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This May Seem Easy For A Lot Of You  
User currently offlineRunway777 From , joined Dec 1969, posts, RR:
Posted (7 years 9 months 1 week 4 days 4 hours ago) and read 17599 times:

This may seem easy for a lot of you. but I have a question involving my PPL course.
Right now we are doing aerodynamics and such. What exactly is the Angle of Attack?
I think I know what it is, but i was just wondering if I could get some clarification, because I keep getting it mixed up with other things

Thanks

16 replies: All unread, jump to last
 
User currently offlineMDorBust From , joined Dec 1969, posts, RR:
Reply 1, posted (7 years 9 months 1 week 4 days 4 hours ago) and read 17598 times:

AoA is the angle at which the wing is moving through the air. The lower the AoA, the closer the wing is pointed directly into the airflow. The higher the AoA, the more the wing is pointed up/down from the airflow.

User currently offlineRunway777 From , joined Dec 1969, posts, RR:
Reply 2, posted (7 years 9 months 1 week 4 days 3 hours ago) and read 17595 times:

OHhhhhh!! okay. i get it now, i was getting confused with the angle of incidenence or something. lol
thanks so much hunn


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 3, posted (7 years 9 months 1 week 4 days 3 hours ago) and read 17582 times:

Quoting Runway777 (Reply 2):
angle of incidenence

Angle of incidence is set at the factory when the wing is bolted on. An airplane in a hangar or upside down in a cornfield has an angle of incidence.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineRunway777 From , joined Dec 1969, posts, RR:
Reply 4, posted (7 years 9 months 1 week 4 days 3 hours ago) and read 17579 times:

yes. i got that much.
thanks tho.

-kalli


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17014 posts, RR: 67
Reply 5, posted (7 years 9 months 1 week 4 days 1 hour ago) and read 17502 times:

AoA is also known as "alpha" right?


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 6, posted (7 years 9 months 1 week 4 days 1 hour ago) and read 17488 times:

Quoting Starlionblue (Reply 5):
AoA is also known as "alpha" right?

Yes, that's the symbol usually used to denote AoA. In daily speak, it is alpha, with sideslip angle being beta.



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 7, posted (7 years 9 months 1 week 3 days 23 hours ago) and read 17458 times:

AoA (angle of attack) is the angle at which the airfoil's cord meets the relative airflow. In this diagram, "a" (or alpha) represents the AoA:


If the AoA exceeds critical, then the airfoil can no longer produce enough lift, and the wing stalls (usually around 15º for a clean wing):


Note: Coefficient of lift (C subL) increases with an increasing AoA until the wing begins to enter a stall.


User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 8, posted (7 years 9 months 1 week 3 days 22 hours ago) and read 17412 times:

Also remember that the AOA is the Angle of the wing chord to the RELATIVE wind. This is an important little thing. It's entirely possible to be in a nose-down attitude and exceed critical AOA as a result.


DMI
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17014 posts, RR: 67
Reply 9, posted (7 years 9 months 1 week 3 days 21 hours ago) and read 17394 times:

Quoting Pilotpip (Reply 8):
Also remember that the AOA is the Angle of the wing chord to the RELATIVE wind. This is an important little thing. It's entirely possible to be in a nose-down attitude and exceed critical AOA as a result.

Indeed. One thing I have had to explain to many aviation enthusiasts (non pilots) is that while stall is commonly associated with low speeds, it is quite possible to stall at high speed by exceeding critical AoA.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline787atPAE From United States of America, joined Oct 2006, 143 posts, RR: 4
Reply 10, posted (7 years 9 months 1 week 3 days 20 hours ago) and read 17358 times:

It's interesting you think angle of attack seems easy to everybody. AOA can be a bear to deal with, with respect to calculations and the physics involved, both in simulation use and in a practical setting. Of the regular pitch axis terms (AOA, pitch angle, and flight path angle), the AOA is the most difficult to think of.

FPA and pitch angle are referenced to the local horizontal, whereas the AOA is referenced to a variable (the velocity vector) that is constantly changing.

Other than the space shuttle, I don't know of any vehicle that uses AOA as a target in the flight control system. Airplanes (and pilots) will use FPA (eg, -3 deg glideslope) and pitch angle (eg, +15 deg on climbout), but I've never heard of anybody trying for a 5 deg AOA.

You have begun a quest for knowledge in the realm of aerodynamics. There's a ton of interesting stuff out there. Aerodynamics always keeps me thinking. It's neat to see the theory work in real life. Good luck!!


User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 11, posted (7 years 9 months 1 week 3 days 19 hours ago) and read 17333 times:

AOA is very difficult even for most pilots. I spent the better part of an hour trying to explain it to my first groundschool class.


DMI
User currently offlineCurmudgeon From Australia, joined Oct 2006, 695 posts, RR: 22
Reply 12, posted (7 years 9 months 1 week 3 days 11 hours ago) and read 17245 times:

Quoting 787atPAE (Reply 10):
Other than the space shuttle, I don't know of any vehicle that uses AOA as a target in the flight control system. Airplanes (and pilots) will use FPA (eg, -3 deg glideslope) and pitch angle (eg, +15 deg on climbout), but I've never heard of anybody trying for a 5 deg AOA.

Some EFIS aircraft have the option of AoA display. The 737 display does show a target range for a 3 degree approach-the range is equivalent to Vref to Vref +20, which is the normal band of recomended approach speeds.

Since nobody I know was trained on AoA, the display is largely in the "gee whiz" category, but it could come in damn handy with an unreliable airspeed indicator.



Jets are for kids
User currently offlineJetMech From Australia, joined Mar 2006, 2687 posts, RR: 53
Reply 13, posted (7 years 9 months 1 week 3 days ago) and read 17150 times:

Quoting Runway777 (Reply 2):
angle of incidenence or something. lol

I don't think it has been mentioned specifically so far, but the angle of incidence is the angle between the aircraft's longitudinal axis and the chord line of the wing. IIRC, this angle of incidence remains the same for all aircraft attitudes.

Quoting SlamClick (Reply 3):
Angle of incidence is set at the factory when the wing is bolted on. An airplane in a hangar or upside down in a cornfield has an angle of incidence.

http://www.sportflying.co.nz/Image152.gif

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 14, posted (7 years 9 months 1 week 3 days ago) and read 17145 times:

Quoting 787atPAE (Reply 10):
Other than the space shuttle, I don't know of any vehicle that uses AOA as a target in the flight control system. Airplanes (and pilots) will use FPA (eg, -3 deg glideslope) and pitch angle (eg, +15 deg on climbout), but I've never heard of anybody trying for a 5 deg AOA.

Plenty of aircraft have AoA indicators. When you have it, it is very convenient indeed! No need to flip through speedbooks to find the correct airspeed for the current weight. You just park the aircraft at the correct AoA for that segment of flight. Fighters commonly have it right up front, I could list quite a few. It has also appeared in a few bizjets I've seen, and I'd bet there are airliners out there with it as well. It is available rather cheaply for GA aircraft.

In the fighters, it is very common to use the AoA as one of the main targets. Carrier based aircraft have indicators right next to the HUD telling them if they are above, below or on thet righ AoA for the approach (even if it is often mistaken to be a fast/slow indicator). In the Saab 37, you fly different alpha approaches depending on whether you are aiming for a short runway landing or not. The F16 has an AoA bracket popping up in the HUD when you drop the undercarriage. Put the flight path marker in the bracket and you are between 11 and 13 (IIRC) degrees AoA.

Any aircraft with a HUD with a flight path marker also has an AoA indicator. The AoA is the difference between the nose reference and the flight path marker.

You can also use AoA instead of a speed indicator. You can use AoA to tell you just how much harder you can pull in a turn. The stall is at a fixed AoA, remember?

To me, as an aero engineer, it is amazing that there are aircraft which do not have AoA indicators right up under the eyes of the pilot. I'd rather be without an ASI myself.



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineDeltaGuy From , joined Dec 1969, posts, RR:
Reply 15, posted (7 years 9 months 1 week 2 days 18 hours ago) and read 17054 times:

Quoting FredT (Reply 14):
Any aircraft with a HUD with a flight path marker also has an AoA indicator. The AoA is the difference between the nose reference and the flight path marker.

Kinda like this- the little Alpha symbol with the 0.6 next to it, on the left side.

View Large View Medium
Click here for bigger photo!

Photo © Carlos Pulido Romera



DeltaGuy


User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 16, posted (7 years 9 months 1 week 2 days 16 hours ago) and read 17025 times:

To add.
The AOA is Variable while the AOI is normally fixed.
regds
MEL



Think of the brighter side!
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