# Questions tagged [flight-dynamics]

Flight dynamics is the study of the physics driving the performance, stability, and control of aircraft. It is concerned with how forces acting on the aircraft influence its speed, altitude and attitude with respect to time.

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### References for lift and drag coeficient formula/values

I'm looking for references for values/formula for lift and drag coenficients. In this paper https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6244461 it is said that $C_L(α)$ and $C_D(α)$ ...
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### What is a "rapid changes in gravitational force"

I've been reading an article on the BBC Website about the 21/May/2024 incident on Singapore Airlines. According to this article: "The rapid changes in G over the 4.6 seconds duration resulted in ...
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### In a straight and level flight if thrust is equal to drag how is aircraft moving forward?

If two forces are equal and acting in opposite direction should not the object remain stationary. Is there an excess thrust which actually pushes the aircraft forward ?
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### How do you compute the net lift force location?

There are a lot of formula that give an approximate solution to the lift and drag forces associated with certain wing configurations. What I'm curious about is how do you find where the net force is ...
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1 vote
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### What are all the ways that wind velocity can affect a paraglider/ canopy before it touches the ground?

Let's assume that a "perfect" humanoid robot flying a ram air parafoil (paraglider or canopy) performs some maneuver for landing exactly the same way multiple times. The only difference ...
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### Doubt in the Coriolis component of the net force acting on the aircraft

I dig a little and got to know that the force equation in 6DOF are nothing but a mathematical depiction of the fact that for a translating & Rotating body in 3D,The net force is the Translational ...
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### Why is the wave drag of a straight wing less than that of a swept back wing?

According to NASA's claims, when the swept back wing is inside the shock cone and the shock is not attached to the leading edge of the wing(subsonic leading edge), the wave drag of the swept wing is ...
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### Turbocharged vs Turboprop cruise altitudes

I know that both turbocharged & turboprop engines offer better performance above 10,000 feet than normally aspirated piston aircraft. My question is to what degree do their optimal cruise ...
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### How to calculate fuel burn rate in Model BK117 helicopter

I am confused which parameters we are use, I have fuel quantity, fuel flow, fuel weight and speed etc is there so how to using and which parameters using the Endurance time calculate in helicopter
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### Hexacopter Vn diagram/ flight envelope/ operational envelope

I am currently intern at a company. They are making agriculture hexacopter, now there is a confusion that does the hexacopter or multicopter have a V n diagram if yes how to make one what's the ...
1 vote
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### What causes the secondary effect of rudder, and which direction does it act?

I understand that rudder deflection causes several things to happen. Primarily the aircraft yaws, and for a positive (trailing edge left) rudder deflection there will be a positive side force ...
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### How does the horizontal component of lift when flying at a bank angle cause the aircraft to follow a circular path?

I understand that when the aircraft is put into some bank angle, the lift vector now acts at that angle instead of directly against gravity, so we can pitch the aircraft up to increase AoA to increase ...
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### Thrust needed to overcome parasite drag that increases with speed

Can anyone explain this passage from page 11-5 of the PHAK: “ For example, if an aircraft in a steady flight condition at 100 knots is then accelerated to 200 knots, the parasite drag becomes four ...
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### Yawing during turns

This is a question about aeronautics. Does an airplane yaw while it is turning?
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### Entry to back-side of power curve

When entering slow flight, when do we enter the back side of the power curve? Is it when we reduce the throttle or when the airspeed decreases to just above 5 knots from the stall speed?
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### Why does the turn tighten in a Spiral Dive as it progresses? Even without applying any elevator control?

Why does the turn keeps getting tighter as the spiral dive develops? Use of elevator control makes sense as it would increase the horizontal lift vector inside the turn. But even without any elevator ...
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### Taxiing with a crosswind

Let us say we have a right quartering headwind, we should “fly into the wind” so yoke to the right then that our right aileron will deflect up and left aileron down. How does this avoid the chances of ...
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### If in a coordinated turn, the horizontal lift vector is equal to the Centrifugal force. Then how is the aircraft still turning?

Image source How does the Aircraft continue to turn when the both the Horizontal component of lift and the centrifugal force are equal?
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### What are the effects of whiteout (snow) and brownout (sand/dust) on helos?

Is there any other effect besides low visibility? Both seem to show very similar conditions.
1 vote
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### What differences would a helicopter designed to withstand many negative Gs have compared with a normal one?

There are a few helicopters that are able to take negative G's, and to this day only one can actually perform aerobatics (ie. Chuck Aaron's BO-105). The BO 105 is a rigid rotor helicopter that has ...
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### Why is a flat turn less efficient than a coordinated turn?

How I understand a flat (rudder-only) turn: AOA between relative wind and the fuselage of the airplane causes a sideslip in the direction of yaw. Vertical stabilizer weathervanes into the relative ...
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### What is the theoretical justification for "proportional navigation (PN)" guidance law?

In missile guidance theory, one of the fundamental guidance algorithms is the so-called "Proportional navigation", which directs a constant-speed missile into a collision course with the ...
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### What would happen to the aircraft and its control surfaces immediately after the loss of all hydraulics?

In cases like the DHL shoot-down in 2003 or the Sioux City crash, both aircraft lost all of their hydraulics because of a catastrophic failure of aircraft structure. What would happen if the aircraft ...
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### Does AOA become 0 after the aircraft flies in a particular attitude for sometime as the relative airflow has changed and how does it affect Stall AOA?

As AOA is the angle between relative airflow and Chord Line. Then after you increase the angle of attack and fly at that angle of attack for some amount of time and the relative airflow changes ...
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1 vote
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### why lift coefficient decreases at supersonic flow?

In Anderson's performance book, he wrote that the higher the speed, the greater the pressure difference between two points, and as a result, the lift coefficient is greater. But when we reach the ...
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### Could you use the flaps to recover from a flat spin

If the plane is in a flat spin, what would happen if you put the flaps down to cause the backward turning wing to be pushed down, and the forward turning wing up, to tip it out of the spin.
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### Maximise Range Vs Pitching Down while flying a Glider in a Downward Air Mass

While flying a glider, if I encounter a downward moving air mass (i.e. sink) while on final, should I fly to maximise range (best lift to drag ratio) or should I pitch downward in order to exit the ...
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1 vote
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### What can cause an unstable phugoid mode?

For clarity, I am wondering about how aircraft design can lead to the phugoid poles becoming complex with a positive real part, so an oscillation with increasing amplitudes. My understanding of the ...
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### Can the use of wide-chord supercritical airfoil blades in a helicopter with coaxial counter-rotating rotors solve retreating blade stall?

The problem with retreating blade stall is that it limits the VNE and the overall top speed of helicopters. Retreating blade stall is basically the tip of the retreating blade having too much AoA at a ...
1 vote
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### Wing incidence angle of tandem wing aircraft

I'm trying to design a tandem wing model aircraft with both wings with the same wingspan. The front wing will have 2 and the rear will have 1 deg of incidence angle, also the front wing will have ...
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### If I am at absolute ceiling, can I climb further by trading airspeed for altitude?

If I am flying at absolute ceiling, can I still climb by trading airspeed for altitude?
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### Flying upside down without feeling it

A friend of mine told me that several years ago she flew on a two-seats general aviation aircraft. She does not remember the exact model, but she remembers well that the pilot flew upside down for a ...
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### How elevator and ailerons affect attack and roll angles?

I was trying to model the flight of an aircraft and i need some function that expresses the change of attack and roll angle in function of the elevator and ailerons (respectively). Does anyone have an ...
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### Longitudinal/Lateral CG envelope for hoist operations

Does a Rotorcraft hoisting CG chart show what the CG will be as the load is hoisted from top to bottom or vice versa?
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### What open-loop control inputs can guarantee non-divergent descents in fixed-wing aircraft?

(Inspired by What's the best way to get through clouds when not instrument rated? which has at its heart a good question, but isn't getting good answers because everyone is jumping on the "...
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### How to slow down while maintaining altitude

Is reducing throttle/power already enough? Or do I have to adjust the pitch as well? If so, I suppose pitching up as well? If pitching up is needed as well, is it because as speed decrease, there is ...
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### Simultaneous yaw damping and sideslip control of aircraft with rudder?

Yaw damping is achieved by using the rudder to generate a yawing moment that opposes any yawing motion. Also, rudder is used to correct sideslip by applying a rudder input in the opposite direction of ...
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### How does increasing the angle of attack increase the lift?

When the pitch of a plane increases (facing upwards), it has a positive angle of attack, and when it decreases to face downwards, it has a negative angle of attack. Increasing the angle of attack ...
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### How does the lift force stop increasing itself after a certain point?

I am currently trying to create a basic flight simulator and am very confused by the concept of lift. This is the equation of lift shown below that I found on the internet.  F_l = \frac{1}{2} \rho v^...
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### Why does the maximum allowable load factor vary with airspeed in some aircraft?

In this ASE answer What is the maximum safe bank angle of a 747?, the author writes: If we stay with stationary turns (without the "falling out of the sky" part), the maximum bank angle is ...
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### Why does a sudden tailwind/headwind change IAS?

I read the following statement: “tailwind quickly changing to a headwind causes an increase in airspeed and performance. Conversely, a headwind changing to a tailwind causes a decrease in airspeed and ...
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### How is Vx speed and Vy affected when climbing?

If my speed for best angle of climb is 60 and rate is 79, if I kept a 500 fpm climb to my cruise altitude of let’s say 4500, would those speed change? The flights are being done on separate occasions.
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### Why the heavier the aircraft is, the higher the airspeed must be to obtain the same glide ratio?

I know weight does not affect glide ratio. But why does higher weight need higher gliding speed?
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1 vote
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### How does elevator control effectiveness change with altitude/ air density?

Suppose an unpowered, rigid, mechanical, lightweight aircraft (e.g. sport glider) is descending at a steady glide in a constant trim (hands off) configuration in a standard atmosphere. The pilot ...
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### FAA's Airplane Flying Handbook says more lift is necessary during a climb. Isn't it the opposite? [duplicate]

"If a climb is started from cruise flight, the airspeed gradually decreases is the airplane enters a stabilized climb attitude. The thrust required to maintain straight-and-leve flight at a given ...
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### Did the dog-tooth notches in the wing of the F-8 Crusader really have anything to do with "yaw stability"?

What was the real function of the "dog-tooth" notches in the leading edge of the wing of the Vought F8U crusader? Wikipedia says:1 Vought's design team... produced... a relatively ...
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### Why does bank angle have no effect on pivotal altitude?

Pivotal altitude is the height for a given ground speed at which the line of sight from the cockpit directly parallel to the lateral axis of the aircraft will remain stationary on an object on the ...
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### Why a kite flying at 1000 feet in "figure-of-eight loops" serves to "multiply the pulling effect of the airflow" on the ship to which it is attached?

In CNN's June 30, 2023 Giant kites could pull cargo ships across the ocean – and slash their carbon emissions “What differentiates it from other wind solutions,” says Bernatets1, “is that the wing is ...
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### Can engines with a fixed nozzle in the angle of attack have the same effect as the thrust vectoring?

If the figure above represents a missile at the angle of attack and we vector resolution the thrust output from the nozzle, we can see that the thrust is divided into sine and cosine parts. Does the ...
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