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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1answer
102 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
105 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
110 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
144 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
143 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 ...
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4answers
656 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
104 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
231 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
86 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
222 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
89 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
215 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
193 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 ...
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2answers
274 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
117 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
380 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
71 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
241 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
240 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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0answers
102 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
36 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
168 views

Is it possible to Fly Aircrafts on Mars?

I have been fascinated with the thought of flying all kind Aircrafts 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
77 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
238 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 ...
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2answers
119 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
133 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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1answer
71 views

Does the stability of a mass change if the center of gravity is above or below the point of thrust? [duplicate]

I was wondering if it makes any difference if the mass is balanced above or below the point of thrust. See image below for clarification: In the image you can see two configurations. The red arrow / ...
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1answer
85 views

what is the actual force causes this issue according to IAS that shows normal descend speed?

When we have tail wind during approach , with respect of Aerodynamic forces that effect on airplane , the whole part of fuselage move forward due to tailwind, also we have about 70kts IAS (in general ...
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7answers
4k views

Plane that always flies into the wind?

Suppose that you dropped an uncontrolled, dummy glider into the air. You want it to always face into the wind by design. Would it be possible? If so, what would such a plane look like?
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1answer
80 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 ...
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3answers
145 views

Why does a banked aircraft create sideslip?

Below is an excerpt from Raymer (Aircraft Design) where he explains the dihedral effect. He states that a banked aircraft (due to say a roll disturbance) will have a sideslip which leads to a ...
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1answer
280 views

Why does turbofan exhaust appear to reverse direction?

Yesterday I was at the airport planespotting. I observed the exhaust of a couple of turbofan engines, and found it curious how the fluid seemed to behave as it was leaving the engine and gaining ...
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2answers
254 views

What are the forces present in a coordinated turn?

During straight and level flight, coordinated flight is assumed when there is no net lateral force (no slip or no skid). But this concept totally breaks down when it comes to turning, in a co-...
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1answer
71 views

At any given weight or altitude, an aircraft will always lift-off at the same? [closed]

A: Calibrated Air Speed (CAS) B: True Air Speed (TAS) C: Ground Speed D: Equivalent Air Speed (EAS) I think the answer is CAS, but I also think it could be TAS but, isn't TAS calculated after ...
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6answers
6k 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 ...
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1answer
81 views

How do you calculate the wing moment coefficient knowing the moment at each spanwise station?

A lot of theoretical formulas exist for finding the moment coefficient for airfoils, but I have been confused by how to get the moments for a wing. I came up with three related questions that have ...
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4answers
1k views

What is the difference between nautical air miles and nautical ground miles?

What is a simple way to understand the difference between the nautical air mile (NAM) and the nautical ground mile (NGM)? How does the wind affect the net displacement of the aircraft as that is the ...
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1answer
97 views

Does thin airfoil theory work at very high angles of attack?

Thin airfoil theory says that lift coefficient is directly proportional to the angle of attack in radians. I haven't been able to find any limit, short of stall, for applying this theory. It would ...
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2answers
391 views

What is Neil Armstrong teaching in this image?

It seems to me that in this image Neil Armstrong is teaching something related with aerodynamics forces (lift, drag...), but I don't know exactly what is that "Triangle" that He drew (It doesn't seem ...
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1answer
65 views

How are coefficients of equation of sideslip angle in the paper “A general Solution to the Aircraft Trim Problem” calculated?

I am sure many of you guys must have read the paper, "A General solution to the Aircraft Trim Problem" by Marco, Duke and Bernt. I am working with the turning of the Aircraft and I am not able to ...
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2answers
128 views

Do horizontal stabiliser force direction change with CG variation for a given aircraft? [duplicate]

I am wondering about the direction in which horizontal stabilizer provide force. I know that it can provide either upforce or downforce. But I am wondering whether is it determined for a particular ...
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5answers
462 views

How does retracting flaps help extend the glide of an aircraft?

As per the video from Smithsonian channel BA flight 38's captain retracted the flaps of the Boeing 777 by 5 degrees to extend glide, to travel further. Why?
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1answer
53 views

What does induced flow exactly means on helicopters flight? How is it different from downward deflection of air?

I believe all airfoils deflect air downwards at an angle at a velocity V. What is the difference between the downward-vertical component of the deflected wind and the induced velocity in Helicopter ...
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4answers
550 views

How do slats actually work?

I want to know what is the difference between slats and flaps and the mechanism of the slats This what I know and researched about flaps: Flaps are a kind of high-lift device used to reduce the ...
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1answer
86 views

What causes lift in aerofoil: Bernouli's principle or Newton's third law? [duplicate]

Reading materials online, I observe some explanation based on Bernoulli's principle, quoting the difference of air pressure above/below and difference of speed of airflow. While some say's Bernoulli's ...
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3answers
444 views

Do adding high thrust in plane prevents it from stalling?

I am convinced that fighter jets (every flying object) do stall. So from quora, Why don't fighter jets stall? But most of the fighters have thrust:Weight ratio > 1 which means that they are not ...
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3answers
131 views

How does vertical stabilisation work?

I know that similar questions are available all over the internet, including this website. However, none of the answers make full sense to me. I'm looking for simple answer (explain-like-I-am-5 type ...
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2answers
202 views

Why did the Wright brothers take steps to increase the amount of vertical surface area forward of the CG on some of their aircraft?

Why did the Wright brothers take steps to increase the amount of vertical surface area in front of the CG on some of their aircraft? Could this have actually improved the flight characteristics in ...
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1answer
213 views

When a paraglider pilot applies brake on one side and maintains the brake pressure, why does the roll rate eventually come to zero?

I recently started to study paragliding and I am confused about the rolling movement created when a brake is maintained. I was reading this answer How do paraglider controls work? and I am not clear ...
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2answers
165 views

Helicopter Flight: What is the reason for decrease in Induced drag with increase in speed?

As per the figure the induced drag will decrease only if the AoA of the blade is decreased — But in the forward flight, cyclic input increases and decreases the AoA throughout the blade rotation cycle....

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