Home-United States20 years ago - Is there a 660 in your future?

20 years ago – Is there a 660 in your future?

SOUTHEASTERN U.S. — Could there be an Ayres 660 Thrush in your future? Is it possible that you, like four other operators in the U.S., have decided that bigger is better? With all the hoopla of the Ayres 660 finally making its way to the ag aviation marketplace, four operators have made the decision to buy a 660 and so far, none are regretting it. AgAir Update visited with three of these operators and conducted a telephone conversation with the fourth, asking questions about how they liked their investment thus far.

Ayres Corporation has dedicated an enormous amount of time and research to produce an excellent ag aircraft. In doing so, operators have only found minor issues that Ayres Corporation has been addressing.

Stokes Flying Service

Dennie Stokes has been operating Thrush aircraft since he started his flying service in 1981. Starting out with an R-1340-powered Thrush, Dennie has operated just about every model Ayres Corporation has to offer with the PT6 engines. Presently, Stokes Flying Service operates three 510-gallon Thrush, one with a PT6A-34 engine and the other two with PT6A-45 engines. In May of this year, Mid-Continent Aircraft Sales delivered Stokes Flying Service an Ayres 660 with the PT6A-60 engine to add to the fleet. Another Ayres 660 was delivered in September and has the PT6A-65 engine.

Stokes Flying Service operates primarily from three locations, with two only a few miles apart. At the Parkin operation, the primary base, Stokes bases the 660 and a -45/510. From Dennie’s home in Earle, his son Tracey flies a -45/510. And, pilot Andy Davis works a -34/510 from Seypell, Arkansas. It’s too early to tell where the second 660 will be based, but most likely it will see service in Earle with Tracey at the controls.

Dennie is satisfied the 660 has a respectable swath of 75 feet for herbicide applications, 75-80 feet for insecticide and 72 feet for Roundup work. The swath for Roundup applications was pulled in three feet for an extra margin of comfort. The applications are typically flown at 140 mph using SATLOC GPS for guidance. Dennie’s 660 just had the latest SATLOC model with new screen technology and a 686 Pentium computer installed. Also, Dennie has installed a modified step that prevents the spray from accumulating on it.

Dennie says the elevator is about equal to the forces needed to move the elevator on a 510. However, Dennie says there is rarely a need to adjust either the elevator trim (in a turn) or the rudder trim once the aircraft is out of the takeoff mode. The ailerons are extremely sensitive and well-balanced, with their design extending to the wing’s tip.

Dennie reported the PT6A-60 with its 1,050 shp has ample power for operating from Stokes Flying Service’s Earl and Parkin airstrips. Dennie hasn’t had any difficulty developing full power (red line on torque) on 100° F days. Typically, Dennie flies the 660 with 80 gallons of fuel per side from a 2,000-foot paved runway. 650-gallon loads are a piece of cake, an easy load for the 660. Stokes Flying Services’ second 660 has the PT6A-65 engine, 1,300 shp. Dennie explained there were some short farmer-furnished unimproved strips where he felt there would be a need for more power during takeoff.

How much more work from the 660 can an operator expect? At the time of this interview, Dennie had flown the 660 more than 265 hours, working both dry fertilizer on rice and various liquid applications. His definition of more productivity is the 660 stays right with the -45/510 Thrush, load for load, only the 660 is carrying an additional 1,000-pound payload, for a total of 3,800-4,000 pounds of urea. Additionally, when the 660 lands closely behind the 510, it will be loaded with its extra 1,000 pounds of fertilizer and depart down the runway ahead of the 510. Dennie attributes this to the new hopper lid Ayres Corporation designed for the 660. It opens up wider, quicker with the two over-center latches and the ends are equal in size for a quick fill from Stokes Flying Service’s 12-inch auger.

Dennie figures the 660 is a solid 30% more productive than his -45/510s, since he is carrying 30% more material, load for load. As for the -34/510, Dennie says that during the course of the day, the 660 on longer ferries could “lap” the -34/510, getting in an extra one or two loads; an estimate of 30-35% more productivity with the 660.

Stokes Flying Service uses both the Transland 22007 deep throat spreader and the Breckenridge 12-vane spreader. Either one gives a good pattern for dry fertilizer. According to Dennie, the Breckenridge mounted on the 660 provides a little wider swath, while the Transland flies and handles the heavier volumes of fertilizer applications better. Stokes Flying Service has bought its own dry evaluating equipment from WRK and will be doing more pattern testing this fall.

Stokes Flying Service has the modified step added to their 660.


Stokes’ and Henry’s 660 has the thicker mesh engine air inlet screen, while the later versions of the 660 (Wil-Co’s pictured) are outfitted with a thinner mesh screen allowing for more air to enter the plenum. Both Stokes’ and Henry’s mesh screens will be modified by the factory.

Henry’s Aerial Service

If there is one thing I found to be true, it was the consistency of the comments made by each of the new Ayres 660 Thrush operators. No one knew anything about what the other had told me, but in every case, the same numbers, ideas and comments were emerging.

In Brinkley, Arkansas I visited with father and son, Eddie and Darrin (the son) Henry of Henry’s Aerial Service. They traded-in their -34/510 Thrush to Pete Jones of Air Repair for their new Ayres 660 Thrush. They kept their -42/510 (850 shp). In the six weeks Henry’s Aerial has operated their 660, they have logged slightly more than 150 hours. “We put the 660 to work at the tail end of our rice season spreading fertilizer. I like it,” simply put by Darrin. The 660 has been performing well for the Henrys. It is powered by the PT6A-60 engine. They have had no difficulty making power to easily depart from a 2,000-foot strip.

Darrin is assigned the 660, while Eddie flies the -42/510. Darrin gives the new hopper lid high marks. He is equally satisfied with the way the aircraft handles in windy conditions.

Like Stokes Flying Service, the Henry’s 660 carries 1,000 pounds more fertilizer than the 510 Thrush, is fast to and from the field, and quick when it comes to loading. Henry’s 660 will work from any strip their -42/510 will work from with an extra 1,000-pound payload.

Eddie commented, “The 660 flies a little differently than the 510. But, we’ve found it easy to get used to.” Dennie and Darrin both commented that the 660 easily carried 650 gallons.

The Henrys are using the Breckenridge spreader with a 65-foot swath at 200 pounds per acre application rate. Cutting to the 100-pound rate extends the swath to 80 feet. Dry fertilizer is applied at 155 mph.

Five-gallon work is flown using a SATLOC with flow control and CP Nozzles at 75 feet, while herbicide work and ten-gallon work is applied using 70 feet for a swath width.

“We are really happy with the way the 660 handles, especially the aileron control. It is a safe aircraft that gives you plenty of pre-stall buffet before any kind of a stall occurs. And, our farmers really like the 660, actually thinking the aircraft is going slower. We guess it is an illusion from its size,” both Eddie and Darrin concluded.

The Henrys reported their 660 was burning about 75-80 gallons of fuel per hour with power settings ranging from 30 psi down to 23 psi while working the aircraft. Eddie and Darrin commented they would like to see a bottom fuel loading system become available for the 660. The Henrys also told me they were getting longer life from their K&N barrier air filter, changing the first one after 130 hours. They believe because the filter is recessed in the plenum it is coming in contact with less dirt.

Henry’s Aerial’s 660 is outfitted with a full three-inch stainless steel spray system by Transland; all the way to the end of the booms. With 82 CP Nozzles, the system easily delivers 10 gallons per acre application rates at 150 mph.

Wil-Co Flying Service

Leaving a pair of happy Thrush pilots, I traveled further south to De Witt, Arkansas to visit with Barry Wilson of Wil-Co Flying Service. Barry had just taken delivery the day before of his new 660 Thrush. Outfitted with a PT6A-65 engine, it is painted with Alumagrip in traditional Thrush yellow.

Wil-Co Flying Service operates two -34/510s and one -42/510 Thrush. It will be selling one of the -34/510s and replacing it with the 660 (see AAU Trader’s cover, September 2000). Because Wil-Co’s season was about to end, I wondered aloud why Barry would buy the 660 this time of the year.

“Bill, I was one of the first to express an interest in buying a 660 a few years ago. I’ve had to add an extra Thrush while waiting for the 660. I could have waited until spring, but Pete Jones had this aircraft outfitted just the way I wanted it and the deal he made me was too good to turn down. I don’t know if I’ll need the extra horsepower of the -65, but if I do, I’ll have it. We work from several unimproved strips, and I simply have to be able to get off with a load,” Barry explained.

Most of Wil-Co’s work is wheat and rice. That means a lot of fertilizing. Barry feels the 660 will relieve the pressure on the pilots to stay caught up during their busy season of May through July. “When I was figuring on buying the 660, I was counting on a 20% increase of productivity. We have been operating our 510s 700-750 hours a season. A 600-hour season would be much better and that’s what I’m looking for from the 660.” Barry was delighted when I told him the Henrys and Dennie Stokes figured the 660 was more like a +30% increase in productivity over the 510.

Barry Wilson has been quite a success story. He flew for Double A Flying Service for six years, before he and his grower partner, Drew Counce, opened their  own operation in De Witt six years ago. They have always operated the Ayres Thrush and are completely satisfied with the aircraft’s reliability and overall toughness. Barry has built up Wil-Co Flying Service to the level where it is working three Thrush ag craft a combined 2,000 plus hours a season. With the 660, some of the pressure will most assuredly be removed.

Not one to put off projects, Barry plans to begin setting up his 660’s spray system and spreader (Transland’s 22007) this fall with Dr. Dennis Gardisser. The SATLOC unit needs to be installed and Barry is planning on returning the 660 to Air Repair for the installation.


This is the hopper lid on Wil-Co’s 660, the new one everyone is so excited about. AAU believes this would be a good modification for the 510.

Air Repair

After I left Wil-Co in Arkansas, a quick flight over the Mississippi River placed me at Pete Jones’ Air Repair in Cleveland, Mississippi. Air Repair delivers an Ayres 660 slightly modified. The wing is marked to easily find the fuel cap, an assist handle is installed to help with mounting the wing from the front, all the side panels are taped off with clear anti-chafe tape, the boom pressure gauge transducer is mounted inside the aircraft, protecting it from the elements, a start-flight counter is installed, all bolt heads, nuts, and rod end bearings are coated with Par-Al-Ketone, the aircraft is treated with Corrosion X, a deflector plate is mounted to the forward end of the tail wheel spring and a drain hole for rain water is drilled in the tail gear.

“These are small, but important items that we’ve found help keep our customers happy with their investment in a Thrush,” Pete explained. Pete has been a Thrush dealer since 1995 and usually delivers 6-10 new Thrush each year. Air Repair has one more 660 coming off the assembly line in 2000.

Air Repair, Inc. modifies its 660 customers’ aircraft with several mods, of which three are pictured above; (L-R) deflector plate for tail wheel spring, transparent leading edge tape for horizontal stabilizer and an assist handle attached outside the hopper aft of the firewall.

Tri-Rotor Spray and Chemical

Upon arrival back at the office in Georgia, a call to Larry Smith of Tri-Rotor Spray & Chemical in Ulysses, Kansas was made. Larry has an agav operation that can meet just about any requirement that a grower would need. His company has a fleet of three turbine-powered ag planes that includes an Ayres 660 (sold to Tri-Rotor by Dave Johnston of Johnston Air Service in Tulare, CA), an Air Tractor AT-602 and an AT-302 powered by a Garrett TPE-331-1 (after removing the Lycoming 101 turbo prop engine). The Ayres 660 is powered by a PT6A-65, while the AT-602 is powered by a PT6A-45 engine.

However, in addition to Larry’s three ag planes, his company also uses three Hiller helicopters, one turbine-powered and two recip-powered. And, to compliment the six aircraft, Larry’s company uses two ground machines as well; a well-rounded company when it comes to meeting the spraying needs of its customers.

When I telephoned Larry, he had been busy spraying army worms in alfalfa, gravy work at the end of a good year. Pilot Danny Craig had already logged over 250 hours in the Ayres 660. Danny has told Larry that he really likes the stability of the 660. It flies like a Thrush and handles great on the ground or in windy conditions. Larry’s comment was Ayres Corporation had made a lot of good improvements to the Thrush line with the introduction of the 660.

Operating from 3000 MSL, with temperatures +90°F full loads any time of the day are the norm. In Kansas the 660 typically flies over row crops planted under pivot systems with 1/2 mile runs covering 125-acre blocks. Currently, the 660 is in Plains, Texas working a boll weevil contract. In the winter, the 660 will work in Yuma, Arizona treating produce crops. The overall annual average application rate for Tri-Rotor is 4.46 gallons per acre, according to Larry’s calculations.

“The 660 is a money maker. It can be slowed in the turns allowing for a shorter turn radius and a quicker return to the field. And it’s very fast for ferrying, all adding up to a high-production aircraft with its full hopper capability anytime, anywhere,” summarized Larry, with his opinion of the 660.

In Summary

A 660-gallon ag aircraft has its own special niche. With a few modifications, a fleet of 660s have already been ordered by Kelner Ayres Center in Thunder Bay, Canada for forestry work in the North woods. It has the capacity to work hard in the rice environment, work fast ferrying from strip to field and back, while at the same time able to fly slow for tight, hard to get to jobs. The 660 is truly a versatile ag aircraft filling its flying role spraying row crops in Kansas, produced in Arizona, and spreading fertilizer in the Delta, with forestry/fire missions on the horizon in Canada. It has been a long wait, but one that surely will have been worth it.





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