Questions tagged [angle-of-attack]

Usually refers to the angle between the oncoming air and the wing.

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66 views

How to calculate aerodynamic efficiency at minimum power conditions?

The drag polar of a propeller driven aircraft is $C_{D}=0.039+0.071 C_L^2$. The lift curve slope of the wing ($C_{L_\alpha}$) is 0.09/deg and zero lift angle ($\alpha_{L=0})= -1.5^o$. Stall angle of ...
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147 views

Is the highly optimized high subsonic cruise airfoil less safe for higher AOA flight? [duplicate]

An examination of the 737 airliner wing profile and that of a blue whale leads to the question of whether the high Reynolds number subsonic cruising airfoil and the low speed, high AOA airfoil are ...
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142 views

Does the AOA and G-Force increase if a fighter uses the afterburner during a max G level turn?

My understanding is that if you apply power (increase the thrust) for a jet in level flight, it will momentarily pitch up, and then gain some speed. So, if a fighter pilot lights their afterburner ...
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How does the critical Angle of attack changes with Increasing Reynolds Number?

I am simulating NACA 2415 Airfoil for different Reynolds Number i.e. 2 million,3 million and 4 million on ANSYS Fluent. The difference between the critical Angle of attack is quite vast. For the 4 ...
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“Snowglobe”-type attitude indicator [duplicate]

I'm an aviation enthusiast (I do not, nor have I ever worked in the industry), and after researching several various emergencies (reading text documents, reviewing CVR transcripts and watching ...
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Does flying an airplane upside down imply negative AoA? Why?

I saw the statement below in this answer: Note that for normal level unaccelerated flight $C_L$ is always > 0. The minimum $C_L$ is a negative value for negative AoA, and would mean that the ...
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1answer
68 views

What material and shape should be used for angle of attack sensors?

Does the material and shape of the vane for an angle of attack sensor have to be identical to the material and shape of the wing? What properties should I consider?
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795 views

Why does RPM for a fixed-pitch propeller change with an aircraft's pitch?

Talking bout a C-152 - If I pitch the aircraft down, and without adjusting the throttle, the RPM would show an increase. Pitch up, and without adjusting the throttle, the RPM shows a decrease. I've ...
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31 views

Is it more efficient to use inlet guide vanes or variable pitch blades

Again, its all in the question. two scenarios for a ducted prop in hover: inlet guide vanes close to the prop to control the angle of attack just a prop with a variable pitch mechanism. obviously, ...
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Sideslip vs Freestream Azimuth Angle

Why is the sideslip angle, $\beta$, defined as $$\beta=sin^{-1}\left(\frac{v}{|{\bf v}|} \right)$$ and not the same as freestream azimuth angle $\psi$ $$\psi=tan^{-1}\left(\frac{v}{u} \right)$$ ...
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322 views

Angle of attack difference between outer wing and inner wing during a descending turn and climbing turn

I understand that during an ascending or descending turn the angles of attack of the inner wing and outer wing are different. However, I don't understand why then ascending and turning, the outer ...
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78 views

Why is the angle of attack not proportional to the stagnation point?

While I was studying my PPL today, I've encountered a question right below and I wasn't really satisfied with the answer. Which statement about the airflow around an aerofoil is correct if the angle ...
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8answers
491 views

Could the stick position be used as a Angle of Attack indicator?

True or False: The stick determines elevator position and elevator position determines angle of attack. When the critical angle of attack is exceeded, the wing stalls. So, given a design with enough ...
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3answers
275 views

Is there a simple relationship between angle of attack and lift coefficient?

Is there an equation relating AoA to lift coefficient? I have been searching for a while: there are plenty of discussions about the relation between AoA and Lift, but few of them give an equation ...
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238 views

Why does an increase of airspeed result in a decrease of angle of attack?

In Chapter 02: Aerodynamics of Flight of Helicopter Flying Handbook, on page 10, it says: Induced flow velocity is increased, resulting in a decrease in AOA. I don't understand how airspeed can ...
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1answer
73 views

How are airliners AoA-Sensors calibrated?

Airflow around the fuselage is not free, even near the aircraft nose. I assume some correction is applied to the measured angle to get the corresponding freeflow angle. How is the reponse curve for ...
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166 views

How are AOA sensors tested after working on them?

If a maintenance or replacement has been done for an AOA sensor, would the mechanic be able to test if the sensor now works correctly? Can such a sensor be tested on the ground? If there is no ...
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267 views

Why is airspeed different in climbs and descents although the AoA doesn't change?

Here are the background facts: This excercise has the objective to familiarise the student with the slow flight characteristics. The steps are: 1)Establish straight and level, 90% RPM, 15 units ...
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765 views

Is drag coefficient lowest at zero angle of attack?

The drag coefficient of a symmetric airfoil is lowest when its angle of attack is zero. I'm not sure if this is true in general.
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4answers
579 views

Why are the AOA sensors placed outside the aircraft?

Why should the AOA sensors be placed outside the aircraft? Is it not the angle between the chord line of a wing and a vector representing the relative motion between the aircraft and the surrounding ...
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2answers
380 views

How does the Angle of attack vary from the root to the tip of a propeller for a fixed pitch prop?

I came across a video while learning about propellers where it showed the angle of attack increased from the root of the propeller to the tip of propeller whose pitch was fixed. I somehow cannot get ...
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What's the theoretical background of the critical angle of attack?

The critical angle of attack seems to be at all (most?) airfoils around 15-20°. Why is that? Why is it in this range and not lower or higher? Is it just the result of optimizing airfoils? Or is it ...
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What is being depicted w.r.t. AoA in this video?

I was looking at this video of the AF447 crash simulation and at about 4:45 the angle of attack diagram shows a few things I don't understand (frame above). I get the orientation of the airplane, ...
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What were the advantages of the L-1011 AoA sensor design?

The Lockheed L-1011 had an unusual type of AoA sensor. Instead of the usual vanes it used a tube with two rows of holes in it about 90° apart. A diaphragm sensed the pressure differential between the ...
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939 views

Has the number of angle of attack sensors been reduced in Boeing 737 Max, in comparison to the older models?

Boeing 737 is flying since 1967. I would like to know first how many ' angle of attack sensors' does it have, and has they number been reduced for Boeing 737 Max, in comparison to the older models ...
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How many AOA sensors does the 737 MAX have?

How many AOA sensors does the 737 MAX have? Given that it's reported in the media, that one faulty AOA probe activated the MCAS on the Lion Air flight, I was wondering if anybody also knows how an ...
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249 views

What effect does the angle of attack have on lift and drag?

In general, what effect does the angle of attack have on lift and drag? I understand the the B-25 take-off run was normally in excess of 1500 ft, the exact value dependent upon load, density altitude,...
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289 views

Why are the positions of an aircraft's angle-of-attack vanes dependent on airspeed?

According to this answer to an earlier question of mine, the positions of the angle-of-attack sensor vanes on the A330/A340 are dependent not only on AoA, but also on airspeed (and, according to @ymb1'...
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Wind shear questions

I had a discussion and I'm curious on an experienced pilots knowledge. When taking off, let's say from telluride. You have a tailwind, but when you get off the ground you experience and windshear ...
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167 views

Why does the rotor thrust decrease at smaller tip clearance for shrouded rotor?

Consider this system, rotor with shroud: From this research, we see that: at the same rpm, the rotor thrust decreases,the shroud thrust increases as tip clearance decreases. But why does the rotor ...
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What is the glide ratio on the CE-S550 Citation S-II?

I couldn't find it in the AFM. Is it different then the square winged citation II?
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208 views

Wing pitching moment decomposition into two terms

Summary: Assuming constant angle of attack $\alpha$, speed $V$, and lift $L$ applied at the center of pressure CP (whose position is $x_{CP}$), the distance $(x_{CP} - x_O)$ between the moment ...
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Will an Airbus A320 plane go into an unrecoverable nosedive and crash if a single angle of attack sensor fails, like on Lion Air JT610?

For example, has an Airbus gone from cruise flight into an automated unrecoverable nose dive until it hit the ground because an AOA sensor failed in flight? Moreso, are there any cases of an AOA ...
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2k views

Which 737 generations doesn't have Alpha Vane (Angle of Attack sensor)?

I was wondering if all generations have this angle of attack sensor, especially after recent 737 MAX Lion Air accident.
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Can quadcopters still fly with propellers at an angle?

Can quadcopters still fly with propellers at an angle? By this I mean like the whole motor mounts will be situated along a certain slope (so as to be neither horizontal nor vertical). UPDATE I meant ...
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852 views

In an Airbus A320, when alpha protection is active, is pitch protection no longer available?

The A320 FCOM chapter 27 flight controls, normal law, protections, shows a diagram how the sidestick input is used when protections are active. When high angle of attack protection is active the side ...
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5answers
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Does headwind on takeoff affect g force?

I'm aware that headwind or tailwind does not affect rate of climb or descent but only the angle. I'm not sure if it affects the g force or not. I'd assume it affects g force because using trignometry, ...
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Different between Angle of Incidence (AoI) and Angle of Attack (AoA)

Following discussion here, I am still confused about the difference between AoI and AoA. As I read in many references and watched in many YouTube videos especially this one: 1). AoI is tje angle ...
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Why does the angle of descent increase in a constant headwind while decreases in a sudden encounter with a headwind, in a descend?

I'm currently studying aerodynamics. I have realized that a sudden encounter with a headwind during descent will result in the aircraft generating more lift, thus angle of descent decreases. I haven'...
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Can airplane performance be increased by cruising “on step”?

Old timers swear aircraft performance can be increased by getting an aircraft "on step" similar to how boats are operated. They claimed a couple extra miles per hour (airspeed was in MPH then) were ...
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Why does the stagnation point on airfoil move with the angle of attack?

What is the physical explanation for the reason the stagnation point is where it is? And, why does it move further down the lower side of the airfoil with an increase in angle of attack?
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Why did this A320 stall protection demo not hold Valpha max?

This video is about the Airbus A320 High angle of attack protection At 4:54 - 5:13 why did it pitch down? I know it is trying to maintain Valpha max but if it would ...
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Is the lift produced by a wing with a 10° flap equal to the lift created by a wing with 10° AOA but with no flap?

After reading this article I would like to know if the lift produced by a wing with a 10° flap is equal to the lift created by a wing with 10° AOA but with no flap?
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138 views

Twist optimization for a low speed aircraft

I'm currently designing an aircraft with the following specifications- s=1.8m^2, AR=7-8, trapezoidal planform with a taper ratio of about 0.45, a load of 25KGs and a cruising speed of 13-15m/s. I'm ...
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Why is the critical AoA of most flaps 40° when most airfoils stall at 15°?

A plain flap deflected 40 degrees is largely stalled (...) Flaps stall at 40° according to an answer on Quora, why is this so when typical airfoils stall at 15°?
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What is the average angle of attack of GA airplanes during takeoff?

What is the average angle of attack of GA airplanes during takeoff?
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Do negative angles-of-attack create lift?

(wikimedia.org) A typical curve showing section lift coefficient versus angle of attack for a cambered airfoil. Based on the graph above, do negative angle-of-attack values create lift? How?
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Does airspeed affect the critical angle of attack on an airfoil?

I understand that the critical angle of attack is mostly affected by the shape of the airfoil. However does the airspeed of the airfoil or the density of the air affect the critical angle of attack? ...
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670 views

Why do aerobatic planes have symmetrical wings?

Besides the fact that symmetrical wings fly the same inverted as upright are there any other reasons why aerobatic planes prefer symmetrical wings? Can symmetrical wings achieve a higher critical ...
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339 views

Do wingtip vortices cause a decrease in the lift component of aerodynamic force, and do planes need to pull more AoA to compensate?

So, from what I know about wingtip vortices, they shift the angle of the relative airflow to where the effective angle of attack of the airfoil is lowered. Since the aerodynamic force is always ...