Radio Failure During a Blind Pick Over a Parapet
A 60-ton all-terrain crane is positioned on a downtown street to lift a 4,500 lb rooftop mechanical unit over a 14 ft parapet. The operator cannot see the landing area or the load once it passes the parapet. A signal person on the roof controls the lift by two-way radio. During the swing, the radio goes silent. The operator sees a worker on a nearby balcony gesturing with an arm signal that could be interpreted as “stop,” but that worker is not the designated signal person and is not in the lift plan. The load is suspended about 3 ft above the roof, outside the operator’s direct view. The operator’s horn works. The site has a written lift plan requiring one qualified signal person and a backup hand-signal method. The backup signal person is on the ground and cannot see the load. The operator must decide within seconds whether to continue, stop, or lower.
1. What should the operator do immediately when the radio goes silent and the load is suspended?
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The operator should stop all crane motion and hold the load. Continuing the swing or boom movement without communication is unsafe because the load is outside the operator’s view and the landing area is not visible. The operator should not lower blindly; the load is only about 3 ft above the roof, and an uncontrolled lowering could set it down off-center or on an obstruction. The operator should sound the horn to alert personnel and wait for the designated signal person to re-establish communication. If the lift plan includes a specific lost-communication procedure, follow it. The key judgment is that a suspended load outside the operator’s view requires positive, designated communication before any further movement.
2. How should the operator interpret the balcony worker’s arm signal?
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The balcony worker is not the designated signal person and is not part of the lift plan. The operator should not treat an ambiguous gesture from an unauthorized person as a movement command. However, anyone may give an emergency stop signal, so if the gesture is clearly and unambiguously “stop,” the operator should stop and remain stopped. Because the signal is ambiguous, the operator should not resume or change movement based on it. The correct action is to hold, sound the horn, and wait for the designated signal person or a prearranged backup signal person who can see the load. Relying on an unauthorized signal would violate the lift plan and create conflicting communication.
3. What pre-lift planning would have prevented this, and what is the recovery sequence?
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Pre-lift planning should have included a backup radio, a designated alternate signal person with line of sight to the load, a clear lost-communication procedure, and agreed hand signals. The plan should also identify a safe set-down location visible to the operator or a relay signal person. The recovery sequence is: stop and hold; sound the horn; re-establish radio contact or establish line-of-sight hand signals with the designated signal person; verify the load and landing area; then resume only under positive communication. If communication cannot be restored, lower the load only under a preplanned safe procedure with a spotter who can see the load, or secure the area and wait for a qualified signal person.