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How to Conduct Drop Tests of
Aerial Retardant Delivery Systems

Drop Testing

Grid Preparation

Place a supply of clean cups and lids every 200 to 500 feet along the grid so workers can resupply quickly between drops. These should be stacked on pallets rather than directly on the ground to prevent them from being damaged by rain and to keep the cups and lids dry. Boxes for picking up cups need to be distributed along the length of the grid. A safety meeting and briefing is performed as soon as workers arrive (figure 3). Each grid worker carries a canvas bag with a shoulder strap. The bag contains two sections, one for lids and the other for empty cups. Workers should fill their bags with cups and lids before the first drop. Each grid worker also needs a grease pencil and a supply of rubberbands. If sample cups were left in holder cups overnight, they must be checked for moisture from rain or dew. Otherwise, sample cups must be placed in the holder cups throughout the grid with a rubberband holding the sample cup in place.

Figure 3—The morning safety meeting and briefing before a day of
drop tests.

Sample Collection

The grid worker is the real workhorse of the drop test. After the drop, grid workers: 1—cap cups, 2—mark cups, 3—pick up cups, 4—replace cups. Each task should be completed before proceeding to the next task. For example, once the drop has settled, all cups that have been hit must be capped as soon as possible to minimize evaporation. Forest Service supervisors are dispersed evenly among the grid workers. Using hand-held radios, the supervisors ensure that each step is progressing at about the same pace throughout the entire drop area. Personnel can be diverted from areas where tasks are being completed more quickly to areas where they are being completed more slowly.

Capping Cups

Once the drop has settled to the ground, the cups are capped. Grid workers use the lids in the canvas bags (figure 4) to cap the cups. Workers walk up and down the rows, completing each row before proceeding to the next. Caps should be placed on all cups that have at least a drop of material in them. Empty cups should not be capped. No worker should have to cap cups in more than four rows. A grid with 40 rows requires at least 10 grid workers. A grid with 100 rows requires at least 25 workers. Depending on the width of a drop, a row can be capped in about 1 minute. Ideally, the entire grid should be capped in 5 minutes or less. The entire grid must be capped before proceeding to the next step.

Figure 4—Placing caps on cups after a drop has settled.

Marking Cups

Marking (figure 5) begins after all cups have been capped. Each cup has a row and column number designation written on the cup holder. The grid worker uses a grease marking pencil to write this number on the cap. The procedure is similar to capping. Complete each row before proceeding to the next row.

Figure 5—The number on the side of the cup
holder is written on the cap that seals the cup.

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