I'm in the process of looking for a Turbo Twin Comanche. Most of the Turbo models I see advertised are STC turbo upgrades, using the -B1A engines. I would prefer to have the -C1A engines which were designed for turbo-charging applications.

My question is this: Is there a list of PA-30 serial numbers that left the factory as turbo models (with the -C1A engines)? The PA-30/39 parts manual only lists the -B1A engine (page 1J3), and the FAA registry simply lists Lycoming IO-320 Series.

To my knowledge no. I do think that the later the model Twinkie, the more likely it is to have factory turbocharging and hence likely the -C1A engines. I have never seen a PA-30C or a PA-39 with STC'ed turbocharging, though I would doubt that there was one or two out there.

You might check with Charlie Melot from Zephyr Engines about the actual differences. I recall reading that the differences were minor. An oil jet to cool the pistons and the -C1A does not have a scavenge pump which can be a troublesome item to obtain or have overhauled.

One thing I would check is whether the STC specifies 100 octane fuel. One of the advantages I see in the normally aspirated twin is the ability to burn a lower octane fuel. That might be important in years to come. That was one of the myriad of reasons I had for chosing an NA twin over a turbo, even though I live in the west.

Thanks, Kristin. I'll give Charlie a call, and pick his brain. You raised a couple more questions:

1) Do you know who now holds the turbo STC?

2) I read somewhere that the "C" model has stronger engines than the "B" model (valves and guides); is that true?

3) do you fly much in the teens with the NA model? When I lived in CA, I was always up above 10,000 to get across the borders.

Frank,

I believe that Rayjay originally had the STC's and that they have changed hands a few times. The FAA has a database of STC's for each aircraft type so you can look it up there and see who the current is. I don't know who has it know, but someone else might and I hope they chime in here.

I don't know if the -C!A would be considered stronger or not. I would defer to Charlie Melot on that one. I do know that the turbo has a lower TBO and significantly higher maintenance costs.

I normally fly higher than 10K. I have cruised as high as 16K in my normally aspirated twinkie. Unless I lived in the intermountain area of Idaho, Washington, Utah, Nevada, Wyoming, etc., or needed to go there often, I would not own a turbo. The additional costs of operation don't make sense if your mission doesn't require it.

The Comanche has a great wing. It doesn't lose speed rapidly with altitude increase, but the efficiency improves noticeably. I have run the aircraft at 16,000, burning 11 gph total, and was seeing 145kts true. Pretty good for a twin. The turbo, by comparison, requires that you burn extra fuel to keep the engine cool when the turbos are cranked in. In addition, at low altitudes, the turbo installation costs you in performance when it is not being used. A NA twin will get off the ground at low altitude more quickly and climb faster. The turbo won't catch up until you are above 8,0000. I see you are in Vermont. I can't imagine going turbo for eastern operations, but others might have another take on it.

FYI .. the STC for the turbo TC is number SE14WE, and is now held by RAJAY Parts, LLC.

Kristin, I gotta say that my PA 30 turbo usually out performs NA Twinkies above 8,000. I've never had mine to 80,000, but that would be something to aspire to! We could find a couple of pressure suits and have a race.

Frank:

You'll have to check each airplane. Mine left the factory with B1A engines in 1965, then had the turbos and tip tanks added shortly thereafter. In 1985 (if memory serves) the B1A engines were swapped for factory new C1A engines, which are what I am flying behind today (since overhauled).

I'm sure that over the years many airplanes have had similar swaps. Wouldn't surprise me at all to find one that started with C1As and ended up with B1As, particularly if the owner wanted new engines after Lycoming stopped making the C1A. For what it's worth, I don't know of any practical differences in day to day operations.

Jay

 

I'm with Kristen, unless you really need to go high regularly and need high SE ceilings then I would go for a NA PA30. The turbos are "gold" when needed but otherwise more expensive to run (unless you do your own maintenance) and are slower below 6-8000 feet. The induction system is prone to leaks and can take a bit of effort to rectify.

I would offer the other viewpoint, I have been flying across Europe UK<-> Cyprus for the past four years and the terrain and weather avoidance advantages of the turbo fit have justified the (not trivial ) additional maintenance effort and cost. Another advantage in crowded European airspace is ability to accept ATC clearances in the teens, easily. It is common for clearances across TMAs to be given at FL120-150. Built in oxygen and Turbos make it straightforward. I have put a lot of effort into the baffle seals to ensure adequate cooling.

While I am still doing long trips ( I hope to get to New Zealand later this year) I will keep the Turbos. If I were to re-engine and knew I was staying in UK / Western Europe I would probably go normally aspirated. The ac is a PA30C CR Turboed with C1A engines

I am not the first to say "it's all about the mission"