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In rec.aviation.owning Mike Rapoport wrote:
wrote in message ... In rec.aviation.owning Mike Rapoport wrote: The Caravan has a 940hp engine flat rated to 675hp. Turbines are typically flat rated so that the engine can make rated power to reasonable altitudes and temperatures without having to design the gearbox for the full thermodynamic horsepower. To keep the comparison with piston engines apples to apples you need to use thermodynamic ratings. http://www.pwc.ca/en/3_0/3_0http://w.../3_0_2_1_2.asp OK, that explains that. To put some numbers on things, the engines in my MU-2 have a specific fuel consumption of .55lb/hp/hr and a piston engine is about .45 and diesels can be under .40. Huge (ship) diesels can be under .30. Compare your model aircraft engines with the TFE731-60 used on the Falcon 900EX which uses .405lb/lb thrust/hr Aha, numbers! So if one assumes the motivation to switch from a piston to a turbine is the price of gas is roughly twice Jet-A, the crossover point would be a turbine that did about .8 (to allow for the weight difference in the fuels). Any idea how small (in appropriate terms of hp) current technology can make a turbine with that consumption? -- Jim Pennino That would be the economic crossover point if the engines cost the same. Of course a plane that needed twice the fuel (in lbs) to achieve the same performance wouldn't have much useful load or range. Dropping a diesel in an airplane costs a bunch. The justification is the cost is recovered in lowered fuel costs. Your second point is certainly valid though and a minor problem with the diesels according to the AVweb article on them. -- Jim Pennino Remove -spam-sux to reply. |
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