New answers tagged aircraft-physics
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Assuming steady-state linear flight and the other constraints stated in the question--
The idea that a component of the Lift vector is helping to pull the glider forward along the glider's trajectory as viewed from the ground is only true when the glider's achieved glide ratio relative to the ground is better than the L/D ratio (which is also the still-air ...
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In steady state linear flight, lift, weight, drag, and thrust all act 90 degrees from one another, as depicted in our knowledge of flight book. An airplane flying along parallel to the ground, 0 degrees pitch, the 4 forces of flight.
Remove thrust (engine out!), we now have the 3 forces of flight. We pitch forward for Vbg, and glide steady state (constant ...
2
In thermals.
More precisely: Every time when the updraft strength increases. The glider will continue on its original path due to inertia while the airflow will have a positive angle when referenced to the path of travel. Now the aerodynamic force will point slightly forward and accelerate the glider.
Experienced pilots use this by pulling more than 1 g ...
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Any glider is powered in part by its lift vector at all times when in normal flight (as opposed to a loop, roll, or other aerobatics, where a reserve of kinetic energy is used and often partially converted to potential). The lift vector is always angled slightly forward when in gliding flight.
The energy for this comes from conversion of potential energy (...
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Is it possible to have a stable aircraft (aerodynamically) in a condition where stabilizer updore is necessary for level flight?
No. Not by the definition of static or dynamic stability.
There are two systems that have to be considered. The first is the wing itself. The airfoil has a center of pressure that moves fore and aft based on angle of attack....
-1
Really 2 questions here:
Since angle of attack is between the relative wind and the chord line, how does turning increase it?
For the average GA wings pictured, in cruising flight, the wing is generating more than 4x more lift force than the engine thrust force. When rolled to the side, the wing will start to pull the plane side ways. Acceleration in ...
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This answer will approach the question by focusing on a more narrow case:
"In a conventional wing + tail configuration, is it possible for an aircraft to be stable even if the tail is creating an upforce rather than a downforce?"
The Center of Lift (or Center of Pressure) is the point where we can treat the wing's lift vector as acting, without having to ...
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Yeah it's right if we consider that the relative wind is parallel to the ground.
In french,the "angle d'incidence" is the angle between the chord line and the relative wind in contrary to us and uk which it's the angle between the chord line and the longitudinal axis.(fr="angle de calage")
In french :In fluid mechanics, "l'angle d'incidence" is the angle ...
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Having been a commercial pilot and instructor for over 36 years I deal with this daily. The 747 or any aircraft is essentially balanced at the center of gravity. The positive moment will equal the negative moment on the cg. The aerodynamic force created by the horizontal stabilizer is easily calculable and is based on the lift coefficient, surface area of ...
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I assume you are asking about the NET aerodynamic pitch torque that the 747 can generate. In this case the pitch torque created by tail just to maintain linear flight doesn't count. Nor does the pitch torque created by the tail to overcome "aerodynamic damping" in the pitch axis during a steady-state (constant airspeed, constant bank angle, constant turn ...
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The pitching force is coming from the horizontal tail's downforce resisting the airplane's net nose down pitching forces, so the real question is how much downforce is being applied and how far away is the tail's downforce from the lifting forces holding the plane up.
For a given set of parameters, you need to know the All Up Weight, the Center of Gravity ...
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How does the angle of attack vary in turns?
While many of the answers focus on the need for the angle-of-attack to be higher in a turn than in wings-level-flight if altitude is to be maintained with no change in power setting (or alternatively if altitude is to be maintained with increased power but no change in airspeed), your question seems to be asking ...
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I found your exact question a little confusing, so let me answer with a quote from a current British PPL exam preparation book:
The wing's angle of incidence - the angle between the wing chord-line and fuselage - is fixed by the construction of the wing and the angle at which it is bolted onto the fuselage
Source: AFE Book 4 - Aircraft General Knowledge
...
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Speaking as a commercial pilot, pilot instructor and skydiver I think I can answer this.
An aircraft has a centre of pressure, which is the lift vector that comes out of the wing and opposes the weight. As you increase the angle of attack of the wing, up to around 16 degrees angle of attack, the centre of pressure (lift) moves slowly forward. When you ...
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Stall as a term refers to the speed of the airflow where the lift produced by the wing becomes significantly less than the weight carried by the wing.
when that condition occurs the airflow (actually the wing moves through the static air) is too weak to sustain a stable flight and the entire plane takes an uncontrollable path down. The previous attitude of ...
2
A stall is not a free-fall. It is a loss of laminar airflow over the wing, resulting in a loss of lift. The response to a stall is to stop the (usual) roll induced by one wing stalling before the other. Then drop the nose - most aircraft will do this by design - until you achieve a flyable speed with proper airflow over the wing. The problem here is that ...
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If the cables break on an elevator (and the safety brakes fail), you won't be in true freefall. You'll still have friction from wind resistance, from the guide rollers on the rails, etc. The same is true in an airplane. Even if you're falling straight down, you'll still have wind resistance.
In addition, lift doesn't just drop straight to zero when the wing ...
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Is a “stalled” aircraft free-falling?
No!
If I was in an elevator in a sky-scraper, and the cable broke, I would free fall and feel weightless (until hitting the ground of course). When I stall an airplane(power-off) and the wings stop producing lift, why doesn't the same effect occur?
Because in a stall, the aerodynamic force component acting against ...
4
It is just angle of attack.
Most anything can have an angle of attack. If you must be specific, you mention 'angle of attack of ...' Due to complexity of aerodynamics, most external elements of an airplane have their own local angle of attack. AoA sensors measure their angle of attack, and it is usually not even converted to 'wing' or 'fuselage'; it is ...
4
From A.C. Kermode; Mechanics of Flight, London, Pitman, 8th Edn, 1972, p.75 (his bold):
"We call the angle between the chord of the aerofoil and the direction of the airflow the angle of attack.
"This angle is often known as the angle of incidence; the term was avoided in early editions of this book because it was apt to be confused with the riggers' ...
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If you’re talking about the angle between the longitudinal axis and the relative wind rotated about the vertical axis, I’m not sure there is a term per se except for coordination of flight. The angle is not typically measured but of the angle is towards the inside of the flight path this is considered a slipping condition. When on the outside of the flight ...
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There is a term called "deck angle", which is the angle of the cabin floor, or deck, (and normally parallel to the longitudinal axis) relative to horizontal in a given flight condition. More or less the same thing as "pitch attitude". These however, don't cover your question because they are relative to the horizontal.
There is another term which I think ...
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The rotation of the powertrain (or GMP) consisting of the engine and the propeller causes what are called engine effects. These effects depend on the power supplied by the engine, the speed of rotation of the propeller and the speed of the airplane, for a given airplane.for right-hand propeller, that is to say which rotates clockwise when viewed from the ...
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Most single-engine types are stable and low-powered enough that torque is not a problem. The pilot will compensate in the usual way if one wing drops. A pilot may also trim the ailerons to counteract it during cruise, so that the plane flies level without any extra control input.
Historically, it was manageable enough on the early pioneer aircraft until the ...
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One big reason is to make room for external stores such as fuel, weapons and electronics packs. A low-wing design must have longer and therefore heavier and bulkier undercarriage if ground access to the underwing hard points is to be adequate.
Also, the upper surface of a high wing is larger and cleaner, providing better lift over the fuselage and reducing ...
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Here is a simple way to think of this problem:
Without thrust from its engine, the airplane begins instead to "coast downhill" like someone on a bike- and the pilot can choose whatever "slope" he or she wishes to follow, consistent with the need to keep the wings generating lift and the control surfaces to generate directional control forces.
In a ...
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At maximum cruise speed, altitude and payload, most airliners are trimmed into several degrees of pitch-up attitude to maintain constant altitude. At that point, the plane is delicately balanced at those conditions to minimize drag and maximize range.
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I assume by "middle pitch" you're talking about the pitch during cruse? In which case, the answer is, unfortunately, "it depends". Changing pitch changes the amount of lift, and the amount of lift needed depends on the weight of the plane. So, an airplane with more passengers and cargo will need a slightly higher pitch.
Changing speed also changes lift, ...
-1
The weight $W$ of the glider has two components, $Wt$ and Wn. $Wt$ is in the same direction as $V$ and $Wn$ is perpendicular to $V$. Aerodynamic $F$ also has two components $L$ and $D$, where $L$ is perpendicular to $V$ and $D$ is parallel to $V$.
When $L = Wn$:
$Wt> D$, the linear acceleration of the glider is positive; $Wt <D$, the linear ...
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Single engine airplanes experience torque proportional to the amount of engine power used. Pilots mitigate this torque by applying engine power smoothly and gradually. Since the torque on most planes will be applied to the airframe in the counter-clockwise direction from the point of view of the pilot, the pilot further mitigates this torque by applying Some ...
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As far as i know, the plane is not stabled, pilots always have to stablilize the plane by themselves when they push the throttle up.
In fact the effect of the torque of the engine is not big enough to significantly effect the plane's flight, although it is noticeable on some planes.
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The weight $W$ of the glider has two components, $Wt$ and Wn. $Wt$ is in the same direction as $V$ and $Wn$ is perpendicular to $V$. Aerodynamic $F$ also has two components $L$ and $D$, where $L$ is perpendicular to $V$ and $D$ is parallel to $V$.
When $L = Wn$:
$Wt> D$, the linear acceleration of the glider is positive; $Wt <D$, the linear ...
5
If you are asking about the forces involved in an uncoordinated turn, Thrust, Drag, Lift, and Load (weight) still apply. But, let us define Lift as acting perpendicular to to the wings in a direction opposite Load. While Load is acting perpendicular to the wings in the direction of gravity plus the aircraft’s momentum. When you are banked, or you are in a ...
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It's important not to overthink it. I'll keep it simple. A coordinated turn means you are keeping the tail lined up with the nose in the airstream. If you are uncoordinated, you are flying sideways in the airstream to some degree or another; the side of the fuselage is being presented to the airflow.
If you learn to fly in gliders, it's obvious because ...
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Can someone tell me which force during an uncoordinated turn is too
big or too small and literally what makes a turn uncoordinated in
terms of forces?
The slip-skid ball (inclinometer ball) will be off-center whenever the component of the net aerodynamic force that we see when looking at the airplane in a head-on view is tilted "sideways" in the ...
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It isn't all that difficult if you understand the three different axis, and the corresponding rotation about each axis. (roll, pitch, and yaw)
In your question you described a coordinated turn. (no slip or skid) An uncoordinated turn is simply when there IS slip or skid. This occurs where there is either not enough, or too much yaw. This happens when ...
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Unfortunately, this is an opinion based question. My opinion is based on the fact that my first few hours of helicopter instruction were harder than my first few hours of fixed wing instruction.
Takeoff in a helicopter was fairly easy after hover taxiing to the takeoff pad and hover turning 360° with yaw control to visually clear the area. Landing in a ...
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In addition to all the good content in all the other good answers, one more point should be made: when the airmass is moving horizontally and/ or vertically, the glide ratio over the ground is different than the glide ratio through the airmass, and therefore the glide ratio over the ground is different than the L/D ratio.
When gliding into a headwind, the ...
2
Why does an airliner have a shallow descent when heavier, opposite to
gliders with ballast?
Actually, gliders share this characteristic with airliners, if we are talking about flight at some given high airspeed that is well above the airspeed for the best L/D ratio.
First a few general observations about gliding flight, based on something borrowed from ...
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