Narrative:

On takeoff from runway 9R the tail pipe hot light came on at 400 ft. Ran checklist, declared emergency, landed on runway 27L. Entered a discrepancy in aircraft maintenance log. Then maintenance was performed on aircraft. Then 2 FAA inspectors came out to the aircraft and checked out aircraft and maintenance log, and pilot information. We then used aircraft for revenue flight. Very heavy rain on ground saturated tail pipe hot sensors. Callback conversation with reporter revealed the following information: the reporter stated the cause of the #2 engine tailpipe hot light warning was the 3 tailpipe sensors were saturated with water from a heavy driving rain. The reporter said this has happened before to other saab 340 aircraft, but this was the reporter's first experience with water saturated sensors. The reporter said the danger with this false warning is the reaction to pull back on the power and the result is immediate autofeathering of the propeller. The reporter stated a procedure is in place to gain 400 ft altitude before reducing power and allowing the propeller to autofeather. The reporter said the airplane was checked by maintenance and returned to service.

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Original NASA ASRS Text

Title: 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.

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.