A SAAB 340B ON TKOF DECLARED AN EMER AND DIVERTED DUE TO #2 ENG TAILPIPE HOT LIGHT ILLUMINATED.

Narrative

ON TKOF FROM RWY 9R THE TAIL PIPE HOT LIGHT CAME ON AT 400 FT. RAN CHKLIST; DECLARED EMER; LANDED ON RWY 27L. ENTERED A DISCREPANCY IN ACFT MAINT LOG. THEN MAINT WAS PERFORMED ON ACFT. THEN 2 FAA INSPECTORS CAME OUT TO THE ACFT AND CHKED OUT ACFT AND MAINT LOG; AND PLT INFO. WE THEN USED ACFT FOR REVENUE FLT. VERY HVY RAIN ON GND SATURATED TAIL PIPE HOT SENSORS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE #2 ENG TAILPIPE HOT LIGHT WARNING WAS THE 3 TAILPIPE SENSORS WERE SATURATED WITH WATER FROM A HVY DRIVING RAIN. THE RPTR SAID THIS HAS HAPPENED BEFORE TO OTHER SAAB 340 ACFT; BUT THIS WAS THE RPTR'S FIRST EXPERIENCE WITH WATER SATURATED SENSORS. THE RPTR SAID THE DANGER WITH THIS FALSE WARNING IS THE REACTION TO PULL BACK ON THE PWR AND THE RESULT IS IMMEDIATE AUTOFEATHERING OF THE PROP. THE RPTR STATED A PROC IS IN PLACE TO GAIN 400 FT ALT BEFORE REDUCING PWR AND ALLOWING THE PROP TO AUTOFEATHER. THE RPTR SAID THE AIRPLANE WAS CHKED BY MAINT AND RETURNED TO SVC.