A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Simulators
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Lift and Angle of Attack



 
 
Thread Tools Display Modes
Prev Previous Post   Next Post Next
  #1  
Old August 3rd 03, 09:24 PM
Peter Duniho
external usenet poster
 
Posts: n/a
Default Lift and Angle of Attack

"Dave Daniels" wrote in message
...
[...] Firstly, can the lift acting on an aircraft go negative?


Yes, though a non-symmetrical wing (the most common type) will not have an
exactly reversed lift-to-angle-of-attack profile for negative angles of
attack. That is, negative five degrees of AOA won't produce the same amount
of lift downward as positive five degrees of AOA produces upward. Most
wings are designed to optimize lift in the upward direction and so will get
more lift for the same angle of attack in the positive direction, compared
to the negative direction.

[...] Secondly, does the angle at which an aircraft
is banked affect the angle of attack?


The only thing that affects angle of attack is the airplane's attitude
relative to its path of flight. If I were writing a simulator, I would just
use the velocity vector and the attitude (bank, roll, and pitch angle) to
determine angle of attack. Whether roll angle affects the angle of attack
depends on your definition of "affects" and how exactly you're calculating
angle of attack. But generally speaking, if the flight path is not exactly
aligned with the longitudinal axis of the airplane, the roll angle does
affect the angle of attack, albeit in a small way.

Aerodynamically there's another thing to consider, which is that the force
called lift is directed perpendicular to relative wind. In anything other
than straight and level flight, this means lift is not exactly opposite
gravity. In order to calculate vertical acceleration, the simulator code
will have to break the lift vector into multiple components, one of which
will be the vertical component acting against gravity. Again, roll angle
(among other things) needs to be accounted for to figure out the vertical
component of lift.

[...] Thirdly, induced drag: I have read that this
is inversely proportional to the square of the aircraft's
velocity, but I do not see how this follows from the equations I
have seen. It appears to me that the greater the velocity, the
greater the induced drag. I must be missing something fundamental
here. Can anyone explain it?


For a constant angle of attack, increased airspeed means increased induced
drag. However, it also means increased lift. Induced drag is a by-product
of lift. In normal cruise flight, induced drag actually goes *down* as
airspeed increases, because lift remains constant. The only way to keep
lift constant is to reduce angle of attack as the airspeed increases, and
reducing the angle of attack reduces drag faster than increasing airspeed
increases it.

Pete


 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tamed by the Tailwheel [email protected] Piloting 84 January 18th 05 05:08 PM
Newbie Qs on stalls and spins Ramapriya Piloting 72 November 23rd 04 05:05 AM
A very basic question Ramapriya Piloting 45 November 9th 04 02:57 PM
Rag and tube construction and computer models? BllFs6 Home Built 24 April 12th 04 12:20 PM
Angle of climb at Vx and glide angle when "overweight": five questions Koopas Ly Piloting 16 November 29th 03 11:01 PM


All times are GMT +1. The time now is 07:37 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.