B737 CREW ON ILS APCH TO CLE RWY 24L JUST BELOW 1000 FT IMC ARE UNEXPECTEDLY INSTRUCTED TO SIDESTEP TO RWY 24R.

Narrative

I WAS CLRED AND WAS EXECUTING ILS RWY 24L APCH AT CLEVELAND. ATIS INFO: WIND 160 DEGS/6 KTS; VISIBILITY 6 MI (LIGHT RAIN); CEILING 1300 FT OVCST; TEMP 6 DEGS; DEWPOINT 6 DEGS; ALTIMETER 29.98. AT APPROX 3.5 DME; JUST BELOW 1000 FT AGL; AND STILL IMC; TWR SAID; 'COMPANY FLT NUMBER; CLRED TO SIDESTEP TO RWY 24R.' THERE WAS NO PREVIOUS NOTIFICATION OF A SIDESTEP BY EITHER APCH OR TWR. I RESPONDED; 'COMPANY FLT NUMBER; DOES NOT HAVE THE AIRFIELD IN SIGHT.' TWR THEN TOLD US (I CANNOT RECALL THE EXACT VERBIAGE) THAT IF WE COULD NOT SIDESTEP WITHIN A HALF MI; HE WOULD HAVE TO SEND US AROUND SINCE THERE WAS AN ACFT STILL 'IN POS' ON RWY 24L. AS TWR WAS SAYING THIS; WE BROKE OUT OF THE WX (APPROX 750-800 FT AGL); AND I PICKED UP THE AIRFIELD. I IMMEDIATELY RELAYED THAT I HAD THE AIRFIELD IN SIGHT AND WAS EXECUTING THE SIDESTEP MANEUVER. WE STABILIZED ON FINAL RIGHT AT THE 500 FT AGL MINIMUM; AND CONTINUED THE VISUAL APCH TO AN UNEVENTFUL LNDG ON RWY 24R. I THINK THE DECISIONS I MADE WERE LOGICAL AND SAFE; HOWEVER; A NUMBER OF QUESTIONS CAME AFTERWARDS THAT MADE ME WONDER IF I HAD DONE SOMETHING THAT WAS NOT LEGAL; OR IF THE TWR OPERATOR'S ACTIONS WERE NOT LEGAL. FIRST; I DID NOT THINK THE TWR COULD DIRECT AN ACFT ON AN INST APCH (ESPECIALLY IN IMC) TO PERFORM A VISUAL APCH (SIDESTEP) TO ANOTHER RWY. SECOND; THERE IS NO SIDESTEP PROC PUBLISHED FOR A SIDESTEP FROM RWY 24L TO RWY 24R (THERE IS A PROC FROM RWY 24R TO RWY 24L; WE DISCOVERED LATER); SO HOW DO I KNOW THE RWYS ARE WITHIN THE 1200 FT REQUIRED FOR A LEGAL SIDESTEP? FINALLY; FROM 750-800 FT AGL; WHEN I GOT THE AIRFIELD IN SIGHT; I WAS BARELY ABLE TO ARRIVE IN A STABILIZED POS FOR A VISUAL APCH ON RWY 24R BY THE TIME I REACHED 500 FT AGL. THE FOM (RECENT CHANGE) SAYS WE ARE PERMITTED TO MANEUVER TO A SIDESTEP RWY BELOW 1000 FT/3 MI AS LONG AS WE'RE STABILIZED ON FINAL BY 500 FT AGL. GIVEN A 3 DEGS VISUAL GS AND A MAX OF 1200 FT HORIZ SEPARATION TO SIDESTEP RWYS; SHOULDN'T WE HAVE A MINIMUM SIDESTEP ALT SO THE CREW DOESN'T HAVE TO GUESS? THESE QUESTIONS RACED THROUGH MY MIND IN THE FEW SECONDS I HAD TO MAKE THE DECISION TO ACCEPT THE CTLR'S DIRECTIONS; AND THAT IS THE REASON FOR THIS ASAP RPT.