NTSB Identification: LAX06LA290.
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Accident occurred Saturday, September 09, 2006 in Van Nuys, CA
Probable Cause Approval Date: 06/30/2008
Aircraft: Schweizer 269C-1, registration: N323CP
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The certified flight instructor (CFI) and pilot under instruction (PUI) were going to perform a practice autorotation onto the taxiway. The airspeed was 65 knots indicated airspeed (KIAS), the manifold pressure was 21-23 inches, and the altitude was about 500 feet above ground level (agl). Shortly after initiating the maneuver, the low voltage warning light illuminated. They scanned the operating gauges and tachometer, which indicated a loss of engine power. The CFI took control; the helicopter landed hard, and the tail boom separated. Post accident examination revealed that the engine would run rough at idle with full mixture applied. The engine produced 2,000 revolutions per minute (rpm) with the mixture leaned. Examination of the fuel servo revealed no anomaly other than the idle spring missing from the mixture link, and that the idle was out of adjustment. Initial flow test results were out of limits in the idle range, but satisfactory at maximum throttle. With proper adjustment of the idle link, test results were within specified limits in all ranges. The purpose of the idle mixture spring is to control the movement of the mixture adjustment. If this spring is not installed, the mixture setting can vibrate to higher or lower settings. Maintenance records indicated that maintenance personnel had recently made an adjustment to the idle setting.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Inadequate maintenance adjustment and missing mixture spring, which resulted in a loss of engine power during approach.

Full narrative available

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