Usually planes are able to fly when air moves across the wings which generates lift. But how do fighter jets able to maintain lift while performing aerobatic maneuvers?
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If the engine thrust is more than the weight of the aircraft, it can push itself up, without needing the wings lift, to stay airborne.
Three things:
– Excess power: more than required for its weight. Big boom at back, big speed in front. So they can even accelerate while flying straight up vertically.
– Unstable: Unlike regular aircraft which like to be stable and fly straight, fighter jets are usually inherently unstable. While this might sound scary, it means that it responds very quickly to the pilot’s control inputs.
– Wing loading: The wings are blended with the fuselage in most modern fighters, so the g-force load is distributed evenly. In other words, hard maneuvers won’t break the plane.
All of this contributes to a concept called *supermaneuverability.* For normal aircraft, you can maneuver them only by altering the airflow over the wings, ailerons, elevators, rudders etc. For fighters, you can control them in situations which exceed pure aerodynamic mechanisms. Hence they are *super* maneuverable.
There are a lot of misconceptions about lift. One big one is how significant the Bernoulli effect is on lift, this is the common explanation of “air moves over the wings which generates lift.” The more important component to lift is the simple act of air hitting the wing at a slight angle, air bounces down, Newton’s third law pushes the plane up.
As long as your plane is slightly angled against the direction of your motion/the air around you, then the plane will have a force on it. Sometimes this is the whole wing, sometimes this is just an aileron.
And sometimes you don’t even need lift. As long as there’s a good mile between you and the ground, its ok to “fall” for a little while before bringing your aircraft back to a position where it generates lift. And if you can create enough vertical speed, you also buy yourself a little more time before you need lift. A loop involves turning your plane up to convert all your horizontal speed to vertical speed by means of lift due to higher angle of attack. That vertical speed can get you pretty high before gravity starts calling again.
Lastly, those engines on fighter jets are powerful, sometimes they have a bigger thrust to mass ratio which means they alone can provide enough force to fight gravity. Though you don’t necessarily need strong engines to do acrobatics.
In order for a plane to fly, it has to push its own weight in air downward. Then, as per Newton’s Law, the plane in turn gets its own weight in force upward and flies. It can push air in a variety of ways. The airfoil curve of the wing is just one way— there is also outright deflection (the wing pointing up and air bouncing off the bottom side), an engine pointing downwards, or even some planes have ducted fans or downward-pointing fans to take off on short or even no runway. Anything that forces air down makes the plane go up.
The basic answer is their engine is so god damn powerful it can hold the aircraft up by itself. Everything else is how does it distribute that power. Literally, the only thing that keeps a fighter jet in the air is the raw power of the engine when the wings are not producing lift.
I’ll try an ELI5 verison: Think of a pendulum. It swings back and forth. At the bottom of the swing it has no ‘height’ but lots of speed. At the top of either swing it has a lot of ‘height’ but no speed. All it does is trade speed and height back and forth. Both are forms of energy; potential and kinetic. You’re allowed to trade those two, there is even a math formula for it.
This is all aerobatics is, energy management, trading one form for the other. An aircraft can do this as long as there is some airflow over its control surfaces so the pilot can steer it.
The wings really help because air is a fluid so there is drag, wings are good at trading height for speed while creating little drag. But drag always wings, drag steals energy so eventually you need to add my energy back into the pendulum/plane system. You can do that by either losing height over time or having an engine that adds energy back into the system.
Some further things to help you grasp. A plane doesn’t always need to be generating lift, it can be ‘falling’ and that’s fine. An example of this is a plane is at 90 degrees of bank, it will not keep altitude, it will fall some. It’s fine. Also, some planes can fly level while being upside down, generating lift.
I think the better question you should ask to understand this is how does a glider do aerobatics?
Source: Had to do a bit of aerobatics as part of my flight training in an underpowered plane. It’s all about energy management.
In the 1960s and 1970s, NASA performed lifting body experiments…and concluded that if you put enough power on any aircraft, ANYTHING will fly! It does not need wing to fly (see rocket), it just makes it more efficient. Now we add vectored thrust, and you have super maneuverability on aircraft.
The ELI5 version is that they still create lift while doing most aerobatics. More advanced aerobatic planes have semi or fully symmetrical airfoils so that they generate lift upside down as well as right side up.
The higher level explanation gets into what lift actually is…. And this discussion can hurt even college level physics students heads. We will skip Coandă and just lightly touch on Bernoulli and Newton.
Bernoulli the theory is that the shape of the wing creates a low pressure area on the top of the wing and the higher pressure at the bottom tries to fill that lower pressure. You can demonstrate this by taking a dollar bill, holding it between your index and middle finger by one end and letting the bill lay on top of your ring and middle fingers. You then gently blow across the top and when you get the angle correct the bill will float off your fingers.
Newton can be shown with the exact same set up, but blow on the bottom of the bill and it will just float off your fingers as well.
Just for fun the Coandă effect has to do with how the fluid mass wants to stay attached to a surface, when that surface flows down at the end the fluid stays attached and as it runs off the back of the wing it has a slight downward motion which pushes up.
The simple point is that all of these are part of what creates lift and that does not change when an airplane is doing aerobatics. For example in a level competition roll the top of the wing is creating lift, then when you get the wing vertical the fuselage of the airplane is actually creating lift (pure Bernoulli) and the the bottom of the wing and then the fuse, then the top of the wing again. And it is not like they turn off or turn on suddenly. It might start at 100% wing and zero fuselage and then as you roll it goes 90/10, 80/20, 70/30 till you reach 50/50 and then it starts reversing 40/60, 30/70 till it is 0/100 wing/fuse and then just keeps going till you are 100% inverted wing etc.
The posters claiming pure power… Most aerobatic planes, and most planes period, don’t have a more power than weight. For example the Extra 330SC weighs 1720 pounds and has 315HP… It simply can’t hover because it does not have the power to weight ratio needed.
Because we really don’t know how aircraft works. We have some theories that explain the idea behind it, but none of them cover the entire phenomenon of flight as we know it.
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