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How to Conduct Drop Tests of Aerial Retardant Delivery Systems

Appendix A—Examples of Test Matrices

The matrix (right) was developed during planning for a helicopter bucket drop test. The objectives of the test were to quantify drop patterns at three different dumpvalve openings and at three different speeds, using water and retardant. Because helicopter availability was limited, all drops were made at 50 feet above the ground. To reduce costs, only two retardant drops were made, both at commonly used speeds and valve openings.

Valve opening (percent) Drop speed (knots per hour) Fluid
100 40 Water
100 60 Water
100 60 Retardant
100 80 Water
60 40 Water
60 60 Water
60 60 Retardant
60 80 Water
30 40 Water
30 60 Water
30 80 Water

The test matrix (below) was developed during planning for a constant-flow airtanker drop test. The objectives of the test were to:

  • Quantify drop patterns at different volumes and flow rates while dropping at the same speed and altitude
  • Compare drop patterns of water and retardant when all other variables are equal
  • Compare drop patterns among replicate drops when all variables are equal

A drop speed and altitude were selected that best represented "typical" operational levels. Replicates were completed with low, medium, and high flow rates. During the test, additional drops were made at different drop heights and speeds to compare drop patterns of a gel product. These drops were made with the same low, medium, and high flow rates.

Load Volume (gallons Coverage level Flow rate (gallons per second Fluid Evacuation (seconds) Estimated pattern length (feet) Repetitions
Full 1,200 1 190 Water 6.3 1,390  
Full 1,200 1 190 Retardant 6.3 1,390  
Full 1,200 2 315 Water 3.8 840  
Full 1,200 2 315 Retardant 3.8 840  
Full 1,200 3 440 Water 2.7 590  
Full 1,200 3 440 Retardant 2.7 590 3
Full 1,200 4 560 Water 2.1 460  
Full 1,200 4 560 Retardant 2.1 460  
Full 1,200 6 640 Water 1.9 420 3
Full 1,200 6 640 Retardant 1.9 420 3
1/2 600 1 170 Water 3.6 790 3
1/2 600 1 170 Retardant 3.6 790 3
1/2 600 4 560 Water 1.1 240  
1/2 600 4 560 Retardant 1.1 240  
1/3 400 0.5 60 Water 6.6 1,450  
1/3 400 0.5 60 Retardant 6.6 1,450  
1/3 400 1 175 Water 2.3 500  
1/3 400 1 175 Retardant 2.3 500  
1/3 400 2 270 Water 1.5 330  
1/3 400 2 270 Retardant 1.5 330