What was found
AIRCRAFT WAS PARKED AT MGA STATION DURING PASSENGER BOARDING FOR FLIGHT AV397 FROM MGA TO SAL WHEN, FOLLOWING APU START, THE FLIGHT CREW REPORTED A STRONG SMOKE ODOR AND VISIBLE SMOKE. THE FLIGHT CREW ACCOMPLISHED THE QRH PROCEDURE SMOKE/FUMES AVIONICS SMOKE & PAX SUBSEQUENTLY DISEMBARKED ACFT. NO EMERGENCY DECLARED. SMOKE ODORS WERE REPORTED BY THE FLT CREW, CABIN CREW, AND PAX. ACCORDING TO MAINT, THE VISIBLE SMOKE WAS OBSERVED EXTERNAL TO ACFT. MAINT PERFORMED TROUBLESHOOTING IAW TSM 05-50-00-810-831-A. AN OPS TEST WAS PERFORMED IAW TASK 21-23-00-710-005-A, AMM FAULT ISOLATION PART 18, PACK TEMP CONTROL SYSTEM. TROUBLESHOOTING MATRIX ASSOCIATED WITH TSM 05-50-00-810-831-A IDENTIFIED THE APU AS MOST LIKELY SOURCE OF REPORTED ODOR/SMOKE CONDITION. MAINT RECORDS SUBSEQUENTLY DOCUMENTED, POSSIBLE CAUSE OF SMOKE IS APU. THE APU WAS DEFERRED IAW DMI/MEL REF 49-10-01 CATEGORY C, REVISION 42, UNDER AUTHORIZATION NO. 689-TSR-2026-09-002. FOLLOWING DEFERRAL, ACFT OPS FLIGHT AV397 FROM MGA TO SAL WITH APU DEFERRED & NO FURTHER REPORTS OF SMOKE, FUMES, OR ODOR RECEIVED.