A B737-300 INCURRED DAMAGE TO THE INBOARD COWLING ON #1 AND #2 ENGS WHEN THE LEADING EDGE DEVICES WERE EXTENDED WITH THE ENG COWLING OPEN.

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EVENING CREW BROUGHT OVER ACFT APPROX XA00. I; ALONG WITH 2 OTHER MECHS; FINISHED PRE-DOCK FUNCTIONS; PUT THE AIRPLANE IN HANGAR; AND HELPED HOOK UP GND PWR BY XB00; AT WHICH TIME THE MECHS BEGAN THE SCHEDULED 'C' CHK. AS I WAS WALKING BY THE NOSE OF THE ACFT AT APPROX XB30; A MECH ASKED IF ANYONE WAS IN THE COCKPIT. I ASKED HIM WHAT HE NEEDED. HE REPLIED THAT THE LEADS WANTED THE FLAPS OUT ELECTRIC. I SAID THAT I WOULD GO UP IF A LEAD WOULD CLR THE ACFT. A LEAD GAVE ME THE THUMBS UP; VISUALLY; AS I WAITED AT THE FORWARD ENTRY DOOR. I ENTERED THE COCKPIT AND CHKED TO MAKE SURE THE STANDBY RUDDER BREAKER WAS OUT AND COLLARED. I SET THE ALTERNATE FLAP SWITCH TO STANDBY; LISTENED FOR STANDBY PUMP TO NOT START. I SET UP/DOWN SWITCH TO 'DOWN.' I MONITORED FLAP INDICATOR AS FLAP TRAILING EDGE MOVED TOWARDS 1 DEG. I MOVED THE FLAP HANDLE FROM 0 DEGS TO 40 DEGS TO RELIEVE TENSION ON FLAP MOTOR. WHEN I HEARD A NOISE LIKE A LARGE LADDER FALLING TO THE FLOOR; I IMMEDIATELY: 1) SET THE UP/DOWN SWITCH TO 'OFF;' 2) SWITCHED THE ALTERNATE FLAP SWITCH OFF; 3) MOVED THE FLAP HANDLE TO 1 DEG TO MATCH FLAP POS; 4) HEARD SOMEONE YELL TO TURN HYDS OFF AND IMMEDIATELY DID SO. THE KRUGER FLAPS DEPLOYED AND DAMAGED THE INBOARD CORE COWLS ON #1 AND #2 ENGS.