It’s usually the thing we lead off with when the season starts; truckloads of fertilizer rolling into the airport and being staged at various remote air strips across the country.
The thing I like about dry work is it cycles quick. You’re flying a little higher, so the wires and trees are a little easier to navigate. It’s a faster paced operation that keeps everyone and everything moving along at a brisk pace. Most of the time the runway is close enough to the field being treated that there’s not much ferry time and the load flows out of the airplane rapidly. It can be darn tiring if you’ve got a lot to do.
Flying with a spreader on instead of spray booms requires a bit of a mental change. You’re thinking of the job in pounds instead of gallons, swath widths are generally figured to best fit the field within reasonable parameters. Even numbered passes are always best, though it doesn’t always work out that way.
A spreader is a big draggy thing that needs to be considered when preflight planning. It is more often than not overlooked. If you’re coming from months of spraying, you need to adjust your flying to compensate for the extra drag and weight of a big hunk of stainless steel hanging underneath your airplane. It affects your take off roll and your turns. A spreader will noticeably increase your stall speed and extend your runway requirement. If you get in a bind, you most likely won’t be able to jettison enough of your load in time to save your butt.
Not all fertilizers are created equal. You can cram the hopper full of urea, but other fertilizer mixtures and compounds are fairly heavy. Liquid fertilizers are notoriously heavy. We spray UN32 liquid fertilizer quite often. At 11.06 pounds per gallon, the job has to be taken in smaller bites. We figure our loads to compensate for weight. A 362-gallon load of UN32 is equal in weight to 500 gallons of water. If you’re adding water and other materials, you’ll have some math to do to make sure you’re not overloading your airplane. The window in the hopper makes it look like you’re taking light loads, the end of the runway however will tell a different story altogether. Do your math and keep in mind the conditions you’re working in.
Dry urea weights somewhere around forty-eight pounds per cubic foot. Other dry fertilizers can weigh more. For example, 11-52-0 will be about sixty pounds per cubic foot. Using sixty-two cubic feet as a base number for a 500-gallon hopper, a full load of urea will be approximately 2,900 pounds, that’s a 360-gallon load of water. In a AT-502, or 510 Thrush, you could almost take off from the parking lot with that. Almost. However, 11-52-0 works out to just over 3,700 pounds, equal to a little over 450-gallons of water. That’s a big difference. Given the conditions that exist at the time of application, including the available runway length, a smart pilot will consider all variables when he’s figuring loads.
We don’t have scales on our loader trucks, so it’s difficult to get an exact weight for what’s going in the hopper. We use a density scale, a little gadget you fill with the material, balance it on the edge of a pocket knife blade, read the scale and that tells you what the material weighs per cubic foot. It’s basic and simple and doesn’t require batteries, hydraulic fluid, or any sort of education beyond walking and chewing bubble gum at the same time. Take the number the density scale gives you and multiply it by the cubic feet of your hopper. You can easily adjust how you want the airplane loaded by using this handy dandy device.
Fertilizer season also tends to correlate with bad weather during late winter and early spring. This is when rain storms, wind, fog and mud play their biggest roles of the year. Many loads of fertilizer and seed have been applied in the rain. Countless trucks and belt loaders have gotten mired in the mud at the end of a runway or access road. Rain makes everything slippery and messy. Urea spilled on the wing root quickly cancels out the non-skid material and the area the loader is working on becomes a slip and fall hazard. I’ve seen wing jumpers fall off airplanes before, I’ve done it myself and I can tell you, it hurts. I’ve seen pilots spool up their propeller while a man was still working at stuffing the hopper. There’s no need for that. Take a little extra time if you have to. It doesn’t do any good to be quick if you have to stop because someone got hurt. Besides that, it’s just plain rude. If your wing jumper needs to move quicker, then give him some more training, or find out what’s causing the delay and fix it.
Challenges when doing dry work is making sure you get the material spread out evenly and don’t run short or too long. A little long is good. A little short is way bad. Track your loads and the number of loads that you get from the trailers. If you get seven loads from one trailer, then you should check your progress and confirm you have covered the right number of acres, plus a few, for seven loads.
We have mirrors on the crossbar in the center of the aircraft hopper, so we can see the gate at the bottom. If you don’t do that, you should. It’s a big help. I usually consider the crossbars at the bottom of the hopper to be the empty point. I bring a little back. After a half dozen loads, I know I have enough saved back for a headland or a short pass.
Fly well and stay safe!