The Importance of Choosing the Right Aerial Ladder during High Angle Evacuations

Written By: Jason Ilowite

By: Jason Ilowite

Many of us in the Fire Department rescue world have trained on, and possibly conducted a high angle evacuation utilizing an Aerial ladder as a high directional. This is a topic that has an extremely large amount of variance when it comes to specific rigging of systems, however there are some standard rules that should be taken in to consideration when deciding which Aerial to use for the job. As we all know, each Aerial has a rated tip load, and as such requires us to know the mass of our rescue package as specifically as possible. Perhaps the most important determination to be made by knowing what our rescue load weighs is whether or not an attendant will ride with the patient. Let’s examine the contributing factors that should form our decision.

Forces applied to the tip of the Aerial: If rigging the Aerial to use the tip as a Change of direction for both lines of your system, we must account for these forces. As an accepted rule a 90 degree COD applies about 1.5 times the load to the COD anchor. This angle can easily change with extension of the aerial device, and further multiply force so it should be monitored closely. This is a simple, yet valuable piece of information to consider when deciding which type of Aerial to use. NFPA has told us that we should factor a rescue package to be 600lbs, split between a victim and a rescuer. The vast majority of “straight stick” aerials have either a 250lb, or 500lb tip load. If we choose to put an attendant on the basket with the victim, we will be applying potentially 600lbs to the tip on a 90 degree Change of direction, giving us a total of 900lbs. This would not be a safe operation. However, the vast majority of “Towers”, or those aerials with a bucket have a tip load of 1,000lbs. As such, if you determine that the patient must have an attendant, utilizing a Tower is the only safe option. Reference the below pictures to further exemplify the effect of COD forces on the tip of an aerial device.

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So now that we know what will happen when we apply a two person load to the tip of an aerial, we must determine when we truly need a second person. Which Patients need an attendant? This is also something that generally has some opinion associated with it however using common sense here should be sufficient. In general Patient’s that are unable to maintain their own airway (vomiting, needing artificial ventilations etc..) need an attendant to ride with them. This is a determination that must be made early on in the operation because as stated above, plays a major role in deciding which type of Aerial to use.

With all this being said, a simple conclusion can be formed on this topic. The intention of this article was not to get in to specifics of rigging systems using aerial ladders because that differs based off of many variables. What should be gathered from reading this is if a high angle evacuation using an aerial ladder requires the use of an attendant, the Aerial should have a minimum tip load of 1,000lbs. The rescue team needs to be intimately familiar with critical angles as it applies to the force being applied to their ladder truck. The evolution can still take place using an aerial with a lesser tip load, however an attendant should not be part of the system.


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13 thoughts on “The Importance of Choosing the Right Aerial Ladder during High Angle Evacuations”

  1. Thanks for this, It’s a great guide to follow. I’d love to see more of the physics and information regarding the critical Angles as they associate with the Ladder. Also the use of the ladder as a “crane” and the potential overloading of the rigged system in that application.
    Thanks Again, Keep up the strong work!

  2. Thanks Thomas, the purpose of this was a very generalized awareness of tip loading and forces. If you’re anything like me you’ve seen quite a good bit of questionable practices regarding this subject; so I figured maybe some common understanding could be gained from writing this. I have big plans to conduct a lot more testing on the aerial/stokes topic in the future and plan on getting more in depth with specific rigging, and effects of certain set ups. Stay tuned, thanks again!

  3. Jason, thanks for the write up. As I see it in your pics the resultant is not vertical and doesn’t reflect a load in the same manner at which the aerial is tested, rather putting a fair bit (scientific term) of force back into compression of the aerial and not necessarily applying torque at the pivot. Have you guys done any testing quantifying the difference between them?

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