Our hangar group which includes retired airline pilots, an Applied Physics
PhD and a couple of engineering guys has kicked this issue of pattern stalls
around over the last few weeks.  From that discussion I posit a theory for
why Lancair guys are getting killed in the pattern.  Conclusion: it takes
more than a bad stall characteristic to get you killed.   (You already knew
that.)


Fact: our resident RV-6 owner/pilot reports that the early RV's (before
RV-7) had a wing design that resulted in a sudden stall with big wing drop.
Sound familiar?  The RV-7 which replaced the RV-6 has a completely different
wing profile to address this issue.  However, RV-6s are not falling out of
the sky and killing people in the pattern.


Fact: RV-6 wing loading is 1600 pounds on 110 square feet or 14.5 pounds per
square foot.  A Lancair IV (short wing) loading is more like 3200 pounds on
98 square feet or about 33 pounds per square foot.  When you fly an RV6 in
the pattern at normal pattern speeds (75-80 knots, flaps out) and pull back
on the stick turning final, it flies up.  When you fly a Lancair IV around
the corner at 120 knots and pull up, it slows down - fairly rapidly -
because of the big change in angle of attack arising from high wing loading
(lots of momentum acting against a small wing panel).


Fact: Flying at 120 knots in the pattern, the Lancair IV will have a turn
radius that is 2.25 times larger  (1.5 squared) greater than the RV flying
at 80 knots (same angle of bank).


Now let's combine all these facts and propose an accident scenario.  The
Lancair pilot enters downwind well behind slower traffic that is flying a
pattern in close to the runway.  Mistake one: he is too close to the runway.
It is a busy day, lots of chatter, and he slows to his customary 120 knots,
gear and flaps out.


He then turns base, but his turn radius is 2.25 times larger than the RV he
was following for the same angle of bank.  As he rolls out on base, he can
see that he will overshoot the runway centreline.  Still lots of radio
chatter and he is watching the RV touchdown and roll out on the runway to
make sure he has room.


Having crossed the runway centreline and while watching the RV and listen to
the chatter, he banks a little more steeply than  normal on his turn to
final and pulls back, but he has not seen his airspeed indicator for maybe
15 seconds.  A bit low to begin with, airspeed starts to decay rapidly.  He
gets most of the way  around the turn,  the airspeed continues to decay at
an accelerating rate, he gives the stick a little more of a tug to tighten
the turn since he is now well past the centreline, and the airplane stalls
out of a 30-45 degree bank at 500 feet.   End of pilot and airplane.


Accidents arise from a series of events.  The events here were:

1)    Downwind leg in too close following the "normal" traffic.  Solution:
fly a very wide downwind regardless of where the slow guys are flying.

2)    Decay of airspeed not noted after first turn or during second turn.
Solution: Eagle eye on the air speed indicator all the time, particularly
when making the turn downwind to base and then base to final.  Limit to 15
degree bank.

3)    Pulled back on the stick after passing the runway centreline to
tighten the turn while at too low a speed.  Solution: Never pull back on the
stick or roll in more bank angle to tighten the turn when in the pattern.
Stick with the 15 degree bank limit in the pattern.


I still find myself flying my downwind too close to the runway when
following traffic.  It is force of a very old habit that must be broken.
But  when I fly a big pattern and make a large U-turn from downwind to final
with no more than 15  degree bank, the margins at 120 knots remain large and
it all works out much more nicely with sped control being much easier.


The RV 6 stall can be nasty, but it is not the nasty stall that kills
Lancair IV pilots.  My theory: pattern in too close, air speed not watched,
turn to final pulled too tight because of the pattern air speed was allowed
to decay and pattern being too tight to begin with.  Stall spin crash burn.



The yellow alarm lights should go on when you are in close to the runway, or
when the cross wind blows you toward the runway on downwind.  Be careful.


Your comments welcome.


Captain Tuna, Chicken of the Skies