Equation to figure out how many feet per floor to raise 100 ft aerial,if aerial spotted at 26 ft from building?

Replies to This Discussion

Permalink Reply by Jay Granger on August 28, 2008 at 8:25am

Tom, this is a test question for our promotional test. I appreciate your answer,is very helpful. Thanks!

Permalink Reply by Drew Smith on August 31, 2008 at 11:39pm

One way might be the Pythagorean theorum which ia a math equation for a triange. (http://en.wikipedia.org/wiki/Pythagorean_theorem)

If the triangle has one side that forms a 90-degree angle then this works. In your scenario there is a 90-degree angle: The ground and the building wall. That leave the ladder as the third side of the triangle and to figure that length you use:
a = the length of one side of the 90-degree angle
b= the length of the other side of the 90-degree angle
c = the length of the third side (which is unknown)
(a X a) + (b X b) = (c X c) then find the square root of C to know the length.

Well, all of this is fine and well and I know you said it's a test question but..
*The turntable is about 7 feet off the ground so the true length of C cannot be calcualted this way
*Any "100 ft aerial" is generally only 100 ft when raised to 75-degrees. At a lower elevation, the aerial reaches less (because you do not have that 7 feet of heights from the turn table)
*If the apparatus is "spotted 25-26 feet from the fire building" is this measured from the center of the turntable, the side of the apparatus or from the fully extended stabilizer/jack/outrigger? Based on the answer to this question the ladder may need more length.
*What is the standard height per story being used - 10 feet?

If this is on a promo test what is the references source that this answer supposedly comes from?

I'm not trying to be negative but it appears that you should be given more info.

Finally, from a practical standpoint, if the apparatus is only 25-26 feet from the building:
1) You are in the collapse zone unless it is a two or less story building (some might say 1 or less story)
2) You may not be able to reach a 2nd or 3rd floor window because the unextended ladder is still to long to fit. If the distance between the window and turntable is 30 feet and the ladder with all sections still fully retracted is 34 feet it won't fit.

Permalink Reply by Jay Granger on September 4, 2008 at 2:47pm

Drew, thanks for the reply. All of your questions are ones we are currently complaining to our union about. This is a practical test. The truck is positioned 25-26 ft from a 3 story building and we must perform a series of different raises. Our SOP's never allow us to raise the ladder without a spotter to direct us as to where we are in relation to the building. During the test though we have no spotter and therefore must basically guess as to how close we are.They have someone who will let you know if you are about to hit something but that is it! We are trying to make our voices heard, but I doubt any changes will come and this test will end up like most held in court and then thrown out.

Permalink Reply by Antiquefirelt on September 27, 2008 at 11:17am

As noted above the Pythagorean Theorem is the geometry used to determine the answer mathematically. And also noted was the issue with where measurements are taken. In a practical evolution, I'd suggest raising the stick steeper than the objective and extending to a point above the objective then tipping in. It's easier for me to spot the tip when angling down into position than extending out directly to the objective. This is also how we teach placement for rescues so that the occupant doesn't get tempted to jump onto the aerial.

Permalink Reply by Pascal Marchand on October 5, 2009 at 10:35am

Hello Adam

From my experience and what i teach, the Pythagorean Theorem is a good reference to give an average when positioning the apparatus. Then the tip you gave us to go above the objective and tipping down is good for roof operation but in rescue we dont want to tip down on a victim because we dont want her to grab the underside of the ladder. In rescue what we teach here is that your last move will always be an extension or rotation. You'll bring the tip of the ladder at about 10 to 12 feet of the objestive the do the final adjustment that will assure you that on your final move, extension or rotation, depending on the situation, you'll get staight at the victim. And as soon as the victim touch the aerial you stop your manoeuver.

I'm not saying that it's the only way to do, but it's our way and it worked well so far

Regards

Pascal

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As noted above the Pythagorean Theorem is the geometry used to determine the answer mathematically. And also noted was the issue with where measurements are taken. In a practical evolution, I'd suggest raising the stick steeper than the objective and extending to a point above the objective then tipping in. It's easier for me to spot the tip when angling down into position than extending out directly to the objective. This is also how we teach placement for rescues so that the occupant doesn't get tempted to jump onto the aerial.

Permalink Reply by 2qupy1u0od7h4 on January 28, 2011 at 8:39am

No need for me to reiterate the math side of theoretical positioning, and that is really all it is good for, theory & written tests (unless you have a ruler affixed to your aerial).  Practice & experience is still the best method, in reality try to establish landmarks on the aerial as it extends, as to how far out it is.  In some cases I've seen departments that paint small alignment marks indicating how far out the ladder is.  I always keep 2  9"-12" broom stick handles on our platform with a couple of bungi cords apiece.  I affix these to the base of the platform on each corner with about 6-9" sticking out from the paltform.  As I maneuver in towards the building I can see when the stick touches the building and I know I'm 6-9" away.  This way I don't have to "sneak up" on the building and it causes no damage to either the platform or the building.

  As for the best way to approach a victim for rescue, each has it's own merits and arguments. The victim will try to jump down & in, the victim will try to jump up & grab.  Situation will probably dictate what tactic you should use.  As Pascal stated I have found that either rotaing or extending in, top rail of platform slightly below victim level works best for me.  If they do try to jump, it offers the least chance for miss/injury by the victim.

 

  I know that this is probably outdated and doesn't really answer your question but your question has too many questions attached to it as you are aware.  Drew hit the nail on the head though.  As a legitimate test question it has to have a reference and the reference needs to give you the information you need to determine the answer.  Hopefully your department has resolved this by now and that the above information helps in the reality of your aerial operations.