The following article is part of a regular column printed in AgAir Update that looks back 20 years.
AMERICUS, GA — It was just too interesting, too inviting, to have two Turbine Braves based within 30 miles of each other with a different combination of turbine engines. I had to see if I could set up a couple of evaluation flights for these two remarkable ag planes, and form my own opinions.
The first Turbine Brave I flew was nine years ago. Jim Mills of Turbines, Inc. in Terra Haute, Indiana was fabricating the conversion. He had the aircraft at Kosola and Associates in Albany, Georgia for engineering design work. I flew the aircraft and found it to have amazing performance (see AAU June 1992). One of these Turbine Braves was a twin to the one I flew several years ago.
PT6A Turbine Brave
Frankie Williams of Souther Field Aviation is the owner of the PT6A-powered Brave, with a -20 engine. Frankie traded Jim Mills an Ag Cat for the 1976 Brave. After operating the Turbine Brave through the 2000 season, Frankie says he couldn’t be more pleased. “Bill, I have a lot of small fields, with some of them as far away as 15-20 miles. With the speed and the agility of the Turbine Brave, I found the aircraft to fit my operation perfectly,” explains Frankie. He operated Cessna Ag Trucks/Huskys for more than 9,000 hours.
In 1998-99 Frankie operated a 400 Brave, piston-powered. His annual average production rate was 84 acres an hour. With the Turbine Brave, working the same fields, the annual average production rate increased to 105 acres an hour (25% increase), with less maintenance, less effort and more safety.
Frankie works his Brave at 130-135 mph, using 20 pounds of torque at 2,000 rpm. The PT6A-20 is rated for 550 shp at 39 psi and 2,200 rpm, however for the Turbine Brave installation, the engine is derated to 400 shp with a torque limit of 29 psi. This torque limit is always obtainable, under any environmental conditions. Thus, there is never a shortage of horsepower. Frankie typically limits his takeoff power setting to 25 psi and 2200 rpm. Fuel burn at working power settings averages 28 gph.
The aircraft is outfitted with 40 CP nozzles, using the middle size hole at 40 psi; most of the work is 3-5 gallons per acre. Swath marking is with an Ag-Nav GPS unit. Although Frankie’s fields are so small GPS is not really needed. However, since Souther Field Aviation is an Ag-Nav dealer, it seemed appropriate to operate one, offering his customers an immediate back-up if needed.
Frankie explained that typically a PT6A-20 with a fresh IRAN cost under $100,000. With his particular Turbine Brave, he figures he has about $175,000 in the aircraft with the conversion.
Pre-Century Turbine Brave
About 30 miles east of Americus, near the rural community of Unadilla, Georgia, a Garrett Pre-Century Turbine Brave resides, owned by David Chancy of A&C Aviation. Many of you know David from a company, Davidon, that he is in partnership with Don Hays, the DRP-955 folks. This company also manufactures the Hi-Tek Rotary Atomizer for controlled droplet sizes applied at low volumes.
David bought his Brave from a local operator where it had been abandoned under pecan trees for eight years. The A&C Aviation shop literally stripped the aircraft to the “bare bone”. The piston engine was discarded and replaced with a Garrett Pre-Century 43BL, derated from 575 shp to 400 shp. The engine core was purchased from Dodson International and sent to Smyrna Air Center. Calvin Mudgett at Smyrna Air Center dismantled the engine and gearbox, inspecting and repairing as necessary (IRAN). He advised David that after 1,000 hours to return the engine for another inspection. Depending on what is found during the inspection, the cost could be a little as $5,000 for 1,000 hours of operation. The Pre-Century engine is considered a 2,000-hour engine.
Part of the rebuild for the A&C Aviation’s Brave included powder coating the fuselage, landing gear and all bolt-on parts. This process is used extensively with race cars. The powder coat process is a method of corrosion protection, with one coating to bare metal that serves as the primer and paint. The rest of the aircraft, i.e. wings, side panels, etc. were primed and painted normally.
Although Frankie Williams’ PT6A-powered Brave is a Mill’s Conversion with an STC, David Chancy’s Garrett-powered Brave conversion is based on a 337 field approval. The design work for the Garrett Brave comes from J.R. Davis of Texas, that was later picked up by the late Bob Song of Kansas.
The Evaluation Flights
Graciously, Frankie and David allowed me to fly the two aircraft. The weather was reasonably cool, with neither aircraft filled with water. However, the PT6A Brave outfitted with a spreader and the Garrett Brave with an all-new design liquid spray system, both possessed excellent flying characteristics.
I flew the PT6 Brave first and immediately noticed upon roll-out on the pull-up from a spray run the ailerons went to the stops before the aircraft began its roll. I found the same for the Garrett Brave. It didn’t really make a negative difference, actually it was somewhat of a comfort, knowing the risk of over control is substantially reduced. I didn’t consider it a problem.
Both aircraft worked across the field in the 130-140 mph range. I noted the Garrett Brave was faster. However, that could be the difference in the way a pilot sets the power. With the PT6 the engine’s torque limit is 39 psi, however, for the Brave installation the cockpit torque gauge is red-lined at 29 psi, limiting takeoff shaft horsepower to 400.
With the Garrett Brave the pilot pays more attention to the ITT gauge with a limit of 535°C that basically translates into 400 shp. The engine’s limits are actually 575 shp at 576°C. The working ITT setting is 480°-490°C, while I flew the aircraft at 450°C. When I pushed the throttle forward until the ITT gauge reached 500°C, the airspeed picked up to an indicated 150 mph, lots of wind noise and more or less an uncomfortable feeling. Maybe this was because I had been told the indicated airspeed was 15 mph less than the WAG GPS indicated! I think most ag pilots would agree 165 mph airspeed is a bit too fast!
I talked extensively with both Frankie and Garrett Brave pilot, Jeff Reed, about how the two aircraft performed during the summer with a load. Both related the same basic observations. The aircraft is light to the touch. It is quick to and across the field with a load. Both aircraft work any time, under any condition with 250 gallons. At the end of the day, both pilots are as comfortable with the last load as he was with the first.
With Frankie Williams and David Chancy, each was looking for a cost-effective way to upgrade their flying services to turbine engine power. Frankie for years had operated the Continental opposed engine, while David is still operating the PZL-3S 600 hp radial engine. With the trend to lower application rates, the desire for turbine reliability and productivity, Frankie and David feel they have found this with the Turbine Brave.
