REFLECTOR:Stall Characteristics

Scott reflector@tvbf.org
Sat, 15 Nov 2003 07:10:48 -0700


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