Ground Pattern Performance of the
Western Pilot Services Dromader

Flow rate, drop height, and air speed all have an effect on the drop pattern. Since this type of airtanker is normally used over a narrow range of heights and speeds and because each gating system produces a single flow rate, information about an average drop is presented (Figure 2 and Figure 3).

Figure 2—Drop pattern characteristics for the Western Pilot Services
Dromader with Transland Gate at an air speed of 92 knots (106 mph)
and a drop height of 40 feet. The contour lines are at coverage levels of
0.5, 1, 2, 3, 4, 6, 8, and 10 gallons per 100 square feet.

Figure 3–Drop pattern characteristics for the Western Pilot Services
Dromader with Melex Gate with an air speed of 91 knots (105 mph)
and a drop height of 80 feet. The contour lines are at coverage levels of
0.5, 1, 2, 3, 4, 6, 8, and 10 gallons per 100 square feet.

The proper amount of gum-thickened retardant (expressed as coverage levels in gallons per 100 square feet) differs depending on the fuel model. Table 1 shows the coverage needed for specific fuel models using both the National Fire Danger Rating System (NFDRS) and Fire Behavior Fuel Model descriptions.

Table 1—Retardant coverage levels needed for specific fuel models.

The results of drop tests allow managers to estimate the length of line a specific airtanker produces at various coverage levels. Table 2 can be used to determine the maximum line length at each coverage level produced by water using the Transland gate. Table 3 can be used to determine the maximum line length at each coverage level produced by foam using the Transland gate. Table 4 can be used to determine the maximum line length at each coverage level produced by gum-thickened retardant using the Transland gate. Table 5 can be used to determine the maximum line length at each coverage level produced by water using the Melex gate. Table 6 can be used to determine the maximum line length at each coverage level produced by foam using the Melex gate. Table 7 can be used to determine the maximum line length at each coverage level produced by gum-thickened retardant using the Melex gate.

Table 2—Water tests producing the longest line at various door openings using the Transland gate.