Private flights: better piston engines, or turboprops?

Un Piper Mirage 2012
Un Piper Mirage, with pistons engine


Piper Meridian
Piper Meridian, turboprop

Characteristics and performance of piston engines for private flights, compared to those of turboprops.

I have already compared here turboprop to jet engine. In short, the first is very similar to the second, even if turboprop is more advantageous for medium distance private flights, up to 600 km, while the jet, thanks to its better efficiency above 9000 m, is more advantageous for long distances, when it is profitable to climb over 9000 m. In order to compare the piston engines with the turboprops, I take for example two planes almost identical by capacity and characteristics: the Piper Mirage, private plane with piston engine, and the Piper Meridian, turboprop.

Altitude: the turboprops are more efficient between 6500 and 9000 meters, while the pistons, which are not pressurized, are normally limited to 4000 m or less. It goes without saying that a private turboprop plane goes up in altitude roughly twice as fast as a private plane Speed: turboprops advantage. The turboprops fly at -450-550 km / h, while the pistons have a cruising speed of about 350 km / hour.

Private flights distance: it follows that the shorter the flight, the more it is advantageous to use pistons. Indeed, for a flight of 150 km, climbing to 7000 m, where the turboprops consume less, would be a waste of fuel, but flying lower would involve a minor efficiency of the turboprop, with increased consumption.

Consumption: almost equality: the Piper Mirage consumes around 75 l per hour of flight, while the Piper Meridian needs 115 l per hour. however, given that the latter flies about 80 km / h faster, and consumes kerosene, cheaper than avgas, or leaded petrol for airplanes, there is only a slight advantage for the piston engine, especially for shorter flights. It should also be considered that leaded gasoline for airplanes is difficult to find at certain airports of the world, in particular in Asia.

Weight and size of the engine: advantage turboprops. In the case of the Piper Meridian, the engine weighs only 160 kg, while the piston engine of the Piper Mirage weighs 230 kg. Look at the two photos above to understand that the smaller size of the turboprop allows better aerodynamics.

Purchase price of the aircraft: pistons advantage. A Piper Mirage costs around 1 million euros, while a Piper Meridian costs almost 2 million euros. Maintenance cost: turboprops advantage. Like car engines, piston engines on airplanes have spark plugs, filters, belts or timing chains, cylinder head gaskets, coils, oil to drain. The biggest difference is that they don’t have a clutch, nor gearboxes. Therefore, they need fairly frequent periodic maintenance, similar to that of a car, and therefore quite expensive. Turboprops are much simpler and require less maintenance.

Engine life: advantage turboprops. The Piper Mirage engine is recommended for 2000 hours of flight, while the Piper Meridian engine is recommended for 3600 hours. Indeed, a piston engine consists of approximately 250 parts which move, often producing a lot of vibrations, while the turboprops have only ten parts which rotate.

Conclusion: a private piston aircraft is more profitable and can be suitable for flights up to approximately 250 km. Beyond this distance, a private turboprop aircraft is a better investment.

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