Hi Dave,
Actually, the 2050 RPM in the 415-D Flight Manual is for the C-75. The
CD also had the C-75, but no Flight Manual. While the CD model
airframe is identical to the 415-D (except for elevator rigging), at
the lighter 1260 Lb. Gross, 415-CD performance figures would be
"better" than those in the D Model Flight Manual.
Ercoupes were delivered with a special version of the Continental
Operating Manual in addition to the Ercoupe Instruction Manual. While
I eagerly read everything that ERCO published, I also understand that
in the years since 1946 technology and experience have changed the
"best", or most efficient way to operate our little four-bangers.
I don't believe X-30012 is available as a download. Both Skyport and
Univair sell Continental Manuals. Because of the added information and
the fact that Continental has continued to update their X30012
Operating Manual over the years, I would urge everyone that operates an
Ercoupe to purchase and become familiar with the information in this
manual. Order from Skyport (part number "CONTOPS"); or from Univair
(part number AC4WM), but verify these as the X-30012 manual. My copy
is February of 1980. If the version currently shipping is later,
please let us know.
I look to C-90 and 0-200 information in deciding whether cruising at
2575 RPM is (1) safe in terms of stress and (2) consistent with
achieving TBO in terms of longevity. Good practice in the '40's of not
leaning below 5,000' is, in my opinion, inappropriate considering that
altitude above mean sea level on a standard day is an arbitrary single
meaningless value to an engine whose performance instead relates to
density altitude. With the demise of 80/87 fuel, the adulteration of
auto fuels, and the excess lead content of 100 LL there is much more to
know and to do for the proficient pilot. With EGT probes on each
cylinder, we can now see in "real time" how poor our induction system
is at distributing a uniform fuel/air mixture to our four cylinders;
and how a bit of carb heat can improve such distribution (and
operational efficiency when combined with proper leaning techniques at
appropriate en route cruise altitudes).
Correction(?): It just dawned on me that those RPMs recently
referenced from page 106 and 107 of the Overhaul Manual (X-30010 of
2/80) may relate to test cell break-in operations with a test club
instead of a "normal" propeller.
Regards,
William R. Bayne
.____|-(o)-}____.
(Copyright 2009)
--
On Nov 19, 2009, at 14:29, [email protected] wrote:
Bill and everyone,
Since you can't achieve 2575 RPM on the ground doing a static runup, I
would say the 2050 RPM in the 415-D Flight Manual for the C-85 is a
more realistic approximation of full throttle. 2000 is just under
what I can get at static full thottle, and I get around 2150 on the
runway as the airplane begins its roll; RPM then increases as speed
increases. But I agree with your analysis, and that it was probably
related to propeller life as well as engine operating RPM. I just
don't see the need to do a 2000 RPM run-up to check my mags.
1700-1800 should suffice as long as I'm also checking my full throttle
RPM on the runway and am prepared to reject the takeoff if I'm not
getting 2100 RPM or above as I start the takeoff roll. Also agree
that since there is no idle cut-off function for the Stromberg mixture
control, that is not applicable to engines with the NAS3A1. Just wish
I had a copy of the 1980 X-30012 document to supplement my X-30010.
If you have a PDF or know where to download it, I would appreciate it!
Thanks,
Dave
