Questions tagged [aircraft-physics]

Physics as they apply to aircraft. Including aerodynamics, flight dynamics, stability and control, aircraft hydraulic and electric systems, engine thermodynamics.

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84 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 ...
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2answers
913 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 $V$ ...
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0answers
108 views

Does the routine flown by the Thunderbirds in the F-16 feature true sustained knife-edge flight?

Does any aerobatic routine flown by the USAF Thunderbirds in the F-16 feature true sustained knife-edge flight? By "true sustained knife edge flight" we mean that the aircraft is maintaining ...
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1answer
70 views

What counts as the wingspan of a tandem-wing aircraft?

When calculating the wing-span of a tandem-wing aircraft, like the QAC Quickie Q2, which set of wings do we use for that value? There are two sets of wings, and they both provide lift. In the class, ...
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4answers
151 views

Explained intuitively, why does aspect ratio affect induced drag?

Over the last few hours, I've been trying to intuitively understand induced drag, and how aspect ratio affects it. I already know the equations, but while they explain the relationship, they do not ...
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1answer
107 views

Question about the difficulty of a couple of airplane maneuvers [closed]

I have a hypothetical scenario and I was wondering if any experts might be able to speak to it. I will lay out the scenario, with a couple of specific questions, and maybe some honest answers will ...
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1answer
56 views

How does the airflow above an airfoil account for the downward turning-action of the airflow below the airfoil?

Wikipedia provides an explanation of the lift force in terms of flow deflection and Newton's laws, emphasis mine: An airfoil generates lift by exerting a downward force on the air as it flows past. ...
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1answer
138 views

Why does a force on a propeller act 90° “ahead” due to gyroscopic precession?

This is a common explanation: A tailwheel airplane is on the takeoff roll and the tail comes up, the propeller disc rotates forward. That's akin to someone pushing on the top of the disc. The force ...
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4answers
93 views

What is the influence of yaw on P-factor?

From William Kershner's “The Advanced Pilot’s Flight Manual”- page 2-17, P-Factor: If the airplane is yawed, the P-factor effect is encountered. A left yaw would mean a slight nose down tendency and ...
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3answers
151 views

Can plane climb without increase pitch angle?

As I know plane climb "with nose up", but can plane climb without change pitch angle? Can I force plane to climb like this: If I fly in straight level flight at 100km/h and now increase ...
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2answers
175 views

How should I attach an aircraft model in a wind tunnel when testing wind gust/yaw stability?

Where should I attach the rod to the aircraft model when simulating wind gust /weather vane effect in wind tunnel testing? At the center of gravity, behind the CG, in front of the CG...?
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3answers
169 views

Does aircraft allways rotate about center of gravity like weather vane about pivot point?

When gust of wind hit plane form side,does plane allways rotate about center of gravity like weather vane about pivot point or CG as pivot point is just "math areegment" for easier solve ...
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2answers
125 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 ...
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4answers
4k 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 ...
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6answers
179 views

Is the elevator really an 'angle of attack control' as described in Stick and Rudder?

I've been reading Wolfgang Langewiesche's book Stick and Rudder and am a little confused about the definition of the elevator as the "Angle of Attack Control" or rather, the idea that each ...
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1answer
83 views

How would flow angle change along the length of an airfoil?

Let's assume I have: windspeed of 15 m/s blade length of 10 m rotational speed of one revolution per second Can someone please help me calculating how the flow angle would change along the length of ...
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4answers
174 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 ...
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3answers
234 views

On the Ka-50 coaxial helicopter, why does the bottom rotor flap up on the right side instead of in front during forward flight?

In the game DCS World flying the Ka-50, when flying forward at high speeds, the bottom rotor will flap up on the right side of the helicopter (also note that the top rotor is flapping up on the left, ...
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2answers
83 views

How to properly compute the stable vertical path load factor

I've been told by someone else that in a stable flight when the vertical path of the aircraft is maintained, the Nz value is equal to cos(pitch)/cos(bank), but I can't seem to figure out how that is ...
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0answers
33 views

Is axial dynamics important for the helicopter equations of motion?

While analyzing helicopter performance, why do we always ignore the axial dynamics from the equations of motion?
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1answer
88 views

Why does pressure remain constant in the boundary layer?

From Fundamentals of Aerodynamics by JD Anderson. It can be shown experimentally and theoretically that the pressure through the boundary layer in a direction perpendicular to the surface is constant....
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2answers
127 views

What is the physical difference between an airplane having let's say 150 horsepower to an airplane having 250 horsepower?

I was wondering what defines horsepower in an airplane piston engine and how can it be changed?, is horsepower changing during flight?
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2answers
143 views

Bernoulli Principle — Reversed [closed]

The Bernoulli Principle states that as the velocity of a fluid increases, the pressure of that fluid decreases. However what if it were to be reversed: As the velocity of the fluid decreases, the ...
2
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6answers
449 views

Why can't you have sail-powered airplanes?

So, sailing boats take the kinetic energy of a crosswind and turn it into thrust by using their sails as lifting surfaces, and the discussion I had in the comment section of this question made me ...
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1answer
113 views

After decades of solid research, mostly led by Robert J Englar, why is Circulation Control, the Circulation Control Wing not in use at all?

Any research on the CCW by Robert J Englar at Georgia Tech from the 60's into the 2000's. Many papers have confirmed Englar's work and in many cases, advanced it. This research has proven extreme lift ...
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4answers
154 views

What's the relationship between AOA and airspeed?

We know that any aircraft will stall at its stall speed (for a specific weight, CG position, etc.) but also, that the same airplane will always stall at the same angle of attack. I´ve read that IAS is ...
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2answers
143 views

What is the purpose of downthrust?

Many light general aviation aircraft-- and perhaps many other aircraft as well-- are designed with some of amount of downthrust in the engine mounting, relative to the centerline of the fuselage. ...
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2answers
152 views

How does the aircraft keeps propelling forward when airflow and thrust are not aligned?

Assume an aircraft is flying at an angle of attack of 10 degrees, and that the incidence angle between the aircraft fuselage and the wing as well as the angle between the wing and the engine mount is ...
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3answers
153 views

Is “excess thrust” possible in a steady state vector diagram?

Being recently very much sold on the lift-weight-thrust closed triangle (with weight forming the hypotenuse) model for climbing flight, I proceeded to put the logic through its paces (validation) and ...
4
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4answers
673 views

Effect of touchdown on angle of attack, tailwheel vs tricycle

I have a theory but I can't find any documented confirmation. Please let me know if my theory seems right: My theory: During a regular touchdown, a tricycle gear equipped airplane, since the main ...
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1answer
113 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 ...
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4answers
251 views

Are there any situations where having high lift but low lift to drag ratio would be beneficial?

From my understanding, high lift to drag ratio could make an aircraft efficient during cruising conditions. This is when the aircraft is in equilibrium, lift is equal to weight, and thrust is equal to ...
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2answers
91 views

Does an airfoil drag coefficient takes parasite drag into account?

Im trying to understand why does L/D MAX, (the top of the polar curve that computes CL & CD ratio for any airfoil) is also the lowest point of the total drag curve. Im guessing the reason is that ...
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2answers
233 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-...
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1answer
111 views

What is the angle $\epsilon_{cl}$ in this diagram?

Here is an image showing the geometric significance of $\epsilon_{cl}$. To me it looks like the angle between the tangent of the underside of the trailing edge and horizontal (V infinity). Here is a ...
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4answers
326 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 ...
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2answers
207 views

Is the turn radius at fixed bank angle really independent of aircraft type?

I'm curious about the relationship between an aircraft's turn radius and the bank angle. This formula describes the relationship between the two: $$ R = \frac{v^2}{g \tan(b)} $$ Where $R$ is the turn ...
4
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2answers
313 views

Do aircraft weigh less on an eastward flight than a westward flight, due to the Eötvös effect?

Aircraft speed is added to earth rotational speed when flying to the east, centrifugal force is increased compared to a westward flight. That means the aircraft weight is reduced = smaller lift, means ...
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1answer
126 views

Why westward flight takes longer time? [duplicate]

• Why fly from east to west takes longer time then flight form west to east and does this apply to both hemisphere?
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1answer
409 views

Can the load factor during glider winch launch be measured with the G-meter?

I am looking at the flight envelope of a glider, the velocity - load factor diagram. I read that generally the air-frame, the G-meter and the pilot 'experience' the load factor as a G force (an ...
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0answers
74 views

Can I use Stihl fs250 engine for ultralight aircraft? [duplicate]

RPM 9000 Hp 2.2 Engine weight 6kg Plane weight 40kg Body weight. 70 Propellers(2blades) length 30 inches Wings length 120 inches
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3answers
352 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?
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6answers
282 views

Does angular momentum contributes in lifting a helicopter? [closed]

I want to know whether it is possible to make a helicopter with blades that rotate counter-clockwise (CCW) seen from below. I have difficulty understanding the angular momentum in this situation. As ...
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1answer
166 views

How to find the angle of attack?

I'm trying to calculate the angle of attack (AOA) using aircraft some data. From what I understand the AOA is just the angle between the aircraft's forward unit vector (out the nose vector) and the x-...
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0answers
37 views

Why is the assumed Lift-to-Weight-Ratio for the limit drop test for heavy aircraft (FAR-25) higher than for small aircraft (FAR-23)?

The FAR-25.725 assumes a Lift-to-Weight-Ratio L/W = 1 for the landing gear drop test while the FAR-23.725 assumes only L/W=0.667. This factor affects the load inertia factor n which is also needed for ...
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2answers
228 views

Is it possible to Fly Aircraft on Mars?

I have been fascinated with the thought of flying all kind of aircraft on Mars. To begin, I don't know much about the fundamental things or requistes for flying. Is it possible with the the things we ...
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0answers
78 views

What happens when a “ground effect” plane approaches the sound barrier?

Does the shock wave inhibit or contribute to lift? What is the ideal speed to fly near or on the speed of sound while using the ground effect?
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3answers
423 views

What is the impact of camber on CLmax?

I was reading Aerodynamics for Engineering Students by Houghton and saw the following graph: A lot of other sources say that increasing camber increases CLmax, like the graph below. I am a little ...
2
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2answers
146 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-...
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3answers
143 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 ...

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