Questions tagged [angle-of-attack]

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

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79 votes
7 answers
35k views

Why does the B-52 take off without rotating?

In the answer to this question it is noted that the B-52 takes off without rotating and climbs out in a nose-down attitude. Why was it designed this way?
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37 votes
2 answers
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How does an alpha (AoA) vane work?

The alpha vane (also called AoA vane) is an external probe used to measure the angle of attack. I have been trying to understand how exactly it works, but I can't find any clear explanation or ...
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2 answers
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What does it mean when pitch numbers move all over the HUD screen?

In this video from an F-16: You can see pitch angle move out of screen or be on the side at the end.
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19 votes
1 answer
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Why does my wind tunnel experiment give two different stall angles of attack?

When I increase the angle of attack from 0 to 20 the stall begins at 18 deg. When I decrease the angle of attack from 20 to 0 the stall ends at 13 deg. Why the difference and what value (13 or 18 deg) ...
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19 votes
1 answer
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What is the stall AoA for the space shuttle?

Once flying as (fast) glider in order to land, what was the angle of attack it would have stalled? I'm really interested in the angle of attack for such wings and not the speed.
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15 votes
1 answer
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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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13 votes
4 answers
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Can a taildragger land tail first?

Inspired by this question... How does a taildragger take off? Does it rotate? I imagine if a taildragger has to land front wheels first it has a very limited range of Angle of Attack (if the pilot ...
13 votes
2 answers
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Why are the angle-of-attack sensors on most airplanes mounted on the forward fuselage rather than at the wing roots?

A source of reliable angle-of-attack information is important for airplanes, as flight at an excessively-high angle of attack can cause the airplane to stall, which is generally considered to be an ...
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12 votes
4 answers
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Why is angle of attack information not displayed in the cockpit?

Would not it be useful to have the angle of attack information displayed on the flight display? I know that we have shakers that alert pilot when the critical AOA is exceeded, but still we have cases ...
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12 votes
2 answers
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Why does stall speed decrease when flaps are deployed?

I've been told that deploying the flaps on approach enables the following: Potentially steeper approach Slows down the plane Lower stall speed It's the last one that confuses me. Given the equation ...
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12 votes
2 answers
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How does flight control surface authority change with AOA?

I am working on semi-realistic (let's just call it "believable") flight simulation component set for a game engine. One of the topics that I tried to research but could not find reliable information ...
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11 votes
3 answers
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What is the wing angle of attack of a Boeing 737 in cruise?

I would like to know the angle of attack that a 737 flies at during cruise. I am specifically interested in the wing angle of attack (if you know the cruise nose-up attitude and the wing incidence ...
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11 votes
1 answer
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How to calculate the Lift Coefficient for the A320?

I'm trying to figure out the lift coefficient of an A320. What I'm doing is the following: during cruise, the lift is equal to the weight of the aircraft ($mg$) so that I used the cruise table taken ...
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10 votes
6 answers
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Why do planes fly at a high angle of attack when flying slow?

I've noticed that when a plane does slow flight, the pilot increases the angle of attack (AOA). What is the purpose of this? F-18 - Slow Pass
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10 votes
2 answers
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Why doesn't critical angle of attack increase with airspeed? [duplicate]

Critical angle of attack is related to the Coefficient of Lift, which is a function of Reynold's number. Reynold's number depends on the speed of the aircraft. So why doesn't the Critical Angle of ...
10 votes
1 answer
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Does lift coefficient vary with the wind velocity for a given angle of attack?

I have this question in my mind. I have been trying to look for this in different books about aerodynamics and I couldn't find the answer. I know I could check the answer experimentally, if I had a ...
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10 votes
2 answers
434 views

Why is this angle of attack sensor tab not symmetrical between the leading and trailing edges?

Here is an Angle of Attack (AoA) sensor I took from here. If you are interested to know the AoA detail, just click the link. You may see what is inside it. But not sure what airplane's AoA sensor it ...
9 votes
1 answer
1k views

How does increasing the RPM result in a higher AOA for the blades?

I know that an increase in velocity (TAS) reduces the AOA and that makes sense. But how just simply increasing the blade rotation (RPM) results in higher AOA?
9 votes
3 answers
1k views

Can variable incidence wings replace ailerons?

If a wing can change its incidence angle, can aileron be omitted in the design? Since aileron are used to increase lift and decrease it. so is the incidence angle. How would the two solutions ...
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9 votes
1 answer
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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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8 votes
2 answers
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Will the autopilot raise the AoA above the critical AoA to maintain altitude?

NOTE: This question is regarding commercial airliners (eg: Boeing 737, Airbus A320, etc.. This is for any given configuration of the aircraft) Will the autopilot raise the AoA above the critical AoA ...
8 votes
4 answers
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Are there wool threads for displaying angle of attack?

Like there is a wool thread on a glider's canopy for showing relative wind on yaw axis. Are there or have there been a wool thread as a long term mean of showing angle of attack? For instance placed ...
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8 votes
4 answers
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Why aren't angle-of-attack data sanity-checked before being fed to other aircraft systems?

For most fixed-wing aircraft, accurate angle-of-attack information is utterly essential for safe flight, due primarily to the risk of stalling the aircraft if the AoA of one or both of its wings ...
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8 votes
2 answers
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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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7 votes
6 answers
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Can induced drag be negative?

For an aircraft in straight and level flight, lift-induced drag is the horizontal component of the force perpendicular to the wing chord. Positively cambered aerofoils generate lift starting at small ...
7 votes
2 answers
1k views

Why do airliners on autopilot climb during cruise?

Several years ago I was a passenger on a near cross-country flight when the pilot came on the PA and announced that we were climbing towards our cruise altitude, on autopilot, and as our fuel load was ...
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7 votes
3 answers
437 views

Could airliners fetch data like AoA and speed from an INS?

If I understood what an inertial navigation system (INS) is, it should be able to calculate speed and orientation of the aircraft. If this is possible, why do airliners solely rely on sensors to ...
7 votes
2 answers
2k views

Why Air France 447 could not reduce angle of attack?

I just finished reading this article and couldn't understand why in 3 minutes and 30 seconds even though there was no reliable speed data, pilot could not level the plane? Isn't the angle of attack ...
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1 answer
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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.
7 votes
3 answers
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Is induced drag caused because of the tilt of the wing backwards?

In this question: Why is induced drag less on a high span wing? In the answer it was stated that wing tip vortices do not cause induced drag. If this is the case then what causes the induced drag. ...
7 votes
4 answers
584 views

Why do smaller RC helicopters have visible twist in their rotors, and slightly bigger ones do not?

Smaller, cheap, RC helicopters generally have very pronounced twist in their blades, and also vary their chord - slightly larger, slightly more expensive RC helicopters have no visible twist or chord ...
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6 votes
9 answers
785 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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6 votes
3 answers
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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 ...
6 votes
3 answers
23k views

What is the typical angle of attack aircraft fly at and at what angle of attack do they stall?

At what angles of attack do aircraft typically fly at? How much of a margin is there before aircraft stall due to an increase of an angle attack due to factors such as gusts or rotation of the wing ...
6 votes
2 answers
2k views

What are those devices sitting on top of instrument panel in this Baron?

On this Baron YT video: what are the two devices sitting on top of the instruments panel, on both sides of the compass? I though at first it is some kind of HUD (Head-...
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6 votes
2 answers
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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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6 votes
3 answers
419 views

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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6 votes
2 answers
851 views

Do airliners adjust altitude for latitude?

According to this NASA article, the troposphere extends from about 5 miles at the poles to about 9 miles at the equator. Though the height of the troposphere is defined by the height of the tropopause ...
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6 votes
1 answer
473 views

Is it possible to get into a spin situation while coordinated?

Is there any possibility of spinning while coordinated? Of course, any CFI would tell you no, but I wonder if the the following situation could result in a spin while coordinated: Slow level flight ...
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6 votes
2 answers
5k views

Is it possible to fly horizontally with zero angle of attack?

If an aircraft has a zero angle of attack and the wing doesn't, is it possible to fly horizontally? Because as the book says, there is no lift in this condition, Is this zero angle of attack of the ...
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6 votes
5 answers
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What happens during a powered descent?

I was having a discussion with my friend about equilibrium condition in flight: Scenario: While going in straight and level flight, say I reduced my airspeed by 30 mph. At the same time keeping the ...
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6 votes
4 answers
581 views

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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6 votes
1 answer
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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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6 votes
2 answers
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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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6 votes
1 answer
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What are the definitions of elevator angle of attack and critical angle of attack?

Angle of attack is the angle between the chord line of the wing to the direction of relative wind. So angle of attack helps the aircraft climb. Then what is the angle between the chord line of the ...
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5 votes
7 answers
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Why angle of attack is always shown against the relative wind parallel to horizon?

I have a question about Stall, which I have difficulty to understand. According to the theory, stall happens when : 1- Speed is slow then a certain limit. 2- Angle of attack is greater than a ...
5 votes
4 answers
823 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 ...
5 votes
2 answers
2k views

What's the pattern of airflow over the airfoil at high angle of attack?

When at high angle of attack the boundary layer tends to: A. stagnate and stop B. loop around the upper camber line C. decrease air pressure along the chord The answer is A, but as I see it, B ...
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5 answers
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How does the angle of attack vary in turns?

I read somewhere that when the aircraft banks to turn, its angle of attack increases.Since angle of attack is the angle between the relative wind and chord line, how does turning increase it? Is it ...
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5 votes
5 answers
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Are we changing the angle of attack by changing the pitch of an aircraft?

For example: if I pitch the airplane up, but also increase power and am able to maintain the same speed, then no, the AoA hasn’t changed, although it may have varied in the transition between one ...