Know Your Aerial

Matt Leonard from Montgomery County (MD) Fire Rescue Station 3 submitted this awesome document measuring their 2019 Seagrave 95′ Aerialscope – Which happens to be one of our favorite tower ladder brands.

After the department purchased a new aerial, we wanted to know it’s exact measurements in different configurations. We used a 100’ tape to measure the reach of the aerial fully retracted and fully extended when at an angle of -8*, 0*, 45*, and 72*; including 20* over the cab. The aerial in question is a 2019 Seagrave 95’ Aerialscope and this article is not a knock or praise for said brand, rather just to demonstrate the capabilities and limitations of aerials. We took two types of measurements, 1) platform distance from the apparatus where we attached the tape to the tread plate by the outrigger and measured out to the end of the platform; and 2) platform distance from the ground where the tape was attached to the top of the rub rail (which is also the same level you stand) and measure down to ground level.

 

This specific aerial has a Cab Avoidance feature which prevents the aerial from contacting the cab. The computer limits the operation within a certain degree from both sides and while overtop the cab. A Ladder Override switch is available and will allow you to move into this zone (and to crush the cab) if needed.

With the Cab Avoidance activated automatically by the computer, the lift cylinder stops well short of the cab preventing contact. Activating the Ladder Override switch will allow continued movement. However, to put into perspective how much extra travel is available prior to near contact while at full extension, the image below was taken from the turntable, looking to the officer side. The cone on the right indicates the location the Cab Avoidance activated, and the cone on the left indicating how much greater travel is available while activating the Ladder Override and stopping just prior to cab contact.

The image below better visualizes the Cab Avoidance zones. The red lines indicate the activation point, with the yellow lines indicating how much extra travel you have prior to near cab contact. Knowing you have a certain extra amount of travel is beneficial when you do not have the time or opportunity to stop and check your distance while operating the aerial in an emergency situation.

Again, this article is not to knock any manufacture. All tools and equipment have limitations. The point is to know what you’re working with and able to accomplish with the tools at hand given their weak points. While not every number may be critical or remembered, knowing and memorizing the big numbers is key. NOTE: All measurements were obtained in a parking lot and not perfectly flat ground with the apparatus superstructure fully deployed. Should you attempt the same measurements with a similar apparatus, expect some variations of these numbers.

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