REFLECTOR:Stall Characteristics

[Tom Martino]

Here is a very basic, yet important question.

Does the original CG envelope hold true for all subsequent aircraft or
will the envelope vary with modifications.

For example, some of us may have heavier wings, different engines and
props, variation in interiors, etc.

I realize that with most aircraft with basic envelope holds true and you
simply calculate the CG based on the loading and "station" of the
loading.  Is that so with an experimental aircraft that could be
different from one completion to another?

Is there a way (a safe way) to calculate your CG range?  Or should we
use the original factory envelope?  (By the way where is that envelope
published?)

Any info would be appreciated!
 

-----Original Message-----
From: Scott [mailto:scott@tnstaafl.net] 
Sent: Saturday, November 15, 2003 7:11 AM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:Stall Characteristics

Scott B,

Thanks for that follow up.

Glad you got a hold of "The Expert" for some horses mouth info.
Danny's 
expert opinion is right in line with the pilots I have spoken to who
have 
performed aerobatics( I know Dan, Puffer and Rutan said don't do it ),
in 
canard aircraft.

I think this would be good grist for the mill, for your next article in
the 
next V.V.

Scott D.

At 05:08 PM 11/14/2003, you wrote:
>John and fellow Reflectorites -
>I read in John's post that he is concerned that stalls in the Velocity
might
>be something that is ready to bite the unsuspecting pilot.  I don't
think
>that is the situation at all.  I think the aircraft should be stall
tested
>throughout the published cg range during flight testing (there is a
>recommended flight test procedure for this).  I am not worried about
doing
>stalls in the Velocity as long as the aircraft is within cg limits.
>Velocity routinely demonstrates stalls during demonstration flights -
from
>normal pitch bucks to the "dreaded" cross-controlled base-to-final
stall
>scenario.  The stall behavior is so benign that it isn't - as least in
my
>opinion - anything to worry about ... it's pretty much a "non-event".
In
>that regard, I agree with you that there isn't a need to "practice"
stalls,
>since the technique for recovery is simply relaxing the stick.  But if
you
>want to demonstrate the stall behavior of the aircraft to friends and
>neighbors ... why not?  In answer to your question -  No, under normal
>circumstances, I think it is nearly impossible to unintentionally cause
a
>deep stall.   (Note: there is an instance where a Velocity entered the
wake
>turbulence of a commercial jet aircraft - and it is thought the
aircraft
>entered an inverted deep stall condition from which the pilot was
unable to
>recover.  Also - slips to landing are not recommended because it
"upsets"
>the lift relationship between the canard and the main wings - which
could be
>a cause for concern if the slip were aggressive, and the airspeed slow,
and
>the cg fully aft.).
>My theorizing and concerns about deep stalls focused on what might
happen if
>the aircraft were stalled at near zero airspeed - like following an
>aerobatic hammerhead type of maneuver.  I think many of us are
interested
>this - even though we never envision ourselves in this type of attitude
or
>situation.
>I have read quite a few articles on the web, including an article
authored
>by the infamous test pilot who purposefully flew one of the earlier
Velocity
>models into a deep stall - was unable to recover - and elected to
"ride" the
>aircraft into the Atlantic Ocean (even though he was wearing a
parachute).
>The more I read, the more I am turning to agree with (the other)
Scott's
>opinion that the aircraft nose _will_ drop through the horizon
following a
>deep stall - meaning, today's Velocity will not enter a sustained deep
stall
>condition (providing it is loaded within the normal cg envelope).
>I spoke today with Danny Maher, the designer of the Velocity, and asked
his
>opinion about all of this - knowing that he has done extensive study
and
>testing of deep stalls in the Velocity.  Danny had this to say:
>(paraphrasing his responses)
>1.    "People need to realize that the Velocity is a "normal" aircraft
and
>that it is not designed to do aerobatic maneuvers ... so don't do
them."
>2.    "We (Maher and company) did extensive flight testing of the
aircraft
>using a movable 200 pound weight on a pulley - where we tried to force
the
>aircraft into a deep stall at various cg locations.  It is difficult to
get
>the aircraft to enter into a deep stall.  We set the weight well behind
>today's recommended aft cg station and had to 'work' at getting the
aircraft
>to deep stall.  Of course, back then we had gap seals on the elevators,
>which make it more difficult to stall the canard.  We needed to 'pump'
the
>stick at slow airspeed to get the main wing to enter an accelerated
stall,
>which then resulted in a deep stall condition.  In every instance, when
the
>weight was in the normal cg range, the nose dropped through the horizon
>during the recovery - and the aircraft would not sustain itself in a
deep
>stall.
>3.    Danny also went out of his way to say this - "If you enter a deep
>stall, you better have lots of altitude to recover".
>In my mind I thought forward elevator - and thus forward motion - was
needed
>to keep the aircraft from entering a sustained deep stall.  Danny's
findings
>say that this is not the case - the nose will drop through the horizon
and
>the aircraft will not sustain itself in a deep stall, providing the
aircraft
>is loaded within it's recommended cg limits.  The nose drop happens
slowly
>(not like a dart) - and the aircraft will loose "a lot" of altitude
during
>the stall recovery.  An aircraft with a constant speed propeller will
help
>the aircraft accelerate out of a deep stall more quickly.
>Interesting stuff, huh?
>Best regards,
>Scott B.
>
>
>
>
>
>----- Original Message -----
>From: "John Dibble" <aminetech@dixie-net.com>
>To: <reflector@tvbf.org>
>Sent: Wednesday, November 12, 2003 12:58 PM
>Subject: Re: REFLECTOR:Stall Characteristics
>
>
> > It seems to me that stalls should not be practiced in a Velocity for
the
>following
> > reasons:
> > 1)    The remote possibility of a deep stall that can't be recovered
from.
> >
> > 2)    Recovery from normal stalls is automatic so there is no need
to
>practice a
> > recovery technique.
> >
> > I suppose it is good to experience one or two so you know what they
feel
>like and also
> > to determine the power-off stall speed of the airplane.  Sometimes
on
>final with two
> > people at 70 kn, I feel a gentile, slight, slow oscillation of the
nose
>which is easy
> > to correct with down trim or power as needed.  Is it possible to
>unintentionally cause
> > a deep stall?
> >
> > John
>
>
>_______________________________________________
>To change your email address, visit 
>http://www.tvbf.org/mailman/listinfo/reflector
>
>Visit the gallery!  www.tvbf.org/gallery
>user:pw = tvbf:jamaicangoose
>Check new archives: www.tvbf.org/pipermail
>Check old archives: http://www.tvbf.org/archives/velocity/maillist.html

_______________________________________________
To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector

Visit the gallery!  www.tvbf.org/gallery
user:pw = tvbf:jamaicangoose
Check new archives: www.tvbf.org/pipermail
Check old archives: http://www.tvbf.org/archives/velocity/maillist.html