N744MK First Flight Revisited
Posted: Sun Feb 19, 2012 11:16 am
Sorry about another novel, but here goes.
Thanks again everyone. All great info! Especially the stories of low
thrust with props at too fine a pitch. I suspect it'll be a much different
airplane when I fly it next with less weight in the back and the prop
coarser. There is a silver lining. I learned three important things about
my plane:
1. I can still climb with the prop at it's extreme fine pitch setting (30")
albeit, not very well.
2. The plane is controllable with the CG close to the rear limit. It
didn't fly well but it was controllable.
3. I can overcome stick forces with the elevator trim at it's pitch up
limit. (Remember I managed to wire it backwards. While trying to trim the
pressure away shortly after takeoff I managed to trim the wrong way all the
way to the stop. Fair amount of forward stick pressure needed but I could
do it.)
Yes, Ken, the prop limits can be set. You are supposed to fly without stops
and determine the best climb pitch (somehow) and then land that way. Then
you peer in between the blades and see where the spool the electric motor
controls is and estimate how many washers to add to the shaft to limit
motion of the spool. Then you are supposed to fly again and determine best
cruise pitch, land that way, and estimate washers for the other side of the
spool. What a pain!
Oil Pressure - pegged, max. Found the nut on the sender was gone. Even
though the wire was still on the sender it somehow doesn't like not being
tight with the nut.
Oil Temp - 240
Coolant Temp - 170
Coolant Pressure - forgot to look. It's down low next to my left knee. I
was pretty busy flying the airplane.
EGT - pegged until power reduction, then 1600. I'm fiddling with timing for
this. Past timing adjustments showed huge changes in EGT with very small
timing changes.
FYI - For first flight my cowl had no openings except the scoop at the
bottom directing air to the radiator and outlets on the sides of the cowl in
the upper cowl doors for exit air. I am going to add two 3-inch openings on
each side of the prop mostly to send cooling air to my vacuum pump on the
right side but also to help cool the heads. I don't want too much cold air
in there though because I don't have any carb heat. With the carb on top,
no ram air, and bolted essentially directly to the engine and all that hot
air rising I don't think I need it. Interestingly, the temp and dew point
were 4 and 2 degrees C on the day of my first flight. I did think about
carb ice briefly before I took off. I'm keeping the inlets small because I
want to avoid pressurizing the cowl from the forward inlets because that
could compromise the good pressure differential I currently have across the
radiator based on the coolant temps I am seeing.
I checked my carb floats yesterday. I ran the fuel pumps for a while
(engine not running) and checked pressures with one pump and with both.
It's about 7.5 psi either way. I noted 5 psi in the shop ages ago but I
think that was with the engine running which apparently makes a difference.
After running the pumps I pulled the float bowl level screws and the fuel
was just below the hole for both the primaries and secondaries. The floats
are operating normally.
I pulled all of the spark plugs and they were all black. Mixture is
definitely too rich. I am going to clean them and try using leaner settings
on the mixture control including leaning for taxi. I have been doing a fair
amount of low RPM taxiing and may have had the mixture too rich for that,
even though I did have the control pulled out a bit.
Mike
044SR
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Bob
Patterson
Sent: Sunday, October 08, 2006 7:53 AM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Super Rebel / Moose Empty CG
Hi Mike !
Don't think your C of G is too bad, and you ARE lighter than several
Meeses !! Here are Brent's numbers: Right wheel 955 lb, -1.4",
Left wheel 956 lb., -1.1", tail 79 lb. 242", C of G empty was 8.4"
and a total empty weight of 1,990 lb. - still lighter than some M-14's.
Put a bit over 100 lb. at the front of the baggage area, and half
tanks - seems to work OK, perhaps still a bit forward, but able
to get the tail down for nice 3 pointers. Initially felt it was
too far aft, just like you, but, with more flying, it's becoming
comfortable.
I suspect your impressions were worse because of low thrust - had the
same experience yesterday when the governor went to full fine & stayed
there ! Over 6,000 rpm, and barely able to climb !! I've learned
a whole lot about governors !!!! Seems they work best with aircraft
oils, of 100 or 80 weight ( automotive 50 or 40) - they work less
well with thinner automotive oils - like 10W30 ... ans a WHOLE LOT
less well with thin auto oils that are over 260 degrees !!! When
the oil got too hot, the governor stopped working, and everything
went full fine ! :-( How were your water & oil temps ??
You would find that it seems to take a lot of forward pressure
to raise the tail on takeoff, that's pretty normal ... and with
more thrust, you'll be impressed. Opening up that LS-6 of Brent's
with normal fine pitch was pushing me back into the seat, and
climb stabilized at 2,000 FPM, at 70 knots !!! And that was still
only turning about 4,500 rpm at WOT - need to set it finer still.
When it shot up to 6,000 rpm, the thrust fell of dramatically -
just barely enough to sustain level flight ...
There is a fairly large pitch change with flaps - not unreasonable,
but you really want to re-trim for the loads.
Sounds like you are on the right track - be good to find out what
pitch angle Hartzell suggests for a fixed prop on the O-540 - just
to get a ballpark range. Suspect that something like 50 inches
might be a good start ... just (SWAG) guessing.
You might find it hard to do good landings with the standard SR
gear - the longer Moose legs make a dramatic improvement in ease
of landing !
Keep flying & fine tuning - it's a blast once you get it all
figured out !!
--
......bobp
http://bpatterson.qhealthbeauty.com
http://apatterson2.qhealthzone.com
http://apatterson2.qbeautyzone.com
-------------------------------orig.-------------------------
On Saturday 07 October 2006 04:58 pm, Mike Kimball wrote:
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Thanks again everyone. All great info! Especially the stories of low
thrust with props at too fine a pitch. I suspect it'll be a much different
airplane when I fly it next with less weight in the back and the prop
coarser. There is a silver lining. I learned three important things about
my plane:
1. I can still climb with the prop at it's extreme fine pitch setting (30")
albeit, not very well.
2. The plane is controllable with the CG close to the rear limit. It
didn't fly well but it was controllable.
3. I can overcome stick forces with the elevator trim at it's pitch up
limit. (Remember I managed to wire it backwards. While trying to trim the
pressure away shortly after takeoff I managed to trim the wrong way all the
way to the stop. Fair amount of forward stick pressure needed but I could
do it.)
Yes, Ken, the prop limits can be set. You are supposed to fly without stops
and determine the best climb pitch (somehow) and then land that way. Then
you peer in between the blades and see where the spool the electric motor
controls is and estimate how many washers to add to the shaft to limit
motion of the spool. Then you are supposed to fly again and determine best
cruise pitch, land that way, and estimate washers for the other side of the
spool. What a pain!
Oil Pressure - pegged, max. Found the nut on the sender was gone. Even
though the wire was still on the sender it somehow doesn't like not being
tight with the nut.
Oil Temp - 240
Coolant Temp - 170
Coolant Pressure - forgot to look. It's down low next to my left knee. I
was pretty busy flying the airplane.
EGT - pegged until power reduction, then 1600. I'm fiddling with timing for
this. Past timing adjustments showed huge changes in EGT with very small
timing changes.
FYI - For first flight my cowl had no openings except the scoop at the
bottom directing air to the radiator and outlets on the sides of the cowl in
the upper cowl doors for exit air. I am going to add two 3-inch openings on
each side of the prop mostly to send cooling air to my vacuum pump on the
right side but also to help cool the heads. I don't want too much cold air
in there though because I don't have any carb heat. With the carb on top,
no ram air, and bolted essentially directly to the engine and all that hot
air rising I don't think I need it. Interestingly, the temp and dew point
were 4 and 2 degrees C on the day of my first flight. I did think about
carb ice briefly before I took off. I'm keeping the inlets small because I
want to avoid pressurizing the cowl from the forward inlets because that
could compromise the good pressure differential I currently have across the
radiator based on the coolant temps I am seeing.
I checked my carb floats yesterday. I ran the fuel pumps for a while
(engine not running) and checked pressures with one pump and with both.
It's about 7.5 psi either way. I noted 5 psi in the shop ages ago but I
think that was with the engine running which apparently makes a difference.
After running the pumps I pulled the float bowl level screws and the fuel
was just below the hole for both the primaries and secondaries. The floats
are operating normally.
I pulled all of the spark plugs and they were all black. Mixture is
definitely too rich. I am going to clean them and try using leaner settings
on the mixture control including leaning for taxi. I have been doing a fair
amount of low RPM taxiing and may have had the mixture too rich for that,
even though I did have the control pulled out a bit.
Mike
044SR
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Bob
Patterson
Sent: Sunday, October 08, 2006 7:53 AM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Super Rebel / Moose Empty CG
Hi Mike !
Don't think your C of G is too bad, and you ARE lighter than several
Meeses !! Here are Brent's numbers: Right wheel 955 lb, -1.4",
Left wheel 956 lb., -1.1", tail 79 lb. 242", C of G empty was 8.4"
and a total empty weight of 1,990 lb. - still lighter than some M-14's.
Put a bit over 100 lb. at the front of the baggage area, and half
tanks - seems to work OK, perhaps still a bit forward, but able
to get the tail down for nice 3 pointers. Initially felt it was
too far aft, just like you, but, with more flying, it's becoming
comfortable.
I suspect your impressions were worse because of low thrust - had the
same experience yesterday when the governor went to full fine & stayed
there ! Over 6,000 rpm, and barely able to climb !! I've learned
a whole lot about governors !!!! Seems they work best with aircraft
oils, of 100 or 80 weight ( automotive 50 or 40) - they work less
well with thinner automotive oils - like 10W30 ... ans a WHOLE LOT
less well with thin auto oils that are over 260 degrees !!! When
the oil got too hot, the governor stopped working, and everything
went full fine ! :-( How were your water & oil temps ??
You would find that it seems to take a lot of forward pressure
to raise the tail on takeoff, that's pretty normal ... and with
more thrust, you'll be impressed. Opening up that LS-6 of Brent's
with normal fine pitch was pushing me back into the seat, and
climb stabilized at 2,000 FPM, at 70 knots !!! And that was still
only turning about 4,500 rpm at WOT - need to set it finer still.
When it shot up to 6,000 rpm, the thrust fell of dramatically -
just barely enough to sustain level flight ...
There is a fairly large pitch change with flaps - not unreasonable,
but you really want to re-trim for the loads.
Sounds like you are on the right track - be good to find out what
pitch angle Hartzell suggests for a fixed prop on the O-540 - just
to get a ballpark range. Suspect that something like 50 inches
might be a good start ... just (SWAG) guessing.
You might find it hard to do good landings with the standard SR
gear - the longer Moose legs make a dramatic improvement in ease
of landing !
Keep flying & fine tuning - it's a blast once you get it all
figured out !!
--
......bobp
http://bpatterson.qhealthbeauty.com
http://apatterson2.qhealthzone.com
http://apatterson2.qbeautyzone.com
-------------------------------orig.-------------------------
On Saturday 07 October 2006 04:58 pm, Mike Kimball wrote:
manualJust out of curiosity and for comparison between Chevy V8, M14, and
Lycoming, can you folks with flying SRs or Meeses tell me where your empty
CG ended up? Mine was 7.87 inches aft of the datum, which is 1.63 forward
of the forward limit if you go with the limit numbers that were in my
doesn't(9.5 - 21.38 inches aft of the datum).
I've also been doing some weight and balance scenarios and something
daughterseem right. With my wife and I (370 pounds) in the front seats, my
(115 pounds) in the back seat, 140 pounds in the baggage area, and 60
gallons of fuel that puts the CG right about where it was for first flight
(19.5) which produced poor flight characteristics. I thought the Super
Rebel should be able to do better than that. And with my engine I figured
on being nose heavy. Seems like I need to add some weight forward of the
firewall! How can that be?
Mike
044SR
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