REFLECTOR: MODIFICATIONS

Douglas Holub doug.holub at comcast.net
Sun Jan 2 23:25:46 CST 2005


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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