tom@uunet.UU.NET (Tom Kimpton) (07/01/89)
From: caeco!iconsys!tom@uunet.UU.NET (Tom Kimpton)
In article <7575@cbnews.ATT.COM> fiddler@Sun.COM (Steve Hix) writes:
:
:
:From: fiddler@Sun.COM (Steve Hix)
:
:> [mod.note: For those of us unfamiliar (me included)... I take it
:> alpha == angle of attack. Now, what's angle of attack ? Does (I'm
:> guessing from context) an alpha of 30 degrees mean the plane can
:> fly level with its nose 30 degrees above level ? - Bill ]
:
:No. Not quite.
:
:Take a line between the leading and trailing edges of the wing.
:That's a chord. Measure the angle between the chord line and
:the direction the air going due to the aircraft's motion.
:
:The angle is what you're looking for.
:
:(Roughly, a wing's lift [and drag] increase with increasing angle of attack.
:Up to a point...past that point, lift falls off, usually with a related
:separation of airflow from the wing. At that point the wing stalls.
:
There was an article in the 22 May 89 issue of Aviation Week &
Space Technology, "NASA Adds to Understanding of High Angle
of Attack Regime", that talks about high angle of attack research
using an F/A-18. Good article: "The former Navy F/A-18 has completed
83 flights and reached stabilized angle of attack up to 55 deg."
"At 34 dg. AOA, in stablilized flight, most of the lift appears
to come from the aircraft fuselage and LEX (leading edge extension).
Most of the wing is stalled and the vertical tails appear to be
largely blanked out, wich minimizes lateral and directional
control at these flight conditions."
Also a related article in 29 May 89: "Modified F-15B to Demonstrate
STOL, Maneuver Capability".
--
Tom Kimpton UUCP: {uunet,caeco,nrc-ut}!iconsys!tom
Software Development Engineer ARPANET: icon%byuadam.bitnet@cunyvm.cuny.edu
Icon International, Inc. BITNET: icon%byuadam.bitnet (multi-user acct)
Orem, Utah 84058 PHONE: (801) 225-6888fiddler@Sun.COM (Steve Hix) (07/05/89)
From: fiddler@Sun.COM (Steve Hix) In article <7903@cbnews.ATT.COM>, caeco!iconsys!tom@uunet.UU.NET (Tom Kimpton) writes: > From: caeco!iconsys!tom@uunet.UU.NET (Tom Kimpton) > In article <7575@cbnews.ATT.COM> fiddler@Sun.COM (Steve Hix) writes: > : > :> alpha == angle of attack. Now, what's angle of attack ? Does (I'm > : [ discussion of AOA related solely to the wing deleted...] > > There was an article in the 22 May 89 issue of Aviation Week & > Space Technology, "NASA Adds to Understanding of High Angle > of Attack Regime", that talks about high angle of attack research > using an F/A-18. Good article: "The former Navy F/A-18 has completed Thanks for the reference! My ignoring of fuselage effects on total lift comes from having taught general aviation-related ground school for too long. Most civil aircraft can get away with ignoring such things...but modern fighters can't. Talked to an F/A-18 driver at the Moffett Field airshow yesterday. (He likes the Hornet a lot. Though he admitted that he liked *all* the aircraft that he's flown to date, says that they just keep getting better and better. An obvious enthusiast. :} ) Asked him what the (roughly) 1" x 2.5" vertical tab on the forebody strake was for, assuming it was related to controlling spanwise airflow at high AOA. He said it was secret. But he'd tell us for $1. (Nobody in the mob even twitched.) He relented, and sait it was to keep the vertical stabs from cracking. (No smile.) Earlier versions of the Hornet had some problems with cracking around the vertical stabilizers. First fix(es) related to stiffening them, but didn't help much. Adding the tabs smoothed out airflow over the vertical stabilizers enough to cure the problem. Aerodynamics is still an art. Probably a black art.