56

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 ...


38

Yes it can. The steady-heading sideslip (SHSS) maneuver is used in flight testing to demonstrate static lateral/directional stability (similar maneuvers exist as sideslip approach in crosswind, or stabilized control with one-engine-inoperative at low speed). In this maneuver, rudder is applied to hold a sideslip, which generates an opposing side force and ...


32

This is a basic physics question, involving Newton's third law of motion (For every action, there is an equal and opposite reaction.) When a centrally mounted engine applies force to turn the rotor, the equal and opposite reaction creates torque on the fuselage. With a tip jet, the force is applied by the jet shooting its exhaust perpendicular to the blade,...


27

Good question! There's a bit of a misconception: when the elevon moves up, it actually decreases lift. It pushes air up which pushes the wing down. This explains the roll behaviour, but how does decreasing the lift make the plane go up? The key here is that the lift is reduced only at the rear of the plane. In other words, the rear of the plane is pushed ...


26

The short answer is no. All the glider feels is its flight relative to the air. What the ground is doing beneath it is not relevant, the wind could be blowing a hundred kilometers an hour and the glider would just be carried along without feeling a thing. This is why unpowered balloons always drift with the wind. To detect and respond to ground speed ...


25

Static stability means that a deviation from a trimmed state produces forces which return the system to this trimmed state. If these forces produce an overshoot which increases over time, such that the system oscillates around this trim point with increasing amplitude, the system is dynamically unstable. The long period oscillation (phygoid) of gliders is ...


24

You are absolutely right, a load factor of greater than 1 is impossible to avoid in a proper barrel roll. The barrel part of its name comes from the spiral path the aircraft needs to perform in order to add a centrifugal acceleration which is greater than gravitational acceleration at the top of the roll. This is the condition to ensure a still positive ...


24

This approach of using an engine is called pulse and glide. It generally works because each engine has an optimal power setting at which it converts fuel into power most efficiently. If the most efficient power is higher than is required, something should be done to accumulate and later use the excess energy. Raising the vehicle up looks like a solution, ...


21

The ground is not flat, and indeed slightly angled. This is enough to "hover". Specifically, the ground slope should be equal or more than the max L/D ratio of the hang glider at the current wind speed. The wind should go 'up' as much as the glider goes 'down' per unit of distance. The ground seems to go up about 2m over a distance of maybe 10m, ...


19

As the answers to your original question already explained, you do need extra lift to accelerate upwards. Once the wing is set into a vertical motion, however, lift again exactly equals weight to keep the wing at a constant vertical speed (if we neglect thrust and drag for a moment). No extra lift is needed to maintain that vertical speed. Only when you want ...


19

In an aircraft that is climbing at a constant vertical velocity, the total of the upward-directed vertical forces is the same as the total of the downward-directed vertical forces. Were it not so, the vertical velocity would not be constant, since any non-zero balance of the vertical forces would result in an acceleration...


18

If an aircraft is statically stable, it will always return to equilibrium after a disturbance. But what happens after can either show instability or stability. This is where the dynamic stability comes in. You can think of an aircraft at equilibrium at a particular speed, altitude and angle of attack and it is suddenly faced with a disturbance which changes ...


17

It is easier if we look only at the forces experienced by the aircraft, and in an inertial frame of reference In this revised diagram, the vertical component of the lift balances the weight, which is vertical. There is a remaining horizontal component of the lift, and this causes the turning. "Centrifugal force" does not exist (and is not needed) in an ...


17

Yes, it's entirely possible. You can use the rudder to oppose the turn induced by the roll, and thus fly straight. However, doing so means that your nose is pointed off at an angle from your direction of flight, so this dramatically increases drag. In fact, this is a common technique (at least among general aviation pilots) for losing altitude without ...


16

There are multiple configurations which are possible with tail or canard, which based on their locations and whether they produce lift or down-force, results in a stable or unstable aircraft (taking the aircraft center of gravity into account). The figures below show some of the possible configurations. Source: f-16.net In the most general case, there is ...


16

Here is one thing that WILL save fuel-- where possible-- such as when flying VFR. Note that this strategy only applies within the layer where thermal convection or orographic uplift are significant, not at higher altitudes where the air is generally not rising or sinking to any significant degree (apart from wave lift in which case the strategy will still ...


15

Short answer: No. Long answer: When the flight path is not horizontal, lift will not be vertical but perpendicular to the direction of motion (in still air). Thrust will also have a vertical component and is different in magnitude from drag, because excess thrust is needed to increase the potential energy of the plane. Note that the vertical component of ...


14

Source: Wikipedia. Origin of the theory Klaus Holighaus, one of the famous glider pilots of the 70s, and himself a glider designer at Schempp-Hirth, is at the origin of a controversy when he recommended not to turn with the ball centered, and especially when climbing in thermals. Mr Holighaus did see two problems with the perfectly coordinated turn: It ...


14

All aircraft are subject to performance changes due to fuel burn, and since weight, lift, thrust and drag are all tied together for every aircraft in the same way the changes scale nicely. Let's look at some extremes: One of the most interesting examples of this was the Concorde. Since the Concorde flew ~20K above every one else in the sky in those days it ...


13

The problem of the picture you are looking at is that both the actual and the apparent forces are shown. The real force is the centripetal one (that in turn is only the horizontal component of the lift force), the centrifugal one does not exists, is only an "impression" of the centripetal one as seen by a person standing in the aircraft (a non inertial ...


13

From a deleted question: by @ffejrekaburb From an email from the author of the SeattleTimes article, Dominic Gates: The description of MCAS provided by Boeing for regulators (FAA and foreign) during certification, is this: MCAS “was added to address potential nose-up pitching moment at high angles of attack at high airspeeds outside the ...


12

Of course, just put the center of gravity back to its rear limit and fly slowly. Then all of them will produce positive lift on their tails. Stability is not produced by a downforce at the tail. The newest book I read which claimed this was from 1911 (I happened to read the 1913 edition). Stability is produced by making the lift per area of the forward ...


12

suppose you dropped an uncontrolled dummy glider into the air... Dropped is the key word. Upon release the glider, if it were directionally stable, should "point" into the "wind". The key is the definition of relative wind. This would be air flow relative to the air craft. Any heavier than air craft must have some relative wind to ...


11

Is this use of "straight and level" correct? What is the definition of straight and level, if any, regarding heading, attitude, speed, altitude? In the airplane flying handbook the FAA defines straight and level flight as Straight-and-level flight is flight in which heading and altitude are constantly maintained. My understanding and the ...


11

Think of the aircraft engine as one isolated system and the rotor as another isolated system. In its simplest terms, torque is the force required to move mass in a circular motion. Torque is caused by the engine providing power to the rotor shaft which moves the mass of the blades. The torque is the interaction of the stationary engine trying to move the ...


10

A tandem wing airplane has two sets of wings, each providing upward lift. One is near the front of the plane, one is near the back, and the center of gravity is between them. (source: nurflugel.com) The Rutan Quickie is one such plane: (souce: wikimedia) This design is actually fairly old; it even predates (successful) heavier-than-air flight, as it was ...


10

When you say, No power invested by the propeller goes into potential energy of the wing; the climb of the wing is done purely by lift. you're missing where the energy of the wing comes from. Lift isn't a magical power that creates potential energy out of nothing: it just turns airspeed (kinetic energy) into height (potential energy). In your example, the ...


10

First of all, in the diagram they show the force on each wing being the same. In a steady roll, i.e. when the roll rate is constant, the forces are the same. A non-zero moment causes angular acceleration, so when the aircraft is rolling with constant rate of roll, the moment must be zero, which means the lift on both wings have to be equal. That rules out ...


10

The diagram is not a correct force diagram in the inertial frame of reference. In the inertial frame of reference, the horizontal force on the aircraft is unbalanced. This causes the aircraft to accelerate in the direction of the net horizontal force, perpendicular to the direction of flight, and this curves the path of the aircraft. The law of "equal and ...


9

This makes sense and is approximately what happens if you reduce thrust during trimmed straight and level flight. The aircraft will go though a series of damped oscillations, called 'phugoid' until it finds its new equilibrium state. The new state will be the original airspeed, but now in a constant descent.


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