Author: Jim Hiller
Edition: Model Aviation - 2005/03
Page Numbers: 112,114
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RADIO CONTROL JETS - 2005/03

Jim Hiller, 6090 Downs Rd., Champion OH 44481

Waiver Renewal and Fail-Safe

A while back I discussed the effect that the 2006 turbine-waiver-renewal requirements would have on us. I need to make a correction: after a thorough review of the rules as passed by the Executive Committee, existing turbine-waiver holders do not have to perform a demonstration flight in 2005 for the 2006 renewal. Thanks to Ilona Maine for her effort in researching and clarifying this issue. Ilona has sent this update out to all turbine-waiver holders with their AMA renewals.

The turbine shutdown within two seconds of fail-safe activation is a requirement. I bring this up again to remind all turbine pilots that the turbine will only shut down on fail-safe if you program your radio’s fail-safe to shut down the turbine.

Ilona sent out information on the best way to test this. Try simulating a fail-safe event on the ground:

  • Secure the airplane and start the turbine.
  • Shut off your transmitter and count to two.
  • By then, the fuel pump should be shut down, which instantly extinguishes the combustion flame on a kerosene-burning turbine. The engine will continue to wind down, but that is expected and not part of the two-second shutdown requirement.

Be careful and properly restrain your model when performing this test.

Cold-Weather Starting

It’s getting colder here in Ohio, and winter flying is the only flying we get short of traveling to Florida. I use Coleman Powermax as my starting gas, and cold temperatures affect it greatly. The cold reduces the gas pressure—often to the point where I cannot get enough starting gas into the turbine to reach the heat and rpm necessary to complete the start sequence.

To combat this, I keep my starting-gas bottle warm by storing it under my coat or in a heated car. If you’re having trouble starting your turbine in cold weather, check your ground-support unit to ensure you are getting enough heat and rpm during the start sequence to advance to the fuel-pump start sequence. Winter flying with turbines can be fun—there is no cold chill from the propeller blast. Just hit the start switch and go fly.

Market Growth and Smaller Turbines

Last year saw huge expansion in the turbine market—not so much from new manufacturers as from growth in variety and an increase in turbine size and power. We now have turbines from roughly 7-pound thrust through 35-plus-pound thrust, available from multiple sources.

The newer, smaller turbines in the 7- to 14-pound-thrust range let us fly smaller, more affordable models, many of which started life as ducted-fan models. These smaller power plants have brought new life to many old 91-size ducted-fan models by providing much more power with minimal weight gain. Because these turbines are smaller than the ducted-fan setups they replace, they often allow room for the additional fuel a turbine requires.

Specific Turbine Models

  • Wren MW-44 / SimJet 700: The Wren MW-44 and its SimJet equivalent, the SimJet 700, are in customers’ hands and flying well. They push old 45-size ducted-fan models around with authority. Jet Hangar Hobbies supplies the MW-44, which provides ideal power for the company’s line of ducted-fan models now converted to turbine power.
  • FunSonic (Robart): Robart Manufacturing has been distributing the FunSonic for slightly more than a year, and it is finding a great place in the market. It is the smallest and lightest of the 12-pound-thrust turbines and comes with accessories including the ECU, battery, fuel pump, and related items. Onboard starting is accomplished by an electric motor engaging the compressor wheel to spin up the turbine. As do nearly all of today’s smaller turbines, the FunSonic has low thrust at idle. This is important when converting a ducted-fan model to turbine power—few of these older sport aircraft have drag-inducing flaps to aid in setting up for landing, so good low-idle thrust is as important to the enjoyment of flying as full power.
  • Wren MW-54: Stepping up in size, the Wren MW-54 (available from Jet Hangar Hobbies) is offered in a 12-pound-thrust version or the Mk.II in a 14-pound-thrust version. You can get it as a kit or prebuilt. The kit is a great way to learn turbine construction and maintenance. A nice option is the full onboard autostart; to reduce weight you can omit the onboard starter motor and use a removable electric starter instead.
  • SimJet 1200: The SimJet 1200 has been around for quite a while and remains popular. Distributed by Great Northern Models in North America, it comes with onboard autostart. One option from SimJet is an IR ground-support terminal: you stand next to the airplane, point the terminal at the model, and read your running turbine’s performance numbers.
  • PST 12-pound turbine: The 12-pound-thrust PST turbine features onboard autostart and is distributed by HeliJet International.
  • Artes Bee and Super Bee: Manufactured in Mexico City and distributed by Artes Jet USA of Los Angeles, the Artes turbines come with fully automated digital ECU (FADEC). My Artes came with an optional air-start line plumbed in. I’ve flown many models with this engine and found it reliable. The FADEC is a good, lightweight controller with many operator features and is quiet in terms of radio-interference noise. I have not had a single shutdown from my programmed fail-safe with this ECU, including in twin-turbine installations; the shutdown sequence is almost immediate.

Service and Support

Service is an important consideration when purchasing a turbine. For the FunSonic, which is manufactured overseas, Robart services minor issues in its shop and ships to the original factory for major repairs.

SimJet service is done on a limited (though developing) basis by Great Northern Models in Canada, which shops major repairs to the overseas factory when required.

Paul Pignet of Artes Jet USA arranges service for Artes turbines. For major repairs, he will overnight a completed UPS shipper with the proper information and international shipment forms. You package your engine and call UPS, which will deliver it to the Mexico City factory for repairs. I used this service to update my turbine and was satisfied with the ease of it.

The Artes name carries meaning for those who have flown turbines for the past decade. Jesus Artes was part of the team, including Kurt Schreckling, that brought the KJ-66 to production as a kit and supplied components for many turbine manufacturers. The KJ-66 is the basis for much of the class of 17-pound-thrust turbines that developed up to the 28-pound-thrust turbines we fly today.

Performance and Fuel Usage

I have been fortunate to have flown almost all of the turbines mentioned, and I’ve been impressed. These smaller power plants are some of the nicest-handling turbines and among the fastest-accelerating from idle to full throttle. Most are as fast as the AMT Mercury, which is the benchmark for throttle-up time.

Fuel usage allows you to fly the 12- to 14-pound-thrust turbines with 50 to 64 ounces of onboard fuel and achieve good five- to seven-minute flight times. These smaller, lighter airframes and landing-gear systems cost significantly less than those of the larger turbine models, which has motivated a growing group of modelers to try turbine power.

Sources

Transcribed from original scans by AI. Minor OCR errors may remain.