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Thread: Climb prop C-90

  1. #41
    hotrod180's Avatar
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    Ouch!
    Cessna Skywagon-- accept no substitute!

  2. #42
    jnorris's Avatar
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    I have a 76AK-2-44 on my C-90. A 42 would work better for climb, but it climbs well enough to do what I want it to do, and I like the cruise speed I get.
    Joe

    Fortis Fortuna Adiuvat

  3. #43

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    As I mentioned...this one is for my experimental so I went with Catto....this quote is from Nicole Catto...
    "our 78x34/35 is a pretty extreme power prop. It's slow. Some people really like this one,it gets off the ground fast, also a great prop for floats. the most common prop on this application (O200A) is our 76x36/37. The 36 over speeds a little bit at wide open throttle, so it's very responsive off the ground. The 37" pitch doesn't have a longer takeoff roll but will probably hit around 2750 rpm at WOT straight and level." I went with the 76x36.

  4. #44

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    Quote Originally Posted by mvivion View Post
    This thread has gone for 34 posts, with some incriminating evidence posted by those who are operating certificated airplanes--maybe.

    Here is what the 7EC type certificate says about propellers and propeller RPM:

    Engine Limits For all operations, 2475 r.p.m. (90 hp.)
    Airspeed Limits Level flight or climb 100 m.p.h. ( 87 knots) True Ind. Glide or dive 135 m.p.h. (117 knots) True Ind.

    Propeller Limits Static rpm at maximum permissible throttle setting: (For fixed pitch Not over 2350, not under 2125. No additional tolerance permitted. wood propeller)

    Diameter: not over 72 in., not under 70 in.

    So, if your current propeller pulls between 2125 and 2350 STATIC (as in full throttle, on the ground, NOT moving) then it is within legal limits. Repitch it to get better climb or cruise, and if it then runs static outside those limits, it is not legal.

    And, for those folks advertising on the world wide web that their C-90s on certified aircraft are running 2600 rpm.....note that the Continental TCDS (and the above 7EC TCDS) says Maximum rpm for the Continental C-90 is 2475 RPM for ALL operations.

    If you're experimental, obviously, you can do whatever you want with your engine.

    But, for the OP, these are the limits for your engine. 2200 to 2300 for takeoff is probably pretty close to that static limits noted above.

    Also, a review of the TC for your airplane will also tell you what propellers are approved for the plane. The TC is the first place you should go for basic information like this....THEN troll the internet.

    MTV





    Engine Limits
    If I am reading this wrong I apologize,but the type certificate i have says 2625 for max T/O.
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    Ernie

  5. #45
    mvivion's Avatar
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    Quote Originally Posted by eviens View Post
    If I am reading this wrong I apologize,but the type certificate i have says 2625 for max T/O.
    Click image for larger version. 

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    The type certificate for the AIRPLANE takes precedence in this case. The OP described the 7AC Champ as the subject. There are lots of cases where the airframe manufacturer placed more strict limits on an engine than did the engine manufacturer. Also note that the same maximum rpm limits (2475) are specified for the C-90 installed in the Piper J-3 and PA 11.

    I presume that this is because the airframe is limited to 90 hp. and the higher rpm produces higher horsepower. Nevertheless, the airframe limits are specific to the airplane, and specify the propeller limits as well.

    Granted, five horsepower may seem like nothing, but the airplane is not legal if it's propeller doesn't turn in the prescribed range at static full throttle.

    MTV
    Last edited by mvivion; 09-19-2016 at 04:07 PM.

  6. #46

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    Ok thank you,I was looking at the engine limits not the airframe limits.
    Ernie

  7. #47
    mvivion's Avatar
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    Quote Originally Posted by eviens View Post
    Ok thank you,I was looking at the engine limits not the airframe limits.
    Not at all, thanks for posting ALL the data. If nothing else, that's useful to EX folks.

    MTV

  8. #48
    L18C-95's Avatar
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    The L18C has a higher limit for five minutes with red line at 2475 and top of green at 2350. Static on my 76 is 2300, but off the tach. I need to throttle back as soon as I start to level in the cruise. Top of green is 95mph indicated, which is reasonably correct. I cruise at 2300 RPM with 90 mph indicated.

  9. #49

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    "The 37" pitch doesn't have a longer takeoff roll but will probably hit around 2750 rpm at WOT straight and level"

    With an O-200 at WOT in level flight, I like to be capable of hitting 3000 rpm. I keep it from doing so by means of instrument panel placard and retarding the throttle (standard procedure for a certified plane).

  10. #50

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    I received and email from Catto yesterday...my prop is done. As I said, I went with the 76-36 on their recommendation, I was really torn between this and the 34 pitch, but I opted on the conservative. I look forward to finishing my project and finding out for myself how my setup matches up. I believe this is the right choice for my mission, but The proof can only come from the flying since the original thread was meant for a C90 and we veered off to O200, I wonder if the same prop would be the ticket on a 90. I have a C90-12F in my Tcraft on floats, but that's a certified setup, so a trial run of the new Catto would be "Illegal" on that platform, I'm sure I have enough willpower to prevent that from happening....I have a Sen 76AK-2-40 on that ship and its a winner. Still,, a comparison would be "nice".

  11. #51
    skywagon8a's Avatar
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    Quote Originally Posted by Dan Gervae View Post
    I have a C90-12F in my Tcraft on floats, but that's a certified setup, so a trial run of the new Catto would be "Illegal" on that platform, I'm sure I have enough willpower to prevent that from happening....I have a Sen 76AK-2-40 on that ship and its a winner. Still,, a comparison would be "nice".
    It certainly would do no harm to test it on the Tcraft with some high speed taxing and other water maneuvers without the "intent" of flying.
    N1PA

  12. #52

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    Lol, I'm sure a lot of our membership would like to see results of some such testing. Sometimes during such a test one would encounter a gust of wind that would render him airborne and then the prudent thing (safe thing) would be to do a go around.

  13. #53
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    Quote Originally Posted by Dan Gervae View Post
    I received and email from Catto yesterday...my prop is done. As I said, I went with the 76-36 on their recommendation, I was really torn between this and the 34 pitch, but I opted on the conservative. I look forward to finishing my project and finding out for myself how my setup matches up. I believe this is the right choice for my mission, but The proof can only come from the flying since the original thread was meant for a C90 and we veered off to O200, I wonder if the same prop would be the ticket on a 90. I have a C90-12F in my Tcraft on floats, but that's a certified setup, so a trial run of the new Catto would be "Illegal" on that platform, I'm sure I have enough willpower to prevent that from happening....I have a Sen 76AK-2-40 on that ship and its a winner. Still,, a comparison would be "nice".
    I'm interested in what you think of the new prop.


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  14. #54
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    Quote Originally Posted by Dan Gervae View Post
    Lol, I'm sure a lot of our membership would like to see results of some such testing. Sometimes during such a test one would encounter a gust of wind that would render him airborne and then the prudent thing (safe thing) would be to do a go around.

    No one around here is that careless to allow such a thing to happen; nor would anyone here ever consider anything that might be outside the FAA rules of operation

    EVER!
    I don't know where you've been me lad, but I see you won first Prize!

  15. #55

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    Good to know we are in the same camp

  16. #56
    BC12D-4-85's Avatar
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    As a suggestion re the Sen vs Catto...at least do a static pull with both on the same platform. Find a farm or veterinary scale used to weigh big stuff and give it a tug.

    I have the same Sen prop on my Taylorcraft and it does what I want. I contacted Catto and was told the same (76-36) but haven't followed through with the order as I didn't want to end up with an expensive oar or wall decoration.

    Have some fun and let us know someday...

    GAP

  17. #57
    skywagon8a's Avatar
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    By the way, the Tcraft is a part 4 airplane. Part 4 states that you can use an unapproved wood prop. So, even though the TC specifies an approved wood prop, part 4 says it does not have to be. Hint Hint.
    N1PA

  18. #58
    BC12D-4-85's Avatar
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    Interesting and thank you for the obs. This is over my job class but I have seen CAR 4 5/1938, Par. 04-61 discussed versus TCDS A-696 Item 1. I suspect those involved weren't as familiar as you with the implications. I know I wasn't as a reader. But that is an excellent point...the question is which Reg pertains? Maybe that has already been answered and any further enlightenment would be appreciated.

    As far as PK vs EDO, my intent isn't to imply the PK's aren't without merit in conditions like in the rough marine environment, but...in June 1980 I had the opportunity to fly two similarly equipped C-185's on the job for test purposes. Typical hot and calm Fairbanks day in the low '80's. Both planes were IO-520's with long two blade props that turned tach redline and had similar WFO T/O manifold pressures (logged the info). All-up weight was similar ~60 gallons and one soul. The one with PK 3500's (new in 1979 and latest model as of that date) I'd flown more the previous season than the newer one to me on EDO 3430's. No comparison at partial throttle/high D/A takeoff...the EDO's performed better under those conditions for T/O, and displayed a lesser tendency to pitch nose down on landing on glassy water. The PK's would go about 55 mph max indicated on the water (partial throttle with no flaps); the EDO's accelerated beyond that indicated airspeed if kept on the water. No GPS in those days so the speed may be relative. All history now of course.

    GAP

  19. #59

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    Send the prop to me in Maine I'll try it on my c-90 pa-11, as far as I'm concerned the FAA owe me one with the loss of a month+ of medical, I'll call it even and won't hurt your prop .

  20. #60
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    Quote Originally Posted by Douten View Post
    Send the prop to me in Maine I'll try it on my c-90 pa-11, as far as I'm concerned the FAA owe me one with the loss of a month+ of medical, I'll call it even and won't hurt your prop .
    I know of a champ near by that would try it too


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  21. #61
    skywagon8a's Avatar
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    Quote Originally Posted by BC12D-4-85 View Post
    Interesting and thank you for the obs. This is over my job class but I have seen CAR 4 5/1938, Par. 04-61 discussed versus TCDS A-696 Item 1. I suspect those involved weren't as familiar as you with the implications. I know I wasn't as a reader. But that is an excellent point...the question is which Reg pertains? Maybe that has already been answered and any further enlightenment would be appreciated.
    This is from the http://www.supercub.org/forum/showthread.php?50672-Best-STC-for-0320-Conversion thread. I suggest that you get in touch with Ben K. (Fat Kid) since he is closer to you than me and likely uses the same FSDO.
    PROPELLERS§
    4a.597 Propellers. Propellers shall be of a type and design which has been certificated as airworthy in accordance with the requirements of Part 14 of this sub chapter or shall have been approved as airworthy in accordance with previous regulations, except that wood propellers of a conventional type for use in light airplanes need not be certificated. In certain cases maximum engine bore limitations are also assigned to propellers. Propellers may be used on any engine provided that the certified power ratings,speed ratings, and bore of the engine are not in excess of the limitations of the propeller as certificated, and further provided that the vibration characteristics of the combination are satisfactory to the Administrator.

    The Catto is a wood prop. Install it and all that is required is a Log Book entry.

    Ben K.


    Quote Originally Posted by BC12D-4-85 View Post
    As far as PK vs EDO, my intent isn't to imply the PK's aren't without merit in conditions like in the rough marine environment, but...in June 1980 I had the opportunity to fly two similarly equipped C-185's on the job for test purposes. Typical hot and calm Fairbanks day in the low '80's. Both planes were IO-520's with long two blade props that turned tach redline and had similar WFO T/O manifold pressures (logged the info). All-up weight was similar ~60 gallons and one soul. The one with PK 3500's (new in 1979 and latest model as of that date) I'd flown more the previous season than the newer one to me on EDO 3430's. No comparison at partial throttle/high D/A takeoff...the EDO's performed better under those conditions for T/O, and displayed a lesser tendency to pitch nose down on landing on glassy water. The PK's would go about 55 mph max indicated on the water (partial throttle with no flaps); the EDO's accelerated beyond that indicated airspeed if kept on the water. No GPS in those days so the speed may be relative. All history now of course.

    GAP
    I did a similar comparison test with EDO 3500s and Wipline 3730s. The Wip would not get on the step yet the EDOs flew away, both with the same heavy load.
    N1PA

  22. #62

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    Tom knows a PA-11 with C-90 that will test it too...

    Dave

  23. #63
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    So @Dan Gervae, how did the tests fair?

  24. #64
    40m's Avatar
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    When I was going through this exercise of trying to match a prop to my tweaked 0200 I too was hesitant to purchase a Catto without a comparison. Ms Catto was as helpful as she could be but I still felt like it was a $3000. gamble. With some digging I was put in touch with a guy who is some how affiliated with Catto, he is extremely knowledgeable of cubs and performance, he sent me a Catto 7636 to try, I purchased a 7638 which I'm very pleased with.
    I'll leave this up for a spell for those currently interested. Call me and I will pass along his contact info.

    Glenn 40M
    802-683-7331

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