NTSB Identification: ATL90MA051.
The docket is stored on NTSB microfiche number 43957.
Accident occurred Thursday, January 18, 1990 in ANSONIA, OH
Probable Cause Approval Date: 03/05/1993
Aircraft: LEARJET 23, registration: N331DP
Injuries: 2 Fatal.

NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft accident report.

AT 0515 EST, THE FLT WAS CLRD FOR TAKEOFF ON A FLT FM YPLISANTA, MI TO LOUISVILLE, KY. ABT 17 MIN LATER, THE FLT CREW BGN TO DISPLAY INDCNS OF A DETERIORATION OF THEIR ABILITY TO CTL THE ACFT. AT 1ST, THEY DEVIATED FM INSTRNS TO HOLD WEST OF THE FINDLAY VOR AT FL220. AS THE FLT CONTD & WAS CLRD TO FL270, THE CREW DISPLAYED CONFUSION ABT MAG HDGS & BASIC INSTRNS. AT 1048 EST, THE ACFT DEVIATED FM THE EN ROUTE HDG & THE WRONG HDG WAS READ BACK AFTER A HDG CORRECTION WAS GIVEN. ALSO, THE ACFT CONTD CLIMBING (TO FL291), THEN RADAR & RADIO CTC WERE LOST AT 0551 EST. THE CTLR NOTED THE PLT'S SPEECH WAS SLURRED & SOME PORTIONS OF THE CONVERSATION WERE UNINTELLIGIBLE. SUBSEQUENTLY, THE ACFT CRASHED IN A STEEP DIVE. NO PREIMPACT PART FAILURE WAS VERIFIED, THOUGH IMPACT FORCES & POST-CRASH FIRE RESULTED IN EXTSV DMG OF THE ACFT. THE ACFT WAS EQUIPPED WITH OXYGEN & PRESSURIZATION SYS. NO AUDIBLE WARNING WAS NOTED ON ATC RECORDINGS TO INDC THE CABIN ALT HAD EXCEEDED 10,000', THOUGH THE ACFT WAS EQUIPPED WITH SUCH A DEVICE.

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

THE FLIGHT CREW BECAME INCAPACITATED FOR UNDETERMINED REASONS AND LOST CONTROL OF THE AIRPLANE.

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