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Date: Fri, 16 Oct 2009 15:57:53 -0400
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Subject: Re: [LML] Re: FAA RESCINDS INFO LETTER
From: "John Schroeder" <jschroeder@perigee.net>
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Great lesson and reasoning. Thanks, Fred. Does your  hangar group think  
some of the accidents also involved lack of proper rudder control during  
the turn, especially when they tighten the bank?

John Schroeder
LNCE


On Thu, 15 Oct 2009 08:58:41 -0400, Frederick Moreno  
<frederickmoreno@bigpond.com> wrote:

> 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
>
>
>