98
Air-to-Air guided missiles are little airplanes. If there are only fins at the tail, it's a ballistic rocket, basically a fin stabilized artillery shell accelerated by a rocket motor instead of an explosion in a pipe.
On missile like AMRAAM, Sidewinder, or Sparrow, the vanes are wings and the missile is a rocket powered aircraft that can climb, descend and ...
55
An 'aerodynamic force' (just one force...) appears when a body is immersed in a fluid stream. By convention, two components are chosen, one of them parallel to the stream direction, called 'drag', and the other one, perpendicular to that 'drag' is termed 'lift'.
54
It depends on exactly how you define "lift" and "weight". You might say intuitively that lift is all the forces acting on the aircraft in the upward direction, like this:
In this case, lift must equal weight, otherwise the aircraft would be accelerating. That is, it's rate of climb would be changing.
But it's more usual to define lift this way:
Here, lift ...
49
Interesting question. Purely empirically, it is the lift-to-drag ratio you are looking for. If you take this value as given for any particular aircraft, you have a direct answer for how much more effective wings are. It is the ratio of the lift to the total drag. The engine only needs to overcome the drag.
With L/D equal to unity you would need the same ...
46
Yes, otherwise airplanes would be unable to go upwards into the sky.
44
This podcast with one of the pilots answers just about every question on the shuttle carrier you could have and it's worth a full listen. But to cover the flight dynamics, I would skip to 50:33 minutes, where the pilot states (please note there is no official transcript of the podcast and I typed this as I listened to it, please see the official podcast for ...
42
Yes, a wing can (given sufficient forward speed and angle of attack) generate lift greater than the weight of the aircraft. As with any "unbalanced" force, this will result in an acceleration of the airplane in the direction of the lift, according to Newton's Second law. $$\mathbf F=m~\mathbf a$$
Please note, the entities in bold face are vector quantities....
41
To get to the bottom of it, it might help to look at lift at a molecular level:
Every air molecule is in a dynamic equilibrium between inertial, pressure and viscous effects:
Inertial means that the mass of the particle wants to travel on as before and needs force to be convinced otherwise.
Pressure means that air particles oscillate all the time and ...
38
Short answer: This design will probably work, but it will not be very efficient. It can be tweaked into flying, but when you start tweaking, you would continue such that the outcome would look differently.
Now let's look at your questions one by one:
How feasible is it to use a propellor larger than the wingspan? Is
there any law of physics that ...
37
Juan de la Cierva's first autogiro did roll over, twice, and he then applied the principle of blade flapping, a stroke of genius. Flapping is created by allowing the blade to move up and down. Depending on rotor head design this is done in different ways:
By a flapping hinge at the hub, allowing vertical rotation.
By a teetering hinge on two-blade designs, ...
32
Short answer: by exerting a downward force on the air around them.
Long answer: Some outreach people at NASA's Glenn Research Center have written up a very good multi-page explanation, dealing individually with each contributing effect, as well as some discussion of why explanations you might have heard at school don't work. Since the navigation there is a ...
32
A wing can be tested in any orientation as long as the load is applied correctly. The classic wing test photo is the 787 in a fixture showing its extremely flexible wings.
I thought it might be fun to add an ultimate load test, so here is the 777 tested to failure. Sorry for the early 1990s video quality.
Boeing 777 wing fail at 154% design load
31
Your misunderstanding lies in your thought that lift is smaller than thrust, while in fact, lift is much larger than thrust.
The lift is provided by the wings. Their purpose is exactly to create a lift force (upwards force) while requiring relatively little thrust (forwards force). How well they do this is expressed by their lift-to-drag ratio (L/D ratio). ...
30
Short answer: Yes, our understanding of lift is complete, but solving the equations for some practical cases needs more resources than what is technically sensible.
Lift is a matter of definition
First of all, lift is only one part of the aerodynamic forces. It is the component normal to the direction of airflow. Since the aircraft will distort the local ...
29
With regard to energy expenditure and power,
for a given amount of force that is to be produced by accelerating
an air mass,
more power is required when you accelerate a small air mass
in each period of time than when
you accelerate a large air mass.
This is because the force is proportional to the change in momentum
of the air mass, whereas the power is ...
28
No, it could not fly much faster with the available energy.
Lift is a question of wing area and dynamic pressure. Solar Impulse 2 has 269.5 m² wing area to carry its 2.3 tons of mass. This is a wing loading of just 8.53 kg/m²; much less than even gliders have (they start at around 30 kg/m²). This allows it to fly very slowly; if we assume it ...
28
Your airspeed does not remain constant because of inertia: it takes more time for the airplane to adapt to the new relative wind, compared to the time it takes for the wind to change.
Example One: you're flying 80 knots and the headwind is 20 knots. Over a time of 3 minutes, the headwind gradually reduces from 20 knots to 10 knots. Since the change is ...
27
@PilotHead is correct, but to elaborate a bit on why traditionally weight was put on the bottom is largely because its just easier. If you are Boeing you can afford to build a rig large enough to hold a plane down while you pull the wing up. If you are building a home build in your garage its far simpler to put some sand bags on it and let gravity do the ...
26
In a traditional aircraft the majority of the power from the engine is used to keep the aircraft moving forward at a certain speed. Very little of that power is actually needed to create lift.
Consider a simple paper airplane. It flies for a long time with no engine at all, until the drag on it causes it to slow down and if loses lift and descends to the ...
25
The vortex lift is the method by which highly swept wings (like delta wings) produce lift at high angles of attack.
In the case of wings having sharp, highly swept leading edges like delta wings, the leading-edge separation vortex phenomenon occurs at subsonic speeds. However, the separation does not destroy the lift as in the case of low sweep wings; ...
24
First, let's agree on terminology: What you saw in airshows is a vertical flight path. Flying horizontally first, the airplane pitched up until the nose was pointing straight into the sky.
Surprisingly, no thrust is needed to perform this maneuver. Even gliders can do it. What happens is that kinetic energy is converted to potential energy, the rate of ...
23
Thrust is needed to overcome drag, and a good airplane design can create a lot of lift for little drag. In the case of an A-320, the lift-to-drag ratio is 18 in cruise (a little less during take-off), so to lift those 78 tons needs only 4.33 tons of thrust. All it needs is the right amount of forward speed, and the engines only need to maintain this speed.
...
22
For a parcel of air to generate a lift force as it flows over the wing requires the wing to tip that air parcel's momentum vector downwards slightly; the reaction force that the wing experiences as it does this is what we measure as lift.
In the case where the airflow over the top of the wing separates from it, the parcels of air flowing by do not get ...
22
The missile's wings are very large for it's mass, and produce a great deal more lift than the wings of the aircraft firing the missile.
One thing to note from the OP's linked video is that the F-35 and the chase plane are traveling at the same speed, so the F-35 appears stationary. However, that aircraft is likely traveling in excess of 0.8 Mach. Therefore, ...
20
With current technology the L/D might go up to 70 or 75, and going higher would require an almost impractically large wing span. Gliders need to fly in tight circles to use updrafts, and the larger the wingspan becomes, the bigger the speed difference between inner and outer wing will be. Also, landing such a wide wing without dropping a wingtip will be very ...
20
A lot of aircraft generate negative lift- not in the wings, but in the tail plane. This is used for stability. Consider a trimmed aircraft as shown below:
Image from grc.nasa.gov
On most aircraft, the center of gravity (through which weight acts) of the airplane is located near the center of pressure (through which lift acts) of the wing. If the center of ...
20
The reason is a temperature difference between the lift gas and the surrounding air, and probably water uptake by the hull when descending through clouds.
A given mass of hydrogen will create a constant lift force, regardless of pressure or altitude, when at equal pressure and temperature with the surrounding air. Therefore, a change in altitude will not ...
20
In the video you posted, the missile appears to continue falling even after the motor ignites -- you can see the missile start to overtake the aircraft even as it continues to drop:
By the last frame, it appears to have taken a slight nose-up attitude to maintain altitude:
19
I am a CFI who teaches at a large (+200 students) flight school in the United States. You might be surprised to hear this, but...
We really don't worry about how a wing works that much.
As far as I'm concerned, the technical explanation for how a wing works is a subject for the engineers who build and design such things. Private pilot applicants (at ...
19
What it is
Vortex lift needs two conditions:
High leading edge sweep (ideally 60° and above)
High angle of attack, the more sweep, the smaller the angle when vortex lift becomes effective.
Vortex lift is caused by flow separation at the leading edge. While this indicates a severe stall on unswept wings, the separated flow along a highly swept edge will ...
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