Serious Decisions Are Necessary When Specifying Aerial Apparatus

By William C. Peters

The town of Littleville started out as a dev- elopment of one- and two-family houses and a few scattered businesses that welcomed home the veterans of World War II. The town was protected by a volunteer fire department with a few engine houses. Over the years, the town developed into a small city, with garden apartments, a downtown area with apartments over stores, and the expansion of family homes.

Today, Littleville has evolved into a metropolis. Large-square-foot, expensive “McMansions” were constructed, townhouse developments sprung up, several taller office buildings were built, big box stores dotted the highway, and an eight-story hotel/convention center is being considered.

 
 (1) Elevated stream application from a platform and a ladder pipe. (Photos by Ron Jeffers.)

The current career fire department engine companies are at a disadvantage, operating with minimum staffing. The trusty 35-foot extension ladder carried on each pumper is outmatched by the rapidly expanding size and height of the newer buildings in the city.

The fire chief has received permission from the city council to research the requirements and prices of a new aerial apparatus to protect his city. The chief didn’t want to make a wrong decision, so he went on a quest to analyze the size, configuration, and operating parameters of the various aerial apparatus available to efficiently serve the citizens of his city.

Aerial Ladder vs. Elevating Platform Apparatus

The primary duties of a ladder or truck company are forcible entry, rescue, ventilation, overhaul, and salvage. Many features of the aerial apparatus help to accomplish these tasks. In addition to a complement of tools, equipment, and ground ladders, the aerial device is the main feature of the vehicle to consider first.

Straight stick aerial ladders have been in the fire service for many years. Originally constructed of wood, the aerial ladder eventually evolved into a truss metal structure. The infancy of the modern platform began in Chicago, where a utility “cherry picker truck” was outfitted and used as a firefighting aerial device.

 
 (2) Firefighters must climb to the tip of an aerial ladder to operate.

The function of the aerial device is to efficiently reach higher points on a building for occupant rescue, topside ventilation, and elevated water stream application.

When trying to decide between an elevating platform and an aerial ladder apparatus, consider the advantages and disadvantages of each.

 

 
 (3) Dual monitors are being operated comfortably from inside a platform.
  • Load-carrying capacity. The minimum rated capacity of an aerial ladder is 250 pounds carried on the outermost rung of the fly section, with the aerial ladder placed in the horizontal position at maximum horizontal extension with the stabilizers fully deployed. The minimum rated capacity of the elevating platform, in the same configuration, is 750 pounds in the platform. Both are rated without water in any water delivery system. Both are available in higher-rated capacities.
  • Safety and ease of use. The platform provides firefighters with a safer and more comfortable position for rescue, ventilation, exterior overhaul, and aerial stream application. Firefighters must climb to the tip of an aerial ladder to effect a rescue or to operate a master stream while those in platforms can “ride” to the intended target.
  • Comfort and confidence of the victims. Victims, especially the young, elderly, and infirm, are more confident when being removed by platform than when climbing down an aerial ladder.
  • Victim removal. Incapacitated victims on litters or in baskets are easier to remove with a platform. Sliding a stokes basket down an aerial ladder is an involved process; lowering a victim by rope is time-consuming and requires great skill.
  • Elevated stream capabilities. In addition to providing a more comfortable location to apply an elevated stream, most platforms have greater elevated stream capabilities, including dual monitors, on some models.

It appears that the platform apparatus wins the contest hands-down. Operationally, this may be true, but platform apparatus have some disadvantages as well.

 

 
  (4) The travel height of platform apparatus is generally greater because of the heavier aerial structure and the platform height.
  • Travel height. The travel height of a platform apparatus is generally greater than a comparably mounted aerial ladder because of the heavier aerial structure necessary to carry the load and the height of the mounted platform.
  • Apparatus weight. Because of the heavier aerial device construction, platform apparatus are usually heavier, which might be of concern in areas that have bridge or fire station floor-weight restrictions. This increased weight also requires higher-capacity vehicle components such as axles, brakes, tires, and driveline. Many straight stick aerials can be mounted on chassis with a single rear axle.
  • Size. Platform apparatus are generally larger in size, which can inhibit access to tight areas of the city, narrow residential streets, and alleys in commercial districts.
  • Stabilizer number and spread. The higher carrying capacity typically requires four or more outriggers and stabilizers with a wider spread. This could place limitations at incident scenes on narrow streets.
  • Cost. Because of the larger, heavier aerial device and vehicle components, as well as the intricate hydraulic systems operating from both the turntable and the platform, platform apparatus cost more to purchase.

 
 (5) Tight areas around the rear of buildings might lend themselves to a smaller aerial ladder rather than a platform apparatus.

Apparatus Size/Aerial Length and Load Rating

You must consider the physical size of any aerial apparatus as part of the purchase. Platform apparatus are larger and heavier than aerial ladders, and aerials are larger and heavier than pumpers. You must make provisions in the station for the additional length and height of aerial apparatus.

There are some ways to reduce the travel height of an aerial if it is a problem. The turntable location has a direct effect on the vehicle’s overall height. Trucks with the turntable at the rear of the apparatus, typically referred to as “rear mounts,” have the aerial ladder extending forward over the cab. This presents a high profile, especially with platforms. Some manufacturers have lowered the turntable and notched the cab roof to lower the aerial’s riding position. The notch protrudes down into the cab and reduces headroom in the center position.

 
 (6) The higher aerial carrying capacity of the platform apparatus requires a wide stabilizer spread.

Another step you can take is to purchase an apparatus with the turntable located directly behind the cab, typically called a “mid-mount.” This configuration brings the aerial device down considerably, reducing travel height; but in many cases, it causes the apparatus to be longer as the aerial device cannot take advantage of being spread over the entire length of the truck from front to back. To counter this situation, some manufacturers produce ladders with more but shorter ladder sections. The disadvantage to this is that the width of the ladder tends to be narrower than on an aerial with fewer sections.

Consider the advantages and disadvantages of mid-mounts and rear mounts:

  • Aerial reach. The rear-mount aerial typically has greater reach at lower angles of elevation off the sides and rear of the truck. In addition, you can operate it at nearly zero degrees over the front of the truck. Since it is mounted to the rear, it has less reach when operated over the front in a nose-in position. A mid-mount has a greater forward reach when operating at higher angles over the cab but reduced reach to the rear and rear corners of the apparatus.
  • Overhang. The overhang on the rear mount is over the front of the truck, and the mid-mount is over the rear. Although the platform or aerial out front is more visible to the driver, it can sustain considerable damage if it strikes an object on a turn. The same is true of the mid-mount with the platform or aerial over the rear. The overhang at the rear can be extremely long, creating a problem while exiting the fire station or backing up. Obviously, the driver has less of a view of what is behind the truck, and if you don’t use a vigilant spotter with good communications skills, you could damage the platform or aerial.
  • Compartment and hosebed space. Generally, rear mounts have more available compartment space. They are, however, sometimes limited in where you can store hose. In many cases, the hose is stored forward of the turntable and fed through chutes to the rear. Quite often, mid-mounts have better hose storage capacity directly at the center rear of the apparatus.

Another feature that contributes to the physical size of the apparatus is the length and load rating of the aerial device. The minimum dry load rating of an aerial ladder is 250 pounds and of a platform is 750 pounds. Capacity ratings are required to be listed in 250-pound increments (the estimated weight of a firefighter in protective gear). “Heavy-duty” 500- and 750-pound tip-load ladders are available as well as 1,000-pound and up platforms. Obviously, higher rated aerial devices weigh more and are generally larger in size.

When the configuration of the response area is made up of taller buildings that are relatively close to the street, a standard aerial ladder that can reach the roofline should provide adequate service for rescue, roof ventilation, and elevated master stream application.

 
(7) Rear mounts generally have a taller travel height than mid-mounts.

The aerial device’s vertical height is determined from the top rung to the ground at maximum elevation. In the case of elevating platforms, it is from the top of the platform handrail to the ground. The horizontal reach of an aerial device will be less than the rated vertical height because of the subtraction of the distance from the ground to the turntable that is calculated into the vertical height. Also, horizontal reach is measured from the center of the truck’s turntable.

You can see that aerial vertical height is not the only consideration. In the case of low angles and long extension, a longer aerial used at less than full extension will be stronger because of the added overlap of the aerial sections. A 100-foot aerial would probably be long enough to reach the highest point at the roof of most suburban buildings, as well as have adequate strength to be used with less extension at lower angles to the roof of the common two-story home set back from the street.

(8) A heavy-duty mid-mount platform with a relatively low travel height.

Smaller Size Aerial Apparatus and Envelope Controls

Since the 1991 edition of National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, aerials and platforms are required to carry their rated capacity at zero degrees and full horizontal extension, which practically eliminated aerial ladder failures that were plaguing the fire service. A rather significant change was included in the 2009 edition that recognized the European design of aerial device that incorporates “envelope controls.” This system allows the apparatus to be set up with less than full stabilizer spread but prevents the aerial from moving into a position that would cause the truck to become unstable.

The minimum aerial ladder rated capacity remained 250 pounds at the outermost rung with the aerial placed in the horizontal position, at maximum horizontal extension. Added was the wording “with the stabilizers fully deployed.” Also added was that the minimum rated capacity shall remain constant throughout the entire “operating envelope” of the aerial ladder. What this means is the weight-carrying capacity of the aerial remains constant, but the reach and angle of operation may be limited automatically if the stabilizers are not fully deployed.

 
 (9) Rear mounts generally have better reach at lower angles off the sides and rear of the truck.

Similar wording was added to the rated capacity of elevating platforms. It remained at 750 pounds minimum with the water delivery system dry and 500 pounds with the system full “and the stabilizers fully deployed.” The platform has to be capable of operating in any position while carrying its rated capacity. Once again, if the stabilizers are not fully deployed, the position the platform can be put in must be automatically limited.

Aerial devices are their strongest and most stable when they are in line with the vehicle and at an angle closest to vertical. In this position, most loads are transmitted down through the turntable and stabilizers to the ground. When the elevation is decreased, the extension is increased, and the aerial is rotated, the forces that act to cause the aerial to become overloaded or the truck to become unstable increase. To prevent the aerial from becoming unstable, an interlock system is provided. An interlock is a device or arrangement by means of which the functioning of one part is controlled by the functioning of another. Added to the interlock section is the requirement to prevent the operation of the aerial device in an unstable position when the aerial device can be operated with the stabilizers not fully deployed on at least one side of the vehicle. Once again, this defines the requirements of envelope controls.

 
(10) The overhang on a mid-mount can present a problem on turns and while backing up. The rear mount has the same overhang situation to the front, where it is more visible to the driver.

Since the operator will need to know what his capabilities are on the “short-jacked” side, an indicator is required. On an aerial device that can be operated over the side with the stabilizers not fully deployed, the standard calls for an indicator, located at the operator’s position, that allows the operator to determine the maximum extension in relation to the angle of elevation and the extended length of the stabilizers. On this type of aerial, when the operator is approaching an unsafe condition, a warning sounds and the aerial stops operating, thus preventing an operational accident.

If the area served by the fire department physically prohibits the setup and operation of a larger apparatus, one of these smaller aerials might be just what is needed.

 
 (11) Rear mounts generally have larger compartment space available because of the higher mounting of the turntable.

Quints

Another apparatus configuration to consider is a quint. A simple quint in fire service terminology is equipped to perform five functions: fire pump, water tank, hose load, ground ladders, and aerial device. The NFPA definition of a quint is somewhat more specific. The fire pump needs to be of a minimum of 1,000-gallon-per-minute (gpm) capacity, the water tank capacity is required to be a minimum of 300 gallons, it must carry the same hoseload as a pumper, it must have 85 total feet of portable ground ladders, and the aerial device must have a waterway.

You can have an aerial apparatus with a pump and a tank that is not a quint. Perhaps the hoseload is less than that of a pumper, or the tank is less than 300 gallons. You can also have a pumper with an aerial device that is not a quint. In this case, it might not have enough ground ladders. You should understand these facts when drafting the specifications.

 
(12) Vertical height is not the only consideration when specifying an aerial. Quite often, you have to operate at a low angle and long extension on the fire scene.

Quints are becoming more popular in the fire service, but keep in mind that when you try to perform too many functions with one apparatus, all the functions could suffer. The physical space needed to carry hose, water, and ground ladders and mount an aerial device causes the apparatus to become larger than a typical pumper. Because of weight limitations, you might be restricted to carrying less water than you normally carry on your pumpers. A 75-foot aerial is a popular configuration for a quint but could come up short when the building is set back from the road access. Quite often the hosebed configuration on a quint is not as convenient as it is on a standard pumper without an aerial device, and often the quint is out of position to operate the aerial. Another disadvantage is that quints cost more money.

The fire service leader who thinks that he will be able to perform all of the functions of a pumper and an aerial at the same time with the same apparatus is fooling himself. Engine companies have distinct fire scene duties, including securing a water supply, stretching hoselines, and attacking the fire. Ladder companies have the duties of forcible entry, ventilation, and search and rescue. Unless the rig is staffed with about 10 people and is strategically placed in the perfect location, some of these duties will not be accomplished.

 
(13) In this demonstration, the aerial is able to rotate to the “short jacked” side safely. The elevation and extension are being monitored automatically to prevent the aerial from operating in an unstable condition.

Waterways and Ladder Pipes

One of the required features of an aerial apparatus is the ability to provide elevated application of fire streams. On apparatus equipped with an aerial ladder, you can accomplish this with either a portable ladder pipe that clamps on the end of the fly section when needed or a prepiped waterway.

At first view, the waterway appears to have the advantage in speed of setup and operation. Although this is true, the disadvantage is the waterway pipe, which is typically mounted under the ladder and telescopes with the ladder’s extension and retraction. When the monitor is fixed at the tip of the ladder, both the pipe and monitor get in the way during rescue operations. To counter this, “pinnable” waterways can be provided. The operator has the choice to lock the waterway at the tip or one section down, allowing the fly to be clear. I have found that even at the third section, the pipe and monitor still create an obstruction when operating to the roof of a three-story tenement close to the street.

 
(14) Smaller compact “European style” aerials can work well in jurisdictions where larger apparatus cannot physically set up.

Another issue with the use of a “pinnable” waterway is safety. I was part of the National Institute for Occupational Safety and Health (NIOSH) Firefighter Fatality Team that investigated the death of a deputy fire chief in Pennsylvania who was struck by a waterway monitor that launched off the end of the ladder when the pipe was charged. During that investigation, NIOSH uncovered more than a dozen instances of this happening in the past. The NFPA apparatus committee reacted by requiring stops on the end of the aerial to prevent the waterway from separating from the ladder on new apparatus. Any department that is currently using a pinnable waterway should make sure every member is familiar with the procedure of securely locking the waterway in either position.

In addition to the speed of getting a prepiped waterway in operation, the remote-control feature allows personnel at the turntable or pump panel to operate the stream while in a position of relative safety. This could be especially significant during a hazardous-materials call or in heavy smoke.

 
 (15) The 75-foot quint is a popular apparatus configuration in this country.

Portable ladder pipes are equipped with halyards to control the pipe’s up and down positions. If you specify a portable ladder pipe, models that have electric controls that mimic the operations of a prepiped waterway are available. Placing a member on the tip of an aerial ladder flowing water, especially at low angles (below 45o), is not recommended.

The cost of a prepiped waterway is higher than that of a portable ladder pipe. If you rarely use an elevated stream, it might be prudent to go with the less expense.

 
(16) When the waterway is “pinned” at the lower section, it generally leaves the tip of the ladder clear for rescue and ventilation duties.

Accessories

When specifying aerial apparatus, you can add many accessories to enhance fireground operations.

Breathing air to both platform apparatus and the tip of an aerial ladder is optional. If it is specified, requirements are outlined in NFPA 1901. Many times when purchasers specify a breathing air system, they include an outlet, respirator, and storage box at the turntable to supply the operator without having to wear a standard SCBA. This might be even more necessary on units where the turntable operator is seated.

 
(17) Portable ladder pipes with electric control don’t require a firefighter to be at the tip or controlling it from the ground with rope halyards.

Platform apparatus provide the most opportunities for mounting and using accessories. Brackets for lowering litters; hoisting arms; and roof ladder mounting devices for securing a ladder to the platform, allowing a firefighter to climb down to roof level when a parapet obstructs access to the roof surface, are just a few.

You can mount roof ladders inside the fly section of aerial ladders and platforms. Some people choose to mount it to the outside of the base section to keep the walkway clear. An ax and pike pole at the tip of an aerial are also handy tools to have available.

 
(18) Floodlights at the tip of an aerial can get damaged easily.

The apparatus standard calls for lighting at the base of the ladder and one spotlight or floodlight at the tip or in the platform to observe the effect of the stream. You can spec additional floodlights and line voltage electrical power to the tip of the aerial or into the platform. Use care if you add lights to the tip of an aerial, as they break easily.

Raised pole lights at the rear of a platform work well and are out of the way. Aerial walkway rope lighting using light emitting diodes is becoming popular. This is a good safety feature.

A prepiped waterway on an aerial ladder and a monitor on a platform are required to deliver 1,000 gpm. A popular configuration on a platform is to equip it with two monitors, one manually operated and one electrically controlled from both the platform and turntable. Some add versatility by putting a smooth-bore, stacked-tip nozzle on one and a spray nozzle on the other.

 
(19) LED rope lighting can safely illuminate the climbing area of the aerial ladder.

Gated handline discharge connections in the platform are common. I suggest including a hose storage box for one or two full lengths of hose and a short (10-foot) length of hose and nozzle for use during up-close external overhaul from the platform. You can add a hose discharge to the tip of the aerial from the waterway system as well.

The purchase of an aerial apparatus is a major community investment; you must consider it carefully. By performing diligent research, you will have the necessary information to make informed decisions as to proper size and configuration as well as the selection of necessary features and options for maximum efficiency.

 

(20) Dual platform monitors, one with a spray nozzle and one with a smooth-bore stacked-tip nozzle, are a popular configuration.

WILLIAM C. PETERS retired after 28 years with the Jersey City (NJ) Fire Department, having served the last 17 years as battalion chief/supervisor of apparatus. He served as a voting member of the NFPA 1901 apparatus committee for several years and is the author of the Fire Apparatus Purchasing Handbook, the apparatus chapters inThe Fire Chief’s Handbook, and numerous apparatus-related articles. He is a member of the Fire Engineering editorial advisory board and of the FDIC executive advisory board.

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