[NSRCA-discussion] Airplane angle of attack

Wed Oct 3 04:47:27 AKDT 2007

Understanding that a lot of misinterpretation can happen in reading or
talking about things without actually being directed in person on the
subject article, I dismissed the following story. Now after this post it
has me curious again and I would be interested to hear comments from
people who may have been told the same.  

The story comes as a result of a couple of local pilots who were working
on a well-known $2K arf from 2005-6 era that had no reference lines on
the fuse, nor measurements in the plans referring to Thrustline or any
clue as to where to start on fuselage angle to engine-wing-stab setups.
Communication with the designer resulted in the customer being told that
it should be done by appearance.  (eg: the way you wish to see your fuse
angle in level flight cruise.)

That seems very subject to interpretation and I would think if a person
were a few degrees off it would make a significant difference on
aerodynamic behavior during maneuvering. (mixing etc)

There's probably a post on this somewhere, but Bob's comment led me to
think of that setup dilemma.   I've never seen or heard of an airplane
kit/arf without some reference to thrust line, until I heard my local
friends told me about this one.

Is this scenario familiar to anyone out there? 

(Gee, do I push send or not.......ok I'll send it.)

Chris White

________________________________

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Bob
Richards
Sent: Wednesday, October 03, 2007 7:13 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Airplane angle of attack

I never meant to draw any conclusion about the knife edge performance of
airliners or bombers in my original post. I was merely stating that the
reason we PATTERN FLIERS adjust the incidences of the wing and stab (ON
OUR PATTERN PLANES) has to do with aerobatic performance. As far as I
know, the reason the designers of airliners, bombers, and most
full-scale airplanes pick a incidence value has to do mainly with
efficiency in cruise.

Bob R.

rcmaster199 at aol.com wrote:

	I remember watching a clip of a full size multi engine bomber
type in test flight. The test pilot banked hard to knife edge near the
ground (maybe 500 ft) for some unknown reason and swiftly proceeded to
put it in. Don't remember the plane's or test pilot's names. 

	Full scale fuselages are designed to minimize drag as much as
possible (for max range) so they tend to be pencil thin comparatively
speaking. Pencil thin fuses do not fly knife flight well nor are they
intended to do so. And the higher the weight the worse the problem. At
risk of being glib, that test pilot found the outside of the envelope.

	MattK

	-----Original Message-----
	From: chris moon <cjm767driver at hotmail.com>
	To: nsrca-discussion at lists.nsrca.org
	Sent: Tue, Oct 2 4:28 PM
	Subject: Re: [NSRCA-discussion] Airplane angle of attack

	The optimum AOA on airliners is a function of wing design. It's
the 
	operator's job to try and stay near the optimum AOA for maximum 
	efficiency. Lighter gross weights require either higher
altitudes or 
	lower true airspeed to be most efficient. Likewise, heavier
weights will 
	have you faster and or lower. I guess what I'm saying is that
the 
	optimum AOA is essentially dictated by wing design and we juggle
the 
	other variables in order operate the wing as efficiently as
possible. 

	I have rolled the 737, 757, 767 and A320 in the simulator and
they make 
	poor pattern planes. I'm sure there is a significant downgrade
for a 
	single roll that loses 5000+ feet of altitude. Don't even ask
about 
	knife edge performance. 

	Chris 

	Bob Richards wrote: 
	> That makes sense to me. The AOA depends on the load. In an
extreme 
	> case, very lightly loaded, I don't think you would want to fly
with 
	> the fuselage in a nose down attitude, that would probably be 
	> inefficient. Better to have it slightly nose up in cruise with
a full 
	> load. JMHO. 
	> Of course, the reason WE would trim wing incidence would have
more to 
	> do with overall flight characteristics during aerobatics,
particularly 
	> with pitch coupling in knife edge flight. 
	> Bob R. 
	> 
	> 
	> */chris moon /* wrote: 
	> 
	> Tried to post this before but it did not go through. 
	> 
	> The optimum cruise angle of attack for jetliners is somewhere
between 
	> 2.5 and 5 degrees nose up. Usually closer to 2.5 or 3 degrees
for an 
	> econ cruise. As fuel burns off and the gross weight goes down,
the 
	> airplane will need a lower angle of attack to maintain flight
which 
	> will take us away from our optimum angle (lower). So, we will
either 
	> climb to where the air is "thinner" and require a higher aoa 
	> (angle of 
	> attack) to get us back to the 2.5 or 3 degrees or, slow down
and 
	> maintain the lower altitude thus requiring us to increase the
aoa 
	> back 
	> to optimum. The answer to your question is yes, a jetliner
flies at a 
	> nose high aoa in cruise. Lift from the fuselage would probably
be 
	> negligible other than "impact" lift - the force of the
relative wind 
	> against the raised fuselage bottom. 
	> 
	> Chris 
	> 
	> 
	>
------------------------------------------------------------------------

	> 
	> _______________________________________________ 
	> NSRCA-discussion mailing list 
	> NSRCA-discussion at lists.nsrca.org 
	> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion 

________________________________

	Climb to the top of the charts!  Play Star Shuffle:  the word
scramble challenge with star power. Play Now!
<http://club.live.com/star_shuffle.aspx?icid=starshuffle_wlmailtextlink_
oct>  = 

	_______________________________________________
NSRCA-discussion mailing list  NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion  

________________________________

	Email and AIM finally together. You've gotta check out free AOL
Mail
<http://o.aolcdn.com/cdn.webmail.aol.com/mailtour/aol/en-us/index.htm?nc
id=AOLAOF00020000000970> !

	_______________________________________________
	NSRCA-discussion mailing list
	NSRCA-discussion at lists.nsrca.org
	http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20071003/6bdd41ee/attachment-0001.html 