PA-12 Catto

[Colorguns]

Has anyone tried for a field approval for a Catto prop on PA12 with a placard stating the aircraft to be limiting the seating to 2 occupants?
This is based on the Part 23 simple aircraft 2 seats and under 250 mph. Seems this might fall in that category? If placard to limit seating.

Doug


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[KevinJ]

I’ll bump this thread because I’m also curious. I’m sure someone with deeper knowledge will step up and cut and paste the reg. saying why it can’t be installed legally. The little experience I have with Catto props tells me they are better in almost every way and most -12s would greatly benefit from their lighter weight. This once again may fall into the “ask for forgiveness” category.....Seems like the “ask for forgiveness” topic has come up so much lately that it could almost be its own forum category.

[Steve Pierce]

Run that by Craig Catto, he has a PA12.

[algonquin]

My -12 is a 2 seat airplane, the airworthy Certificate said utility category which restricts it to two Seats. If you can use that I'd be interested in a Cato prop for it. But then again a engine for it first,lol. Maybe another year.

[Nodak33]

Any one experience the performance and characteristic differences in the Catto to the Borer 82/43 on 160hp 320 on take off and landing. What is a guy to expect the first time flying with one?

I have a friend with a -12 and he has a 84/37 catto on order and was wondering I told him i would ask around and see what i could find out.

Is there a CG difference? I can imagine with all the weight off the nose the tail rises slower, Or does the performance and thrust of the Catto compensate for that.

Any info would be great guys. Thanks.

[PerryB]

The 82" Catto performs nearly identically to an 82" MacBorer with 3" more pitch. In other words the 82-39 Catto and the 82-42 Mac have nearly identical performance envelopes. Those are the two props I have, and I've done static, WOT runout, ROC and time to climb tests. I finally got bored and declared them a dead heat. The Catto statics a shade lower, but runs out at the same RPM and speed, and ROC and time to climb (brake release to 1000') was a wash. Less than a second difference on an average of 3 runs each. The Catto moves the CG back something like .7" on a Kenmore installation.
If I can find the notebook where I recorded my climb data I'll post actual numbers, but if the diameters are both 82" then subtract 3" pitch from your favorite Borer when ordering a Catto Cub-type (as they call it). In addition to the GC advantage, the Catto produces less gyroscopic effect. Most noticeable in yaw, because the pitch feel has already been biased for the better by the aft CG.

--- Doug, If you manage to pull it off. you're going to a lot of peoples new best friend. Me included!

[Nodak33]

So speculating with the above information PerryB. What should the 84/37 react like ? Longer and flatter (higher static). They recommended it rather than the 82/39 for the density altitude in the south during the summers I am told. Would my friend be correct in assuming there is an option for harder braking if the CG is moved back as well?

[PerryB]

I'd like to be able to try the 84/37 just to see how it performs and how cruise is affected. Braking? Theoretically yes you can stand on the pedals a bit harder. Practically, that's a stretch.

[TurboBeaver]

Nodak33,
Dont look for more static rpms with that big Catto. And the tail is going to come up faster than ever,
You are moving more air. You really wont notice the CG advantage until you are landing light, at idle rounding out your elevator will seam more response at just above stall speeds. You will likely see similar or slightly more rpm in climb outs. And unless the Borer has been super tuned for pitch angle consistency, track, and balance it will likely NOT be as smooth as
A Catto prop in the air. If you have a strong 160 you are likely to have folks on the ground saying" your prop is more noisy than it used to be". Not sure what tip speed of an 84" prop is at 2750 but it is really barking out......sort 185ish in pitch but lower in volume.
Lol

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[PerryB]

At 2750 an 84" prop has a tip speed of 687 mph, so I don't see it getting noisy. Also It won't make 2750 at climb-out. More like 2550 unless it's REALLY flat. At 2550 its tip speed is 637 mph.
A 185 with an 86" prop turning 2850 (which it actually does of course) is doing 729 mph at the tip, so it's a lot closer.

[KevinJ]

Hypothetically speaking, would a 160hp cub have enough hp to make something like an 86/35 worth while? At what point does the length, no matter how flat the pitch, bring about diminishing takeoff results?

[TurboBeaver]

At 2750 an 84" prop has a tip speed of 687 mph, so I don't see it getting noisy. Also It won't make 2750 at climb-out. More like 2550 unless it's REALLY flat. At 2550 its tip speed is 637 mph.
A 185 with an 86" prop turning 2850 (which it actually does of course) is doing 729 mph at the tip, so it's a lot closer.

Perry,
That is all true.........however I only mentioned the 2750 as when you take off with a 84/36 drop the nose it will very quickly come up to redline and as the aircraft passes you at a right angle the noise projected to the bystanders is very noticeably sharper than from any "Borer" prop we have ever listened, to. Having flown Borer props on Cubs since the late 1970's from 38"/44" on lots of different engines, I am a firm believer they rate highly on the list of performance props for STOL operations. However in later years I have also become a "Big Fan" of the larger Catto props and how they perform. I was not implying that a big Catto was AS loud as a buzz job with an 88" prop but it may surprise you how loud it is! Though your mileage my vary. Fly safe.
E

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[cub12]

if any one is interested i have a catto 84/37 for sale. pm me for details.

[flynlow]

I worked on a field approval with my FDSO for a 0290 1951 PA18
Made lots of calls, Craig Catto was involved...finally after all the negotiating, the verdict was “you cant put a experimental prop on a certified airplane”



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[PerryB]

if any one is interested i have a catto 84/37 for sale. pm me for details.

Don't tempt me....
If one more prop shows up on the hangar wall, my Wife will probably burn it down.
* Here's my question, has anybody figured out the pitch/diameter correlation? For example, if you have an 82 you really like and want to go to an 84, how much pitch do you need to lose? Two inches, three inches??
This is all PURELY hypothetical from my standpoint of course.......

[KevinJ]

-4”....hypothetically of course

......that’s from a borer to 84” catto

[PerryB]

I was meaning if I went from my 82-39 Catto to an 84-?? Catto. I'm thinking either 36 or 37.

[TurboBeaver]

I was meaning if I went from my 82-39 Catto to an 84-?? Catto. I'm thinking either 36 or 37.

Perry,
The 84" prop pitch is soposed to be 36" if your a 150 and 37" if your 160 for Seaplane ops. Should be the equivalent of a 82/41 for 150 and 82/43 for 160. I seam to hear alot of guys saying the Catto's tend to lean a bit harder to turn static to same rpm as the Borer, yet seam to be turning same or more at T/O.......
84/36 on a midtime 0320 unmolested engine. Static 2375. Breaking ground about 2500, 70mph climb out 2600. Just numbers for reference. Tach was not strobed, so those numbers could be off. However the differential is probably accurate. Not sure if this helps or not?
E

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[hotrod180]

Has anyone tried for a field approval for a Catto prop on PA12 with a placard stating the aircraft to be limiting the seating to 2 occupants?
This is based on the Part 23 simple aircraft 2 seats and under 250 mph. Seems this might fall in that category? If placard to limit seating. ….

This kinda reminds me of when LSA / sport pilot first came out.
Someone wanted to do an STC which converted a Cessna 120/140 to an LSA,
by installing a placard limiting the gross weight to 1320.
Nope, it didn't fly.

[algonquin]

A PA12 can be either a three or two seat aircraft. I talked about this with my FAA rep and he said its all part of the TC and can be used in accordance with that either way. Utility and standard cat. Mine has until its on the airworthy cert. that's why I was asking.

[skywagon8a]

This kinda reminds me of when LSA / sport pilot first came out.
Someone wanted to do an STC which converted a Cessna 120/140 to an LSA,
by installing a placard limiting the gross weight to 1320.
Nope, it didn't fly.

This has been true from the very beginning. They specifically said that you could never reduce the certified maximum gross weight in order to comply with the LSA weight restrictions.

[skywagon8a]

They also said that if you increase the gross weight above 1320 (through an STC or any other method) you can not go back down in order to comply with LSA.

[Nodak33]

Worth every penny...TurboBeaver, you were spot on. Man do these things pull. Only have about a hour on it though, and they do take some getting used too. Things change on final, a bump to the throttle and she wants to fly again...Right now...

[TurboBeaver]

Worth every penny...TurboBeaver, you were spot on. Man do these things pull. Only have about a hour on it though, and they do take some getting used too. Things change on final, a bump to the throttle and she wants to fly again...Right now...

Sweet ride! Thats a sharp 12. Soon as you get used to it, you wont want anything else on there. Smooooth operator this Craig Catto!
Enjoy

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