Bell 212 N873HL accident near Balch Camp, California

Probable cause

The pilot’s inadequate performance planning for the operation that resulted in an excessive gross weight for the operating conditions, leading to a loss of altitude during maneuvering and contact with trees. Contributing to the accident was the pilot’s decision to continue the flight despite a series of malfunctions with the water deployment system, and his subsequent inability to jettison the load, preventing a successful recovery from the loss of altitude.

NTSB analysis

The pilot was conducting aerial firefighting with a helicopter equipped with a water reservoir that, when released, would discharge a maximum of 375 gallons of water. The pilot had completed eight water drops at altitudes of 6,000 to 7,000 ft mean sea level (msl) before flying to an area with an elevation of about 8,000 ft msl. He first flew to the water reservoir, where he deployed the snorkel and activated the pump to fill the onboard water tank. The pilot was initially unable to open the water tank doors, but was subsequently successful after he cycled the tank power switch. He then reactivated the water pump and loaded water into the tank until he observed engine torque increase to about 75% - 78%, which equated to anywhere between 90-180 gallons of water. He then flew to and orbited the fire area, which was about 8,000 ft msl and surrounded by 100-ft-tall pine trees, and started his approach from a slightly higher elevation; however, he noticed that the helicopter required more power than normal to maintain altitude. When the pilot slowed the helicopter, he felt that he was still using more power than normally required and decided to jettison the water load. After two unsuccessful attempts to release the load by depressing the drop switch, he increased power and began a turn towards a meadow when he heard the low rotor rpm horn annunciate. The main rotor then contacted a tree and the helicopter descended rapidly to the ground, where it was destroyed by a post-crash fire.

Postaccident examination of the airframe and engine was incomplete due to fragmentation and thermal damage from the post-crash fire; however, the examination revealed no evidence of a mechanical failure or malfunction.

The pilot computed the allowable payload at a pressure altitude that was 2,000 ft less than where the accident drop occurred. This calculation was for the beginning of the workday; an updated load calculation was not performed, as the pilot would typically take on less water to accommodate environmental changes. The actual load calculations that factored in the helicopter’s remaining fuel quantity, altitude, and temperature at the accident site indicate that the helicopter was likely closer to 10,160 lbs total weight, 160 lbs over the helicopter weight limit for the conditions. With no evidence of a mechanical anomaly, it is likely that the pilot was unable to maintain altitude due to the weight of the helicopter and the altitude when he made the left turn and was slowing down. When he increased collective control during the turn, the low rotor rpm horn annunciated as the helicopter was operating at its maximum performance. The reduction in rotor speed resulted in a loss of lift, which resulted in a descent into trees.

During two water pickups on the day of the accident, the pilot observed that the water pump required additional effort before it shut off. The pilot was also unable to open the water tank doors when he refilled the tank before the accident. He used the emergency jettison function by turning off the master switch to cycle the water tank doors. Despite multiple malfunctions, the pilot still chose to continue the flight. When he decided to abort the water drop at the fire location, the pilot experienced a similar issue with the tank doors not opening with the doors open switch. However, the pilot likely did not have enough time to attempt an emergency jettison, which would have reduced gross weight and allowed him to maintain altitude.

There were no historical maintenance records that showed abnormal performance of the water release system on the accident helicopter.

Text from the NTSB. Open the NTSB docket for WPR23LA338 for the full record.