Runway777 From , joined Dec 1969, posts, RR: Posted (6 years 6 months 1 week 3 days 6 hours ago) and read 4081 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
MDorBust From , joined Dec 1969, posts, RR: Reply 1, posted (6 years 6 months 1 week 3 days 6 hours ago) and read 4080 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.
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 3, posted (6 years 6 months 1 week 3 days 6 hours ago) and read 4064 times:
Pilotpip From United States of America, joined Sep 2003, 3082 posts, RR: 12 Reply 8, posted (6 years 6 months 1 week 3 days 1 hour ago) and read 3894 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.
Starlionblue From Hong Kong, joined Feb 2004, 15870 posts, RR: 66 Reply 9, posted (6 years 6 months 1 week 3 days ago) and read 3876 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." - from Citadel by John Ringo
787atPAE From United States of America, joined Oct 2006, 143 posts, RR: 4 Reply 10, posted (6 years 6 months 1 week 2 days 22 hours ago) and read 3840 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!!
Pilotpip From United States of America, joined Sep 2003, 3082 posts, RR: 12 Reply 11, posted (6 years 6 months 1 week 2 days 22 hours ago) and read 3815 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.
Curmudgeon From Australia, joined Oct 2006, 695 posts, RR: 22 Reply 12, posted (6 years 6 months 1 week 2 days 13 hours ago) and read 3727 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.
JetMech From Australia, joined Mar 2006, 2587 posts, RR: 53 Reply 13, posted (6 years 6 months 1 week 2 days 3 hours ago) and read 3632 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.
Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair.
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 14, posted (6 years 6 months 1 week 2 days 3 hours ago) and read 3627 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.
DeltaGuy From , joined Dec 1969, posts, RR: Reply 15, posted (6 years 6 months 1 week 1 day 21 hours ago) and read 3536 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.
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