This is one of those “oxymoronic” questions that has really gotten under my skin lately.
Everybody “knows” that wings generate lift because the longer path over the top of the wing creates a “low pressure” zone that pulls the plane upward.
Except that planes can fly upside down.
“Theoretically” the wing should be providing “lift” in the downward direction that should force the plane to fall.
(And “theoretically” bees can’t fly either.)
So. . . . .
Why doesn’t an inverted aircraft crash? And how does an aircraft maintain stable inverted flight?
For example: Can something like a Cessna 172 or a Diamond Katana fly inverted? Or is that the exclusive provence of planes like the Red Bull aircraft that have turbocharged rocket engines powering the propeller?
Note:
I am deliberately excluding military jets and such like that are essentially rockets with wings.
Simple question, simple answer (from ChatAI - other AIs such as Skynet many be available)
Flying an airplane upside down, also known as inverted flight, is possible due to the principles of aerodynamics and the design of modern aircraft. While not all airplanes are designed for sustained inverted flight, aerobatic and certain high-performance aircraft are capable of performing maneuvers in which they fly upside down.
Here are the key factors that allow an airplane to fly upside down:
Lift and Gravity: Lift is the upward force generated by the wings, which opposes the force of gravity pulling the aircraft downward. Inverted flight requires the wings to generate lift in the opposite direction. This can be achieved by maintaining a positive angle of attack (the angle between the wing’s chord line and the oncoming airflow) and appropriate control inputs.
Control Surfaces: Airplanes have control surfaces such as ailerons, elevators, and rudders that allow pilots to control the aircraft’s attitude and direction. During inverted flight, the pilot must use these control surfaces to maintain the necessary control inputs to counteract the natural tendency of the aircraft to pitch and roll.
Engine and Fuel Systems: The aircraft’s engine and fuel systems must be designed to function properly in inverted flight. Most modern aerobatic and high-performance airplanes utilize inverted fuel and oil systems that allow continuous fuel and oil flow even when the aircraft is upside down. This ensures that the engine remains operational and lubricated.
Structural Integrity: Airplanes designed for aerobatics or advanced maneuvers are built to withstand the stresses and loads associated with inverted flight. The wings, fuselage, and other structural components are reinforced to handle the inverted flight conditions without compromising the safety and integrity of the aircraft.
It’s important to note that not all airplanes are designed or certified for inverted flight, and attempting to fly a regular aircraft upside down can be extremely dangerous or even catastrophic. Pilots require proper training and a thorough understanding of the aircraft’s limitations and capabilities to safely perform inverted maneuvers.
The “everyone knows it’s the shape” is actually wrong, in that people think round on the top and flat on the bottom is what that means; that just optimizes the airflow to reduce drag. Lift is generated by the combination of forward motion through the air and the angle of attack of the wing; complications of flying inverted are more about fuel pumps and structural integrity than the aerodynamics.
All of this. Some underpowered aircraft will have trouble maintaining enough of a negative angle of attack to overcome the inverted inefficiency of asymmetric wings.
Oil distribution while inverted is also a big issue.
some planes can fly upside-down as in they are designed to do so. Some planes can fly upside down for a little bit before you cause mechanical damage and fall out of the sky. Some planes just don’t have the oomph to get over 30 degrees roll without stalling and falling out of the sky.
But given that this is a simulator, you can find out what can fly inverted without the risk to life and limb…
TLDR: When inverted, compensate by pulling down a bit on the stick. Down = up when inverted, and creates lift that the wing normally would produce without further input when right side up.
Another way of possibly thinking about it is a wing is an upside down ridge when your angle of attack is positive. When inverted, your angle of attack will be negative to provide lift, and the ridge analogy is just as if you were looking at a real ridge from the windward side.
In dynamic soaring a ridge creates a wind sheer where there’s more energy above the ridge than below. This principle exists in water as well. Where the water is “fixed” or no wind and the wind above the water is moving faster.
The wind behind the angle of attack (below the ridge) is moving slower or fixed.
The wind above the ridge (or in front of the angle of attack) is moving faster.
This is because it’s not obstructed.
This phenomenon provides energy to the system. In sailing a keel fixes you to the water which moves less than the wind; and the sail fixes you to the sail.
In this system (this is literally how it works in sailing a ship) the energy is transferred from the sail to the keel/hull.
Some of this energy results in motion because it has to go somewhere. You’re artificially slowing down wind above and taking that energy and putting it to use into the water.
I see no reason why a plane’s lift actually doesn’t work the exact same way.
It takes energy from the faster-system and distributes it to the lower system. Some of that energy translates into acceleration. The angle of attack directs the acceleration in a way that provides vertical thrust.
This is “lift” because it can be accomplished without any power from a power plant. Or rather the wing is the power plant.
This is also how a windmill works, only it generates much more power because the fixed portion is anchored to the ground so the wing doesn’t convert energy into moving itself into the wind. It’s prevented from doing so.
When flying inverted, lift from angle of attack simply overrides the lift from the airfoil. In fact, some light aerobatic planes have a symmetrical airfoil, meaning there is no front-back difference in distance between the top and bottom of the wing. All lift is generated from angle of attack.
However… There are a few maneuvers that maintain positive lift even when inverted. Here’s a perfect example:
