REFLECTOR: Recovery from Deep Stalls

Fri Feb 1 18:52:43 CST 2008

Scott,

Thanks for the overview.  Great historical perspective.

John Youngblood
On Feb 1, 2008, at 1:55 PM, Scott Baker wrote:

> Regarding deep stalls -
>
> I am not familiar with the stall characteristics of canard aircraft  
> other
> than the Velocity.
>
> I believe there might be a general lack of knowledge and perhaps some
> misconceptions regarding deep stalls amongst Reflectorites.
>
> The flight test articles (see links below) focus on the deep stall
> phenomenon in Velocity aircraft shipped prior to 1992.
> It is important to note the difference between "deep stalls" and  
> "sustained
> (unrecoverable) deep stalls".  Through flight testing and analysis of
> accident reports from several deep-stall Velocity accidents prior  
> to 1992 -
> Danny Maher learned the aircraft could enter an unrecoverable  
> sustained deep
> stall, given extreme rearward CG conditions.  For those who have  
> not read
> the articles, please do.  They offer fascinating information.
>
> As a result of these studies, Danny changed the shape of the main  
> wing at
> its outboard location to provide more lift at slow airspeeds;  
> reduced the
> size of the fuel header tank (which was behind the flight CG  
> envelope); and
> changed the orientation of the rear fuel containment bulkhead  
> (inside the
> strakes) so that they projected in a forward angle - thereby moving  
> the
> center of the fuel mass forward.(contributing to moving the  
> aircraft center
> of mass forward).  Following these changes, one is still able to  
> bring the
> aircraft to a deep stall - but what's most important, the aircraft is
> recoverable from a deep stall.  I spoke to Danny about this - and  
> he attests
> that the aircraft is not only recoverable from a deep stall - it  
> will do so
> on its own and without stall recovery inputs by the pilot.  Having  
> never
> attempted to put the aircraft into a deep stall, I defer to Danny's
> knowledge and testimony on this subject!
>
> As a former Velocity demonstrator pilot - and also in my  
> experiences as a
> CFI giving Velocity Flight Transition Training, I have performed  
> literally
> hundreds of stalls in various Velocity models.  These include power  
> off
> stalls during straight and level; and during turns with bank angles in
> excess of 45-degrees; power on stalls with a climb angle of 45- 
> degrees pitch
> up attitude; and accelerated stalls at bank angles of 60-degrees and
> greater.  I have purposefully put the aircraft in prolonged pitch-buck
> situations when following slower traffic on final approach.  The  
> point I
> wish to make is this - a Velocity will not enter a _deep_ stall during
> normal maneuvering - nor any of the exaggerated maneuvers that I  
> have just
> described - providing the aircraft is within its recommended CG  
> envelope.
>
> Is there a stall "Boogie Monster"?   I've observed that while Lancair
> publishes a Vs of 74-mph; pilots often fly using an approach speed  
> closer to
> 110mph, well over the 1.3 x Vso approach speed rule-of-thumb.  What  
> gives?
> Why do so many Lancair drivers fly approaches 30mph faster than the
> published stall speed?  I've asked Lancair pilots how their  
> aircraft behaves
> during stalls - and was very surprised that several have _never_  
> performed a
> stall in a Lancair!  Apparently the Lancair IV's response to an  
> uncommanded
> stall is so bad that many pilots simply "do not go there".  Is  
> there a stall
> "Boogie Monster" that haunts Velocity aircraft?  I've never seen him.
>
> That being said - I've never taken the Velocity out in search of deep
> stalls.  One would need to work at it.  Gathering air speed and going
> vertical would do it (I'm not suggesting we all go out and do this,  
> by the
> way!).  According to Danny, recovery should be as simple as letting  
> go of
> the controls.  There is, however, a recommended recovery procedure  
> follow a
> deep stall.  The steps are simple - apply full throttle; full RPM  
> (if using
> a variable or constant speed propeller); full forward elevator; and  
> wait.
> If the aircraft responds to rudder authority, attempt to put the  
> aircraft
> into a wing-over.  The goal is to get the pitch attitude pointing  
> down and
> bring air speed to the flight controls.  --> Note to those who have  
> flight
> tested their aircraft into a deep stall - please share your  
> experiences!
>
> Several other tidbits of info - there are enough differences in stall
> characteristics between Velocity models that caution should be  
> taken not to
> accept statements about the stall behavior of one Velocity as being
> identical to others.  They are the same; but different ;-)  Several  
> recent
> contributions to the Reflector talk about landing the aircraft from an
> aircraft carrier like "flared" attitude.  This might work for one  
> Velocity,
> but not the other.  I can tell you that one of our Velocity XL demo
> aircraft, fully loaded, produced small oscillations in pitch at 75   
> to 80
> knots during approach - still well above stall speed.  Not a good  
> situation
> to perpetuate down to landing.  I just want to point out that this  
> is in
> contrast to the behavior of John D's and Al G's aircraft.
>
> Best to all,
> Scott B.
>
>
>
>
>
> ----- Original Message -----
> From: <doug.holub at tx.rr.com>
> To: "Brett Ferrell" <reflector at velocityxl.com>; "Velocity Aircraft  
> Owners
> and Builders list" <reflector at tvbf.org>
> Sent: Friday, February 01, 2008 10:51 AM
> Subject: Re: REFLECTOR: Velocity video
>
>
>> Wow. Mr. Rutan encourages all EZ owners to test for deep stall  
>> above 8000
>> feet while wearing a parachute.  If the airplane does enter a deep  
>> stall,
>> bye-bye airplane.
>>
>> Doug Holub
>> ---- Brett Ferrell <reflector at velocityxl.com> wrote:
>>> Dave,
>>>
>>> I don't think it generally is recoverable, that's the problem.   
>>> Here are
>>> a couple of old articles on Deep Stall, offered in the name of
>>> education/safety (fair use) since they're on my website without
>>> permission.
>>>
>>> http://www.velocityxl.com/Downloads/CP76/CP76-P2.htm - Canard  
>>> Pusher 76
>>> reprint "The Latest on Deep Stall"
>>> http://www.velocityxl.com/Downloads/VelocityDeepStall.pdf - Deep  
>>> Stall
>>> Solution - July 1991 Sport Aviation
>>>
>>> Brett
>
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