Re: [COUPERS-TECH] C-75 --> C-85 and props

Hartmut Beil Thu, 7 Apr 2005 06:40:50 -0700

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Folks.

A C-85 in our Coupe does not necessary mean your prop has to be less than 71 inches. Here an excerpt from TC-718:

3. Propeller with Continental C-75 or C-85 series engines 15 lb. (-32)

Sensenich 74FC (pitch 48 to 52 in.) (including hub) or any fixed

pitch wood propeller eligible for engine speed and power which

meet static r.p.m. and diameter limits as follows: S/N 113 and up.

Static r.p.m. at maximum permissible throttle setting: not over 2100,

not under 1850. No additional tolerance permitted.

Diameter: not over 74 in., not under 72 in.

8. Propeller - fixed pitch metal, Sensenich M76AK-2 24 lb. (-32)

(a) With C-75 engines only. Static r.p.m. at maximum

permissible throttle setting: not over 2125, not

under 2050. No additional tolerance permitted.

Diameter: not over 74 in., not under 72.5 in

(b) With C-85 engines only. Static r.p.m. at maximum

permissible throttle setting: not over 2250, not

under 2175. No additional tolerance permitted.

Diameter: not over 74 in., not under 72.5 in

Too bad , all McCauley models need to be trimmed to 71 or lower. However, I would not pitch it that low.

I have a McCauley 1A/90 7152 which my Mechanic had repitched to 7148 two years ago, cause he said that's the right prop for my engine. He was right. I could climb as never before in my coupe and rev the engine to redline in level flight, ensuring me that the engine developed full power. One problem was there though. I was slow. The plane was so slow that it was annoying to me. I like to fly x-country and that climb prop was no use for my style of flying.

I had the prop repitched to 7152. That is right on the edge my C-85 can handle. I got my speed back and when I fly with my brother, I have to throttle down to 2000 rpm that he can keep up with me. He's got a 48 pitch. He would have to fly full throttle all the time to be at some speed, but he does not like that, cause the fuel consumption is significantly higher at full throttle.

What I am trying to say is that if you need a climb prop - go for it, but a McCauley 1A/90 7150 is probably a good all-rounder for an Ercoupe, I would recommend to everyone.

Hartmut

----- Original Message -----

From: Ed Burkhead

To: Donald Perricone ; Coupe-Tech

Sent: Thursday, April 07, 2005 2:20 PM

Subject: [COUPERS-TECH] C-75 --> C-85 and props
----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
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,

(Heres one to stir up discussion.)

To start with, your engine hasnt yet been converted from C-75 to C-85. Since you still have a 73 propeller, you probably cant 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 websites Coupe page at:

http://edburkhead.com/Ercoupe/index.htm

Herere 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, Id suggest you send off your prop to a prop shop to get it shortened and re-pitched to your choice. Im 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). Id 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 dont know. Itd sure take a long time, if you could do it.

7152 cruise prop cruise ranges from 90-112 mph. Climb? Youve got to be kidding possible service ceiling between 3,000 and 6,000. At some aircraft gross weights, the engine cant get you up to the higher speed and it wallows along at 90 mph. Maybe the several people whove reported this to me just had wimpy engines. Personally, I wouldnt 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 -----

From: Ed Burkhead

To: Coupe-Tech

Sent: Tuesday, April 05, 2005 6:40 AM

Subject: RE: [COUPERS-TECH] Two questions
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Heres 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
 
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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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Re: [COUPERS-TECH] C-75 --> C-85 and props

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