For several years now, my good friend Michael Wilbur has done an outstanding job of educating the readers of this magazine on the topic of emergency vehicle driving. Obviously, one of the most basic tenets of effective fireground operations is to actually make it to the scene … in one piece...
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Aerial driver/operators must continually be aware of overhead power lines. When parking the apparatus, it is just as important to look up as it is to look at the ground. If possible, the driver/operator should avoid spotting the apparatus in a position that will require a lot of aerial device maneuvering around the obstructions. Remember that the goal is always to maintain a distance of at least 10 feet between the aerial device and overhead electric lines.
Photo by Michael A. Wieder
Contact with any type of wire can have deadly consequences.
Caution should be exercised around other types of overhead lines such as telephone and cable TV lines. Occasionally, these normally harmless lines will be in contact with electrical lines somewhere down the line and may also be energized. Articulating boom operators have two areas of the apparatus to monitor: the platform and the boom, particularly in the area of the boom joint or hinge. Personnel on the apparatus are generally considered to be susceptible to electric shocks regardless of whether they are in contact with the ground or not.
Trees, overhangs, parked vehicles, trash containers and similar obstructions may also affect the operation of the stabilizers and/or aerial device and should be considered/avoided when positioning aerial apparatus.
Angle & Location Of Aerial Device Operation
In many cases, principles of spotting the aerial apparatus are linked with stabilizing the apparatus. Stability of aerial apparatus can be improved by operating the aerial device in line with the longitudinal axis (apparatus body). In other words, the aerial apparatus is most stable when the aerial device is operated directly over the front or rear of the vehicle. Increasing the angle of the aerial device away from the longitudinal axis of the truck decreases the amount of load that can be carried safely. An angle perpendicular to the apparatus is the least stable position available.
By positioning the truck body in a line with the expected position of aerial use, the stability of the apparatus can be increased. Thus, if you have the entire parking lot at your disposal, nose or back the aerial apparatus into position rather than parking parallel to the objective. For rear-mounted aerial devices, backing the apparatus in is the preferred method, as this maximizes the reach of the aerial device. Nosing the apparatus in would shorten the possible reach by a distance equal to the length of the apparatus. The opposite would be true of midship-mounted aerials.
Tillered aerial apparatus may be positioned to increase stability by jackknifing the apparatus. Jackknifing involves turning the tractor at an angle from the trailer. Greatest stability occurs when this angle is approximately 60 degrees from in-line, and the aerial device is extended away from this angle. Good stability occurs at angles up to 90 degrees. Beyond 90 degrees, stability decreases rapidly. The driver/operator must be familiar with the manufacturer's recommendations for that particular apparatus. Modern tillered apparatus may have stabilizer systems that allow them to be adequately stabilized without jackknifing. However, even those apparatus become more stable when the apparatus is jackknifed.
Stress in aerial devices is also increased when the ladder rungs are operated nonparallel to the ground. This occurs when the apparatus is parked on an incline and the aerial device must operate off the side of the truck. These positions create a torsion or twisting action on the ladder or boom and the turntable. When an apparatus must operate off an incline, the operator can reduce these stresses by spotting the turntable downhill from the point of operation.
When approaching from the uphill side, the apparatus should be pulled past the building, and the aerial device should be operated off the back of the truck. When approaching from the downhill side, the apparatus should stop short of the building, and the aerial should be operated over the cab. Ideally, the truck should be operated in the uphill position with the aerial device directly in-line to reduce the stress.
In some cases, it is possible to level the truck somewhat by using the stabilizers to raise one side of the truck more than the other. Generally, this is only possible on grades that are perpendicular to the long centerline of the vehicle. The ability to do this depends on the type of stabilizer with which the truck is equipped. For the most part, it can only be done with single-chassis vehicles that are designed to be lifted completely off the ground.