Questions tagged [flight-mechanics]

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24 votes
3 answers
18k views

Why is this airplane flying in circles randomly?

This G650 has been flying around for over an hour now. Is this somebody with a mechanical problem who is burning fuel before returning to their airport of origin?
alpartis's user avatar
  • 351
20 votes
6 answers
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 ...
Sovereign Inquiry's user avatar
19 votes
4 answers
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 ...
Dat's user avatar
  • 990
18 votes
4 answers
4k views

Do any airplane designs exist that don't involve a flight surface that provides downforce?

Most aircraft maintain longitudinal stability by balancing three forces: The down force acting through the center of gravity (CG) The lifting force acting through the center of lift The down force ...
ryan1618's user avatar
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16 votes
6 answers
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 ...
Justintimeforfun's user avatar
14 votes
5 answers
6k views

Where is the 'zone of reversed commands...'?

There seems to be some confusion about where the 'zone of reversed commands' really is, i.e. where a decrease of airspeed results in an increase of drag. Some references place that zone to the left ...
xxavier's user avatar
  • 11.1k
9 votes
1 answer
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 ...
quiet flyer's user avatar
  • 22.6k
7 votes
6 answers
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 ...
Lucas's user avatar
  • 71
7 votes
3 answers
2k views

In simple mechanical stick linkages, is there crosstalk between the aileron and the elevator movement?

The background story: I'm an aviation enthusiast (who has played a lot of sim in his life and will play lots more :D) but I've never actually flown any plane myself, as in, actually used the controls ...
Jan Nash's user avatar
  • 263
7 votes
1 answer
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). ...
Aris Martínez Ventura's user avatar
7 votes
2 answers
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 ...
xxavier's user avatar
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7 votes
2 answers
945 views

Can the fly-by-wire system of a modern airliner handle an unstable condition?

According to this answer airliners/large passenger aircraft such as an A320 are designed such that they are longitudinally, statically stable under normal flying conditions. What if, for some reason, ...
Daniel's user avatar
  • 823
6 votes
4 answers
2k views

What exactly happens when power is reduced in trimmed, straight and level flight?

I understand that trimming an aircraft at a particular airspeed e.g. 100kts will keep the aircraft flying at that airspeed (100kts) even if you were to e.g. Lower power. This is apparently ...
Flightsimrightnow's user avatar
6 votes
5 answers
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 ...
Phil C's user avatar
  • 61
6 votes
3 answers
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?
user avatar
6 votes
2 answers
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 ...
Matt K's user avatar
  • 71
5 votes
2 answers
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 $V$ ...
Peter Lysgaard Jensen's user avatar
5 votes
1 answer
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-...
M66's user avatar
  • 134
5 votes
2 answers
3k views

What is a rudder or fin stall?

What is a rudder or fin stall, how will the aircraft behave in that situation, and how should the pilot recognise it? What is the recovery procedure? And what is rudder reversal?
Darjan's user avatar
  • 1,155
4 votes
4 answers
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 ...
Aditya Sharma's user avatar
4 votes
2 answers
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 ...
Robin Bennett's user avatar
4 votes
0 answers
194 views

What is Snowbird flapping mechanism?

Reading this question and the great answer to it talking about Snowbird sustained human powered flight visible here, I was wondering and still cannot find nor figure out how power is converted from ...
user avatar
3 votes
2 answers
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 ...
Konrad's user avatar
  • 1,983
3 votes
4 answers
9k views

What is the relationship between Angle of Attack and Angle of Incidence?

The Angle of Incidence (AoI) of most GA planes is 6°. Assuming a plane with an Angle of Incidence of 6 degrees-- How do we calculate pitch attitude if we know the direction of the flight path and the ...
David Teahay's user avatar
  • 2,885
3 votes
3 answers
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 ...
Charles Bretana's user avatar
3 votes
2 answers
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 ...
Justintimeforfun's user avatar
3 votes
2 answers
2k views

Does it ever happen that increasing the prop RPM without moving the throttle actually decreases the thrust and power delivered to the airframe?

A) In an airplane with a piston engine and a constant-speed prop, flying at some given airspeed with the manifold pressure and RPMs in a typical cruise configuration, would it ever happen that ...
quiet flyer's user avatar
  • 22.6k
3 votes
2 answers
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 (...
quiet flyer's user avatar
  • 22.6k
3 votes
1 answer
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 ...
uhoh's user avatar
  • 5,828
3 votes
1 answer
97 views

How to deduce the dynamic general equations for a non-symmetric level turn manoeuvre?

I'm currently studying flight mechanics on a subject at my engineering degree and I'm trying to solve some standard case exercises with the general equations and diferent reference frames. I've been ...
Roger Vallès's user avatar
2 votes
3 answers
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 ...
user avatar
2 votes
2 answers
217 views

XFY-1 Vertical take-off mechanics

Hi I saw this video the other day of an XFY-1 doing a vertical take-off and landing and moving left to right while hovering. See the video Here. After watching this I had a few questions on how ...
FutureCake's user avatar
2 votes
4 answers
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 ...
Dave Walzer's user avatar
2 votes
1 answer
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 ...
quiet flyer's user avatar
  • 22.6k
2 votes
1 answer
880 views

Why isn't Vy lower than the speeds for best L/D ratio and best glide ratio in an airplane with a piston engine and a variable-speed prop?

This answer to a related question implies that if the power available were constant regardless of airspeed, Vy would occur at approximately the angle-of-attack that yields the minimum sink rate with ...
quiet flyer's user avatar
  • 22.6k
2 votes
1 answer
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 ...
DrZ214's user avatar
  • 17.7k
2 votes
2 answers
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 ...
alireza's user avatar
  • 103
2 votes
1 answer
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 ...
alireza's user avatar
  • 103
2 votes
1 answer
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 ...
Auberron's user avatar
  • 1,567
2 votes
1 answer
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 ...
quiet flyer's user avatar
  • 22.6k
2 votes
1 answer
203 views

Is the airspeed for the minimum the same for the theoretical power required curve as for the shaft power required curve?

I am aware that the efficiency of the propeller implies a difference in the values of the theoretical power required curve and the corresponding shaft power required, but does that efficiency ...
xxavier's user avatar
  • 11.1k
1 vote
5 answers
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-...
eball's user avatar
  • 201
1 vote
6 answers
805 views

Forces "felt" by pilot, G-meter, inclinometer--are they the aerodynamic forces generated by the aircraft, or the sum of weight+centrifugal force?

Consider a pilot sitting at the CG of an aircraft, with instruments also located at the CG of the aircraft. (Feel free to consider other cases as a bonus, but the core of the question is aimed at ...
quiet flyer's user avatar
  • 22.6k
1 vote
2 answers
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 ...
alireza's user avatar
  • 103
1 vote
1 answer
4k views

Angle of attack from velocity vector

I found an equation to calculate angle of attack based on the velocity vector in the body frame of the aircraft. $\arctan(v_x/v_z) = \alpha$ 1) Is this correct? When I input in a $v_z$ approaching ...
Boto's user avatar
  • 91
1 vote
2 answers
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 ...
F.L.'s user avatar
  • 21
1 vote
2 answers
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-...
quiet flyer's user avatar
  • 22.6k
1 vote
1 answer
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 ...
Lucas's user avatar
  • 11
1 vote
2 answers
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 ...
guy katz's user avatar
1 vote
2 answers
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-...
quiet flyer's user avatar
  • 22.6k