Additional Tasks

During the drop test, someone needs to:

• Start the weather station data logger to begin 1-second scans during the drop (between drops, the scan rate is 1 minute).
  
  
• Make sure all boxes are properly labeled and kept separate from each other.
  
  
• Instruct the pilot when to drop over the grid, explain the drop configuration, and confirm that the grid is clear.
  
  
• Ensure that the data collection process is running smoothly and that all cups hit by the drop have been capped, marked, picked up, and replaced. The person performing this task has been affectionately referred to as the Grid Mother.
  
  
• Make sure that video cameras are set up each day before the drop tests and taken down each day. The person also ensures that the batteries for the video equipment are charged and that the videotapes are organized.
  
  
• Start the weather station in the morning and download data after the tests.
  
  
• Operate four video cameras.
  
  
• Drive full pickup boxes from the grid to the weighing area and bring empty pickup boxes and other supplies back to the grid.

Most of these tasks do not take long, but all are vital. Specific individuals should be assigned to each task. It should take 15 to 20 minutes from the time the drop settles until the grid is ready for the next drop. After the second or third drop has been collected, four people need to start weighing. Otherwise, it is possible to run out of empty pickup boxes. Since all drops should be weighed the same day they are collected, an early start helps ensure that the day's weighing will be finished as soon as possible. Normally, between 5 and 10 drops will be collected and weighed in 1 day.

Video Documentation

During the drop test, video is recorded from three positions: at the side, end, and corner oblique of the grid. Two cameras, one for an overall shot (side wide) and another following the aircraft (side pan), are operated side-by-side from the side view position. They are positioned in line with the middle row and perpendicular to the edge of the grid. White plywood panels at each end of the grid serve as markers.

The sidewide camera does not move during recording. It provides a wide-angle view of the grid. This camera should be far enough from the grid so that its view includes the plywood panels (see appendix C for plywood panel setup instructions). It should be aimed so that the ground is in view but takes up no more than the bottom fourth of the image.

The side-pan camera follows the aircraft as it passes over the grid. This camera should be zoomed to contain the largest possible image of the entire aircraft while including a view of the ground. The photographer should maintain this view while the aircraft is passing over both plywood panels. Once the aircraft has passed the second panel, the camera should be panned back to the retardant cloud. Document the locations of these cameras and plywood panels based on their distance from the edge of the grid.

The end camera is mounted on a tripod at the end of the grid to capture the grid and the aircraft as it approaches. This camera is aligned with the downrange centerline (middle column) of the grid. The centerline is often marked to help the aircraft pilot adjust the approach. The camera should be zoomed to view the largest possible image of the entire aircraft during the release, while including a view of the ground. The ground should take up no more than the bottom fourth of the image.

The video footage from the side and end cameras is used primarily to determine the aircraft's speed and height.

The oblique camera (on the corner of the grid) provides closer views of the release, the formation of the retardant cloud, and the drop's settling characteristics. For the best images, the operator should stand near one of the corners of the grid with the zoom adjusted so that the view contains the grid and the aircraft as it approaches. Once the drop takes place, the operator should keep the camera trained on the retardant cloud as it forms and settles to the ground. Between drops, the operator can carry the camera to take general interest footage of the grid operations. The photographer should return to the same vantage point at the corner of the grid to record the next drop.

After recording the drop, the camera operators should make their way back to the grid to help the grid workers complete their tasks. Camera operators need to return to their camera positions before the aircraft is on its final approach for the next drop.

Daily Shutdown

Once the last drop of the day has been collected, the side and end-view cameras need to be retrieved. Depending on security, tripods may be left in place. Weather data should be downloaded and supplies of cups, lids, and pickup boxes should be covered with tarps. If rain or dew is expected before the start of the next day's drop tests, all cups (except holder cups) must be removed from the grid.

A short demonstration video has been prepared to help clarify some of the processes described above. A copy in VHS format can be obtained from Greg Novelette at the Missoula Technology and Development Cent er. Grid workers will also be briefed on grid procedures and safety at the grid before the drop test. A revised version is expected by spring 2005.

Grid workers should drink plenty of water, use sunscreen, wear light, comfortable clothing, and wear shoes with ample ankle support.

Weighing Cups

The weighing process includes:

• Removing cups from the pickup boxes
• Sorting cups
• Placing sorted cups onto a carousel
• Transferring cups from the carousel to the balance
• Transferring cups from the balance to a holding bin.

The flow of cups has typically been from right to left, probably to allow cups to be transferred from the carousel to the balance with the right hand. A disgorging apparatus is used

A disgorging apparatus is used to remove cups from pickup boxes. The apparatus, which is about 3 feet long, 2 feet wide, and 4 feet tall, removes cups from boxes easily.

Immediately to the left of the disgorging apparatus will be a 3- by 6-foot table. This space is used to organize cups that have been removed from the boxes.

Immediately to the left of the first table is another 3- by 6-foot table. The carousel, a 4-foot-diameter, round wooden platter with dowel rods placed along its perimeter, sits on the right end of this table. Stacks of sorted cups are placed along the carousel's perimeter. The dowel rods stabilize the stacked cups. The platter can be rotated as cups are removed and weighed.

A computer, monitor, and keyboard are at the left end of this table. A wooden stand in front of the computer straddles the keyboard and supports a balance. The stand is designed to allow the keyboard to be used easily while the balance is in position.

Immediately to the left of the second table is a holding bin where cups are placed after they have been weighed. Because a computer or operator error may require this pile of cups to be resorted and weighed again, the pile of cups is kept in the holding bin until all of the cups for a given drop have been weighed and the data file has been saved.

Two people, the weigher and the stacker, typically operate a weighing station.

The stacker's first task is to organize the pickup boxes for a given drop in ascending order by grid row number. A final check ensures that all boxes are properly labeled according to the drop number and that all the boxes are from the same drop. The disgorging apparatus is used to remove cups from the boxes, one box at a time, and the stacks of cups are placed on the table (figure 7).

Figure 7—Pickup boxes (foreground), disgorging apparatus (right
rear), pre sorted cups (center table), and sorted cups on carousel
(left rear).

A full box contains six columns of cups that yield six stacks. Each cup is labeled using a two-number system. The first number indicates the grid row and the second indicates the cup within that row. For instance, "1,12" refers to the cup in the first row and the twelfth column. The stacker organizes stacks so that cups of each row are in ascending order by column number, with the smallest number on the top of each stack. Stacking is easier if the cups are placed in the box properly when they are picked up. The grid worker should pick up all cups from a given row before proceeding to the next row and fill each column in the box before placing cups in the next column (see picking up cups, page 5).

The stacker places stacks of sorted cups onto the carousel where they will be ready for the weigher. When the weigher removes cups from the carousel and places them onto the balance, the stacker puts more stacks of un weighed cups onto the carousel. The stacker's goal is to keep the carousel full enough so that the weigh er does not have to wait for cups.

The stacker's job is busier than that of the weigher. The stacker is constantly alternating between disgorging boxes, sorting cups, and placing stacks of cups on the carousel. The weigh er's job is sedentary, but requires more attention to detail (figure 8).

The computerized weighing program asks the weigh er questions, such as the aircraft operator's name, the retardant system's name and size, and the characteristics of the grid. After the first session, most of these will be correctly entered by default, but they should be verified at the beginning of each weighing session. Once the weigher has entered the grid characteristics and drop number, the program goes into the weigh mode, where the screen displays row number, column number, weight, and buttons to change the row and column number.

Figure 8—The weigh er removes sorted cups from the carousel and
places them on a balance. A computer records the weight of each
cup.

After the weigher places the first cup on the balance, the enter key, the left mouse button, or a foot switch wired to the mouse is depressed to send the weight to the computer's serial port.

After the program has received and recorded the weight of the first cup, it retains the row number, advancing the column number by one. The weigher removes the first cup and places the next cup on the balance. Assuming the stacker has done the job properly, the number on the next cup should match the number on the monitor. When the weight of that cup has been sent to the computer, the program advances the column number by one, and so forth.

Assuming that each row has 20 cups, after the 20th cup is weighed, the program automatically advances the row number and resets the column number to 1. However, in most cases fewer than 20 cups are collected from a row, and the weigher must prompt the program to enter the next row/column designation.

An important feature of the computerized weighing program is that the program saves data every time a cup is weighed. If the power fails, someone trips over a power cord, or the computer crashes, all of the weights recorded to that point will have been saved. Another important feature is that the program does not overwrite data. For example, if data from a row of cups from one drop gets mixed with data from a row of cups from another drop, the data file will retain entries from both rows.

Errors in cup weight files can be discovered and corrected during data reduction. Weighers should make notes of errors if they become aware of them while weighing. A small notepad is kept beside the computer for this purpose.

Because the weighing area is typically dirty, a keyboard cover is a good idea. Have a few spare computer mice on hand and a spare computer as well.

The weighing program has been designed to be as user friendly as possible. The instructions don't include steps to solve all possible program errors. It's best to have someone nearby who can.

If possible, complete weighing cups the day of the drop. Even though the caps form a tight seal, some material will evaporate over time. Errors in marking or sorting the cups are easiest to resolve on the day of the drop. Boxes of cups from drops on different days cannot be mistakenly mixed if all cups are weighed on the day of the drop. This also ensures that the previous day's reusable supplies will be available at the grid at the beginning of the next day.

Data Reduction

Data collected during the weighing process are reduced to produce ground pattern contour plots and to calculate the coverage area and length downrange (line length) of different deposition concentrations (coverage levels). More information on data reduction is in Estimating Methods, Variability, and Sampling for Drop-Test Data (0257–2826–MTDC).