[rebel-builders] Re: Pitch Stability
Posted: Mon Feb 20, 2012 6:11 am
Hi All
What we've found flight testing ours in pitch is the stick will slowly
return to neutral from very small inputs, but will stay in other positions
if released. Initially we thought friction was to blame and have lubricated
all hinges and cable runs. Whilst better, the same issue remains, and we
have been trying very high pitch attitudes at very low airspeeds to try and
fathom it out.
There is a definite aerodymnamic "notch" that is very easily overcome with a
slight forward pressure on the stick, but it's sufficient to hold the
elevator deflected up if not corrected, and this fails one of our handling
test requirements here in the UK so we've got to find a way round it.
We haven't tried it in a nose down attitude for obvious reasons
Those who know much more about these things than me have decided the spade
area needs reducing, and now I'm waiting for a decision from our CAA as to
which way to apply a fix they want me to try.
I'll keep you posted.
All other handling is superb - stalls are docile, short field landing and
take off are wonderful.
Nig
745E
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Alan
Hepburn
Sent: 03 October 2005 01:13
To: rebel-builders@dcsol.com
Subject: [rebel-builders] Re: Pitch Stability
Bob:
A have the clipped stabiliser tips, but can't personally comment on handling
vs. the unmodified version, as the only unmodified one I've flow had a down
spring on the elevator to try to make it lest sensitive.
I gave Mike Wiebe a ride today, and he comments that, relative to the Rebel,
it is more responsive in both pitch and roll. He said he has on occasion
just about run out of both on the Rebel (the former when approaching slow,
and the latter in gusts on takeoff), and he found the elite much superior in
that respect (now that'll draw some comment I bet!). In normal flying,
you'd only notice this pitch divergence if you went to sleep, as it's quite
gradual, but if you sit back and let it happen it sure gets your attention.
Mike said he'd never seen so much ground in the windshield! And shows every
sign of accellerating right on through Vne, though we didn't let it go that
far.
If anybody can explain what's going on aerodynamically, Id' like to hear.
I also gave my FBO a ride (7,000 hr float driver), and he commented that
there's too much friction in the rudders. I agree. For a start, I'm going
to put pulleys at the cabin/tailcone direction change, and see how much that
improves the situation. Unklike inspectors in W. Ontario, mine did not
mention this, but I think those guys may well have more than just a
theoretical point.
BTW, subject to a climb test, I now have approval for 2,200 lb gross, thanks
to the Email from Keith saying the Montana floats are designed for that
number.
Al
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What we've found flight testing ours in pitch is the stick will slowly
return to neutral from very small inputs, but will stay in other positions
if released. Initially we thought friction was to blame and have lubricated
all hinges and cable runs. Whilst better, the same issue remains, and we
have been trying very high pitch attitudes at very low airspeeds to try and
fathom it out.
There is a definite aerodymnamic "notch" that is very easily overcome with a
slight forward pressure on the stick, but it's sufficient to hold the
elevator deflected up if not corrected, and this fails one of our handling
test requirements here in the UK so we've got to find a way round it.
We haven't tried it in a nose down attitude for obvious reasons
Those who know much more about these things than me have decided the spade
area needs reducing, and now I'm waiting for a decision from our CAA as to
which way to apply a fix they want me to try.
I'll keep you posted.
All other handling is superb - stalls are docile, short field landing and
take off are wonderful.
Nig
745E
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Alan
Hepburn
Sent: 03 October 2005 01:13
To: rebel-builders@dcsol.com
Subject: [rebel-builders] Re: Pitch Stability
Bob:
A have the clipped stabiliser tips, but can't personally comment on handling
vs. the unmodified version, as the only unmodified one I've flow had a down
spring on the elevator to try to make it lest sensitive.
I gave Mike Wiebe a ride today, and he comments that, relative to the Rebel,
it is more responsive in both pitch and roll. He said he has on occasion
just about run out of both on the Rebel (the former when approaching slow,
and the latter in gusts on takeoff), and he found the elite much superior in
that respect (now that'll draw some comment I bet!). In normal flying,
you'd only notice this pitch divergence if you went to sleep, as it's quite
gradual, but if you sit back and let it happen it sure gets your attention.
Mike said he'd never seen so much ground in the windshield! And shows every
sign of accellerating right on through Vne, though we didn't let it go that
far.
If anybody can explain what's going on aerodynamically, Id' like to hear.
I also gave my FBO a ride (7,000 hr float driver), and he commented that
there's too much friction in the rudders. I agree. For a start, I'm going
to put pulleys at the cabin/tailcone direction change, and see how much that
improves the situation. Unklike inspectors in W. Ontario, mine did not
mention this, but I think those guys may well have more than just a
theoretical point.
BTW, subject to a climb test, I now have approval for 2,200 lb gross, thanks
to the Email from Keith saying the Montana floats are designed for that
number.
Al
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No virus found in this message.
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Version: 2012.0.1913 / Virus Database: 2112/4815 - Release Date: 02/17/12
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No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.1913 / Virus Database: 2112/4815 - Release Date: 02/17/12
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