How do crop dusters know where to go? Field IDs, maps and GPS

How do crop dusters know where to go? The job starts as a field ID from the grower, becomes a map with marked hazards, and ends as GPS swath lines in the cockpit. This guide explains each step for Sacramento Valley fields, and what a grower sends so the plane treats the correct field.

How do crop dusters know where to go, from the first call to the field?

A crop duster knows where to go because several people pass the job forward, one step at a time. Each step adds information that the pilot needs in the cockpit. A typical job follows this chain:

1. The grower or the pest control adviser (PCA) identifies the field and the job.
2. The operator turns that information into a work order and a field map.
3. The operator marks power lines, homes, water and sensitive crops on the map.
4. The field boundary goes into the GPS guidance unit in the aircraft.
5. The ground crew loads the product at the airstrip, and the pilot ferries to the field.
6. The pilot checks the field from the air, then flies each swath on GPS.
7. The GPS unit records the passes, and the operator tells the grower when the job is complete.

The ferry is the flight from the airstrip to the field. From our airstrip in Live Oak, Yuba City is about 7 miles in a straight line, and Willows is about 34 miles.

How do crop dusters know which field to spray?

The grower gives a field identification (field ID), and the operator turns it into a boundary on a map. In the Sacramento Valley, many fields of the same crop sit side by side. From the air, one rice field can look like the next one, so an address alone is not always enough. Our mapping software and ag real-estate background usually give us the field layout and acreage from one good ID. We then confirm the boundary with you before the job.

California adds one more ID for pesticide jobs. Before a production agricultural pesticide use, the property operator gets an operator identification number and a site ID from the county agricultural commissioner. The grower must give each pest control business that treats the property those two numbers, according to the DPR pesticide use enforcement compendium, chapter 4. A field, or part of a field, within ¼ mile of a school needs its own site ID.

If you do not know your numbers, our guide on how to find your APN or FSA farm and tract number shows where to look.

Each field ID tells the operator something different, so the best request gives two of them.

What goes on an aerial application work order?

An aerial application work order is the job sheet that goes with the plane. It turns the grower's request into instructions that the loader and the pilot can follow. Each line answers a question that the pilot cannot answer from the air.

The product line always comes from the label and the written recommendation of the licensed PCA. The operator does not choose a product or a rate for a pest. Our guide to pesticide application rules in California explains PCAs, permits and the notice of intent.

Federal rules also require a record of each job. Under 14 CFR 137.71, a commercial operator records the customer's name and address, the date, the material and its quantity, and the pilot. The operator keeps those records for at least 12 months.

This table shows what a complete aerial application work order holds, who supplies each item, and how the pilot uses it.

How does crop duster GPS guide each pass?

Crop duster GPS is a swath guidance system: a satellite receiver and a computer that draw the flight lines for the field. Almost every operator uses it. In the 2019 NAAA aerial application industry survey, 99 percent of operators used a GPS device for swath guidance.

The operator loads the field boundary from the work order. The pilot sets the swath width, which is the strip of crop that one pass covers. The unit then draws parallel lines across the field, one swath width apart. A lightbar or a screen in front of the pilot shows how far the plane is left or right of the next line.

Many systems also log each pass, and some turn the spray on and off at the boundary. The same survey found liquid flow control on 64 percent of ag aircraft and dry flow control on 30 percent. Flow control holds the rate steady when the ground speed changes.

Before GPS, ground workers called flaggers stood at each end of the field. They moved one swath width after each pass to mark the next line for the pilot. GPS took those workers out of the flight path. GPS does not show a new power line or a person in the field. When the map is out of date, how do crop dusters know where to go? The pilot checks the field by eye before the first pass.

What does the pilot check before the first pass?

The pilot examines the field from the air before the first pass, at a height that clears the obstacles. Federal rules expect this step. The knowledge test for ag pilots under 14 CFR Part 137 includes a survey of the work area before the operation starts. The pilot looks for:

• Power lines, guy wires and towers, including new lines that are not on the map
• Trees, wells, pumps and buildings at the field ends, where the plane pulls up and turns
• People, vehicles and equipment in or next to the field
• Beehives, livestock, water and the crop in the next field
• Wind direction and speed, from a smoker on the aircraft, a windsock or a ground report

A smoker puts a thin smoke trail into the air to show the wind. In the 2019 NAAA survey, 81 percent of ag aircraft had one. If the wind is wrong, we wait.

Section 137.49 lets a pilot fly below 500 feet outside congested areas only during the application, including the approach and the turns. The flight must not create a hazard to people or property on the ground. Part 137 also requires a commercial operator to have at least one pilot with a commercial or airline transport pilot certificate. Our posts on why crop dusters fly so low, spray drift and FAA Part 137 explain these rules in full.

How to prepare a field for aerial application

The grower can make the job faster and safer with a few steps before the plane arrives. Do these steps when you request the job, not on the morning of the flight.

1. Send two field IDs, for example the APN and the FSA farm and tract number.
2. Send your operator ID and site ID for a pesticide job.
3. Send the written PCA recommendation with the request.
4. Mark power lines, towers, wells and tall trees on the map.
5. List the homes, schools, canals and sensitive neighbor crops near the field.
6. Tell us where the beehives are, in or near the field.
7. Move vehicles and equipment out of the field and the turn areas.

Caution: People must stay out of the field during the application and until the re-entry interval on the label ends.

8. Tell your crew the date and the field, and keep them out until that interval ends.
9. Give your window: as soon as possible, a set week, or a set date.

Our guides on crop dusting near homes and bees and pesticides answer common neighbor questions. The crop dusting season calendar shows when each job type peaks.

What happens after the plane leaves the field?

The job ends with records. The GPS log shows where the pilot flew and where the system applied the product.

California sets deadlines when a licensed pest control business applies a pesticide on a farm. The same DPR compendium lists them:

• The business gives the grower a completion notice within 24 hours.
• The business reports the application to the county agricultural commissioner within 7 days.
• The business sends the grower a copy of that use report within 30 days.

The grower does not put these applications on the grower's own monthly use report. Keep the completion notice and the use report copy with your field records.

Sutter Butte Dusters flies from our airstrip at 4080 Clark Rd in Live Oak, with five Ag Cats and one Air Tractor 602. We serve growers in Sutter, Yuba, Butte, Glenn and Colusa counties. Send a field address, APN or FSA farm and tract number, and we map the field and check the hazards nearby. Send your field details through the quote form, or call (530) 695-2294, Monday to Friday, 8am to 3pm.