PA28 PLT TAKES OFF WITH INOPERABLE STALL WARNING HORN.

Narrative

WHILE ON THE GND; I WAS PREFLTING THE ACFT. I DID NOT CHK THE STALL WARNING HORN OUT OF HABIT BECAUSE MANY TIMES; THE OTHER AIRPLANES THAT HAD STARTED THEIR ENGS AROUND ME WERE TOO NOISY FOR ME TO HEAR IF THE STALL WARNING HORN WORKED. WHILE PRACTICING STALLS; I NOTICED THAT THE STALL WARNING HORN WAS INOPERABLE. ONCE I NOTICED THE STALL WARNING HORN DID NOT WORK; I STARTED BACK TOWARD THE ARPT. ONCE I LANDED; I RPTED THE PROB TO A MECH FOR HIM TO FIX. I WASN'T SURE IF TAKING OFF WITHOUT A STALL WARNING HORN IS ALLOWED; SO I LOOKED IN THE FAR'S. I FOUND THAT 91.205 STATES THAT A STALL WARNING HORN IS NOT REQUIRED FOR VFR. I SEARCHED MORE AND SAW 91.213; WHICH SAYS THAT IF AN AIRPLANE DOES NOT HAVE AN MEL; EVERYTHING IN THE PLANE MUST BE OPERABLE. THROUGH THIS PROCESS; I LEARNED ABOUT MEL'S AND THE REQUIRED INSTS ACCORDING TO THE FAR'S. I WAS NEVER AWARE OF THE ROLE THAT EACH INDIVIDUAL ACFT'S MEL IN THE POH PLAYED WITH REGARD TO THE FAR'S. I HAVE ALSO LEARNED THROUGH THIS PROCESS THAT NEXT TIME I SHOULD WAIT FOR THE ACFT NEXT TO ME TO LEAVE SO I CAN HEAR THE STALL WARNING HORN BEFORE I TAKE OFF.