Sikorsky S-58ET N33602 accident near El Segundo, California

Probable cause

A partial loss of engine power and the failure of the external hook to release the load for undetermined reasons.

NTSB analysis

While making the final external load lift from the roof of an office building, the pilot reported that one of the two engines lost power. Witnesses assisting in the operation also reported hearing an engine wind down. The helicopter drifted forward, veered off the side of the roof, and impacted trees and landscaping below. The pilot reported that he had about 400 lbs of fuel on board before the accident flight. The weight of the air scrubber that was being lifted was estimated to be 4,700 lbs; the maximum lifting capability of the helicopter was 5,000 lbs. The pilot reported that he depressed the electrical cargo release switch a couple of times before the helicopter collided with the building and terrain, but he did not attempt to use the manual release because it would have required him to remove his feet from the antitorque pedals to activate a foot lever next to the pedals. During the wreckage examination, the cargo hook was found in the closed position. Postaccident examination of the hook did not reveal any anomalies that would have precluded normal operation; however, due to the extensive impact and fire damage to the electrical system, it could not be determined why the hook did not release the load. Organic debris located on the intake screen of the #1 engine and the lack of such debris on the intake screen of the #2 engine indicated that the #2 engine probably was not operating at the time of the accident. A postaccident examination of both engines revealed no anomalies that would have precluded normal engine operation. Had the pilot been able to release the load, he might have been able to make a successful landing.

Text from the NTSB. Open the NTSB docket for WPR11FA163 for the full record.