REFLECTOR: MODIFICATIONS

Mon Jan 3 20:59:38 CST 2005

<...Dan Maher ... adamant that a heavy engine ... even though the c.g is 
correct, could increase risk of a deep stall ...>
I think he was probably talking about inertial coupling.  The phenomenon 
is real, but of no great import in airplanes like Velocity.

<...even though the aircraft is in the proper CG for safe flight, the 
distance of the major mass centers from the center of gravity has a* 
tremendous* effect on the pitch stability ...>
"Tremendous" is a piss poor choice of terms IMO.  Waaaay too shrill for 
this airplane.

<...The further from the CG, ... the center of masses are, the more 
dangerous ... when ... pitched in flight by either the pilot or the 
flight environment ... If the inertia is too great, the aircraft can be 
pitched into a dangerous situation, like a deep stall or a PIO ... 
extremely dangerous in landing situations ...>
In nearly all circumstances, as you pitch the airplane up  in any even 
remotely normal fashion, you eventually run out of pitch authority at 
some point and pitch rotation stops there.  However, if you have mass 
concentrations far from the CG, *AND* you pitch up *very abruptly* you 
*could *establish substantial angular velocity in pitch.  In that event, 
mass concentrations, being far from the CG acquire more velocity (and 
momentum).   If you're near aft CG where very little pitch authority is 
needed, the momentum of all that mass *could* make it "coast" past where 
you would normally run out of pitch authority and go on to very high AoA

It is worth noting that the "deep stall' didn't occur until the 3th 
try.  It is not something that comes at you like a bolt out of the 
blue.  There are many very significant warnings.  Basically, when the 
stick gets real light in pitch, just be very careful, move some weight 
forward if that is practical and don't make any sudden, dramatic pitch 
excursions for the rest of that flight.  Plane should fly and land OK so 
long as you don't get violent.

Be aware of the symptoms of aft CG and be smooth when you're there ... 
Jim S.

Douglas Holub wrote:

>I wish there was a way to determine by testing where the aft c.g. limit is
>on a Velocity, the c.g. at which a deep stall occurs.  My wing is one of the
>original short chord wings, and I haven't installed the wing cuffs yet. I'm
>hoping that the vortex generators will help more than the wing cuffs would.
>
>In the June 5, 1990 newsletter, Dan Maher was pretty adamant that a heavy
>engine, even though the c.g. was correct, could increase the risk of a deep
>stall situation. He writes:
>
>"In our flight testing, we have been experimenting with the pitching moment
>of the aircraft by adding weight in the aft of the airframe, aft of the CG,
>and adding ballast in the nose to compensate for it.  We have found that
>even though the aircraft is in the proper CG for safe flight, the distance
>of the major mass centers from the center of gravity has a tremendous effect
>on the pitch stability, which is manditory [sic] for safe operation. The
>further from the CG, or closer to the nose and tail the center of masses
>are, the more dangerous the aircraft becomes when the aircraft is pitched in
>flight by either the pilot or the flight environment. This pitching motion
>is only overcome by the flying and control surfaces of the aircraft. If the
>inertia is too great, the aircraft can be pitched into a dangerous
>situation, like a deep stall or a PIO which is extremely dangerous in
>landing situations. As a result of this information, we are requesting that
>you do not install constant speed propellers or heavier engines to the
>Velocity. The 200 HP Lycoming, with all accessories, wet, and with a wooden
>propeller, weighs approximately 375 lbs (baffling & mount included). It has
>an arm of 163.5". This is ABSOLUTELY THE AFT LIMIT. A heavier engine
>installation, or one with a longer arm will make the Velocity very
>dangerous. So check the weight of your installation. If it exceeds 380 lbs,
>and/or its CG is more than 18.5" aft of the firewall, DO NOT INSTALL IT. The
>total moment of the installation must not exceed 61,500 in-lbs."
>
>The caps are his.
>
>On the other hand, Alan Shaw told me that the deep stall incidents wouldn't
>have occured if the planes that stalled had been built and loaded correctly
>to begin with, and that the big engines are no problem. And I think he knows
>a lot about Velocities.
>
>In Velocity Views #37 there was mention of another deep stall incident, but
>not much was known about the airplane's configuration. Does anybody have any
>more information about that situation?
>
>Anyway, I wish there was a way we could test for deep stall without risking
>the airplane.
>
>Douglas Holub
>DMO-055, Standard FG with a retractable nose gear, 50% done after 18 years
>
>
>----- Original Message -----
>From: "Dave Black" <dvblack at comcast.net>
>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>Sent: Sunday, January 02, 2005 2:18 PM
>Subject: Re: REFLECTOR: MODIFICATIONS
>
>
>  
>
>>>Tom,
>>>      
>>>
>>    
>>
>>>I am suspecting my safe
>>>envelope would be similar to other Elite RGs ... but the extra
>>>weight in the back would no doubt have an effect.
>>>      
>>>
>>Your safe CG range should be IDENTICAL to all other LongWing Elites. Your
>>engine will not change that. The addition of your heavier engine farther
>>    
>>
>aft
>  
>
>>simply means your particular plane will be more tail heavy.
>>
>>On my shortwing RG (not yet flying) the CG will be at aft limits with a
>>    
>>
>single
>  
>
>>pilot, and at forward limits with two up front. That's just how big the CG
>>    
>>
>box
>  
>
>>is. The rear seat has nearly no effect on CG. With your additional aft
>>    
>>
>weight
>  
>
>>and CG, you will need to load equipment or ballast forward in order to
>>    
>>
>keep
>  
>
>>the CG safe while flying alone. You might want to move the battery farther
>>forward.
>>
>>As far as finding out for certain what your specific CG and weight range
>>    
>>
>is,
>  
>
>>that should be done during flight testing. Load the plane toward different
>>corners of the CG box and see how it performs at various speeds and
>>configurations. Gradually expand the range in all directions. Have a way
>>    
>>
>of
>  
>
>>changing CG during flight in the event you reach an uncontrollable
>>configuration.
>>
>>As I understand it, of the two CG limits the aft limit is the more
>>    
>>
>dangerous.
>  
>
>>While forward CG will reduce elevator authority, exceeding aft CG makes a
>>    
>>
>deep
>  
>
>>stall possible. Just a gut feeling: Your plane is unlikely to exceed
>>    
>>
>forward
>  
>
>>CG in any normal loading situation. But you need to be very careful with
>>    
>>
>your
>  
>
>>aft CG. If CG is out of the aft limits the plane will fly beautifully
>>    
>>
>right up
>  
>
>>until it goes into a deep stall.
>>
>>
>>
>>We once owned a Cardinal RG. Before purchase I noticed at least half of
>>    
>>
>these
>  
>
>>had nose gear damage history. Turns out it was not a defect in the nose
>>    
>>
>gear,
>  
>
>>but in the CG. The plane is right at forward CG with a single pilot, and
>>    
>>
>can
>  
>
>>exceed forward CG with two up front. After doing some W&B calculations, I
>>found that a single 100 pound pilot flying with 20 gallons of fuel could
>>    
>>
>load
>  
>
>>the entire remaining legal weight flush against the aft cargo bulkhead and
>>still be within aft CG limits. There was simply NO way to load this plane
>>    
>>
>out
>  
>
>>of aft CG without also loading it beyond weight limits.
>>
>>When we bought our V35-B Bonanza, I found the exact opposite. In that
>>    
>>
>plane
>  
>
>>you could load virtually the entire useful load under the pilot's feet and
>>never exceed forward CG. Aft CG was very easy to exceed, however --
>>    
>>
>especially
>  
>
>>with that huge cargo area.
>>
>>
>>Dave Black
>>Shortwing RG
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