NTSB Identification: LAX88FA241.
The docket is stored on NTSB microfiche number 39065.
Accident occurred Thursday, June 30, 1988 in PERRIS, CA
Probable Cause Approval Date: 07/09/1990
Aircraft: HELIO HST-550A, registration: N9991F
Injuries: 1 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

AFTER DROPPING SKYDIVERS THE PILOT ENTERED A DESCENT TO RETURN TO THE AIRPORT FOR ANOTHER LOAD OF JUMPERS. HE WAS RECEIVING RADAR ADVISORIES DURING THE DROP FROM A TRACON CONTROLLER. AS THE AIRCRAFT DESCENDED BELOW 4,000 FEET MSL THE CONTROLLER TERMINATED THE RADAR ADVISORY SERVICE. IMMEDIATELY AFTER THE CONTROLLER DISCONTINUED THE SERVICE HE ASKED THE PILOT TO CHECK FOR A STUCK MICROPHONE SWITCH. THE AIRCRAFT CONTINUED ITS DESCENT AND COLLIDED WITH A CAMPING TRAILER AND BUILDING UNDER CONSTRUCTION IN AN EXTREME NOSE LOW ATTITUDE. THE ELEVATOR TRIM WAS FOUND IN THE FULL NOSE DOWN POSITION. NO OTHER MALFUNCTIONS WERE FOUND.

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

FAILURE OF THE ELECTRICAL STABILIZER TRIM CONTROL THAT RESULTED IN AN UNCOMMANDED FULL NOSE DOWN ELEVATOR TRIM COMMAND.

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