Since I was talking to Velocity yesterday about this subject, I'll add my 2
cents worth. Before I purchased my Velocity, I had heard about the "deep
stall" phenomena, and did some research on it (a few yrs ago). Since I'm
not an aero engr, I'll use simple terms.

What would happen was an aft CG stall caused by slowing the plane down(<50
mph)in a nose up attitude such that both the canard and main wing were
stalled. Because the wing fuel tanks straddle the cg, the fuel (a third
full, or less, tanks) will mostly be aft of the CG, puting you into an aft
CG condition (in addition to the plane being right at, or behind, the
prescibed CG). A canard type plane reacts differently in an aft CG stall
than a conventional aircraft in that they descend similarly to a "falling
leaf". This was descibed as a slow flat spin descent at about 20 mph for a
Velocity. Early on, before they made some changes, there were a few pilot
that rode it down, and survived the crash, mostly into water with not much
damage.

The changes included moving of the rear wall of the fuel tank fwd, puting
in additional tank baffling to reduce fuel moving quickly to the rear,
additional of vortilons to keep the airflow going over the wings, etc. Not
too long ago, a builder decided he wanted additional fuel capacity and
moved the rear fuel bulkhead rearward. He got into a deep stall, but was
able to fly out of it by dropping his gear, and applying full power, until
the plane had enough fwd speed to begin flying again. This is the factory
recommended procedure should you ever get in this situation.

The real issues, in my opinion, is to make sure you don't redesign the
plane without getting the factory to okay it, do your initial and operating
weight and balance (cg calcs) to make sure it's right, and do your slow
stall testing at over 4K' altitude (preferably over water or soft ground)
as the factory recommends with a fwd CG. You have to try really hard to get
into this situation, as it is not a normal flying situation, so it
shouldn't be of great concern. Actually, this is a distinct advantage of
canard type planes, because an aft CG stall in a conventional plane, it's
not a happy place.

Chuck

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