PLT OF A CPR LTT ACFT HAS VERTIGO WHEN ENTERING CLOUDS WITH STROBE FLASHING. ALT OVERSHOT RESULTS.

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SUBTLE INCAPACITATION OF PF DUE TO VERTIGO. CREW DEPARTED LGB USING A NOISE ABATEMENT PROC AND VERY LIGHT ACFT WT AT NIGHT. AT 1500 FT MSL A L TURN FROM RWY HDG OF 300 DEGS TO 180 DEGS WAS INITIATED. CLOUD WAS ENTERED APPROX 2200 FT MSL. THE STROBE LIGHTS AND WING MOUNTED TAXI LIGHTS MAY HAVE COMBINED TO CREATE THE VERTIGO; AS LATER INDICATED BY THE PF. WITH THE HIGH RATE OF CLB AND VERTIGO; THE PF FAILED TO SUCCESSFULLY STOP THE CLB AT THE ASSIGNED ALT OF 3000 FT MSL. CREW CALLS WERE MADE AT 1000 FT PRIOR TO ASSIGNED ALT. ALT WAS OVERSHOT BY 300 FT. PNF AIDED IN RETURNING THE ACFT TO ASSIGNED ALT. EXCURSION WAS NO MORE THAN 10-20 SECONDS. WHILE PF ATTEMPTED RECOVERY OF ALT; SCAN WAS LOST AS IT APPARENTLY PREVENTED CONTINUATION OF THE TURN. ONCE ALT WAS REGAINED THE TURN WAS RESUMED. THESE EVENTS OCCURRED AFTER A 14 HR DUTY DAY. ONCE THE STROBE WAS TURNED OFF AND THE CLB RESUMED; NO APPARENT CONTINUATION OF THE VERTIGO WAS EVIDENT. THE ACFT CLBED INTO VFR. THE VERTIGO WAS DISCUSSED AT THE TERMINATION OF THE FLT. PERHAPS THE VERTIGO CIRCUMSTANCES COULD HAVE BEEN THE RESULT OF A NUMBER OF ITEMS WHICH IN CONJUNCTION WITH EACH OTHER MANIFESTED ITSELF. OF REAL NEED ARE LIMITS TO DUTY TIME FOR PART 91 OPERATORS TO 'SHOVE' IN FRONT OF THE ACFT OWNER TO REASON WHY THE CREW MUST NOT BE ABUSED BY CORPORATE AMERICA FOR SAFETY REASONS ALONE.