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# Tag Info

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 ...

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....

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). ...

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

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:

18

Furthermore to @Zeiss' answer, whenever an aircraft is steady-state banked, the lift will be greater than its weight. However, its speed will be constant; instead, the acceleration is centripetal and results in a circular turn. Edit, clarification on pull up maneuver: When an aircraft is pitched up via pitch control, and after the short-period mode settles ...

14

The lift equation is $$L = \frac{1}{2} C_L · v^2 · S · \rho$$ where $S$ is wing area, $C_L$ coefficient of lift, $\rho$ air density, and $v$ airspeed. Using units of measure $\text{m}^2$ for $S$, $\text{m}/\text{s}$ for $\text{v}$, and $\text{kg}/\text{m}^3$ for $\rho$, the result is lift in $\text{N}$ (newtons). Concerning symmetrical airfoils, they work ...

13

Depending on the range and mission of your missile, body lift alone may be enough to keep it aloft. @dotancohen pointed out that a typical missile's wings are large for its mass, but look at the ASRAAM - it has only small tail fins which are there purely for attitude control, rather like an AIM-9X (which already has much smaller wings than the 9M) but with ...

8

Interestingly enough, for the orbiter separation maneuver to work, the Shuttle would need to have a higher lift to weight ratio than the carrier 747. Plenty of people were probably wringing their hands (including me) over the possibility of the orbiter hitting the V stab upon release, but when you see the video, it isn't even close. This was accomplished ...

7

The horizontal stabilizer provides lift, but usually in the negative direction. Could one provide positive lift? The answer depends on cg location. Forward CG, the answer is no. Aft CG, the answer is yes but only if the CG was aft of the center of lift. In other words, the more forward the CG is compared to the center of lift, the more downforce the tail ...

7

Think about it this way. Assume a cambered airfoil, not a symmetrical airfoil. Assume the wing has zero twist and zero incidence. To place the wing at the zero-lift angle-of-attack (zero CL), the fuselage and wing will have to fly at a somewhat nose-down pitch attitude relative to the airflow. This does not yield the lowest possible drag coefficient, ...

5

Your math looks right to me. If an airplane has the statistics that you listed there, then it will accelerate upwards at $16.48\ \mathrm{m}/\mathrm{s}^2$, as you calculated. The occupants will experience about 3 g's of proper acceleration (1 g from gravity, and about 2 g's from the acceleration). But here's what would actually happen, in context. To start,...

5

No, there's no simple equation for the relationship. Here's an example lift coefficient graph: (Image taken from http://www.aerospaceweb.org/question/airfoils/q0150b.shtml.) This is actually three graphs overlaid on top of each other, for three different Reynolds numbers. I'll describe the graph for a Reynolds number of 360,000. We see that the ...

5

For any airplane to fly level at a constant altitude, the amount of lift generated by its wings must be equal to its weight. If lift exceeds weight, the plane starts to climb. If weight exceeds lift, the plane starts to descend. In a constant rate climb/descent, lift equals weight; a simplification that ignores the propulsive force vector. The engine & ...

5

Because a wing produces way more lift than drag. Thrust must equal drag, not lift. ...thrust-to-weight ratio as low as 0.3. That's a drag-to-lift ratio, actually. And that is why you find fixed wing aircraft everywhere, otherwise all aircraft would be VTOLs

5

What is the proportion of lift coming from the wings compared to that of the fuselage? It can be almost zero. The ASRAAM's only fins or wings or lifting surfaces or whatever you call 'ems are at its very tail. Any "lift" they impart, that far from the missile's center of mass, would pitch (or yaw) the missile instead of counteracting gravity. So almost ...

5

In the most simple model for subsonic aerodynamics, drag is split into two components: Zero-lift drag, that is all the drag created when the airplane produces no net lift. This kind of drag has again two components: Friction and pressure drag, that is the aerodynamic drag parallel and perpendicular to the local surface. This drag would dominate in a ...

4

When the wing is moving horizontally, the air produces a force F on the wing, and F has two components, L and D. Because the angle of attack of the wing is generally much less than 45 degrees, D is also much smaller than L. Since the thrust of the aircraft is only balanced with D. Therefore, with a small thrust, a large force L can be generated, L can be ...

4

The space shuttle's wings are small, but they still act like wings. Their lift depends on the actual angle of attack. The space shuttle cannot be neutral for all angles. The engineers had a choice at which precise angle to mount the space shuttle on top of the carrying 747. I would assume that the shuttle is rather close to neutral at cruising speed, to ...

4

Something like it is widely used, only not by this name. Although less elegant and general than Prandtl's paper, the same solution was found 17 years later by R.T. Jones when he optimized the ratio of lift to mass of wings in NACA TN 2249. The figure below is from the concluding page of this report. However, induced drag is not all. By increasing span, ...

4

In the post-stall regime, airflow around the wing can be modelled as an elastic collision with the wing's lower surface, like a tennis ball striking a flat plate at an angle. Lift and drag are thus: $$c_L = sin(2\alpha)$$ $$c_D = 1-cos(2\alpha)$$ I superimposed those (blue line) with measured data for a symmetric NACA-0015 airfoil and it matches fairly ...

4

Forget about tailwind/headwind for flap use. Flaps allow landing with a lower airspeed. And you always want a lower airspeed. The wind itself is irrelevant except that your groundspeed will be higher or lower depending on where the wind is, and which you always want to be slow as possible. On light aircraft you want to avoid tailwind components over 5kt. ...

4

If you have a fixed aerofoil in a wind tunnel, lift increases with the square of the air speed. However a real aircraft usually only needs enough lift to balance its weight, so as it flies faster it will also decrease the angle of attack to keep the lift constant. Conversely, if a pilot wants more lift in order to make a tight turn, he will usually ...

4

The well-known 3D drag model of: $$C_D=C_{D_0}+KC_L^2$$ only holds well for high aspect ratio, flap retracted wing configurations (source: ESDU Item 74035). With flaps extended, a better model would be (source: ESDU Item 97002): $$C_D=C_{D_0}+AC_L+BC_L^2$$ If you rearrange the terms a little bit, you get the model shown in your graph: C_D=C_{D_{min}}...

4

The propeller generates thrust to counter drag. Drag is created by both the forward velocity of the plane through air (parasite drag) and as a byproduct of lift (induced drag). Lift is a also a consequence of movement through air and is used to counter weight. The above is mostly true for conventional, heavier than air, fixed wing aircraft in un-...

4

In straight and level flight at an airspeed V, the weight W is balanced by the lift L, and the aerodynamic drag D is balanced by the thrust T. D is much smaller than L. In a passenger liner, D may be 1/12 ... 1/20 of the weight, or so...

4

It's the component of the aerodynamic force perpendicular to the direction of the air flow, the aerodynamic force being the reaction of the wing to the relative wind.

3

You have volumetric flow rate and diameter, so you have the $\Delta v$ ($v = A \dot V$) and you have the mass flow rate ($\dot m = \varrho \dot V$) and that gives you the momentum per unit of time a.k.a. force ($\dot p = \Delta v\cdot\dot m = F$). Run the numbers yourself, but don't get high hopes—the result is tiny (of course; you need a couple of metres ...

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