I know some folks are running a similar set up now, but this will be the first "legal" path...
The first shakedown run on the stand was completed yesterday, with another 10 + hrs of running on the dyno ahead of us. The jugs have to seat a bit more, but the initial test run showed 164 HP, which is pretty respectable for an O-300. Chris feels that once the engine is a bit more broken in, we should see just over 170HP.
STC will be a long long (long) way off as there will be a bunch more testing to do (and I have to get the airplane its going in built LOL) but this will be a really interesting (and dramatically cheaper) alternative to the Lycoming. STC will hopefully cover the O-300s/145 and will be available at OH (must be completed by Airworx) but we're still at the beginning of this journey.
The key to a good flying backcountry 170 is weight and CG. With only a 2200 gross, we must keep an eye on the scale if we're going to have a useable, if not nicely flying bird. I've seen some reports here lately of extremely heavy 170s, with some going so far as to stuff insane amounts of lead in the tail. Not what we want to do at all…
Before I took it apart, the bird had a starting weight of about 1350#. She’s gutted now, with about 150# in the trash, so she’s gonna be light for sure. The build will be simple, but will have a Sportsman and WingX, so it should pop right off the ground.
The O-300 itself weighs around 5-10 lbs more than the LYC O-360 but hung on the 170, has a slightly further aft CG, which on these “utility” style birds, is important. With no C/S prop or gov, the high HP O-300 setup will be lighter than the Lyc and have a much much better CG. The Cont IO-360 is not a wise option so not really worth discussing, but for ref, that setup is about 65 lbs heavier. (Yikes)
Of course if more power and speed is what you're after, nothing is better than the Lyc STC. The last 180 HP A1A Airworx built for me dyno’d just under 200hp… Impressive for sure.
The reality is that with a fixed pitch climb prop (even with more ponies) we're still probably going to be a 90-100 mph turtle. In contrast, w/ the C/S prop and the big motor, the 180HP 170B is a 135-ish mph bird… can’t compare… but for mucking about locally, the lightness and simplicity should be a really interesting alternative… a huge fun quotient for a relatively cheap buy-in.
The really exciting part about this project will be the cost. No idea about number$, but the engine should be close to the same cost as a standard O/H with only the paper being the additional expense. This means no “kit” to buy, no cowl or nose bowl to modify, no cheeks to install, no panel modifications, no expensive composite prop to mortgage your house for, etc etc etc… Less power for sure, but this is an engine swap that might take place over a long weekend rather than over several months... We can argue over numbers, but in some cases, this could be a savings of the cost of buying a 2nd C170B over an IO-370 upgrade! That delta may be mean a simple glass panel, an engine monitor, a sportsman, some Bushwheels, and plenty of gas to putter about.
Not much more to say now, and I'm certainly no engine expert. If you are interested in getting tangled up in the weeds on the tech side or have questions, you can follow Airworx on FB... That said, I'll report back over the next year or so as things progress, so stay tuned.
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