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How to Conduct Static Tests of Aerial Retardant Delivery Systems
Typically, the test team travels to the operator's facility. On arrival, the test team meets briefly with the operator to discuss test plans and makes a brief inspection of the tank to verify information about the system. The test team works with the operator's personnel when installing test equipment (figure 5). To prevent the possibility of damage to the tank, aircraft, or instruments, the different pieces of test equipment and their mounting locations are discussed before the equipment is installed.
Figure 5—For this float installation, a rivet was drilled out near the
bottom
of the tank and replaced with a small bracket-mounting bolt. When the test
was completed, the float was removed, and the rivet was replaced.
The floats are mounted so that the bottom of each float is as close to the bottom of the tank as possible without interfering with the door or other internal moving parts. The float needs to be long enough so that the head will not be submerged when the tank is filled (or overfilled). A 3/8-inch hole is often drilled in the top of the tank and the float is mounted through it (figure 6). Because the float tracks the fluid level during evacuations, the float must be mounted where the change in fluid level is an accurate representation of flow out of the tank. There should be at least 3 inches of clearance between the float shaft and any tank walls or dividers. No internal shelves or hardware should be nearby to cause surface turbulence during evacuations (figure 7). Problems with some mounting locations may not be noticed until after initial data are collected. In these cases, the float may have to be relocated.
Figure 6—Two floats were mounted in this tank. The float
head at the
left is nearly flush with the tank cover. Because of the of
the tank's vent
design,
the floats could not be mounted through vent openings.
Figure 7—The float on the right is too close to the shelf. As the tank
evacuates,
fluid flows off the shelf, causing turbulence. Avoid mounting floats
in turbulent areas.
The pressure transducer is placed where the reference port is isolated from pressure variation during evacuations. If pressure measurements need to be made in different sections of the tank, the plastic hose connected to the measuring port can be moved to those locations without moving the transducer. The data acquisition hardware can be set up in the aircraft, or in a vehicle or utility trailer parked next to the aircraft. The laptop computer requires 110-volt power.
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