Photo by Michael A. Wieder When possible, operate the aerial device in line with the longitudinal axis of the apparatus.
However, safe driving is only the first step in the overall operation of fire department aerial apparatus. Assuming that you have followed Lieutenant Wilbur's words of wisdom and have arrived safely at the scene, the next step in the equation is to find the best possible position on the scene to park and operate the aerial device.
There are three primary considerations associated with positioning the aerial apparatus on the fire scene:
- Departmental standard operating procedures (SOPs).
- Incident scene conditions and considerations.
- The tactical needs of the incident.
Most departments have their own SOPs for positioning of aerial and other types of apparatus on the emergency scene. These procedures will vary from department to department depending on typical construction types, road conditions, the type of aerial apparatus used and numerous other considerations. Driver/operators must be extremely well versed in the SOPs that affect their particular operation of the aerial apparatus.
However, there are general considerations for aerial apparatus positioning that must be realized by all driver/operators, regardless of the jurisdiction that they serve in. This article highlights some of the incident scene conditions that aerial apparatus driver/operators must consider when determining the final parking spot for the apparatus. Part 2 will focus on the tactical considerations associated with positioning the apparatus on the scene.
The following are some of the factors that must be considered when determining a final parking spot for the aerial apparatus on the fire scene:
- Surface conditions (soft pavement or soil).
- Weather and wind conditions.
- Electrical hazards and ground or overhead obstructions.
- Angle and location of aerial device operation.
- Fire building conditions.
Surface Conditions
The surface condition of the spotting area must be considered when using an aerial device. Apparatus should be parked on soft surfaces only as a last alternative. If working on soft surfaces, operators must watch for settling.
The stabilizer pads supplied with the apparatus are to be used whenever the stabilizer system is deployed. However, placement on soft surfaces may require additional cribbing or support materials may need to be placed under the stabilizer pads to further distribute the weight of the apparatus. When cribbing is used to supplement stabilizer stability, the material must be of adequate size and strength to withstand loading imposed by the aerial device. Ensure proper placement of cribbing to preclude slipping from underneath the stabilizer pads or stabilizer shoes.
The driver/operator must also be alert for surfaces that are stable when the incident begins but which may become unstable as the incident progresses. Frozen soil may be a stable surface as long as it stays frozen. However, apparatus exhaust and warm water from firefighting operations may cause the ground to thaw and become unstable. Even during warm weather operations, dry, solid ground can become unstable from fireground runoff. Be alert for these conditions.
Thin-skinned paved surfaces may be as problematic as soft soil. These are especially common in parking lots. Most parking lots are not constructed with the same techniques and materials as public roadways. In some cases, a parking lot may consist of merely a thin layer of asphalt applied over dirt or a minimal gravel base. The thin surface may not provide a stable enough base for the apparatus stabilizers. If stabilizer pads or cribbing are not placed beneath the stabilizer shoes, the stabilizers may puncture the parking surface, and the truck may tip over when the aerial device is operated off the side of the vehicle. Parking lots that may be problematic for aerial apparatus operations should be identified in pre-incident plans.
Apparatus driver/operators must also be alert for areas that may contain vaulted surfaces. Vaults beneath the ground may be created by underground parking structures, utility chases, drainage culverts, basements that extend under sidewalks or underground transportation systems. These surfaces are unstable for the support of aerial apparatus. Through pre-incident planning, the driver/operator must be familiar with locations where the deployed stabilizer could possibly punch through the surface and cause the aerial apparatus to tip over.
When soft or otherwise unstable surfaces are present or even suspected, avoid the area if at all possible. If it is not possible to avoid the area, the apparatus stabilizers should be properly supported with stabilizer pads and supplemental materials. When possible, park the apparatus in a manner that will allow the aerial device to be operated directly over the front or rear of the apparatus. This lessens the possibility of a stabilizer settling into the surface. It also lessens the chance of the apparatus tipping over even if it does settle into the surface.
Weather Conditions
Weather conditions can affect the spotting of an aerial apparatus in several ways. These include cold, hot or windy weather conditions. Driver/operators must have an understanding of how to deal with the weather extremes that are common to their jurisdiction.
Photo by Michael A. Wieder Always place the stabilizer pads beneath the stabilizer boot, regardless of the surface type.
The most common spotting consideration that faces driver/operators in cold weather conditions is the presence of ice or snow on the parking surface. When possible, the driver/operator should avoid parking the apparatus and deploying the aerial device on snowy or icy roads. However, since this is not always possible, the driver/operator must know how to make the operation as safe as possible. The driver/operator should monitor icy ground for melting conditions that could decrease stabilizer stability. In some cases, after the stabilizer has been lowered onto an icy or snow-packed surface, the ice/snow may melt or break away leaving the stabilizer off the ground. This will require the stabilizer to be lowered further to ensure solid contact with the ground.
Icing of ladders, booms and platforms requires additional caution during operation due to the weight of the ice. The amount of weight added to the aerial device by firefighters and equipment has to be decreased when icing conditions are present. Try to avoid parking the apparatus in a position where the raised aerial device will be subject to accidental contact with fire streams or overspray. If the aerial device is going to be used for elevated master stream operations, avoid parking it so that the stream will be operated against the wind. This will minimize overspray reaching the aerial device. If the aerial device does receive a buildup of ice, it may be necessary to spray it with a de-icing fluid so that normal operation may be resumed.
The primary spotting consideration associated with hot weather is that extreme heat may tend to weaken marginal or otherwise firm paved surfaces. For example, an asphalt parking lot that may provide a marginal level of support during more temperate weather conditions will become soft during periods of extreme heat. This may result in an unstable base.
Moderate to high winds impose a dynamic load on the aerial device and may reduce the overall stability. This is caused by the force of the wind blowing against the device and trying to move it in a direction for which it was not designed. The movement by the wind also magnifies the other loads placed on the ladder by personnel and equipment. When it is necessary to operate during high wind conditions, spot the apparatus in a manner that requires the aerial device to be raised only to the minimum extension needed. It is also helpful to position the apparatus so that the aerial device may be used over the front or rear of the vehicle, parallel to the wind. Driver/operators and company officers should also be aware of locations in the response district and sides of certain buildings that are more prone to gusting wind conditions and avoid them when possible. Always adhere to the manufacturer's recommendations for operations in windy conditions.
Electrical Hazards & Ground Or Overhead Obstructions
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.
Another spotting consideration is whether the aerial device is designed to be operated in either an unsupported (cantilever) or a supported (resting on a wall) position. Follow the manufacturer's recommendations for either condition. If the manufacturer recommends that its device be operated in a supported position, realize that the loading or the amount of extension must be reduced for low angles of elevation during unsupported operations. The maximum loading for any unsupported aerial device occurs when operated at angles between 70 degrees and 80 degrees from horizontal.
The amount of extension affects aerial device stress. As extension increases, aerial loading must decrease. Aerials operating at a low angle of elevation and at long extensions are at their weakest operational position. This type of operating position should be avoided if at all possible. This can be done by spotting the apparatus as close to the intended target as safely possible.
The driver/operator must be familiar with the load limitations of the aerial device when flowing water and when not flowing water. Equally as important is knowing the range of motion that is acceptable for the aerial device under both conditions.
Fire Building Conditions
The condition of the fire building, as well as other building-related concerns, must be considered when positioning the apparatus. Buildings that have been subjected to extensive fire damage or buildings in poor condition before the incidence of fire may be subject to sudden collapse. For this reason, apparatus should be parked far enough away so that they will not be in the collapse zone should a collapse occur. The collapse zone should be at least equal to 1 1/2 times the height of the building.
Realize also that even if the apparatus is not struck by falling debris that it may be subjected to higher levels of radiant heat and smoke following a collapse. This must also be considered when spotting the apparatus. In many cases, the aerial apparatus is the most expensive exposure on the fireground. Keep this in mind when positioning the apparatus. It makes little sense to damage a $500,000 piece of apparatus while fighting a fire in a $15,000 garage.
There are many indicators that a building may become unstable. Signs that a serious exterior collapse may occur include: bulging walls; sagging roofs; large cracks in the exterior; falling bricks, blocks or mortar; and interior collapses. Pre-incident planning aids in identifying buildings with a serious potential for collapse. Buildings that are old and poorly maintained should be targeted. The presence of ornamental stars or large bolts with washers at various intervals on exterior masonry walls indicates that reinforcement ties are in place to hold together otherwise unstable walls.
The intensity of the fire also dictates apparatus placement. Large hot fires require the apparatus to be spotted farther away from the fire building. Consideration must also be given to the fire's potential growth. If the fire has the potential to grow or spread to exposures, the apparatus must be placed so that it is not trapped by the advancing fire. Always leave a way out. Avoid making the apparatus an exposure hazard itself. If the apparatus is to be positioned in a dead-end access, back the apparatus into position if possible. This will make an escape faster if it becomes necessary.
Another consideration for spotting apparatus is the debris that can fall from the fire building. This is of particular concern at high-rise fire incidents. Large pieces of glass, roof-mounted signs, steel gates and other debris may be falling from many stories above street level. This can pose a serious hazard to personnel operating off the apparatus and to the apparatus itself. In these situations, the apparatus should be spotted away from the area in which debris is falling, and all personnel should be kept safe of the falling debris zone.
Conclusion
There are myriad considerations for the driver/operator when determining the best spot on the fireground to park and aerial apparatus. This article only covers part of them.
In our next installment we will look at the tactical considerations that affect aerial apparatus placement on the fire scene.
Michael A. Wieder, a Firehouse® contributing editor, is the Manager of IFSTA Projects at Fire Protection Publications in Stillwater, OK. He holds several undergraduate and graduate degrees in fire protection, safety and adult education. Wieder is the author of the recently released IFSTA Aerial Apparatus Driver/Operator Handbook.
