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Technology & Development Center |
How
to Conduct Drop Tests of
Aerial Retardant Delivery Systems
Preparation for a drop test should begin several months before the test. You will need to contact aircraft operators, airport managers, county engineers, retardant companies, coworkers, national forests, and the National Oceanic and Atmospheric Administration National Weather Service. Major activities include:
Technical information such as flow rates and drop volumes must be gathered for the system being tested. A static test will have to be arranged with the aircraft operator before drop testing. Logistical information such as operational drop heights and speeds must be gathered from the operators, pilots, and fire managers.
A test matrix is an outline listing all planned drops for a given system. Developing a test matrix requires full understanding of the system’s design and operation, the needs and goals of the operator or agency, and any time and cost constraints. The test matrix will give an indication of how big the grid needs to be, the number of days needed for the test, how much retardant will be needed, and the number of people needed. As with many other aspects of drop testing, the test matrix will vary depending on the system being tested. For instance, many helicopter buckets drop the entire load using only one flow rate, while constant-flow airtankers can drop fractions of their load using several selectable flow rates. The operator or agency may just want to qualify the system to Interagency Airtanker Board performance standards at specified drop heights and speeds. Or they may wish to quantify the pattern response for a wider range of variables used operationally. Priorities may have to be established for the goals of the drop test, with the matrix including just the highest priority tests based on the availability of aircraft, personnel, or funding. Once the matrix has been prepared, it should be circulated for comments and possible revision before the start of the test. During the test, the matrix is used to plan each day’s drop schedule and to monitor progress. Appendix A includes several examples of test matrices.
Select a test location at least 3 months before the test. Gather information on all possible locations before deciding which location to use. Required facilities and other considerations include:
These requirements will vary depending on the system being tested. For example, a longer runway with higher load rating will be needed when testing a Type I aircraft. If the test just includes helicopters, a runway isn’t needed. Drop tests are typically performed on airport property. Arrangements will need to be made with airport managers or county engineers. They will need to know how much land will be needed for the grid, how much retardant will be dropped, and how long the test is expected to last. Retardant mixing and delivery to the aircraft will need to be arranged with retardant companies. The local national forest will want to be aware that a drop test is taking place in their area. Radio frequencies will need to be cleared though them.
(Start preparing equipment at least 3 months before the test.) Test equipment should be listed during preparation for each drop test. The list helps test personnel reduce the number of overlooked items, keep track of government property, and prepare equipment for future drop tests. Appendix B is an example of a drop test equipment list. Much of the equipment may be needed for most drop tests, but the list will need to be amended depending on the system being tested. For example, under Grid Points, the required quantity of cup holders and stakes will vary depending on the grid’s size. Items listed under Washdown would not be needed if retardant cups are thrown away rather than washed after use. Some leadtime is needed to identify, select, purchase, and bench test new equipment. A staging area should be established to store equipment before it is transported to the test site. Large durable items should be packed and labeled for shipment. Above all, assure that enough leadtime is available to have the required quantity of cups, holder cups, and stakes. New cups and lids may need to be weighed empty before the test to derive a statistical average tare weight (the weight of the empty cup and lid).
(Start selecting personnel 2 to 3 months before the test.) It takes at least one person to coordinate equipment preparation and at least two others to help with purchasing and administrative tasks. Someone needs to make sure enough Forest Service employees are available during the test. Usually, the Forest Service employees include a core of six to eight individuals with previous drop test experience. Additional personnel can be hired through local temporary employment services, prison crews, youth employment organizations (such as the California Conservation Corps), smokejumpers, hotshot crews, local Forest Service employees, and volunteers associated with the system being tested. The number of additional people needed will depend on the size of the grid.
(Begin making arrangements 2 to 3 weeks before the test.) Travel, lodging, and car rental arrangements need to be made at least 2 weeks before the start of the test. Allow flexibility for departure as the date may change at a moment’s notice. Most test equipment should be shipped to the test site at this time. Forest Service personnel typically carry sensitive items such as laptops, radios, and video cameras with them when they travel to the test site.
Depending on the number of people available and the required tasks, setup usually takes 2 to 4 days (figure 2). A list of setup tasks for the 1999 test at Kingman, AZ, is in Appendix C. This list could serve as a starting point to identify setup tasks for other drop tests. Test personnel can set the grid up once they arrive or it can be set up in advance by contract labor. In either case, instructions for setting up the grid need to be supplied. Appendix D includes instructions sent to the setup team for the Kingman test.
![[photo] Disturbed Test Grid](images/fig02.jpg)
Figure 2—Setup tasks can vary. This grid was overrun by cattle.
It took
several days to straighten the stakes and replace the cup holders.
| USDA Forest Service, Technology and Development Last Modified: 08/16/2025 05:32:29 |
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