimentary aerofoil profile somewhere dominant in its design.

Answer 7

You do get a similar lift factor.If left unchecked or untrimmed during sustained inverted flight the design of the aerofoil would eventually fly you back into the ground. Whilst flying inverted for any length of time, a slight downward or negative trim on the elevator would be required thus cancelling the airframes natural tendency to rise or in this scenario head for Terra Firma.

Answer 8

Probably someone told you that the Bernoulli principle was what caused lift in an airplane wing. That is wrong, of course, since airplanes can fly upside down. But it is even more wrong than that: the Wright flyer had a single-surface wing, and helicoplers have symmetrical airfoils, so Bernoulli could not help either of them fly. The real reason is that the airfoil is set at an angle to the incoming wind, and deflects it downward; the momentum thus imparted results in an opposite momentum imparted to the wing. A web site with the details:
http://www.grc.nasa.gov/WWW/K-12/airplane/right2.html

Answer 9

Wow, lot of crazy answers. Let's stick to the 4 basics: Lift, Thrust, Drag, and Weight. As long as an aircraft has enough airflow over the wing, Lift acts in a 90 degree vector to the wing. Inverted, Lift is still "sucking" the airplane toward the top of the wing. The pilot maintains altitude by deflecting the flight controls. Sustained inverted inverted flight creates more Drag than normal flight, because abnormally excessive flight control deflection and fighting combined effect of Weight (gravity) AND the Lift Vector pulling to the ground. As long as you have enough Thrust and flight control authority, you could fly inverted indefinitely. Yes, your aircraft would have to be designed for this, including fuel and oil pumps. As far as the Concorde, I am sure it could momentarily fly inverted. 707's have been barrell rolled, a 1 G maneuver that if you were blindfolded in the airplane, you would not know it happened.

Answer 10

OK, so you know the basic principle of wing design, with the wing designed to allow differnet flow of air over the top than under the wing, thus reducing the pressure on the top, causing lift? This is part of modern aeoro-design, and works very efficiently, allowing horizontal flight to be possible. But what happened before this design was thought of? Look at the Wright brothers' plane, and other early planes. They had flat wings. How did these work? The engine worked harder to create the force to lift the plane, so horizontal flight was only possible if you were causing the power of the engine to oppose the drag down. Without this force, the plane would descend. This still happens in modern aircraft, but too a lesser effect due to wing design - so in effect the wing design causes the plane to be more efficient. Flying upside down is similar in principle to the old planes - it is less efficient than flying the right way up. The wings still "buouy" the craft in the air, just the engine has to work harder to achieve the same result as opposed to flying the correct way up.