Rotary-Powered Piper Arrow Flies To Oshkosh Airventure 2004

By ANN Contributor Christopher Armstrong

You might say it's the airplane with an engine that goes hmmmmmmm.

Mistral is showing off its test bed aircraft, a Piper Turbo Arrow III, which flew into Oshkosh from the company's plant in Daytona (FL), powered by a 230 HP turbo charged to the AirVenture airshow in Oshkosh (WI). The company says it plans to certify the engines for use in production aircraft, but will also enter the experimental sport aviation market early next year.

Mistral Engines develops and produces rotary aircraft engines in the 180 through 360 HP range. The engines are available to operate on 100LL or unleaded automotive fuel, with a jet-fuel powered spark ignited engine has successfully run on the test bench with development continuing.

The Mistral powered Arrow is being flight-tested at Embry-Riddle Aeronautical University, Also in Daytona Beach (FL). Since first flight in April 2004 over 30 test and data collection flights have been completed.

Engine Specifications

                                         G-190-A1B                                          G-230TS-B1B
Engine type:                    naturally aspirated                           turbo charged Rotary
Power Take off:               190 HP                                               230 HP (5 minute limit)
Power max. continuous   190 HP                                               210 HP
Power 75%                     140 HP                                               170 HP
Weight (dry)                    291 lbs                                              328 lbs
Coolant heat load           198,000 BTU/hour                              206,000 BTU/hour
Oil Heat Load                  90,000 BTU/hour                                29,000 BTU/hour
Intercooler Heat Load     N/A                                                     15,000 BTU/hour

Both engines are cooled by oil and 50/50 water/ethylene glycol coolant They both use a supervised dual-channel digital engine management system with multiple redundant electronic fuel injection with twin electric fuel pumps. The main alternator supplies 70 amps at 14 volts. Overall, the engine is 39 inches long, 18 inches tall and 26.5 inches wide.

The propeller speed reduction drive PSRU uses a 6-pinion planetary gear at a 2.8235:1 ratio resulting in 1700-2000 propeller RPM in cruise. A hydraulic constant speed propeller governor drive. Propeller rotation in the tractor configuration is clockwise, though for pusher airplanes it is counter-clockwise. The engine features a full compliment of accessory drive pads for dual alternators, vacuum pump and a hydraulic pump or air conditioning compressor.

Although the current engines use Mazda 13B engine rotors, engine housings and eccentric shafts, the certification process requires all parts be manufactured specifically for use in aircraft. Mistral is developing the castings and CNC machining programs necessary to make all parts for the engine.  The company is investigating the use of aluminum side engine housings in place of the cast iron housings used in the Mazda rotary. If aluminum housings can be made durable enough, using plasma prayed coatings, Nikasil electroplating or the use of hypereutectic aluminum casting alloy, they would reduce engine weight by 40 pounds.

(Hypereutectic aluminum has a high silicon content of 16% to 18% resulting in much stronger parts.  In addition to strength, the hypereutectic alloy generally runs cooler and has 15% less thermal expansion than conventional engine part alloys.)

Rotary engines have been used by homebuilders for years and have been very reliable. Engine certification is very expensive and time-consuming, but Mistral will find a much broader market if it can complete the process.  At Airventure, two rotary engine installations can be seen in the automotive engine conversions rows along the flight line about half way north to the warbirds. 

FMI: www.mistral-engines.com