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Snaps in the Decathlon



 
 
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  #11  
Old April 14th 04, 10:10 AM
Borislav Deianov
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EDR wrote:
In article , Borislav
Deianov wrote:

I have the same problem as Dave, except I'm flying a Citabria 7KCAB
(fixed pitch, 150hp). And it's only a problem when I fly solo. I can
do a reasonable snap roll with an instructor in the back.


Fly solo from the rear seat.
It snaps reallly well!


The manual I have is for 7ECA, 7GCAA, 7KCAB, 7GCBC, effective serial
numbers -75 and up. It lists the following placard on the instrument
panel: "Occupy Front Seat When Flying Solo".

Run some CG calculations for different fuel loads.


Good idea. Here are the results in several configurations (for the
airplane I fly):

dual, 1/2 fuel 15.59" c.g.
solo, full fuel 12.70" c.g.
solo, 1/2 fuel 11.90" c.g.
solo, empty fuel 10.98" c.g.

7KCAB aerobatic c.g. range: 10.6" - 16.0"

So more fuel will help when flying solo. Unfortunately, I don't have
too much flexibility there, as the FBO likes to keep about 1/2 fuel in
it (to stay under gross on dual flights).

Thanks,
Boris
  #12  
Old April 14th 04, 10:38 AM
Borislav Deianov
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Rich Stowell wrote:
Borislav Deianov wrote in message ...

I have the same problem as Dave, except I'm flying a Citabria 7KCAB
(fixed pitch, 150hp). And it's only a problem when I fly solo. I can
do a reasonable snap roll with an instructor in the back.

[snip]

In your Citabria, establish level slow flight at 80 mph. Leave the
power as is for now (later you can try adding a bit more power, but
for now, work on the rudder/elevator timing).

Lead the snap roll with brisk rudder application followed by
sufficient aft elevator to stall (about a 2 G or so tug on the stick).
As soon as the airplane departs, release a touch of the aft elevator,
etc.


I tried this during my last session and I'm happy to report that it
worked very well! I was able to reliably snap it in both directions.
The roll rate was decent and accelerated a bit after releasing some
elevator input. Wow. I needed 1800 RPM to fly level at 80 mph.

The problem now is that the recovery after one turn leaves me in a
marked nose-down attitude. After a quick pull up to level flight, I
end up at about the same airspeed but 200' or so lower than the
starting altitude. Is there a way around that? More power and an
starting the maneuver more nose up, perhaps?

Thanks for you help!

Boris
  #13  
Old April 14th 04, 06:14 PM
Rich Stowell
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Borislav Deianov wrote in message ...
Rich Stowell wrote:
Borislav Deianov wrote in message ...

I have the same problem as Dave, except I'm flying a Citabria 7KCAB
(fixed pitch, 150hp). And it's only a problem when I fly solo. I can
do a reasonable snap roll with an instructor in the back.

[snip]

In your Citabria, establish level slow flight at 80 mph. Leave the
power as is for now (later you can try adding a bit more power, but
for now, work on the rudder/elevator timing).

Lead the snap roll with brisk rudder application followed by
sufficient aft elevator to stall (about a 2 G or so tug on the stick).
As soon as the airplane departs, release a touch of the aft elevator,
etc.


I tried this during my last session and I'm happy to report that it
worked very well! I was able to reliably snap it in both directions.
The roll rate was decent and accelerated a bit after releasing some
elevator input. Wow. I needed 1800 RPM to fly level at 80 mph.

The problem now is that the recovery after one turn leaves me in a
marked nose-down attitude. After a quick pull up to level flight, I
end up at about the same airspeed but 200' or so lower than the
starting altitude. Is there a way around that? More power and an
starting the maneuver more nose up, perhaps?

Thanks for you help!

Boris



Glad to read things are coming along, Boris! Now for your next
practice exercises:

Exercise 1 -- Establish level slow flight at 80 mph and 1800 rpm.
Increase power to 2000 rpm and initiate a shallow, stablized climb at
80 mph. Perform snap rolls exactly as described earlier, using the
rudder-elevator sequencing.

Practice the same from a climb at 80 mph and 2200 rpm; then again
climbing at 80 mph and 2400 rpm.

Exercise 2 -- Establish level slow flight at 70 mph (probably still
close to 1800 rpm). Leaving the power alone, lower the nose *a little*
and allow the airplane to accelerate. Perform the snap roll as the
needle hits 80 mph.

Practice the same from 70 mph and 2000 rpm, 70 and 2200 rpm, 70 and
2400 rpm. In each case, lower the nose toward the horizon and snap at
80 mph. The idea is to sneak up on 80 mph from 70 mph, so don't stuff
the nose down when trying to accelerate form 70 to 80. Lower the nose
"just enough" to accelerate to 80.

These exercises are designed to steadily and incrementally increase
the rate of snap while still working on the timing of rudder and
elevator actions, all the while not exceeding 80 mph.

Also during the recovery, try not to move the elevator forward at all
-- just full opposite rudder and perhaps full opposite aileron if
needed to prevent over-rotating. You've released a little of the aft
elevator once the snap begins, and this may be all the forward you'll
need from that point on.

Report back...

Rich
http://www.richstowell.com
 




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