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Old 05-15-2012, 07:50 PM   #21
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How does the turbine engine compare to the piston engine as to fuel economy and maintenance expense?
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Old 05-15-2012, 09:57 PM   #22
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How does the turbine engine compare to the piston engine as to fuel economy and maintenance expense?
The turbine burns a fair amount more fuel although the cost of Jet-A is--- or used to be--- considerably less than the cost of avgas. The piston Beaver burns about 23 gph. If memory serves the turbine Beaver burns 40-something gph. But if flies faster and carries more.

Another difference is that it's not really worth hauling a piston Beaver up very high unless you have to clear mountains. All a long climb does is add to the overall trip time, burn lots of fuel, and potentially overheat the engine. My wife and I never take the plane above about 1,000 feet when flying the Inside Passage. We have flown for several hours at a stretch at 50-100 feet under a solid overcast but we never go above a thousand unless we're going back into the mountains.

A turboprop, however, gets more efficient with altitude up to a point. So the turbine Beavers and Otters are typically flown at significantly higher altitudes on their routes than the piston planes.

The real benefit of the turbines is tremendous reliability, reduced maintenance--- not many moving parts--- and greatly extended time-between-overhauls (TBO). Where the radial on the Beaver has a TBO of between 1200 and 1800 hours the TBO of the P&W PT6A-135 can be up around 8,000 hours. And there are monitoring programs operators can use to significantly extend the TBO of both piston and turbines engines.

But there's no free lunch. The cost of overhauling the radial is relatively low. The cost of overhauling a turbine can run well into the hundreds of thousands of dollars.

But the main benefits of the Turbo Beaver and the Vazar Dash-3 Otter is more power and greatly increased reliability. Which translates into lower maintenance and operating costs, too.
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Old 05-16-2012, 02:03 AM   #23
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That 8,000 hour TBO turbine is almost as good as a 10,000 hour TBO Lehman!! LOL

How does the 23 gph and 40gph numbers translate to Miles per Gallon? I was told by a piston Beaver pilot that his plane got about 6MPG usually loaded with loggers and their gear.

If the P&W turbine costs several $100K to overhaul, what is the initial cost of the powerplant?
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Old 05-16-2012, 04:38 AM   #24
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That 8,000 hour TBO turbine is almost as good as a 10,000 hour TBO Lehman!! LOL

How does the 23 gph and 40gph numbers translate to Miles per Gallon? I was told by a piston Beaver pilot that his plane got about 6MPG usually loaded with loggers and their gear.

If the P&W turbine costs several $100K to overhaul, what is the initial cost of the powerplant?
A piston Beaver on floats cruises at 110 mph and burns about 23 gph.. Kenmore's turbine Beavers cruise at 140 mph and burn 41 gph.

IIRC when Kenmore did their Turbo Beaver conversions a new P&W PT6A-135 cost half a million dollars. I suspect they are considerably more today.
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