Tail swing: meaning and why it matters

What it is

A mobile crane's upper works turn on a pin, and the counterweight at the back turns with them. From above, the rear traces a circle around the center of rotation. On many cranes the carrier is narrow, so the rear of the upper works swings out past the carrier's sides. Someone standing beside the carrier, in line with its wheels or outrigger beams, can be inside the path without being near anything that looks like crane.

The same sweep is a hazard to anything fixed. A wall, a stack of material, a parked vehicle or another crane's boom within the circle can pinch or crush a person against it, or be struck by the counterweight.

Controlling the area

OSHA 29 CFR 1926.1424 covers work area control. Its aim is that people stay out of the area where the rotating upper works can strike or crush them. Read the section itself for what it requires. These measures are the usual practice:

• Mark the boundary. A physical barrier such as a warning line or railing at the edge of the hazard area is the common way to show where the swing reaches.
• Control entry. When a worker has to go into the area, the operator is told and holds the swing until a signal agreed in advance says the worker is clear.
• Check clearance first. Before swinging, and before setting up, look at where the rear of the upper works will pass.
• Keep one person watching. A signal person or spotter can watch the rear when the operator cannot.
• Plan the setup. Choose a position with clearance all around.

Tail swing is a different matter from the working area on a load chart, which names where the boom may work with certain ratings. See quadrant of operation.

Common mix-ups

• Tail swing is the same as boom swing. The boom sweeps the load's path. The tail sweeps the rear.
• If I am outside the carrier I am safe. The rear passes outside the carrier.
• Only the operator needs to watch. The operator often cannot see the rear.
• Tail swing only matters when swinging a load. It matters whenever the upper turns.

On the NCCCO written exam

Core task 1.5 covers access, pinch and crush points and personnel, in Site, about 22% of the exam under the 01/25 handbook. Expect a question about marking or controlling the swing area, or about what to check before turning the upper.

Practice it

Read the full NCCCO Core written exam guide to see how Site fits with the other domains. Then read quadrant of operation and outrigger setup, which govern where the crane can work and how it is supported. The crane terms glossary lists the set.

Know the terms? Take the free 10-question check

Take the free 10-question check. It is scored by the Core outline domains and needs no signup, so you see whether site, operations, technical knowledge or load charts costs you the most points. Boom Angle's course then gives you a question bank with each answer key checked by a second solve, timed practice exams, and a study plan built from your exam date.

Sources

Show the list

• 29 CFR 1926.1424: Work area control, OSHA.
• 29 CFR 1926.1402: Ground conditions, OSHA.
• Mobile Crane Operator Candidate Handbook, CCO, Core outline tasks and weights (01/25 revision). Task numbers on this page follow it.