Elite - Pitch Stability
Posted: Sat Feb 18, 2012 1:43 pm
Hi Al !
Where is your C of G - empty, and in your cruise config. today ??
Actually calculated from weights on float wheels ..
That much up elevator sounds like it might be a bit forward, which
could account for some of the odd behavior ....
Might be interesting to put say 80 lb. in the baggage compartment,
with 2 up, and see if there's any difference. (Or, as Wayne often
suggests, add some water to the aft compartments on each side....)
(AFTER judicious calculation, and only a bit at a time !!)
Friction could account for some of it .....
Just thinking out loud -
if the horn is already down, and you push it further down, (back stick
pulse), and release, it would likely tend to stay down, being already
deflected, and having air pressure on it (as well as being trimmed there).
If you pull it up, (forward pulse), you would expect it to
return to neutral, which, with a forward c of g, would give a positive,
increasing, descent......
Maybe, to better evaluate, the trim should be set to neutral,
and the test re-tried --- suspect result would be positive descent
in both cases - again, indicating forward c of g as contributing factor.
Sounds like the drag of the floats is pulling the nose down,
and, since drag increases with speed, that would account for the
increasing rate of pitch change with speed..... and the stab/elevator
combo is not producing enough opposing (downward) force ....
...which suggests - a different angle or increased area for the stab,
OR , back to the c of g being too far forward.... (I suspect most likely)
Please keep us posted on test results !!
......bobp
-------------------------------orig.-------------------------
On Sunday 02 October 2005 08:19 pm, Alan Hepburn wrote:
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Where is your C of G - empty, and in your cruise config. today ??
Actually calculated from weights on float wheels ..
That much up elevator sounds like it might be a bit forward, which
could account for some of the odd behavior ....
Might be interesting to put say 80 lb. in the baggage compartment,
with 2 up, and see if there's any difference. (Or, as Wayne often
suggests, add some water to the aft compartments on each side....)
(AFTER judicious calculation, and only a bit at a time !!)
Friction could account for some of it .....
Just thinking out loud -
if the horn is already down, and you push it further down, (back stick
pulse), and release, it would likely tend to stay down, being already
deflected, and having air pressure on it (as well as being trimmed there).
If you pull it up, (forward pulse), you would expect it to
return to neutral, which, with a forward c of g, would give a positive,
increasing, descent......
Maybe, to better evaluate, the trim should be set to neutral,
and the test re-tried --- suspect result would be positive descent
in both cases - again, indicating forward c of g as contributing factor.
Sounds like the drag of the floats is pulling the nose down,
and, since drag increases with speed, that would account for the
increasing rate of pitch change with speed..... and the stab/elevator
combo is not producing enough opposing (downward) force ....
...which suggests - a different angle or increased area for the stab,
OR , back to the c of g being too far forward.... (I suspect most likely)
Please keep us posted on test results !!
......bobp
-------------------------------orig.-------------------------
On Sunday 02 October 2005 08:19 pm, Alan Hepburn wrote:
seeScott:
Good point. I'll put a mark on the cable and another on the floor, and
withif that's what's happening. There is some friction due to these fairleads
along the cabin floor. It's nothing like a pushrod system, but far better
than the rudder loop.
I also notice that, at least in today's configuration, we were cruising
That'sabut 5 degrees up elevator. Any comments on whether that's normal?
maywith two up and of course the amphib floats. Cruises about 97 kts. It
just be what it takes to support the floats.
Al
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