Features, Fire Apparatus

Cantankerous Wisdom: Drift Tests and Brow Lights

By Bill Adams

Did you ever end up in a discussion where you can’t remember what the original topic was, who started the conversation, and why it lasted for three days? Welcome to the world of morning coffee with some of the Raisin Squad. One of the geezers brought in a photo of an aerial ladder failure that obviously happened years ago. The firefighters in the picture were wearing ¾-length boots, rubber coats, and tin helmets—appropriate rubber goods for the 1970s. It appeared the extended ladder just dropped out of the sky. The gang started in on why ladders fail, who’s at fault, what broke, why do some manufacturers build crap, and how come you never hear about snorkels (elevating platforms) failing.

When one white hair mentioned driver (operator) error should always be considered, the rest unloaded on him for picking on the drivers, especially if grievous injuries occurred. The squad protects “its own” despite the fact that the last time they rode a rig it was legal to ride the back step. They’ll blame lack of training, the manufacturer, mechanical error, lack of maintenance, and newfangled electronic controls and gizmos but never the firefighter. The general consensus was if God or the devil didn’t cause a failure, it was because of little or no maintenance. 

Considering it was safe to elaborate on the topic and attempting to impress them, I brought in a couple of pages copied from National Fire Protection Association (NFPA) 1911, Standard for the Inspection, Maintenance, Testing, and Retirement of In-Service Emergency Vehicles. My contention was the cylinders holding the aerial in the sky could have failed. I explained that sentence says: “The extension cylinder shall be subjected to a drift test as follows:

(1) With the hydraulic fluid at ambient temperature, place the aerial device at 60 degrees elevation at full extension.

(2) Mark the cylinder position or the second aerial ladder section in relation to the base section.

(3) Allow the ladder to stand for 1 hour with the engine off.

(4) Measure the drift and verify that the results do not exceed the manufacturer’s specifications for allowable cylinder drift.”

I said that NFPA 1911 defines drift as “A time-dependent movement away from an established position.” And, it says “…these measurements shall be recorded in the test record so that a year-to-year comparison can be made.” Then, to really impress them, I said that’s so you can tell from year to year if the stick might droop down on its own. They beat that up for a while. “I’ve never heard of an aerial drooping or drifting.” “You’re making that up.” “This has to be something new they just came up with.” One semi-smart geezer said, “Hey—that says the manufacturer allows them to drift down. How much is an allowable drift?” I don’t know. “You should.” He’s right in asking how much should an aerial ladder drop (or drift down) on its own. How many people really know? One Raisin said that if an aerial is above a building’s parapet and it drifts down, it could damage a prepiped waterway. Another said, “Water’s not usually piped to the last fly, and anyhow the ladder shouldn’t be extended that far from the roof’s edge.” I said that doesn’t make it right. “It does in my mind.”

Photo 1

Then out of left field a Squad member mentioned a photo (photo 1) I used in an article. He contended the rig was “illegal” and that I shouldn’t have used the picture. The rig had a scene light mounted above the windshield—they’re called brow lights. It blocked one of the five DOT marker lights. This whacko railed that blocking the marker light was illegal, it could cause an accident, blah-blah-blah and I should have known better than using the photo. I said who cares; that’s got nothing to do with ladders, and besides most rigs with brow lights block marker lights. “Oh Yeah? It’s just like ignoring the questions we had about drift tests. You couldn’t answer when we asked you if it was something new.” 

Photo 2

The next morning I brought in copies of text I found online from a book titled The Other Side: Fire Services, by John Owens. Paraphrasing it, Owens says that In 1952, an NFPA subcommittee reviewed problems associated with testing aerial ladders. In the 1970s, a third-party testing procedure was developed called Cylinder Drift Down. This procedure determines how much the tip of a fully extended aerial ladder or platform would lower within thousandths of an inch when elevated to any degree of elevation and to any length of extension in a short period of time. It is 100 percent accurate.” I thought I’d win the drift discussion. My friends(?): “So what? Who cares? We already forgot about drifting ladders. This is about brow lights. Here, look at these two pictures (photo 2 and photo 3). They don’t block out marker lights. Your picture shows an illegal fire truck. That ain’t right.” I went home. I dislike old people more and more every day.

Photo 3

BILL ADAMS is a member of the Fire Apparatus & Emergency Equipment Editorial Advisory Board, a former fire apparatus salesman, and a past chief of the East Rochester (NY) Fire Department. He has 50 years of experience in the volunteer fire service.