Pilot Training
by Jack Cairns
In the June 98 issue of AgAir Update, a Canadian pilot wrote about what an aspiring ag pilot should expect to find if he worked in Canada.
Now, lets find out from an old time ag pilot with dusting experience in England, Africa, California and the Southeast, plus time spent instructing at the Ayres Ag School, has to say to an apprentice pilot hoping to learn and survive in the ag business in the United States.
The Ayres school produced hundreds of ag pilots while it lasted, and except for a few guys who couldn't walk and chew bubble gum at the same time, no one washed out, except for four of 31 Algerian students who were sent home, and one fellow who showed up with his brothers license and lasted one flight. The school only gave student's the basics of ag flying and 120 hours of ground school, and except for those pilots who had a job waiting, expected the other graduates to further their educations with an operator willing to give them a chance.
The Canadian pilot was misinformed on several counts. The height of an aircraft normally has no effect on the swath width, that is, unless you open the money handle a hundred feet in the air, like some east zone ag pilots did in Egypt with the spray landing in the next field.
The swath width has several facets, among them, boom pressure, number of nozzles, the size of the orifice in the nozzle, their location on the boom and the length of the booms mounted under the wings, plus two of the most important things, the speed of the aircraft and the heat and wind conditions.
The formula in a hypothetical situation using a 400 gal 1340 Ayres Thrush is as follows: Swath width 50 feet x a length of 2640 feet, equals 13.2 acres per swath at 5 gallons per acre at a pressure of 30 PSI and using 40 D-12 orifices delivers 66 gallons at a speed of 120 mph, and takes fifteen seconds per pass. 340 gallons in the Thrush hopper should cover 5 swaths and would return you to the strip without any wasted time. The extra 10 gallons in the hopper protects the pump should the fan brake fail. The first pass uses 66 gallons, but you would still have 2500 lb's in the hopper, so I would trade the 120 mph for a climbing downwind 45 degree right turn to a minimum 90 mph, followed by a gentle 30 degree left turn into the wind, then letting the aircraft slide downhill to line up for the next swath, tweaking the throttle to maintain 120 mph over the fence.
You will notice that altitude plays no part in the turn, only that sufficient height is gained to clear any obstructions below.
The aircraft requires less power on the second pass, so small throttle adjustments will be required to keep that 120 mph. The next pass will use another 66 gallons and the climbing 45 degree right turn and the turn to the left can be made at a steeper angle requiring less time. A larger power reduction will be needed to maintain that 120 mph speed for the third pass. Swath number four will use another 66 gallons, and with most of the load gone, the aircraft will climb like a homesick angel and the turn should take less than 25 seconds. The last pass will find the aircraft hopper almost empty and you can head straight for the strip at pole line height because climbing higher only wastes time.
That scenario could have taken place in the central valley of California, as there's nothing but flat fields stretching as far as one can see, it is the best of all worlds for an aerial applicator.
I have always used whatever power the aircraft needed going to the field. With 340 gallons in the hopper and 40 gallons of fuel weighing 3160 lbs, I usually ran at 2150 rpm and 33 inches and the aircraft was never behind the power curve. Hold 120 mph on each swath run, insures that the quantity of the material is the same on every pass.
In hilly terrain going uphill, power will be required to maintain 120 mph on the first swath, and there is no thrill like having to turn down wind and stagger, often using full power through the rest of the turn almost at a stall. In all my many years of ag flying, I was never ashamed to take a minute or more for that first heavy turn.
I said nothing about using automatic flags to mark the swath. In California, most growers require operator to use human flaggers with a weegee, or other guidance systems. Accuracy is the name of the game, and woe betide the pilot caught wide swathing and streaking the crop. For that reason, California operators have always hired journeyman ag pilots with many years in the business.
Don't be fooled by ag pilots in other areas bragging about using 30 inches and 2000 rpm for the whole load. BS, at those settings the 985 is only putting out around 300 hp and with a 1340, only around 450. Another things is to hear some ag pilots say that using less than full power on the takeoff saves engine wear. Wrong, the 985 and 1340 engines require full throttle on takeoff, because the accelerator jet doesn't open until the throttle is wide open.
I want to know why anyone thinks that ag pilots other than the current crop, haven't' always been professionals? And baling wire and duct tape? Come on, get real, I came in this game many years ago, and I've seen a few airplanes land with telephone wire wrapped around the wings or tail feathers, but they were only an embarrassment for the pilot.
I can't speak about other areas, but I did most of my ag work in California and the South East for thirty years, and a few cowboys managed to get apprentice tickets, but most of them failed to stay the course and were soon gone. I can only assume that the write in question was never in Arizona, the San Juaquin, Imperial or Sacramento valley areas clear up to northern California.