I had flown the GE-powered 510-gallon Thrush almost a year ago at AgAir Update’s Open House and Hangar Party. Then, it had the same 3-blade Hartzell propeller as the P&WC PT6A-34 510 Thrush with the exception the GE prop was shot peened. Dennie Stokes also flew it that day and we felt the aircraft did not have the “get up and go” on takeoff for 800 SHP. This time, at the Thrush factory, the 510G had a 4-blade Hartzell propeller. This prop was the fourth generation of propellers fitted to the H80 engine for the Thrush.
Overall, I was extremely pleased with the performance of the H80 510G Thrush. Flying it with an empty hopper and 228 gallons of fuel on board for the first load, there was no doubt on takeoff the aircraft had “get up and go”. I found the 510G to be about 10 MPH faster than its sister 510P. At 500 feet AGL, 160+ MPH was easy enough to obtain with 90% torque and 1,900 RPM. Full 800 SHP is 100% torque and 2,080 RPMs.
Satisfied with the empty performance of the 510G, I made another load with 350 gallons and I guess about 200 gallons of fuel. The Electronics International MPV-50 instrument gauge (which is the cat’s meow) does not indicate any more than 82 gallons per side, but neither does the old analog fuel indicators, pegging full at about 80 gallons per side.
The true purpose of flying the aircraft with only 350 gallons was to loosen the rust on this ag-pilot’s skills. I can’t remember the last time I flew an ag-plane after running the hopper over on the tarmac. So, I felt it prudent to fly with a piece of a load, just to be sure the “like riding a bicycle, you never forget” saying held true with flying a loaded ag-plane. It did.
For the third load, the fuel level was still somewhere above the indicated 164 gallons and I ran the hopper over onto the tarmac with water. Taxiing out, the aircraft felt like any heavily loaded aircraft with its gross weight somewhere over 10,000 (4,800 empty weight + 1,080 pounds of fuel + 200 pounds of pilot + 4,080 pounds of water = 10,160). The 510G is certified for a maximum gross weight of 10,800 pounds. With water, it would be next to impossible to exceed that limit. Really doesn’t matter, because the aircraft has the ability to carry far more than 10,800 pounds.
Adding power to 100% torque and 2,080 RPMs for takeoff, the tail was up at 1,300 feet and the aircraft was off the ground at about 1,700 feet climbing steadily at 100 MPH. However, there was a reported 7-8 knot headwind and the outside temperature was 74dF. In my opinion, the advantages of the wind and temperature were easily offset by this out-of-practice pilot. No doubt a current Thrush pilot could easily beat my numbers.
I ferried the 510G to the field using 90% torque and 1,900 RPMs. My IAS was 160 MPH, loaded. I used the same power setting for the spray runs and found myself moving across the field at 165-170 MPH. I know the general rule is that airspeed is about 25 MPH faster than the ideal airspeed for spraying, considering the spray pattern. In the case of the 510G, that has been disproved by USDA spray pattern analysis that indicate application speeds up to 180 MPH are acceptable. The pattern may be acceptable, but the pilot better be up to speed too; the trees are coming at you pretty fast.
The fuel flow on the MPV-50 was not calibrated to the GE H80. I know this because it was reading 35 GPH at high power settings. Jody Bays, vice-president of Thrush Aircraft and test pilot, told me I was burning about 80-85 gallons an hour. That’s a lot of fuel, but you are traveling pretty fast. If you can justify the fuel burn, a degree of time can be made up in the ferries. After my 350-gallon load, I believe once the load is worked down, most pilots will reduce the power to about 80% torque and save the fuel.
At Jody’s request, I had previously stalled the aircraft at altitude before approaching a stall in the turns with a load. He was correct in that the aircraft is a gentle giant in that it simply does not do anything unusual in the stalling configuration. I took it to full stall empty, but admit I only approached to a stall (horn blaring, stick slightly mushy) loaded in the turns. Who in their right mind would want to be in a relatively steep turn, loaded and stall the aircraft, not to mention I was low to the ground. There is no reason to fully stall the aircraft loaded and turning; the aircraft gives you plenty of warning beforehand.
I could find zero wrong with the aircraft, except maybe, it needs a bigger hopper. It flies like a dream, not unlike the older, short wing, 400-gallon, rag tail, -34 Thrushes, except it has a 25% larger hopper, double the fuel capacity and will out run the older Thrush like “a scalded dog”. I’m willing to bet the 510G will outrun any Thrush...
Read more about this fabulous (coming from a 20-year Thrush pilot) aircraft in the January edition of AgAir Update.
Until then, Keep Turning...
Bill
