I don't recall what you
prop arrangement is, but the RPM's that you have listed sound pretty low.
Even with a variable pitch prop, I'd think that you'd want 2250-2300 at the
prop, in cruise.
I have a 3-blade Catto fixed pitch; 66 x
85. I get 5000-5100 rpm static on a warm day, and about the same rpm on climbout at
110 kts. Perhaps just a bit too much pitch, but I don’t think the engine
parameters are optimized yet.
Basically the reason for the low rpm
numbers while flying level is because the power was pulled back. MAP was only
19”. What rpm do you get at 19” MAP?
The percent power readout was about
65%, but how meaningful is that since I see on the video of the engine monitor
it showed 110% (290 hp) at 20” MAP as the power was pulled back at the
top of the climb. All it means is that the mixture was too rich. Having to
rely on a test pilot who is not that familiar with the engine operation, or the
instrumentation; definitely is a drawback. But also, until I can get stable
operation of the EC2, it’s hard to draw any conclusions.
I just wonder if higher RPMs wouldn't
improve cooling by increased flow.
I guess you mean on the fluid side. The
data indicates fluid flow is fine, the oil side temp drop across the oil cooler
is only about 15 degrees, while air temp increase is more than 100 degrees. Clearly
needs more air flow.
Buly wrote:
Again, let the engine rev higher,
since right now your performance
numbers for the same weight
are very close to my engine, and should
be 50% higher?
For now I can’t let the engine rev
higher for a given power with a fixed pitch prop. I wish 50% higher; but since
performance goes as the cube root of power; mine should only be 15% higher
(cube root of 1.5)J.
So when I get the wings shimmed, the EC2
stable, more air flow through the wing root coolers; and, oh yeah – schedule
the test pilot (or cancel the insurance and fly myself) we’ll fly again
and have more data. And at some point – if I’m still young enough
to fly . . .
Al (I’ll be more optimistic next
week)
-----Original
Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]On Behalf
Of Al Gietzen
Sent: Friday,
September 15, 2006 2:09 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Flight test
Finally got the proper alignment
of the planets (basically test pilot schedule) for further flight of Velocity
755V – 20B. Plane was in the air for ½ hour this time, basically at
level cruise orbiting the airport. OAT was about 90F and flight was at DA
of about 7000’.
Since the first flight when oil
temps were high, I added a temporary ram scoop under the ‘wing
root’ oil cooler inlet. Oil temp reached near 230 during climb but
later stabilized at 200 - 205F. Coolant stabilized at 180-185F.
I have video recording of EM2
display, and this time the pilot remembered to push the page button, so I have
lots of data. For ‘% power’ readout of 65-70%, engine rpm was
4450, prop 2050 rpm, IAS (according to pilot) was about 145 kts. TAS
readout on EM2 was 165-170 kts, but my calcs indicate this is about 5 kts too
high. Fuel burn was indicating 16-18 gph running rich of peak.
The in-cowl radiator is handling
most of the cooling load; with the wing root rad being very ineffective.
This is consistent with the first flight results on the oil temps with the
matching wing root oil cooler. The scoop added for the OC improved the
air flow, but it is still marginal, with oil delta T of about 20F and air delta
T of about 100F. It is likely the main issue is with the exit
fairings. At least now it flies stably, so I can do some other changes
and see the effects – hopefully get a differential pressure measurement
set up.
Takeoff roll of about 1500’
at 1900# weight is quite good considering fixed pitch prop. It
accelerates from rolling start to 60-65 kts nose lift in 6-7 seconds.
This with an 85” pitch prop. Something special about Catto props.
The thing looks and sounds great,
and I have to be happy that it went up, stayed up for ½ hr, and made a perfect
landing. Main issues right now are on-going problem with EC2 data
corruption; apparently unique to my installation, and possibly
‘noise’ related; and the need for right aileron input in order to
go straight, suggesting a need for wing incidence adjustment.
Al