NTSB Identification: SEA89LA127.
The docket is stored on NTSB microfiche number 41031.
Accident occurred Friday, June 30, 1989 in SNOQUALMIE PASS, WA
Probable Cause Approval Date: 06/16/1992
Aircraft: PIPER PA-28-180, registration: N56759
Injuries: 2 Serious,1 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.

WHILE ATTEMPTING TO CROSS OVER THE CASCADE MOUNTAINS, THE PILOT ENCOUNTERED CLOUDS, WHICH THE ACFT WOULD NOT BE ABLE TO OUTCLIMB. HE ELECTED TO DESCEND BELOW THE CLOUDS & FOLLOW AN INTERSTATE HIGHWAY THROUGH A PASS. HE INADVERTENTLY ENTERED A BOX CANYON. WHILE MANEUVERING TO REVERSE COURSE, THE AIRCRAFT MUSHED INTO TREES. THE PILOT HAD RECEIVED A PREFLIGHT WEATHER BRIEFING, WHICH INDICATED VFR FLT CONDITIONS IN THE PASS. A WEATHER OBSERVATION STATION (THAT WAS PREVIOUSLY IN THE PASS) HAD BEEN CLOSED BY THE NATIONAL WEATHER SERVICE.

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

IMPROPER IN-FLIGHT PLANNING/DESCISION BY THE PILOT, WHICH RESULTED IN THE AIRCRAFT ENTERING A BOX CANYON WITH INSUFFICIENT SPEED AND ALTITUDE TO MANEUVER OUT OF THE CONFINED AREA. FACTORS RELATED TO THE ACCIDENT WERE: THE PILOT'S CONTINUED FLIGHT INTO KNOWN ADVERSE WEATHER CONDITIONS AND THE TERRAIN AND WEATHER CONDITIONS.

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