Bill Freeman wrote:

Paul,

My brother (Kincheloe test pilot) flew a Bonana for about
15 yrs and we discussed this one a lot.  The V tail has a
number of serious problems.  First is poor spiral stability,
second is too low stick force per G, and third is the CG moves
a lot aft as fuel burns off - greatly worsening the second
item.  At aft CG the stick force per G can be less than
1 lb per G.  See the airspeed reaching readline and snatch
the wheel with a 8 lb pull (or less) after your 15 sec of
inattention and the tail departs.

Let's use a better example like the C182.  Strong spiral stability,
high stick force per G, small shift in CG with fuel burn.
Fixing all of GA due to a basically flawed design is not
necessarily required.  Also - the straight tailed version of
the Bonana had something like 1% of the fatal in-flight
airframe failure of the V.  Also my brother's bird had TWO
tail beefups - Mike Johnson's stub spar (a decade ahead of
the FAA) and the FAA/Beech fix on top.  The beef-up
fixed the weak (aeroelestic positive feedback!) tail, but the
others are still there and the accident rate dropped a lot.

That said,   some AC designs are a bit iffy to me.  Cruising
well above the green line in IMC seems pretty scary.  Would
the new stiffness method bring up the green line?  This is
a fair  measure of the risk of whether you turn your AC into chaff by
accident.

Good topic, folks need to really think about these issues to
be safer pilots.  Sadly a lot of pilots are not even sure what
the tech issues are, and what it takes to break up their AC.
Fly a C182 in IMC and be safe as can be, at least structurally.

Bill

You would have loved to been there Bill.

Paul Lamar
 
The Aircraft Rotary Engine Newsletter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org