The cage at the top of the aerial ladder has load cells, because the ladder's reach depends on what is in the cage, and the readout on the turntable tells the operator how many people are up there. At full extension, on drills and on jobs, the cage reads ninety two kilos with nobody in it, and the ladder's computer restricts the reach for a man who is not there.
I am the aerial operator, which means I sit at the turntable and put the cage where the officer wants it.
How the cage is weighed.
Load cells in the cage floor read the weight in it and the readout at the turntable shows it. The ladder's computer takes that weight and the extension and the angle and works out whether the load is safe, and it stops the ladder short of any position where it is not. Two firefighters and a casualty in the cage at full extension is the limit case, and the computer knows it.
An empty cage reads zero, with a few kilos for the tools that live in it.
At full extension the cage reads ninety two kilos empty.
Not at the start of the extension. The reading climbs as the ladder goes out, from the tools' few kilos at the bottom, through the twenties and the fifties, to ninety two at the top, as though something were getting into the cage as it rose, and the computer restricts the reach at the top as it would for a man.
Bring it back down and the reading falls the same way, to the tools, at the bottom.
The cage is empty. I can see it. It is at the top of a thirty metre ladder against the sky and there is nothing in it but the tools.
What has been checked.
The load cells, calibrated with test weights at the bottom, and correct. The computer, updated. The cage, stripped and rebuilt at the annual test.
Another ladder. The brigade has two of this type, and the other one, on our station, on our drill ground, reads the tools all the way up. Ours reads ninety two at the top.
The test weight. The annual test puts a certified load in the cage at full extension and reads it. Our ladder reads the certified load plus ninety two, and the tester wrote that down and then crossed it out and wrote the certified load, and then, when I asked him, wrote the ninety two back in with a note.
Ninety two kilos.
A man in fire kit and a set. That is the weight of a firefighter dressed for a job, near enough, and it is the weight the computer restricts for, and the restriction at the top is exactly the restriction for one firefighter in the cage.
The ladder we had before this one, on this station, lost a man from the cage at full extension in the eighties, on a job that is in the history, and I did not know that when I started, and I was told it by the man who trained me on the turntable, on the day he retired, as the last thing he said before he shook my hand.
What it does on a job.
Nothing, mostly. The ninety two is inside the margin for one firefighter and the computer allows what it would allow with one up, and one up is usually what we send. With two up, the computer thinks there are three, and restricts, and the reach is short by a couple of metres, and there have been jobs where those metres would have been useful.
I have told the officer. He has the note on the appliance's file, and he plans his jobs with the reach we actually have, which is the reach with a third man in the cage.
What I do.
I operate the ladder.
The one thing I have changed is that I do not go up in the cage at full extension alone.
Operators ride the cage on drills to feel the ladder from the top, and I did that every month for years.
In the summer I rode it to full extension, alone, on the drill ground, and at the top the readout at the turntable, which my colleague was watching, went to my weight plus ninety two, and in the cage, which is a metre square with a rail round it, I was not alone. Not by sight. By room. The cage was full, the way a cage with two people in it is full, and I stood against the rail on my side with my shoulder against something that took up the other side, and it stayed there until the ladder started down.