Ground Pattern Performance of
the Marsh Turbo Thrush

Flow rate, drop height, and air speed all have an effect on the drop pattern. Since this type of tanker is normally used over a narrow range of height and speeds, only the effect of flow rate is considered here. Figure 2, Figure 3, and Figure 4 show the drop patterns resulting from flow rates produced by using the 40-percent, 60-percent, or 100-percent door opening.

Figure 2—Drop pattern characteristics for the Marsh Turbo Thrush
with an air speed of 86 knots (99 mph) and a drop height of 24 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 Marsh Turbo Thrush
with an air speed of 83 knots (95 mph) and a drop height of 28 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 4—Drop pattern characteristics for the Marsh Turbo Thrush
with an air speed of 80 knots (92 mph) and a drop height of 31 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 retardant (expressed as coverage level in gallons per 100 square feet) differs depending on the fuel model. Table 1 shows the coverage needed for specific fuel models. It is cross referenced to both the National Fire Danger Rating System (NFDRS) and Fire Behavior Fuel Model descriptions.

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