NTSB Identification: SEA89FA068.
The docket is stored on NTSB microfiche number 41867.
Accident occurred Wednesday, April 12, 1989 in BELLEVUE, WA
Probable Cause Approval Date: 06/16/1992
Aircraft: LAKE LA-4-200-EP, registration: N8521Z
Injuries: 2 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 INSTRUCTOR PLT (CFI) HAD BEEN TRAINING THE STUDENT, WHO WAS A CERTIFICATED PLT, BUT NOT SEAPLANE RATED. WITNESSES RPRTD THAT AS THE ACFT DEPARTED LAKE SAMMAMISH, THE ENG MADE UNUSUAL SOUNDS, THEN IT BECAME SILENT. ONE WITNESS RPRTD HESAW THE AIRPLANE SPINNING IN A FLAT ATTITUDE. AN INVESTIGATION REVEALED NO PREIMPACT PART FAILURE, BUT DURING A TEST, THE SPARK PLUGS WOULD NOT FIRE CONTINUOUSLY AT THE MIMIMUM ALLOWABLE OPERATIONAL PRESSURE. THE ACFT HAD BEEN EQUIPPED WITH AN EXTENDED PROPELLER HUB IN ACCORDANCE WITH STC #SA4NE. THIS MODIFICATION EXTENDED THE PROPELLER REARWARD BY 4 INCHES. THE ACFT HAD FLOWN 255 HRS SINCE IT WAS LAST INSPECTED.

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

LOSS OF ENGINE POWER FOR AN UNDETERMINED REASON AND FAILURE OF THE INSTRUCTOR PILOT (CFI) TO MAINTAIN CONTROL OF THE AIRCRAFT, WHICH RESULTED IN A STALL/SPIN.

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