Subject: Fire Apparatus Rollover Protection
Topic: RollTek Rollover Protection System
Objective: Identify the components of a RollTek Rollover Protection System available on fire apparatus and describe its basic operation.
Task: Given a fire apparatus with a RollTek Rollover Protection System installed, explain how the side-mounted deployable airbags, seatbelt system pretensioners, and special air suspension driver’s seat function in a fire apparatus rollover crash.
The Problem
As a fire department safety officer, I strive to follow current events from the fire service across the United States. I’m always looking for experiences that other departments have had that I can apply to our department’s safety efforts and our training program. From a safety standpoint, there are always lessons to be learned from both good and bad experiences, but for me, the line-of-duty deaths always have a special significance.
Recent U.S. Fire Administration statistics caught my eye regarding the fact that nearly 20-25% of all accidental deaths experienced each year in the fire service are related to vehicles. After looking into this one aspect of our occupational safety, I found that cases involving water tenders (known as tankers in non-NIMS departments) are the most prevalent of these motor vehicle incidents.
The National Institute for Occupational Safety and Health (NIOSH) reports that during the period 1977-1999, 73 deaths occurred in 63 crashes involving tenders. Of those deaths, 54 occurred in 49 separate crashes in which tenders rolled over (http://www.cdc.gov/niosh/hid14.html).
A neighboring fire department recently had its engine crash on a rainy night when the right-side tires went off the edge of the paved road. As the driver steered to correct, the engine went into a skid, rolled and slid onto its officer’s side. Because everyone was seated and belted, the injuries were minor. I saw the rig the next day and it was totaled with lots of damage to the cab. It got me thinking about how protected we are or aren’t as we ride inside our fire apparatus. It also got me thinking about riding seated and belted all the time…no exceptions!
The New Technology
I was surprised and impressed to find a manufacturer out there who was looking into a new technology that can help save our lives in fire apparatus rollover crashes. IMMI, an Indiana-based company, is the only company in the world to manufacture a fire apparatus occupant rollover protection system. IMMI’s RollTek Rollover Protection System uses specially designed deployable airbags installed along each side of the cab’s roofline or along its sidewall area in the crew compartment. There can be as many as six airbags; each designed to deploy across a side window area to protect the occupants in both front seats as well as those in the four possible outboard seat positions in the crew cab area. This combination of deployable RollTek airbags increases the safety and survivability of the crew. In addition, a unique seatbelt pretensioner system snugs the lap-shoulder belt assembly worn by the occupants allowing those individuals to remain securely within their primary restraint system. The special RollTek air suspension seat for the driver and officer has a safety component that lowers it down to a locked position during a rollover crash. This places the occupant in a more protected position within the cab during the rollover collision.
The RollTek system was first utilized by Pierce Manufacturing and marketed as its Side Rollover Protection system in the Pierce Quantum, Lance, Dash, Enforcer and Arrow XT fire apparatus. The system is currently also being utilized by Ferrara (Igniter and Inferno) and KME (Predator). It is anticipated that the RollTek Rollover Protection System will be available in commercial vehicles such as large over-the-road trucks in the near future.
Components and Operation
To understand the components and operation of the RollTek Rollover Protection System, one can compare it to a typical automobile side-impact, supplemental restraint airbag system. The big difference with the RollTek Rollover Protection System is that it activates in the event of a fire truck rollover. The rollover protection system is composed of four integrated components:
1. Rollover Sensor IMMI engineers developed a rollover sensor programmed to constantly monitor and analyze factors such as the fire vehicle’s side angle or tilt of the vehicle, and roll rate. During normal operation, this sensor constantly sends out a signal to monitor the status of each component of the RollTek system. Design engineers were able to develop a “smart” sensor; one that will only deploy the safety systems when truly needed. Engineers found, for example, that if most fire vehicles are tilting or rolling to an angle of 40 degrees, it is an angle at which the fire truck, driven by even the most experienced operator, will be unable to avoid crashing. When the sensor determines that this rollover crash is taking place, it sends an “alert” signal to the advanced occupant protection components.At this point, the RollTek safety system pre-arms itself and the seatbelt pretensioners fire. As the fire vehicle continues to roll, the driver’s air suspension seat lowers automatically. With ground impact only fractions of a second away, the side-mounted airbags deploy into position to protect the outboard occupants from contact with the cab and injury from exterior objects. The sensor activates and deploys up to eight safety components; all within two-tenths of a second elapsed time. Similar to an airbag system in a standard automobile, if normal electrical power is lost, the roll sensor has internal capacitors that store enough power to deploy all the safety devices for one second after power loss. The sensor also contains a crash recorder programmed to record eight seconds of roll data before and two seconds after the crash event.
2. ITS and IHC Airbag System
There are two differently shaped airbags designed for use in a RollTek safety system. One system, called the ITS, or Inflatable Tubular Structure, airbag, resembles an elongated tube. Responders may have seen this style airbag at a side-impact crash involving a late-model BMW automobile. The second style of RollTek airbag is the Inflatable Head Curtain, or IHC. It is pillow-shaped and when deployed covers a larger surface area than the tubular ITS airbag.
The ITS tubular airbag is most commonly mounted along the roofline in the area directly above the front door windows and is used for the front-seat occupants, driver and officer. The larger area pillow-shaped IHC airbag style is most commonly mounted vertically along a sidewall of the cab or on a roof pillar at the front and/or rear windows and provides protection for the crew members riding in the outboard seat positions.
3. S4 Seat Pull-Down System
During a rollover crash, standard air suspension seats can allow the occupant to move out of his or her safe zone, which could result in serious injury or even death. A special component of the RollTek system is the S4 Seat Pull-Down system. These seats are available for both the driver and the officer positions.
The S4 pull-down seat system is based upon a piston/cylinder device powered by a stored gas inflator similar to that used to deploy the RollTek airbags. The unit is about the size of a cigar box. It will always be mounted close to an air-suspension seat and will never be found on a standard, static seat design. The pull-down device may be mounted behind or below the suspension seat. If mounted behind the seat in a vertical orientation, fire apparatus manufacturers typically place a protective shroud over the device to keep foreign objects away from the moving parts. The shroud will be labeled to advise personnel of the S4’s presence. When placed in the seat riser or pedestal, the S4 device is generally not shrouded.
4. Lap-Shoulder Seatbelt with Integrated Pretensioner System
The lap-shoulder seatbelt, which is the primary occupant restraint system for passenger vehicles, is the primary restraint system for responders riding in fire apparatus. It is the foundation upon which any occupant protection system is designed and built. The seatbelt is still the most effective type of occupant protection available. IMMI’s seatbelt system has a built-in seatbelt pretensioner component similar to what can now be found on selected models of passenger vehicles. Called the IGP Buckle Pretensioner, it functions as a safety device to retract the seatbelt buckle. As the buckle is pulled downward, the normal slack in the seatbelt is removed. With the seatbelt snuggly around each occupant, that individual has a greater chance of remaining in the proper position within the seat.
Each pretensioner assembly includes the seatbelt buckle, a steel cable connected to the buckle, several mechanical components and a self-contained micro gas generator. The tube-shaped generator contains an electric initiator, electrical wires and a small quantity of solid propellant. When the pretensioner system receives an electronic signal from the rollover sensor, the pyrotechnic charge fires, pulls the cable and lowers the buckle, removing slack and better positioning the occupant.
The Rollover Scenario
Let’s say that a fire apparatus being driven along a roadway goes off the side of the road and begins to roll over. For purposes of our discussion, we’ll show what happens when the driver, officer and crew are in a vehicle equipped with a RollTek Rollover Protection System. To activate a RollTek airbag, an electrical signal must be received from the rollover crash sensor mounted elsewhere on the fire vehicle. This small electrical current flows to the stored gas inflators causing a special burst disk inside them to rupture.
During this rollover scenario, the S4 seats function by first tightening the seatbelt similar to a passenger vehicle’s buckle pretensioner, but with more available force. This pulls the occupant down into their seat. Immediately thereafter, the S4 pulls the fire truck’s air suspension seat down to its lowest position and locks it down for at least 20 seconds. At IMMI, dynamic testing has proven that this is the safest position for the driver and officer in a rollover crash. These actions increase survivable space in rollover crashes and reduce head, shoulder, hip and knee movement – minimizing contact with vehicle interiors and reducing the chance of head contact with the roof. An additional benefit of the pull-down seat is that it has enough force to pull an out of position occupant back into a normal seating position which provides for better interaction with the side airbags. A tensioned seatbelt and a lowered seat provide the maximum survivable space in the apparatus cab.
Using a stored gas inflator, the RollTek airbag deploys from its stowed position when the gas is released from the pressurized inflator unit. This cigar-shaped inflator unit is eight inches long and constructed of a heavy-gauge metal. The stored gas inflator unit contains a quantity of mixed gases such as oxygen and argon under pressure inside a smaller steel inner cylinder. The gases are pressurized to more than 4,000 psi. There is also a small quantity of a solid pyrotechnic fuel.
The pressurized gases inside the inflator are warmed slightly as they escape. The gases flow through a rubber-lined hose about the diameter of a small garden hose directly into the tubular or pillow-shaped airbag itself. As the pressurized and warmed gases fill the airbags, they deploy across the front door window area. Additional airbags deploy to also protect crew cab personnel riding in the outboard seat positions during the rollover impact.
The ITS tubular airbag inflates to its full eight-by-38-inch size as it assumes the diagonal position across the front door windows of the cab. The pillow-like IHC airbag inflates to its 23-by 16-inch dimension. It is about five inches thick at maximum inflation. During a rollover, the RollTek airbags provide a taut, yet cushioning support for the occupant’s head and neck, reducing injuries and saving lives.
ERG Available
I worked with IMMI to create an Emergency Response Guidebook (ERG) to help emergency response personnel train for vehicle rescue, firefighting, and medical tasks necessary at the scene of an incident where one or more vehicles involved have the IMMI RollTek Rollover Protection System installed. The ERG provides guidance, recommended practices and procedures for dealing with a RollTek Rollover Protection System that has been breached, burnt, deployed or one that remains active having the potential to deploy during normal rescue and extrication activities. The ERG is free and available at http://www.rolltek.com/extrication_education.htm.
TASK: Given a fire apparatus with a RollTek Rollover Protection System installed, explain how the side-mounted deployable airbags, seatbelt system pretensioners and special air suspension driver’s seat function in a fire apparatus rollover crash.
Ron Moore will present “University of Extrication: Hybrid Vehicles Update 2005” at Firehouse Expo 2005, July 26-31 in Baltimore.Ron Moore, a Firehouse® contributing editor, is a battalion chief and the training officer for the McKinney, TX, Fire Department. He also authors a monthly online article in the Firehouse.com “MembersZone” and serves as the Forum Moderator for the extrication section of the Firehouse.com website. Moore can be contacted directly at [email protected].
