Frost control is a lot like cherry drying (or blowing) in that it requires you to move above the crops to circulate air. But while cherry drying requires the helicopter to be low and slow so the downwash really shakes up tree branches, frost control’s purpose is to move warm air in a temperature inversion down into the crop area to keep the temperature above freezing.

Frost control flying is done in southern and central California, Florida, and other places throughout the United States. It’s commonly used to control frost over citrus trees, lettuce, and other crops.

My contracts are always in California’s Central Valley, not far from Sacramento, where I cover almond trees. The nuts are susceptible to damage from freezing temperatures from the time they’ve been pollinated until weeks after the nuts begin to form. As my client explained to me, when the nuts are in a gelatinous stage early on, freezing temperatures can destroy them. Because the “ranches” are huge — sometimes hundreds of acres — its not cost effective to install wind machines, as they do in California’s wine country for grapes or Washington’s orchard country for tree fruit. So the helicopters are called in and put on standby.

More about the flying

There are three main differences between flying to dry cherries and flying to control frost:

  • Altitude. Frost control flights are done at a slightly higher altitude. Generally speaking, you want the helicopter high enough to be above the inversion so it can suck that warm air down. The exact altitude varies, but it’s usually at least 30 feet above the ground.
  • Speed. Frost control flights are done faster, slightly above ETL. The goal is to cover the crops quickly, pulling the air down and letting it circulate around. You might have to cover an area multiple times and it’s vital to get the air moving throughout the crops quickly. My first-year client told me that the warm air above a field is normally depleted within 3 hours.
  • Time. Frost control flights are nearly always done at night, usually between 2 a.m. and just after dawn. In most cases, the coldest time of night is right before dawn, so you might have the benefit of some twilight lighting to see where you’re going. But with weather fronts and other factors affecting weather, it’s possible to have to fly in the middle of the night when it’s pitch black.

My Experience

I’ll be honest with you: I’ve had frost contracts for the past four winter/spring seasons and I have yet to be called out to fly. I’ve been put on standby several times and spent more than a few predawn hours parked on the ramp beside my helicopter in the dark, glad that Dutch Brothers has a 24-hour coffee stand between my motel and the airport. But fly? Nope.

That doesn’t mean I didn’t try it. My very first season on contract, 2013, I gave it a go with my friend Jim, who was also there for his first season. We’re both experienced R44 pilots with thousands of hours logged. But neither of us have much experience flying at night so we wanted to get an idea of what we were in for before the call came.

The first night out, we got into my helicopter, waited until 10 p.m. when it was good and dark, and took off. The first challenge was finding the field. Yes, of course I had the GPS coordinates for it, so I zipped right to the general area, flying at 500 feet AGL to avoid power lines and towers. When I spotted the trees below me, I spiraled down, remembering obstacles like wires in the area. I was about 50 feet up when I realized that the bright patch below me wasn’t the almond blossoms of my field shining in the starlight. It was a body of water I knew was about a quarter of a mile away. I hadn’t scouted that area, but I also knew there was an unlighted wind turbine nearby. I got spooked and climbed out, away from where I knew the tower might be. (The tower is now lighted.) We tried another field with slightly better results, but left equally spooked. Clearly, more preparation was necessary.

I use this app to make a clear outline around my almond fields so I know exactly where I am in the dark.

I use this app to make a clear outline around my almond fields so I know exactly where I am in the dark.

We spent the next day scouting our fields again. I picked up an app for my iPad that I could use to map the boundaries of my fields as a track. I could then use my GPS to get into the general area and then see my position over the outline of the field to know exactly where I was. I drove the perimeters of each of my fields to set this up. Jim used a less high-tech method of pinpointing his fields.

That night we went out again, this time in Jim’s ship to find his fields. We — or I guess I should say he — did remarkably well. I was just a passenger keeping an eye out and giving him moral support. But neither of us was happy about the nighttime flights we faced. He said the field owners should have guys down there with flares to guide us. I told him that they expected us to be able to do our job without their help.

Of course, it hasn’t mattered yet. Neither of us was called to fly that year and Jim didn’t come back for additional seasons. I just finished my fourth season — my contracts start in late February and run 60 days — and still haven’t flown. But every year, when I’m assigned my fields, I take that app out and drive the perimeters to mark them. And, of course, I scout them from the ground and from the air at least once during the day.

Equipment

Like cherry drying, the kind of aircraft most suitable for this work is one that can push a lot of air. Larger aircraft like Hueys and big Sikorskys are pretty commonly used. I’m pretty sure that R44s are the smallest ships they’ll consider.

Light bars rigged to the underside of the helicopter are commonly used for night flying. Another friend of mine who put a ship on contract in 2013 in the same area had a friend build him a light bar with 1400 LED lights. The whole thing could be strapped to the skid legs within minutes and plugged into the electrical system on his Hiller. I never saw it lighted at night, but it was probably visible from space. Of course, his ship didn’t fly that year either.

I bought a pair of DeVore Aviation Triple LED FFRLs (Forward Facing Recognition Lights) for my R44. Back in 2013, they cost about $2,500 to buy and another $2,500 to install. They added about 15 pounds of weight to my aircraft. They have three settings: off, steady on, and pulsing. I tried them that first practice night and was extremely disappointed. They only provide significant light very close to the ground. I wound up replacing my landing lights with LED landing lights a few years later; they do a much better job lighting the area in front of me. Now I use the DeVores primarily in pulsing mode when I’m flying in crowded airspace or doing cherry drying work on a low-visibility day. I’m honestly thinking of having them pulled to get that 15 pounds back when I take my ship in for overhaul this winter. (Anyone want a deal on a pair?)

Revenue potential

In general, the revenue potential for frost control — at least the work I do in Central California — isn’t very promising. Sure, there’s standby pay, but because the pilot doesn’t actually wait around with the helicopter, it’s much lower than it is for cherry drying or other kinds of work. My contract also pays to move the helicopter onsite at the beginning of the contract and pays to get it back home at the end. It also pays a callout fee that covers the cost of me flying commercial from my home in Washington to Sacramento, renting a car, and getting a motel room. And then getting home after spending half the night sipping cold coffee in the rental car beside my helicopter. The hourly fly rate is lower than cherry drying, so I wouldn’t even make that much if I flew.

So why do I continue to do it? Mostly because I’m not doing much of anything else from late February to late April. It’s better to park the helicopter in California and collect a small check than keep it home in Washington and not collect anything. Even when I don’t fly, I’m not losing money. And I actually like spending the first month of my contract in the Sacramento area, winding down my annual snowbirding trip south. So I guess I can say that even without the big bucks, it works for me.

What do you think? Have you done any frost control work? How about sharing your experiences in the comments.