Tue, 20 Mar 2012|
Mike Wilbur discusses the operational differences between an aerial tower and tower ladder.
[MUSIC] [NOISE] [MUSIC] Hi, I'm Mike Wilbur. Welcome to Fire Engineering's Training Minutes. Today we're going to talk about the differences between an aerial tower and a tower ladder. In the fire service and in particularly in the press, many times the nomenclature used to describe these vehicles kinda gets jumbled up. We have terms like cherry picker, platform, aerial device. So we're going to set the record straight here today and try to explain to you the difference between each of these units. You'll also note that one of the towers is a mid-mount and one of the towers is a rear-mount. We talk about scrub area often as it relates to firefighting and the fireground. Scrub area is defined as that area of the building that can be touched with the basket of a tower or the tip of an area ladder. [INAUDIBLE] is dependent on two very important facts: Who built and designed the vehicle; and how the vehicle is positioned when it arrives on the fire ground. Today we have a three-section, rear-mounted aerial tower. It's an aerial ladder that basically has a tower basket attached to the tip. This particular aerial tower, like most, is a three section. Each of the sections generally are about 31 to 32 feet. This is an Apollo 105, it's a Seagrave, it's a mid 90's model. When you attach the basket to the end. We have an overall length from the chassis out to the tip of the basket of 36 feet. Most rear mounted towers have a number out there between 36 and 38 feet. So that means, when you start fire fighting operations, potentially at a [UNKNOWN] or at a tax payer type fire. And you want it to operate at zero degrees, or even a negative angle off the chassis. You would have to have this vehicle 36 feet away. Versus the mid mounted tower that you see to my right. The mid mounted tower has four boom sections, it is a tower ladder. The tower ladder has four booms they're box boom constructed. And it has an escape ladder on top. The basket at the end. With those four sections from the side of the chair, see out to the tip of the basket, is 24 feet six inches. And so you can get this particular tower, much closer to the building line. Then you can get this tower. And we talk about this. As close as you can get to the building increases the side to side scrub area. So, by being able to get a mid-mounted tower we have often talked about which tower ladder or aerial tower has the best scrub area. Is it a rear mounted tower or is it a mid-mounted tower. And by the vehicles design, a mid mounted tower actually has a greater scrub area than a rear mounded tower. As we can get closer to the building, our side to side scrub area increases. Again, with this mid mounted tower, we can get to within 24 feet, six inches. With the rear mounted tower, this boom from the side of the chassis out to the basket is 36 feet, so we have to be 36 feet away, and when we get further away from the building, our side to side scrawl berry is decreased. In some cases it's decreased tremendously. And it actually has a great impact on firefighting operations on the fire ground as to what you can reach and what you can't reach with each individual, piece of apparatus. This is a 95 foot tower. If you measure from the bottom of the box boom down to the ground, you would have to subtract the chassis out if you wanted to use this at a horizontal angle versus a vertical angle. And so we talked about this in a previous segment where you're going to subtract the eight feet from that off the 95, and you are going to have a horizontal reach of 87 feet. This particular vehicle here, with the three section, rear mounted like this, we measured it from the bottom down to the, to the ground. And this, too, has eight feet. It is unusual. This is a low profile chassis, and as you can see here on the apparatus. The turn table was actually dropped here about 15 inches. Normally, when we're out doing classes and measuring the field our rear mounted tower would be about 10 feet of chassi versus the mid mount which is 7 or 8 feet like that particular unit there. So, this is an Apollo 105. So in order to figure out what we could reach on a horizontal plane, we would take 105 subtract the eight feet and we would have a reach with this unit of about 97 feet. But it's not 97 feet one way. It's 97 feet in both directions. But that is if we back the truck right up against the building and flatten the area out like this. The area [UNKNOWN]. But we're not going to do that. We have to be at least one ladder length away. So we're going to get away from the building. And if you take the horizontal scrub area of this particular apparatus, you are going to find out that you would be able to cover about 170 feet. For this particular apparatus here it's 95 feet. We're going to subtract 8 feet from it. We're going to be down to 87 feet. It's 87 feet one side, 87 feet the other side, for a total of 174. Take the unit back off the building one boom length, and I would suggest to you that this unit could cover 160 feet at 0 degrees of angle. And so with both of these trucks at the same building fire, we could cover over 300 feet of building frontage at a building fire. Now I'd like to show you the construction of the boom that differentiates a tower ladder from an aerial tower. [NOISE] Unlike the previous apparatus, the three section rear mounted aerial tower, where the aerial ladder is built in to the tower bucket. And can be used for, not only firefighters but civilians, to egress or exit certain areas on the fire ground. With this mid-mounted tower ladder, the ladder on top of the boom is strictly an emergency escape ladder. It's not designed to have. A civilian's on it, for sure. And only when conditions on the fire ground become very bad and there's problem with the truck would you want to use this emergency escape ladder on the boom of the tower ladder. I hope from this segment that you have been able to learn the true difference between an aerial tower. And a tower ladder. Next time you're on the fire ground you'll become a better and more educated and informed firefighter. And of course when you come to the FDIC show, when you're on the display tour looking at apparatus, you will have a good idea now of exactly what you're looking at. This is Mike Wilbur for Fire Engineering Training Minutes, until next time.