Balance tubes...
The controls are push pull tubes.
These go through a pressure seal...

So if the tube goes through a seal with more pressure on one side it will tend to push the tube toward the low pressure side.

The aerostar adds a second set of tubes and a linkage such that the 2nd tube moves in the opposite direction. So the pressure that pushes one tube pulls the opposite tube by the exact same amount.

This means 2 pressure seals, and a bit more linkage to lube and inspect, but the controls on the aerostar feel really solid and well connected to the airframe.

That makes sense. Thank you.

Stewart - The issue isn't the engine, as you say it's a beast and perfectly reliable. In the Aerostar installation it simply doesn't have enough cooling air to keep the turbo from cooking the accessories and other components. Krueger Aviation in California reputedly worked out most of the bugs with various fixes and kits. I have no first hand knowledge, but several folks I know who would always give any Aerostar the benefit of doubt told me the stories and advised to keep my distance.[/quote]


I owned a J2BD aerostar for a year. the airplane was super fun to fly and very fast. But it was a very negative and expensive experience. Even though previous owners had spent a small fortune on overhauling and rebuilding this particular airplane (aprox $600,000 with Eric krueger), we spent $110,000 on maintenance in less than a year. The airplane broke down in the field 5 times and it would be a scramble to get repairs. And it always went to the shop for repairs after every flight and the bill was usually $5000 - 10,000. I had previously owned a chieftain with same engines and had no trouble taking the engines to TBO. I don't think the problem is with the engines. It's the big honking very hot turbocharger packed into a very tight cowling. Magnetos would get cooked. It's a really tight space. everything would have to get disassembled to make even minor repairs. The mechanics at our local shop literally hated the airplane. We sold the airplane at a substantial loss to be rid of it. The airplane took a last bite at me on the delivery flight to the new owner when the turbo oil seal failed and we dumped most of the oil on that engine. Luckily it was a very short flight and no damage to the engine.

In short the airplane was magnificent to fly. But the maintenance was a nightmare and reliability was very low.

Stewart - The issue isn't the engine, as you say it's a beast and perfectly reliable. In the Aerostar installation it simply doesn't have enough cooling air to keep the turbo from cooking the accessories and other components. Krueger Aviation in California reputedly worked out most of the bugs with various fixes and kits. I have no first hand knowledge, but several folks I know who would always give any Aerostar the benefit of doubt told me the stories and advised to keep my distance.

Iain!

We are just across the strait from each other. I didn't know that bird was for sale again. I'd very very happy to chat with you about our experience with that airframe. I hate to be negative about any airplane but it was a very negative, expensive and demoralizing experience for us. Mike Droege at ZBB did the maintenance and Rick Church at Langley did some structural work on the airplane. I thought we were getting a really good wrung out airplane because of all the money previous owners had spent on it. I was wrong. It continued to be a money pit for us.

Out of curiosity I measured the nacelle of both the Chieftain and the A*. From the engine to the firewall is approximately 10" more on the Navajo, in short about twice the area to accommodate the turbo, associated plumbing and accessories than on the A*. Not to mention the -J2BD is a top exhaust so all the exhaust piping has to shoehorned in across the top of the engine as well in addition to stuffing the big single turbo in back.

I have never worked on the Ho' powered A*, but hats off the the folks who figured out how to fit it all in there, and in spite of their best efforts it's also not to surprising the reliability isn't the best. It's also not a surprise that when Piper decided to up the power to 350 they used an engine very similar to what Ted Smith chose, just one purpose built to produce 350 hp, the -U2A.

Jeff

For what it's worth, the rust issue SB is likely to become an AD:

https://www.aopa.org/news-and-media/all ... star-twins

As of today, John in parts told me they had materials in stock for about ten airplanes after I ordered mine.

I can't remember which shop said it, but they stated that every airplane they inspected had rust inside them. Mine wasn't as bad as the SB on the one side that I looked at, but bad enough that my IA wanted them replaced.

My tubes were inspected and rusty ones replaced two years ago...

Mine were also rusty on the inside of the tube and replaced. The amount of rust was minimal and really of no consequence but I figured it would eventually be an AD so they were replaced. I really don't think that even in the worst case that the rusty tubes would ever be a safety issue as these balance tubes just balance the force of the pressurized fuselage from affecting the control pressures. The tube would have to rust through through completely, break and bind up the controls to be a safety issue. I don't see that ever happening. I would think that almost all tubes will have some rust on the inside of the tube so AAC will need to make some more tubes as I bet just about every pressurized Aerostar will need them.

Did mine about a year ago with the replacements but what I removed looked brand new. If your plane has not lived in an adverse environment I doubt you have much corrosion.

Twice as much volume probably turns out to be three times or more the open air, if you pull out the volume occupied by hoses, mounts and accessories!

Many of the Rajay converted Mooneys had trouble with cooling even when the turbo was not running (manual wastegate). The turbo system just being there obstructing airflow is a big issue!

Mine arrived today.

Hey guys,

I’ve got an opportunity to get into a Superstar II (J2BD engines). What would you all think a good price for it would be from a buyers perspective? Mid time engines, avionics need updated, could use a new interior eventually. It’s been sitting for awhile but engines started and ran up every month or so.

Yes, I know what I’m getting into with this airplane but I’m liking the performance numbers.

Not sure what it's worth but what I DO know is that Lycos don't like to be " started and ran up every month or so" . If the oil is not brought to operating temp for at least 30 minutes you are probably just adding moisture to the crankcase instead of boiling it off.


But you already know what you are getting into so there's that.





Ron

With all due respect, are you sure you know what you're getting into?

Scroll up a bit and read Iain's post.