Narrative:

Cruising at FL250 VMC on IFR flight plan. Sudden smell of smoke and electrical odor. Approximately 15 seconds later, cabin began filling with thick white smoke. Donned air mask, turned off bleed air vents, reduced power. Attempted contact with center, and started high angle descent. Attempted to contact center again as I left altitude, was unable (oxygen mask 'microphone' switch was not on). Had passenger in right seat contact and confirm lower with center. Got approval at approximately 23500 while descending. Action plan to correct -- verify microphone switch on and would declare immediate emergency situation. Deemed failure of mechanical environment center, landed amarillo, tx, without incident or injury.

Google
 

Original NASA ASRS Text

Title: CPR ACFT HAS SMOKE IN COCKPIT AND CABIN.

Narrative: CRUISING AT FL250 VMC ON IFR FLT PLAN. SUDDEN SMELL OF SMOKE AND ELECTRICAL ODOR. APPROX 15 SECONDS LATER, CABIN BEGAN FILLING WITH THICK WHITE SMOKE. DONNED AIR MASK, TURNED OFF BLEED AIR VENTS, REDUCED PWR. ATTEMPTED CONTACT WITH CTR, AND STARTED HIGH ANGLE DSCNT. ATTEMPTED TO CONTACT CTR AGAIN AS I LEFT ALT, WAS UNABLE (OXYGEN MASK 'MIKE' SWITCH WAS NOT ON). HAD PAX IN R SEAT CONTACT AND CONFIRM LOWER WITH CTR. GOT APPROVAL AT APPROX 23500 WHILE DSNDING. ACTION PLAN TO CORRECT -- VERIFY MIKE SWITCH ON AND WOULD DECLARE IMMEDIATE EMER SIT. DEEMED FAILURE OF MECHANICAL ENVIRONMENT CTR, LANDED AMARILLO, TX, WITHOUT INCIDENT OR INJURY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.