HELI DEPARTING LGB CROSSED RWY WITHOUT ATC CLRNC IN CONFLICT WITH OTHER TFC.

Narrative

I WAS BEGINNING A FAMILIARIZATION FLT WITH A STUDENT. THE STUDENT ASKED FOR A DIRECT N DOWNEY DEP. THE CTL TWR APPROVED THE DEP. I THEN VERIFIED THAT WE WERE APPROVED FOR A 'DIRECT' DEP. THE CTLR CONFIRMED. WE TOOK OFF PARALLEL WITH ACTIVE RWY 25R. RWY 30 WAS ALSO ACTIVE AND IN OUR TKOF PATH. NORMALLY; RWY 25R IS CROSSED MIDFIELD AT 500 FT AGL; BUT WE WERE CLRED DIRECT TO OUR DEP RTE; SO I UNDERSTOOD TFC WAS NOT A FACTOR ON RWY 25R. IN NORMAL PATTERN PROCS WE CROSS RWY 30; WHICH IS NEARLY ALWAYS AN ACTIVE RWY. IN A REGULAR N DOWNEY DEP; WE WOULD HAVE CROSSED RWY 30 AND ENTERED THE HELI L TFC PATTERN UNTIL REACHING 500 FT AGL. THEN WE WOULD HAVE CROSSED RWY 25R MIDFIELD AT 500 FT. BUT SINCE A DIRECT DEP WAS REQUESTED AND APPROVED; IT WAS ASSUMED BY THE CTLR THAT WE WOULD NOT CROSS RWY 30 ON TKOF. UPON REACHING RWY 30; I FELT WE HAD CLBED TOO FAR TO THE W AND INSTRUCTED MY STUDENT TO TURN N IN ORDER TO STILL CROSS RWY 25R MIDFIELD. I FORGOT TO TAKE INTO CONSIDERATION THE POSSIBILITY OF TFC ON RWY 30. AS WE TURNED R; WE SAW A SENECA APPROX 150 FT OFF OUR R SIDE. WE TURNED BACK TO THE L AND CONTINUED WBOUND. I REQUESTED A TURN TO THE N; WHICH WAS THEN APPROVED BY THE CTLR. I WAS STRONGLY REPRIMANDED BY THE CTLR FOR XING RWY 30. I BELIEVE THIS EVENT WAS A PRODUCT OF POOR COM AND UNDERSTANDING BTWN MYSELF AND THE CTLR. I AM NEW TO THE LOS ANGELES AREA AND LONG BEACH ARPT. I HAVE HAD MINIMAL TRAINING AND WAS NOT FAMILIAR ENOUGH WITH ALL WRITTEN AND ASSUMED PROCS. I LATER TALKED WITH A SUPERVISING CTLR WHO CLARIFIED MY MISTAKE AND WHAT I SHOULD HAVE DONE ON MY DEP. SINCE THEN; I HAVE DONE MORE TRAINING ON DEP AND ARR PROCS TO ENSURE A SIT LIKE THIS DOES NOT OCCUR AGAIN.