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Thread: Piper Pawnee PA-25 big engine 300hp+

  1. #1

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    Piper Pawnee PA-25 big engine 300hp+

    Hello Everyone.
    New to the forum. Seeking wisdom and knowledge
    Looking to see if anyone has experience or knows of any big engine Pawnee's. 275HP+
    we currently have the 250 version. but are wanting more HP. (who doesn't)
    We use the aircraft for glider towing.
    I was hoping someone might know of an ag operation somewhere that has already fitted a larger 540 to there pawnee.
    Have been trying to do some online searching but haven't found anything.
    The aircraft operates in High, Hot areas towing larger heavy gliders.

    Thank you !
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  2. #2
    WhiskeyMike's Avatar
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    Many years ago there were Pawnees with around 290-300 HP version at Spanish Fork Utah. Many years ago.... like around 1988.
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    Quote Originally Posted by WhiskeyMike View Post
    Many years ago there were Pawnees with around 290-300 HP version at Spanish Fork Utah. Many years ago.... like around 1988.
    Ahh, that's just a few years ago.
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    mvivion's Avatar
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    I believe there was a Pawnee with a Lycoming IO-720. 400 hp. I believe Wilbur Ellis had one a few years ago?

    MTV

  5. #5
    CenterHillAg's Avatar
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    I’d bet you’re thinking of the Piper Brave, some of them had the IO-720, and some have been converted to a PT6-20. I can’t think of any Pawnees with a bigger engine than a 540.
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    skywagon8a's Avatar
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    Have you reviewed the Type Certificate 1E4 for the IO-540? There are several models which are rated at 300 hp which could be a fairly easy bolt in modification. The difference being fuel injection vs carburetor. Of course this is easy for me to say since I'm not familiar with the certification requirements in Australia. Here I could call it a 250 hp engine by painting a red line on the manifold pressure gauge. (That's a hint)

    http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/ed61cf457fee2dc686258250006ac097/$FILE/1E4_Rev_26.pdf
    N1PA
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  7. #7
    mvivion's Avatar
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    Quote Originally Posted by CenterHillAg View Post
    I’d bet you’re thinking of the Piper Brave, some of them had the IO-720, and some have been converted to a PT6-20. I can’t think of any Pawnees with a bigger engine than a 540.
    That could be.

    MTV
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  8. #8

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    Bald head, it's been done in the U.S. with PA-25 Pawnee. In the ~1990's the Fixed Base Operator in Taos, NM had a succession of glider tugs. With field elevation 7094'/2162 metres, Density Altitude was a real factor, commonly running in excess of 10,000'/3050 metres in the good summer soaring season. One of the decent tugs was a PA-25B with a 290 or 300 hp (I forget which) IO-540 Lycoming. It did a good job with all except the heaviest two-seaters, but was difficult to start hot, and cylinders ran a bit hot too. As I recall, it had been converted in Texas by Juan Batch, who was involved with lots of towing, but I may have that garbled. I don't recall which variant of the IO 540 was used, there are quite a few, with subtle to significant differences. It was licenced "Restricted", and probably with a Field Approval. I don't know how that would work in your jurisdiction. [Its successor the following season was a 450hp AgCat, which was quite a treat to tow behind in a Ka6 with a C of G tow release....]

    The Call-Air/Rockwell A-9, U.S. Type Certificate A-758, was available with both 290 and 300 hp IO-540 Lycomings, utilising a 90" version of the Pawnee McCauley fixed pitch prop. It is rumoured that these props sometimes have transported themselves onto the nose of Pawnees, in agricultural operations. The Call-Air is somewhat heavier than an equivalent PA-25, and parts availability may be a problem.

    There is a U.S. STC by AirCare to replace the standard restrictive PA-25 exhaust system with dual straight pipes (three into one on each side, no mufflers), which claims a 15 to 20 hp increase. I fly one of these with Howard Kron's 250 hp STC, but don't know if the lack of mufflers would be permissible in your jurisdiction; it's a little louder than the stock system, but honestly the prop noise is most of it. Frankly, they're overpriced for what they do, but it's an option, and the system is virtually maintenance free; no cabin heat though. Here's a link: http://www.aircareinc.us/aircaresystems/systems.html. Now if Larry Vetterman would come up with a more efficient STC'd system....

    There is also a VERY cool PA-25 with an IO-540, Alaska Bushwheels and many other clever improvements, which used to show up at Supercub fly-ins in the western U.S., based in Utah. I believe the owner/developer frequents this site, and images pop up regularly on the rotating pictures of www.supercub.org . Unfortunately, it's licenced "Experimental" (Racing and Exhibition?), so no glider towing in the U.S.

    I hope this is of some help. Please let us know how you get on with this project.

    Thanks. cubscout
    Last edited by cubscout; 12-27-2018 at 12:38 PM.
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  9. #9
    Randy's Avatar
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    I may be wrong, but didn't some high compression pistons find their way into some Pawnees?
    http://www.nfspistons.com/store/p20/...0_%26_540.html
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  10. #10

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    Hi Cubscout
    Thank you very much for the info. its great help
    The restricted category in Aus allows glider towing under certain sub types. But we will be trying to keep away from restricted if possible.
    When we do the mod we will be doing the full exhaust and prop to try and get the best we possibly can.
    we have plenty of Callair's floating around however, they have been having a few issues with the wooden spar.
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  11. #11

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    Skywagon8a
    i did do a search on the database but you have given me an idea of a few other combinations to try. ill keep searching.
    Yes i aware of the redline mod we have the "250" in ours.
    Certification is achievable in Australia. you just need a suitably qualified person to sign off. It makes it a lot easier if we can show someone who has done it before as the Australian regulator excepts most of the FAA approvals.

  12. #12

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    What's wrong with a Fatman? Comes from the factory with 300 hp IO-540. Several have been used for glider towing in your country and mine.

    Andrew.
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  13. #13
    hotrod180's Avatar
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    Quote Originally Posted by MainlandCub View Post
    What's wrong with a Fatman? Comes from the factory with 300 hp IO-540. …...

    https://en.wikipedia.org/wiki/Gippsland_GA200
    Cessna Skywagon-- accept no substitute!
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  14. #14

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    Quote Originally Posted by MainlandCub View Post
    What's wrong with a Fatman? Comes from the factory with 300 hp IO-540. Several have been used for glider towing in your country and mine.

    Andrew.
    Hi Andrew.
    Yes we know the fatman well. nothing wrong at all. we just have our own Pawnee sitting in the hangar coming up for overhaul shortly.

  15. #15

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    Here's an image of that VERY nice big-engine Pawnee that rotates on the website opening page:



    Thanks. cubscout

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