Narrative:

On climb out 'hydraulic' annunciator illuminated. After completing memory items we followed the abnormal checklist for hydraulic failure. Flight attendant and passenger were notified, lga station (company) was notified, ATC (ny approach) was notified and an emergency was declared. Returned to lga for a normal uneventful landing.

Google
 

Original NASA ASRS Text

Title: AN SF340 LOST ITS HYD SYS ON CLBOUT FROM LGA. EMER DECLARED WITH A RETURN LAND.

Narrative: ON CLBOUT 'HYD' ANNUNCIATOR ILLUMINATED. AFTER COMPLETING MEMORY ITEMS WE FOLLOWED THE ABNORMAL CHKLIST FOR HYD FAILURE. FLT ATTENDANT AND PAX WERE NOTIFIED, LGA STATION (COMPANY) WAS NOTIFIED, ATC (NY APCH) WAS NOTIFIED AND AN EMER WAS DECLARED. RETURNED TO LGA FOR A NORMAL UNEVENTFUL LNDG.

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.