NTSB Identification: LAX88FA215.
The docket is stored on NTSB microfiche number 39092.
Accident occurred Saturday, May 28, 1988 in SHAVER LAKE, CA
Probable Cause Approval Date: 07/09/1990
Aircraft: CESSNA 421C, registration: N98683
Injuries: 4 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 PLT BOUGHT THE ACFT ABOUT 1 MONTH PRIOR TO THE ACCIDENT. HE HAD LIMITED EXP IN THE ACFT, AND LIMITED EXP WITH HIGH ALT FLT AND ITS WX PHENOMONA. THE PLT OBTAINED TWO WX BREIFINGS FOR THE FLT. DURING BOTH, HE WAS ADVISED OF THE FORECAST AND PLT REPORTED CONDITIONS OF MODERATE TO SEVERE MIXED ICING AND TURBULENCE ASSOCIATED WITH A MTN WAVE ON THE EASTERN SIDE OF THE SIERRA NEVADA MTNS. INSTEAD OF FLYING ALONG HIS INTENDED ROUTE ON THE WESTERN SIDE OF THE MTNS, HE CHOSE A DIRECT ROUTE, WHICH PLACED THE ACFT ON THE EASTERN SIDE OF THE MTNS. THE TRACK OF THE ACFT WAS ESTABLISHED BY RECORDED RADAR DATA. THE DATA SHOWED THE ACFT IN CRUISE AT 16,500 FT UNTIL ABOUT 1 MIN PRIOR TO THE ACCIDENT. THE ACFT WAS SHOWN TO CLIMB TO 17,200 FEET BEFORE IT DISAPPEARED. THE LAST RADAR TARGET WAS OBSERVED ABOUT 2 MILES FROM THE IMPACT LOCATION. THE ACFT IMPACTED IN A STEEP NOSE DOWN DESCENT.

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

INFLIGHT ENCOUNTER WITH FORCASTED SEVERE ICING AND TURBULENCE BEYOND THE CAPABILITY OF EITHER THE AIRCRAFT OR THE PILOT , WHICH LED TO AN INFLGIHT LOSS OF CONTROL. FACTORS IN THE ACCIDENT WERE THE PILOTS LACK OF UNDERSTANDING OF HIGH ALTITUDE FLIGHT ASPECTS AND METEROLOGICAL PHENOMENA.

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