Do I need to use smaller propp for break-in?

[Skysurf]

I just bought a DA85 with a Mejzlik 24*12 3-bladed propp. Since I have plenty of time before the airplane is going to be finished and temperatures getting comfortable again, I intend to break it in on a stand. Do I need to get a smaller propp when doing the break-in? If so, what's the theory behind this?

Thanks,

Jesper

[gene6029]

Skysurf, I broke mine in with the 24-10-3blade. I put 5 gals of 32-1 ashless lawn boy with reg pump gasoline. I was getting 7000 rpms on the ground with that prop. After the 5 gals i switched to the 25-12-3blade and amsoil 100-1 mixed at 80-1. My rpms with that prop are 5800 and alot less noisy. I have not yet experienced the gasket leaking some are haveing after roughly 15 gals of gas thru it to date. I would really like to hear how the 24-12-3blde works out for you. This is the only motor i ever broke in with a smaller prop than i intended to fly with. I have in the past just used the prop i intended to fly with as my break in prop. I cant tell the difference myself, but im sure there is.....Gene

[Skysurf]

Hi Gene,

Thanks for the info. I will get the engine next week so I'll check the manual to see what it says about breaking in. I will let you know how the 24*12 3-blade works out. It may be a few weeks before I can get it running, I am trying to get a hold of the MTW TD105K canister (designed for the 85).

/Jesper

[Oldsalt]

I start with the smallest recommended prop size for the first few gallons, so the engine will spin up quickly and won't load up (overheat) during breakin. DA usually recommends breaking in the air, in the airplane, since the engine gets better airflow and can be varied constantly in RPMs. You will really only need to run the engine on the ground long enough to ensure everything is set up correctly and safely. You will want to start with the cowl off so you can get to the needles, linkages and so on. After running for a few minutes and everything is tuned correctly, you will want to give it all a good going over, to make sure that noting is shaking loose, then reinstall the cowl, check throttle response and fly it like you stole it. I would avoid long vertical uplines and trying to hover on the first 8 to 10 tanks. Usually regular sport flying, varying throttle and avoid full power runs, while things get seated and worn in. DA usually recommend Lawnboy ashless oil at 32:1 for the first few gallons. It will leave some black spots and smears out the exhaust and on your plane, which can be cleaned up just like you did for glow fuel. Once you have a few gallons of breakin gas through it, you can contact your local Amsoil distributor and buy some 100:1 Saber. This is the oil DA recommends to maintain your warranty. I usually mix it at 65:1 for summer, since we have allot of plus 100 degree days in south Texas. Winter time, I run 80:1. Many of my flying partners run high test gas at 100:1 all year around on their DA's with no problems. Most are flying DA 50/100/150's and one is running a 170 on that combination.

Hope you enjoy your new gas engine as much a we have enjoyed ours. If ducted properly and properly maintained, they should last a lifetime.

Cheers,
Mike B.

[UflyWhat]

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