Now a maintenance question for youse guys regarding the gear warning horn system, specifically the throttle switches. Reading the Maintenance Manual Landing Gear section it says that the gear horn will sound upon power reduction at around 13-14" mp; our right throttle switch seems to be adjusted properly, but the left throttle will trigger the horn at around 18+" mp or so. We'd like to tweak it down a bit, but can't find any guidance in the Mx Manual; page 4F24 makes a brief mention of the existence of the switches and how to remove/replace the horn assy, but not a peep about how to adjust the switches.

I did remove the throttle quadrant side cover and found the switches with flashlight and mirror, but access looks tight... has anyone had to tweak these things? Any words of wisdom to attack them?

Do throttles seem synchronized in cruise?
If you set both at 18" ar ethe throttles aligned with each other?
IE is it a switch problem or a throttle cable adjustment problem?

Yep, the throttles are matched. This ship (600A) was a "barn find" brought back to life by The Flight Shop; they did a fine job on the engine control rigging... throttles/props perfectly matched and RPM right up to 2575 RPM on takeoff.

Have barely flown her at all, so can't tell yet!

But my cowl flap doors are always open and the closing has been disabled (a high failure rate item those motors, apparently). Prob loses you 5kts at the top end, but keeps cooling at max always. I'm not too worried at the power settings I'll be running, but if you want to go really fast it might be an issue.

The thing I'll be worried about is the dual mag. That's a bad design (with a single point of failure), so will try to stay on top of the maintenance of those. I've heard they should be overhauled every 500hrs to stay healthy, so I'll try to adhere to that.

Interesting tidbit - the SII doesn't have VG's or any limitations on low speed handling, due to the contra-rotating props.

Nice!

Speaking of recent acquisitions, here’s the 600A a buddy and I bought in January; a ‘79 early Piper build with original interior and engines, only 1530 hrs TT! It was a barn find resurrected by the previous owner at the Flight Shop in Utah. We’re gonna be cautious with 47 yr old engines, but compressions are good, minimal drip/leaks and very low oil consumption. Paint is rough, but we’re okay with that for now… we’re still in the giggle phase, this thing is just a blast to fly.

It’s been a long time since Aerostars and Chieftain were front and center, but, IIRC, if it has a D at the end it has a dual mag. The accessory case can be changed to give the engine two individual mags. That change makes the engine a TIO-540-J2B. One thing I definitely remember is removing the dual mag at every 100 hour to check/reset/replace the points. There’s a lot of heat in the engine compartment and the cam followers on the points don’t like it. If the follower wears down enough and the retard points won’t open, the engine won’t start. Other than that, the mags worked good, but a lot of mechanics are too intimidated to work on them. It’s not really that difficult, just time consuming. In over a decade running a fleet of 12+ Chieftains, I don’t recall ever having a mag failure that caused an engine failure.

I have a spare set of S1A5 engines with only 250 hours on them but they were not properly stored and have pitting in the cylinders. They are probably cores only.

I also have a pair of IO-540-S1A5 (MM) engines with under 50 hours SMOH, but they are prop strike engines and are scheduled to go out next month for inspection .

I have lots of 600 parts if you happen to need anything for your 600.

Thanks,
Frank

Turboprop Aerostar. Owned by Bobby Allison

I would have liked to have taken that dude for at least one spin around the patch!
I may have just kept going.

Frank

I would have liked to have taken that dude for at least one spin around the patch!
I may have just kept going.

Frank

It’s my understanding that it had Allison engines on it.
Here is a good article on the airplane .

https://www.bobbyallison.com/pilot.htm

Being turbine engines I would have thought that it would have performed better at higher altitudes .

As for fuel burn, my Super Star II is pretty thirsty, but when you factor in the extra speed it had the equation for the cost and distance traveled pretty much balances out. I am not a LOP guy, I fly for recreation and personal travel and I like to go fast. So, while I don’t punish the airframe, I also don’t make any concentrated effort to conserve fuel. I am always ROP on Bonanzas and Barons and I lean the Aerostars according to TIT. I have very little turbine experience, other than an older Lear 24 back in the early 90’s, but maybe some day.

Thanks,
Frank

Altitude performance is not an inherent attribute of turbine engines. Like piston engines, they rely on outside air. The less air there is, the less fuel they can burn, so the less power they make.

What often confuses people is that turbine engines are often flat rated. This artificially limits the sea level output so that it remains constant (i.e. flat) with altitude. A turboprop that produces 400 HP flat rated to 18,000', for example, is actually an 800 HP engine limited (often by the pilot's hand on the throttle) to 400 HP.

Turbocharged piston engines are also usually flat rate, but we seldom call them that. The turbo works harder and harder as the altitude increases, to keep the same MP. The power-vs-altitude curve is therefore flat until the wastegate is completely closed (the "critical altitude") and then lapses with altitude.

I suspect those Allison 250s were 400 HP wide open at sea level (note that in their original helicopter application, they're "flat rated" by the tranmission's torque limit.) By 18,000', they were ~200 HP engines, at which altitude the turbocharged IO-540s that the Aerostar came with were still producing 295 HP.

My brother, Kurt, has a Tradewinds Turbine A36 with the Rolls Royce (Allison) 250. My friend, Martin, is correct - this is the engine used in Bell Jet Rangers - turbocharged piston engines do better at high altitude than the 250. According to Kurt, it does best between 10k and 15k feet where he will get 205 ktas give or take depending on temperature.

My brother, Kurt, has a Tradewinds Turbine A36 with the Rolls Royce (Allison) 250. My friend, Martin, is correct - this is the engine used in Bell Jet Rangers - turbocharged piston engines do better at high altitude than the 250. According to Kurt, it does best between 10k and 15k feet where he will get 205 ktas give or take depending on temperature.