REFLECTOR:Stall Characteristics

[Scott Baker]

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