Shared Radio Channel and an Ambiguous Signal
A boom truck is setting a 2,800 lb air handler onto a roof. The operator cannot see the roof landing area because of a parapet. A designated signalperson is on the roof with a radio. The radio channel is shared with another crew; earlier a truck driver's voice was heard on it. The signalperson will use hand signals through a small gap if the radio fails. During the lift, the operator hears 'boom down' but cannot tell whether it is his signalperson. The load is drifting toward a roof edge, and a worker on the ground gives a stop hand signal. The operator also sees the load begin to rotate. The signalperson has not completed a pre-lift radio check, and the roof edge has no guardrail. The load needs to move 15 ft beyond the parapet.
1. What communication setup should have been in place before this lift started?
Read the worked answer
A designated signalperson should have been identified in a pre-lift meeting, with a dedicated radio channel or a controlled protocol that prevents other crews from transmitting instructions. The radio should have been tested at the actual working positions, including the blind spot behind the parapet. The operator and signalperson should have agreed on hand signals as a backup, but only if the signalperson can actually be seen. The signalperson needs a clear view of the load, the landing area, and the operator, or a relay signalperson must be used. The roof edge needs an exclusion zone or guardrail, and the ground worker needs a safe position. The operator must know that anyone can give a stop signal and that unclear communication means stop. A shared channel with another crew is not acceptable for a blind lift without positive identification of the signalperson.
2. What should the operator do when hearing 'boom down' from an unknown source and seeing a stop signal from a ground worker?
Read the worked answer
The operator must obey the stop signal immediately. A stop signal may come from any person, not only the designated signalperson, and the operator should not wait to verify who gave it. The ambiguous 'boom down' call is also a reason to stop, because the operator cannot confirm that it came from the designated signalperson. The load is drifting toward a roof edge and beginning to rotate, so holding or stopping the swing is safer than continuing. The operator should hold the load, sound a warning if appropriate, and not resume until communication is re-established with the designated signalperson and the load is under control. The ground worker's stop should be treated as valid, and the area below and at the roof edge should be checked before any further movement.
3. If the radio fails mid-lift and the signalperson cannot be seen, what should happen?
Read the worked answer
The lift should stop. Hand signals through a small gap are not a reliable substitute if the operator cannot clearly see the signalperson, and the operator should not guess at signals for a blind move. The load should be lowered to a pre-planned safe location if that can be done without endangering anyone; otherwise it should be held while a relay signalperson with a clear line of sight is put in place. The new signalperson must be briefed and must be able to see both the load and the operator. The roof-edge exclusion zone must be maintained, and no one should stand under the load. The radio problem should be corrected, the channel should be cleared or changed, and the pre-lift communication plan should be reviewed before resuming. The 15 ft move beyond the parapet should not continue until positive communication is restored.