NTSB Identification: LAX84FU026.
The docket is stored on NTSB microfiche number 26773.
Accident occurred Saturday, April 21, 1984 in CHICO, CA
Aircraft: Teratorn Aircraft, Inc. TIERRA II, registration: NONE
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.

THE ULTRALIGHT WAS BEING TEST FLOWN AFTER ALTERATIONS TO THE ACFT & ITS FLIGHT CONTROL SYSTEM. THE PLT PUT THE ACFT THROUGH SOME MANEUVERS AND DURING ONE OF THEM, DESCRIBED BY WITNESSES AS A CHANDELLE, THE ACFT NOSED DOWN & CRASHED INTOTHE GROUND. THE ACFT DOVE FROM ABOUT 300 FT AGL. INVESTIGATION REVEALED THAT AN ELEVATOR CONTROL SEAT HORN HAD FAILED & SEPARATED IN FLT. PARTS OF THIS FAILED PART WERE NOT FOUND IN THE WRECKAGE. THIS CONTROL PART HAD BEEN MODIFIED WITH MORE SPACING WASHERS THAN REQUIRED WHICH INCREASED ITS TORSIONAL LOADING. AFTER THIS FAILURE, THE PLT HAD NO CONTROL OVER THE ACFT ELEVATOR.

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

FLT CONTROL SYST,ELEVATOR CONTROL..FAILURE,TOTAL

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

MAINTENANCE,MAJOR ALTERATION..IMPROPER..OTHER MAINTENANCE PERSONNEL



Contributing Factors

FLT CONTROL SYST,ELEVATOR CONTROL..SEPARATION

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