|The Thrush 510G demonstrates some of its capabilities for the audience at EAA AirVenture Oshkosh 2013 on Tuesday. (photo by Phil Weston)
By Dave Higdon
August 3, 2013 - With 800 hp of GE M80 turboprop smoothly spinning its Hartzell prop, the Thrush 510G cleared a line of tall trees by scant feet as it smoothly swooped below from tree-top high to crop-top low and started its 100-knot run across the farm field on a track toward the opposite treeline.
Those trees quickly grew taller in the windscreen before a bit of stick back pressure brought the Thrush into a quick, shallow climb inches over the trees; a quick bank right, another sharply left, roll out parallel to the track just flown, repeat.
Welcome to the world of agricultural pilots, the aerial applicators on whom farmers widely depend to help them fertilize and protect the crops that feed a world.
"The airplane flies easy because the pilots who work this get paid by the acre," explained Thrush factory pilot Terry Humphrey. "They'll fly 11, 12, sometimes 13 hours a day, often in rough environments.
"They need a workhorse that doesn't work them."
Air support for farmers
Crop dusting - "aerial applications" formally - is civil fast-moving, low-level air support for farmers; ag planes must excel at maneuverability, flexibility, and efficiency.
Thrush Aircraft designed the 510G to meet those needs and employs the newest contender in the world of turboprop power, the GE H80 - an evolution of the Walter M601 developed after the Ohio company's acquisition of the venerable Czech Republic engine maker.
Thrush designed the two-seater to train pilots in some of aviation's most-demanding flying and it is virtually identical to the single, save for that extra seat.
Thrush received the type certificate for the single several months ago while continuing work on the two-place version. But this is no stripped-down trainer. Standing tall on its conventional gear, the two-seat 510G sports all the basic features of the single-seat model.
Those features include a 3-inch pipe fitting for pressure-filling payloads into a tank, which can deliver up to 66 cubic feet of dry chemicals or 510 gallons of liquids.
"Efficiency and speed - those are key when you get paid by the acre," Humphrey said.
Center-line doors in the belly let the 510G serve as a water bomber for fire-suppression - and the maneuverable Thrush seems particularly suited for the job. "They can get this in and out of spots larger water bombers can't," Humphrey said.
"Depending on the job and the spray volume needed, these pilots may be landing every few minutes." Other jobs, like low-volume spray for grasshopper suppression, can have them droning along for hours on a single load.
Regardless, the plane needs to handle either extreme with equal alacrity. Versatility is key. "These guys might by laying down dry applications on one field and wet on the next, and a couple of fields later, back to dry," Humphrey explained.
Delivering the goods
In some sample flying of the 510G by a crop-dusting novice, the aircraft showed itself to be responsive and maneuverable, but with a little less of the harmony pilots enjoy in more pedestrian machines.
Large ailerons produce quick response with finger and thumb inputs; significant adverse yaw demands active and precise inputs to the large rudder, which delivered on par with the ailerons; anti-servo tabs on each aileron help keep the plane at the bank angle of choice with minimal work.
Pitch pressures increase proportionally as the pilot deviates from its trimmed airspeed, just as you want in a big airplane that spends so much time descending and climbing out of tight spots.
Both visual and audible stall warnings are standard, but the aerodynamic buffet preceding stall served as a wake-up call more insistent than any alarm clock.
The stall break comes gently with no flaps - and not at all with full flaps. But the pilot must attend to the slip/skid ball or risk an undesired result. These were maneuvers sampled with the airplane light.
The 510G weighs in empty at a svelte 4,600 pounds. At its 10,600-pound maximum weight, Humphrey stressed that control pressures and responses are pretty much the same - just at higher speeds.
High-performance low-level flying
Thrush's 510G two-place is flying the week at EAA Oshkosh to show off some of the traits that have already helped launch it toward sales success. Last week China ordered 20, six of them the two-place model.
And its career of low-level, high-efficiency work is just beginning.
"The dual 510G is a workhorse," said Thrush President Payne Hughes. "We're seeing it used for everything. I anticipate it will become one of our bestselling planes."
With an ag plane as the hero in an upcoming movie and after years of watching Gene Soucy work out his Showcat, a converted Grumman Ag Cat, watching Thrush's 510G do its stuff Tuesday serves as a reminder the importance of general aviation to putting food on our tables.