Aerial Setup on a Sloped Lot with a Sinking Pad
At 14:20, Quint 6 is the first aerial on scene at a 4-story, 48-ft office building with fire on the third floor, Charlie side. The only setup area is a parking lot on that side. The lot slopes about 4 degrees to the side, and the apparatus manual in the cab limits operation to a maximum 5-degree slope and requires all four outriggers fully deployed on pads. The asphalt is over a 6-inch stone base, the temperature is 24 F with ice at the low corner, one outrigger pad would land within 2 ft of a storm drain inlet, and a light pole stands 6 ft from the turntable. Third-floor windows are the only access from this side; ground ladders reach the second floor only. The truck's 500-gallon tank is full.
1. Evaluate whether this is a compliant setup and list what must happen before the aerial goes up.
Read the worked answer
It is not yet a compliant setup. Being under the slope limit does not make it safe.
Work through each constraint:
- Slope: 4 degrees is inside the 5-degree limit, but measure it in both directions (fore-aft and side-to-side). If the combined effect puts the apparatus outside the limit, reposition before setup.
- Ice: the low corner is the one that will carry load and slide. Clear and sand or salt it, and use pads; a pad on ice is not a pad.
- Storm drain: a pad within 2 ft of an inlet can crush the structure or drop into it. Bridge it with a steel plate or heavy cribbing, or move the apparatus so the pad lands on solid pavement.
- Light pole: check boom swing and outrigger clearance; 6 ft from the turntable is close.
- Pads and cribbing: all four outriggers fully deployed on pads sized for the load, with the apparatus level within the manufacturer's tolerance.
If any one of these cannot be satisfied, do not raise the aerial. Reposition, work from the Charlie side at a different angle, or use ground ladders for the second floor and interior stairs for the third. The time lost repositioning is far less than the time lost to a tip-over.
2. A firefighter suggests short-jacking the uphill side because the lot is tight. How do you respond?
Read the worked answer
Refuse it.
Short-jacking means operating with one or more outriggers not deployed, which removes the stability the aerial was engineered around. The load chart and the stability calculations assume all outriggers are set.
The failure mode is not graceful: as the boom extends and swings, the center of gravity moves outside the footprint, and the apparatus can tip or the outrigger can punch through the surface. Personnel at the tip and on the ground are exposed with no warning.
Alternatives that actually work:
- Reposition to a flatter spot, even if the aerial angle is less ideal.
- Set up on a different side of the building and reach the objective from there.
- Move the light pole issue or parked cars out of the way with the property owner or police.
- Use ground ladders and interior access for the lower floors and call for a second aerial.
If none of these is possible, the answer is that this building cannot be reached by aerial from this position tonight.
3. Ten minutes into operations, with a firefighter at the tip, the downhill pad visibly sinks about 2 inches and the level indicator shows movement. What do you do?
Read the worked answer
Treat it as an imminent collapse.
- Stop all aerial movement immediately; no extending, rotating, or booming up or down.
- Bring the member at the tip down in a controlled manner along the planned path, or remove them by ground ladder if the aerial cannot be moved safely. Get them off the aerial before attempting any correction.
- Evacuate the collapse zone around the outrigger; the pad can go further without warning.
- Once the aerial is clear of personnel, retract and re-level. Rebuild the pad with proper cribbing and a load-distributing plate, and check the other three pads for the same failure.
- If the surface cannot be made stable, shut the aerial down and switch to another access method.
Report the event to the incident commander and note it for the post-incident review. A sinking pad is an indicator of subsurface failure, not a cosmetic problem, and the aerial should not be reloaded until the cause is corrected.