# Questions tagged [flight-mechanics]

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### Create a new aircraft JSBsim [closed]

I'm creating (modeling) a new aircraft for a personal project. So I want to put it on Flight Gear to simulate the model. I read the JSBsim tutorial, but I didn't get it right. I wanna know the first ...
622 views

### Does climbing or descending affect the rate of turn?

In the past, I used to have this idea that if all other factors remain constant, then climbing increases the rate of turn while descending decreases it. This idea was most likely planted into my mind ...
41 views

### 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 ...
5k views

### How can L/D Max be both Best Glide speed and Max Range speed?

According to the book "Aerodynamics for Naval Aviators", best glide speed AND max range speed for propeller aircraft both occur at L/D max. This is a little confusing because in an A36 ...
43 views

### What is the speed and temperature profile of the boundary layer at the stagnation point?

At the statgnation point where the air velocity is zero, what is the shape of the velocity and temperature profile of the boundary layer? Is the velocity profile of the boundary layer in the form of a ...
96 views

### Does lift decrease in hypersonic speed?

In John Bertin's Aerodynamics book, it is said that when the thickness of the boundary layer is low, the displacement thickness of the boundary layer is also low, and therefore the curvature of the ...
448 views

### Did SR-71s have a switch for seat height adjustment for the pilot or were there strict height requirements in order to fly it?

I've realized that nowadays there are switches present on most modern aircraft which electrically adjust the height of the seating position, and I was wondering if that mechanism was present on the SR-...
1 vote
342 views

### 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 ...
1 vote
313 views

### Pitch=Flight Path Angle + Angle of Attack if bank angle=0?

Question: Is the statement in the title correct? Recently, I am taking a course about flight mechanics (click for the slides). It states that "If bank angle is null, then pitch angle = flight ...
203 views

### How do engine doors work?

"Doors" here refers to something in or around the engine that can close or open, stopping or allowing the flow of air (or some other gas). I've heard of such things in a few engines. GE9X ...
498 views

### Are the gyroscopic precession and P-factor of a pusher propeller in opposite directions?

according to this picture the P factor cuases airplane to yaw to the right but if pilot wants to pitch up , then p factor and gyroscopic precession acts on airplane at the same time but in opposite ...
126 views

### How to convert LVLH-relative angular velocity to ECI-relative angular velocity?

Suppose I have angular velocity of the LVLH frame relative to the Body frame, expressed in LVLH, how can I know what is the angular velocity of the Body frame relative to ECI, expressed in ECI? I also ...
737 views

### What is causing these "corners" on this F-104 V-n diagram?

In this V-n diagram for an F-104 (source: this Wikipedia link), on the left-hand edge of the flight envelope, what is causing the "corners" that we see at the following points? (Numbers are ...
207 views

### Pitching up with constant bank -- how to compute final attitude, from initial attitude and degrees of rotation about pitch axis? (Specific example)

(Note: highly related, but different: How to compute final aircraft attitude, if we know starting attitude and degrees of rotation around each axis? (Specific example)) I'm flying due north (000 ...
409 views

### How to compute final aircraft attitude, if we know starting attitude and degrees of rotation around each axis? (Specific example)

I'm flying due north (000 degrees heading), with bank angle of 0 degrees and a pitch attitude of 0 degrees. I roll the airplane 30 degrees to the right, rotating only around the aircraft's roll axis (...
414 views

### What is airflow direction in turn?

Let imagine that we put wind indicator on rotating merry-go-around. Will wind indicator stay prepedicular to the radius of circle,showing tangetinal airflow velocity? (Wind indicator has equal mass ...
1 vote
202 views

### Why does an aircraft fly a looping when pulling the stick?

let's assume an aircraft flies in straight level flight in the direction of an x-axis with an angle of attack of 3°. When the pilot pulls the flight stick, an additional lift is produced which acts ...
1 vote
425 views

### What causes a slip/skid turn? [duplicate]

Is the rate of turn being too low/high for a given bank angle the cause of slip/skid turn? Or is it yawing too much inside/outside turn causing an imbalance in centripetal/fugal force and thus the ...
906 views

### How to determine the maximum forward airspeed of a plane in an unaccelerated flight?

What is the equation needed to determine the maximum forward airspeed of a propeller driven plane in an unaccelerated level flight? I need an example with units of measurements. The engine is rated at ...
133 views

### Does optimum IAS for climb vary with altitude?

I was in an argument about aerodynamics and we eventually derived an equation as follows. So I'm going by this equation: $$RoC = \frac{\eta_p P-VD}{W}$$ Where $\eta$ represents propeller efficiency. ...
1k views

### Increasing bank angle, load factor and rate of turn

I came across this question and I get why the answer is correct but I don’t really understand why by increasing angle of bank from 20 to 30 the load factor has not increased (option B in the image). ...
260 views

### load factor in high altitudes

if load factor equation is lift devided by weight , so in very high altitude for example 1000 km above the earth atmosphere, there is no air to produce lift so load factor is zero but in newton ...
2k views

### How to calculate optimal flight climb angle?

I am trying to calculate the optimal flight climb angle based off of some basic power calculations for an aircraft on steady climb with an angle of theta. Doing a balance of forces I obtained the ...
1k views

### How does an aircraft's weight affect the V-n diagram?

I have a reasonable understanding of what a V-n diagram shows and what the envelope and the boundaries mean. However, the question I have is how does the weight of the aircraft specifically affect the ...
184 views

### Control surface deflection during takeoff

What is a reasonable (or typical) control surface deflections required for takeoff? I would like to know two ball park values if possible elevator deflection for conventional transport aircraft ...
368 views

### Do pusher propellers create the same yawing moment as puller propellers? [closed]

We know that the effect of P-factor on puller propellers is the yawing moment in the opposite direction. I mean if we had a load (thrust or lift) on the right side of propeller, then the airplane will ...
181 views

### What are the stability criteria of helicopters?

In airplanes, longitudinal stability is maintained if centre of lift lies aft of center of gravity. Like in the airplane shown in the figure below, do helicopters also have stability criteria? They ...
668 views

### Why do airplanes start descending when we initiate a left turn?

Today I watched a video about the Fly-by-Wire (FBW) system (see below) and at 3:20 there is a left turn initiated in a Cessna 152. Then it is shown that with a left turn (only by ailerons), in ...
3k views

### Is a trimmed flight not always an unstable system?

As soon as I am flying in trimmed flight condition, my pitching moment around the center of gravity becomes zero. So my center of pressure has to be located in the center of gravity, so that there is ...
9k views

### What does it mean when an aircraft is statically stable but dynamically unstable?

I am reading this book: "Flight Stability and Automatic Control", second edition, Dr. Robert C. Nelson. In the chapter 2, page 42, the author wrote: Note that the vehicle can be statically ...
1 vote
1k views

### What causes the ball to not be centered in a slip/skid?

I've reviewed quite a few questions on this forum including Forces in a slipping turn is-this-vector-diagram-of-the-forces-at-play-in-turning-flight-correct what-does-the-balance-ball-actually-...
225 views

### Relationship between Load-Factor AND Gliding Ratio

I am wondering about the g-load and its relation to the so called gliding ratio. I read this really good contribution here on this forum: Does lift equal weight in a climb? So the g load factor is ...
1k views

### What is the effect of thrust vectoring effect on the rate of turn?

I just got a question after reading my old Principles of Flight book. The equation for the rate of turn is $\textrm{ROT} = 1,091 \cdot \frac{\tan(\phi)}{V}$, with $\phi$ denoting bank angle and $V$ ...
816 views

### How does an aircraft designer increase dynamic stability?

This question explains that an aircraft can be statically stable (it will seek to return to equilibrium) but dynamically unstable (the amplitude of the oscillations increase) if there isn't enough ...
1k views

### Is the turning motion of a banked airplane caused by true centripetal force?

Virtually every explanation I have read of the aerodynamics of a turning airplane ascribe the turning motion simply to centripetal force, without further comment. I'm hoping someone can check my ...
1 vote
271 views

### In a full-rudder sideslip in a Schweizer 2-22 or 2-33 glider, is the descent rate higher at 50 mph airspeed than at 60 mph airspeed?

Is it really true that in a full-rudder sideslip in a Schweizer 2-22 or 2-33 glider, the descent rate is higher at 50 mph airspeed than at 60 mph airspeed? Likewise, is it really true that in a full-...
129 views

### What are "secondary precessional forces" that apply to boomerangs in flight?

note: This question is about the aerodynamics of boomerang flight and how it differs in microgravity environments. Some background information available here in Aviation SE: Are frisbees and ...
3k views

### What is physics explanation for minimum sink rate airspeed?

I did some research on Minimum Sink Rate, and saw much information defining it, (such as it is the speed at which the aircraft will remain in the air for the longest time, etc.) and how it is ...
308 views

### What does "pitch plus power equals performance" really mean?

It is often said in aviation circles that "pitch plus power equals performance". A. What is it supposed to mean? B. Is it always true? C. If it isn't always true, why is it a useful concept ...
906 views

### 'Gravitational' power vs. engine power

A glider gets the power it needs to fly from the decrease of gravitational potential energy associated to the descent. My question is: for the same weight $W$, airspeed $V$, and a prop efficiency of ...
3k views

### Why is the L/D ratio numerically equal to the glide ratio?

*L/D is ratio of two forces, lift and drag. *Glide ratio is ratio of two distances. Can you explain mathematically how they end up numerically equal and are they always equal?
1 vote
538 views

### Can we show through simple geometry rather than formulae or graphs that the best glide ratio occurs at the maximum ratio of Lift to Drag?

For an unpowered glider, can we show through simple geometry involving force vector diagrams, rather than mathematical formulae or graphs, that the best still-air glide ratio is achieved at the angle-...
1 vote
243 views

### Does this web page really correctly depict the angle that is called "incidence" in the French language in the aviation context?

Does this web page really correctly depict the most common usage of the term "incidence" in the French language in the aviation context, in the context of speaking of an entire aircraft and not just ...
5k views

### Can gliding your plane save fuel?

Aimed towards lighter piston planes including a powered glider, if a pilot wants to extend a plane's range unconventionally, could flying like a glider by climbing and then gliding down or would ...
202 views

### Why does a steady-state non-zero body yaw and/ or roll rate induce side force?

An answer on ASE states The presence of steady-state non-zero body yaw and roll rate induces side force ($C_{y_p}$ and $C_{y_r}$). What is a non-mathematical explanation of why this is so? Is it ...
8k views

### Can a plane bank without turning?

Can planes bank without turning, and if so, how is it possible? A plane's wing is designed to naturally create lift; the explanation for that is that the greater speed of the air moving over the wing ...
3k views

### What is missing from these diagrams of the forces in slips and skids?

See these images that are widely reproduced in many different on-line ground school materials. A) Is the magnitude of the wing's lift vector illustrated correctly in each of the three cases? Should ...
1 vote
2k views

### Forces in a slipping turn [duplicate]

I have trouble understanding why the ball (on the turn & slip indicator) falls into the turn e.g. drop to the left when aircraft is rolled left, when in an uncoordinated turn (slipping turn). What ...