|A rear-mount aerial with a straight stick avoids the problem of the bucket hanging in front of the windshield obstructing the driver’s vision. The Elizabeth (N.J.) Fire Department recently put in service an American LaFrance 104-foot with a straight stick. It’s built on an American LaFrance Eagle cab and chassis, powered by a Detroit Diesel Series 60 515 hp engine with an Allison 4000EVS-PR transmission. Other features include a Harrison hydraulic 10,000-watt generator, a stainless steel body, an EMS cabinet and a Federal Q2B siren.|
|While aerials with platforms are typically more versatile and afford greater safety for the users, some departments have decided platforms on a rear-mount aerials hang out over the front too far and obstruct the drivers’ vision to an unacceptable level. Other departments swear by rear-mount platforms and have nothing but praise for their features. (Ferrara Photo)|
When it comes to the topic of mid-mount aerials versus rear-mount aerials, I want to be right up front and say I prefer a rear-mount.
Call me old fashioned, but in my opinion, a rear-mount aerial provides for more maneuverability, reach and versatility than a mid-mount.
Before I get into specifics, I want to take a moment to discuss the ins and outs of selecting an aerial ladder for your community. Whether you desire a mid- or rear-mounted ladder, one of the most important factors determining the type of ladder to purchase is reach.
Reach is a simple concept in that the ladder should be designed to reach the desired target at a safe angle. So whether it is a 75-, 80- or 100-foot ladder, we must be sure that what we buy will reach the target.
Obstacles such as parked cars, building cornices, power lines and ground elevation all must be included when determining the length of ladder needed. You must also consider the impact an aerial ladder has on your Insurance Services Office (ISO) rating. ISO requires that an aerial must have a rated height of at least 50 feet and must reach the roof of any structure within the department’s response area to earn maximum credit. Actually, I am not as overly concerned with the ISO credit as I am with purchasing an aerial that will allow us to operate safely, as well as effectively.
Bucket Rarely Blocks View
Now let’s get back to the mid-mount versus rear-mount debate. When it comes to a straight-frame chassis truck there is nothing better that a rear-mount aerial. I have heard arguments stating that a rear mount is OK, but only if you have a stick. Once you attach a bucket or platform to the ladder, a rear-mount now poses problems to the driver.
Fire chiefs argue that the bucket will hang over the cab and partially obstruct the driver’s view. I cannot buy this argument.
I can tell you from experience the bucket never gets in the drivers’ way except when at an intersection, stopped and waiting for the traffic light to change. Sometimes, depending on how close the driver gets to the traffic light, the bucket blocks the view of the light.
Protecting The Chassis
Rear-mounts give you the advantage to back to the corner of a burning structure allowing you to place the chassis of the truck away from the building. This enables you to protect the chassis and allows the chassis to work as a counter balance – an important feature, especially in master stream operations.
Another unique feature of a rear-mount is that it will allow you to lower the ladder below the axis of the super structure. In other words, the operator can actually set the ladder tip or bucket below the truck chassis.
You can do the same with a mid-mount, but the swing of the ladder is limited due to the truck chassis being in the way. Another mid-mount limitation, at least in my mind, is the location of the ladder stabilizer jacks. Usually mid-mount jacks are located on the centerline of the turntable. This location could obstruct the ladder from being used off the side of the truck below the axis of the chassis.
Rear-mount ladders have a clear working space off the back of the truck allowing for below axis operations without obstacles.
One important note: an aerial is actually a large truss that is designed to hang in the air. All the stresses placed on the aerial ladder are transferred to the super structure. Once you place that ladder on a structure, ground or other object, you have just upset the balance of nature. A typical steel manufactured 100-foot aerial ladder can weigh many tons. Placing that ladder on a building is causing undue stress on the building and on the aerial. It is vital that you fully understand the proper operating procedures and load limitations of your aerial ladder.
Failure to do so can result in aerial ladder failure and collapse. Today’s aerial ladders come equipped with ladder load sensors. The sensors are designed to measure the amount of stress or load being placed on the ladder. The sensors send a signal to a digital read out, usually a bar scale gauge, located on the turntable pedestal.
Apparatus height should also be considered. Typical rear-mounts tend to be taller than a mid-mount aerial. You should take this into consideration when planning to purchase an aerial ladder. Height restrictions such as low bridges, tunnels and firehouse bay door heights may prohibit the purchase of a rear-mount aerial. There are aerial ladder manufacturers who now offer a “low profile” chassis to overcome the height restrictions.
Two areas of importance that I must include are ladder testing and operator training.
Inspections Are Critical
Whether you have a mid-mount or a rear-mount aerial, it’s critically important to have the ladder inspected and tested yearly by a reputable testing contractor. The strength of the ladder can deteriorate for any of several reasons, including corrosion, fatigue, wear, stress or mechanical failure. Ladder inspection and testing will help detect any structural or mechanical failures. The testing process can detect unforeseen flaws and aid in maintaining the aerial ladder within its design criteria.
Speaking of design criteria, the number one reason aerial ladders fail is due to operator error. Operator training must include an in-depth understanding of the capabilities and limitations of your aerial truck.
One truck design not covered in this debate is the tractor-drawn tiller truck. In my mind, that unit is the most highly versatile, extremely maneuverable apparatus. Able to negotiate tight streets and sharp corners, the tiller truck will out class the common straight chassis truck.
To me, that’s the ultimate aerial.
Editor’s Note: Joe Mercieri is the fire chief at Littleton Fire Rescue in Littleton, NH. He has served 27 years in the fire service, is an active fire service instructor and holds numerous college degrees and certifications.