WEEK 7
H2F brings you the ‘helicopter mayday of the week’ with a short accident report summary. I tell you what happened. You think more about why it happened. We all learn from it. Because that’s what accident reporting is for.
TITLE
Settling with power during firefighting long-line water pickup leads to loss of control.
WHAT?
A Bell 214 helicopter was conducting long-line external load operations in support of wildfire suppression. The pilot was approaching a lake to fill a Bambi bucket suspended on a 150-foot long-line. During the approach, the pilot encountered the onset of settling with power and attempted recovery by lowering collective and initiating a 180-degree turn. During the manoeuvre the bucket struck the water and the long-line pulled the helicopter laterally, after which the aircraft collided with terrain near the shoreline.
WHERE?
Remote area approximately 22 miles northeast of McCall, Idaho.
WHEN?
July 25, 2007. The NTSB final report was published on March 31, 2008.
HOW?
At the bottom of an approach toward the lake for water pick up, the helicopter had insufficient performance at low speed to arrest a rate of descent. Recognising incipient vortex ring state , the pilot attempted corrective action by reducing collective and turning away however, the Bambi bucket entered the water during the manoeuvre. The long-line then pulled the helicopter laterally while the aircraft was turning 20–40 feet above the water, leading to loss of control and impact with marshy terrain adjacent to the shoreline. Examination of the aircraft revealed no mechanical failures.
CONDITIONS?
The operation involved long-line external load work at high altitude in mountainous terrain. The estimated density altitude at the time was about 10,221 feet, which reduced the performance margin. Winds were light and variable. The flight profile required low-speed handling over water with an external load, increasing susceptibility to settling with power and load interaction effects.
OUTCOME?
The helicopter sustained substantial damage. The pilot received serious injuries and the crew chief/passenger sustained minor injuries.
WHY?
- Pilot’s planned approach lead to settling with power and incipient vortex ring state during low-speed descent.
- External load (Bambi bucket) snagging in the water provoking a loss of control.
- High density altitude reducing aircraft performance margins.
- Light and variable wind conditions increasing power required.
REFERENCE?
National Transportation Safety Board. (2008, March 31). Aviation investigation final report: Accident number SEA07TA214 (Bell 214ST, N724HT). National Transportation Safety Board. https://data.ntsb.gov/Docket?ProjectID=66303
https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/66303/pdf
Note:
Accident reports selected from the following open source databases: US NTSB; UK AAIB; Flight Safety Foundation’s Aviation Safety Network; Australia’s ATSB. Ireland’s AAIU; Taiwan’s TTSB; France’s BEA; Spain’s CIAIAC. Germany’s BFU.
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