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Don asked:
> I have a question
for you in regard to propellors. Our Ercoupe 415C
> Serial # xxxx has
a Continential 75 converted to an 85. The prop is a
> McCauley Model
1B90/CM 7346 serial #32956, I find that it was
> converted to the
46" pitch in 1985. The question is: Would this prop
> be considered a
climb prop? What would be the R.P.M. be for take-off,
> climb and
cruise. Also what should we expect the airspeed be for
> cruise with this
configuration.
Don,
(Here’s one to stir up
discussion.)
To start with, your
engine hasn’t yet been converted from C-75 to C-85. Since you still have a 73” propeller, you probably can’t
spin the engine fast enough to get C-85 type horsepower.
As I recall, no prop
longer than 71” is allowed for the C-85, per Aircraft Specification A-718, the
Ercoupe type certificate. You can
get a link to A-718 on my website’s Coupe page at:
http://edburkhead.com/Ercoupe/index.htm
Here’re the quotes from
A-718:
7. Propeller - fixed pitch metal, McCauley 1A90-CF or 1B90CM 26
lb. (-32)
(with engine item 110 only). Static r.p.m. at maximum
permissible throttle setting: not over 2225, not under 2025.
Diameter not over 71 in., not under 69.5 in.
No additional tolerance permitted.
110. Engines 12 lb.
Continental C-85-12 or -12F
Engine limits for all operations: 2575 r.p.m. (85 hp.)
(Eligible with item 1(c), 3, 4, 6, 7, or 8 propeller only).
Eligible on model 415-CD; eligible on model 415-C
provided the following are accomplished:
(a) Modifications specified under item 106 for installation of
C-75 engine.
(b) Wide elevator trim tab (1-3/8 in chord) installed per
Erco dwg. 415-22031 or narrow trim tab (3/4 in. chord)
installed per Erco dwg. 415-22027 (or item 401).
Note: Conversion of continental C-75 engine to C-85 must be
accomplished in accordance with Continental Service
Bulletin M47-16, dated 6-7-48 and the oil sump dip stick
recalibrated to indicate full when sump serviced with 4.5 qt.
oil.
So, I’d suggest you send
off your prop to a prop shop to get it shortened and re-pitched to your
choice. I’m inclined to recommend
7148 length and pitch it for a climb prop with about 104 mph cruise and fairly
good climb. (Note Bill Coons’ report last night on his first flight after
overhaul and getting a new 7148 prop.)
Props for C-85 on Ercoupes
7146 – extreme climb prop
– cruise 100 mph, very good climb for a Coupe. Right on the edge of upper rpm limits in note 7 above. Can
climb to 12,500’ anytime (unless density altitude is extreme – my absolute limit
was 14,500 density altitude in mild turbulence). I’d recommend this pitch for people with high base altitude
airports or short runways. I liked
it for me, since I was so often near 1400 lb. gross and to get above the bumpy,
thermal layer on summer days in the Great Plains.
7148 – climb prop – cruise
104 mph, good climb for a Coupe.
7150 – “normal” prop –
cruise 108 mph, “normal” Coupe climb (not that good). Ability to climb to 8,000’-12,500’ – I don’t know. It’d sure take a long time, if you
could do it.
7152 – “cruise” prop –
cruise ranges from 90-112 mph. Climb?
– You’ve got to be kidding – possible service ceiling between 3,000’ and 6,000’. At some aircraft gross weights, the
engine can’t get you up to the higher speed and it wallows along at 90 mph. Maybe the several people who’ve
reported this to me just had wimpy engines. Personally, I wouldn’t have this option.
Ed
Burkhead
http://edburkhead.com
ed -at- edburkheadQQQ.com
(change -at- and remove the QQQ)
-----Original Message-----
From:
Donald Perricone [mailto:[EMAIL PROTECTED]
Sent: Wednesday, April 06, 2005
10:51 PM
To: Ed Burkhead
Subject: Re: [COUPERS-TECH] Two
questions
Ed:
I have a question for you in regard to
propellors. Our Ercoupe 415C Serial # 657 N93334 has a Continential 75
converted to an 85. The prop is a McCauley Model 1B90/CM 7346 serial
#32956, I find that it was converted to the 46" pitch in 1985.
The question is: Would this prop be considered a climb prop? What
would be the R.P.M. be for take-off, climb and cruise. Also what should
we expect the airspeed be for cruise with this configuration.
Thanks for your help.
Don
N93334
----- Original Message
-----
To: Coupe-Tech
Sent: Tuesday, April 05, 2005 6:40 AM
Subject: RE: [COUPERS-TECH] Two questions
----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
Here’s some extra information on the breather extension tube Lynn mentions. From what I hear, this is much more effective than an oil-air separator:
http://edburkheadcom/Ercoupe/oil_blow_out.htm .
Ed Burkhead
http://edburkhead.com/
ed -at- edburkheadQQQ.com (change -at- and remove the QQQ)
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Tuesday, April 05, 2005 4:53 AM
To: [EMAIL PROTECTED]; [email protected]
Subject: Re: [COUPERS-TECH] Two questions
----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----Hey Ron: It is nice to have the fuel shut-off on the panel. If you take the Kohler valve apart and clean it thoroughly, then lubricate it with fuel lube, you will find it will turn much easier. Be careful in the cleaning process not to use any mechanical means that will scratch or score the valve. There are no seals other than the taper fit, and it can be easily ruined. I believe that ERCO stopped putting the shutoff on the panel somewhere around serial number 2200.
I have no experience with the Airwolf air-oil separator, but use the M-20 separator on the vacuum pump on my Bonanza. It seems to work well. If you are having significant oil blown out the breather of your small Continental, check to make certain that you have the extension on the fitting that goes into the crankcase. Due to the nose down and cant to the right, the Ercoupe seems to have excessive blow-by. Continental came out with an extension on the fitting which makes a big difference in the oil coming out the crankcase vent. You can solder a short (about 1 1/4 inch long) piece of 5/8 copper tubing on/in the fitting which will help the problem and be much more cost effective than the Continental part.
Lynn Nelsen
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