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Thread: IO-390 on wide body Cub - PIREP

  1. #1

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    Question IO-390 on wide body Cub - PIREP

    Can folks having experience with IO-390 on wide body Cub share their impression of flight characteristics? Some here have mused that it will be unfavorably nose heavy.
    Given that I typically fly with loads of >500 lbs, not sure I’d mind.

  2. #2

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    I have IO-390 on a wide body that is modified by extending 2’ making it experimental will comment on. Its tail wheel weight empty on the scales was 107 pounds. I put weight in the rear of the extended baggage to balance the plane when I fly alone and do the same in my stock Cub as they just fly better when lightly loaded with weight in the back. Can not directly compare flight characteristics as the experimental Cub has a modified wing with SQ 2 ailerons, extended chord Keller flaps and slats. What is clear is the IO-390 Cub will haul 1200 pounds like the stock Cub does 600 pounds in take off performance. I prefer the power for most of my flights even if just going flying by myself as I can operate in 1/2 the distances for takeoff and landings, certainly the trick wing helps get it in shorter.
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    stewartb's Avatar
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    Since I started with a Superior IO-400 and experienced easy to manage oil temps, I went with 10-1 in my IO-390. As expected it makes higher oil temperatures. With dual oil coolers running ROP cruise I'm around 195* oil temp. CHTs are 330-350 depending on power setting and mixture. With a Whirl Wind 200A the thrust doesn't disappoint. My plane is also extended in length, has extended wings, and a big tail. The aft baggage is placarded for 10# max per BCSC but I have at least 50# stuffed as far back as I can get it. Without that the plane is difficult to fly as it wanders in every direction. I don't know what the three-point tail weight is with fuel and stuff in the baggage but it's heavy enough that it's difficult to lift. Compared to a 360/Catto combo the IO-390/Whirl Wind combo is about 60# heavier on the nose. I'd probably stay in the 360-370 displacement with a fixed pitch if I was planning a standard length Cub.

  4. #4

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    I played with W&B for two of the MOAC builds.

    #1 was the factory demo with an IO-370, Catto prop, slats, 31” Dessers, 10” wheels BBW tailwheel, Monster shocks, 3x3 gear and basic VFR instruments @ 1,059 lbs and 12.9 cg empty.

    #2 was their heaviest build with an IO-390, 3-blade Hartzell Pathfinder prop, slats, PSTOL flaps, 31” Dessers, 3x3 gear, Monster shocks, Acme stinger, BBW tailwheel, G3X & G5 & GTN650 nav/com, autopilot w/trim, @ 1,235 lbs and 12.1 cg.

    #2 required a 15 lb ballast.

    When I ran my normal loads, which are 200-220 lb pilot, 200 lb passenger, 100 baggage and 54 lbs rear baggage, plus 10g fuel, I found that I was exceeding rear cg limits.

    We will rarely fly light & solo. The MOAC has squared wingtips, an 18% larger rudder, and the thrust line mod. I’m planning on adding some permanent tiedowns and always carrying about 50lbs of gear in rearmost area.

    Thoughts on IO390 + ground adjustable Sensenich?
    Last edited by JohnnyR; 01-14-2022 at 11:17 AM. Reason: Typo

  5. #5
    stewartb's Avatar
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    From my early experience? Slats should move the Forward CG limit aft at least 1”.

    The 390 has too much power to use a fixed pitch. You’ll give up the benefit you paid for.

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    Johnny
    What happens if you get rid of the 15 lbs of ballast? What is the max weight on the MOAC?
    DENNY

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    When I played with the #2 MOAC spreadsheet numbers and deleted the 15 lbs ballast, the airplane required back seat passenger and baggage to stay within forward CG limits.

    2,000 lbs

    Quote Originally Posted by DENNY View Post
    Johnny
    What happens if you get rid of the 15 lbs of ballast? What is the max weight on the MOAC?
    DENNY

  8. #8
    stewartb's Avatar
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    I’ve heard a couple of guys with planes like mine have the tail posts filled with lead shot. I’m not willing to add permanent ballast. I keep enough stuff in the plane to manage CG. And dog is my copilot.
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  9. #9

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    Yep. Mine is 80 lbs and she's po'd if I don't bring her with me.

    Quote Originally Posted by stewartb View Post
    I’ve heard a couple of guys with planes like mine have the tail posts filled with lead shot. I’m not willing to add permanent ballast. I keep enough stuff in the plane to manage CG. And dog is my copilot.

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