MIL INSTRUCTOR ALLOWS CHANGE IN DEP INSTRUCTIONS TO DEVELOP INTO A POTENTIAL CONFLICT BEFORE STUDENT INSTRUCTOR ARE CHALLENGED BY DEP CTL.

Narrative

MY ACFT; A KINGAIR; HAD BEEN CLRED FOR THE ILS RWY 17R AT HARLINGEN/VALLEY INTL ARPT. VALLEY APCH HAD GIVEN THE DEP INSTRUCTIONS OF 'FLY HDG OF 030 DEGS; CLB AND MAINTAIN 2000 FT.' UPON SWITCHING TO TWR; THEY INSTRUCTED US TO RPT THE LOM (SEBAS). AFTER RPTING SEBAS INBOUND; TWR INSTRUCTED US TO 'CONTINUE' AND WITHIN 1 MIN CLRED US FOR 'THE OPTION RWY 17R.' AFTER EXECUTING A TOUCH-AND-GO; TWR GAVE US THE FOLLOWING INSTRUCTIONS; 'FLY RWY HDG; CONTACT DEP.' PASSING 700 FT MSL (664 FT AGL) DURING THE CLBOUT ON RWY HDG; I ASKED MY STUDENT WHAT VALLEY APCH HAD GIVEN US FOR DEP INSTRUCTIONS; MAINLY TO CONFIRM THAT THERE WAS A CONFLICT AND WE NEEDED TO CLARIFY THE INSTRUCTIONS WITH THE CTLR. HE IMMEDIATELY TURNED TOWARD 030 DES AND CONTINUED THE CLB TO 2000 FT MSL. AT THIS POINT; I SHOULD HAVE CLARIFIED THE INSTRUCTIONS MYSELF; BUT WANTED TO LET THE STUDENT HANDLE THE RADIOS. HE FINALLY MADE THE CALL AFTER WE WERE ESTABLISHED ON A HDG OF 030 DEGS AT 2000 FT MSL. UPON CHKING IN WITH VALLEY APCH; THE CTLR ASKED IF TWR HAD INSTRUCTED US TO FLY RWY HDG. I IMMEDIATELY RESPONDED; 'YES SIR; THEY DID.' HE CALLED THE B737 TFC AT OUR 3 O'CLOCK POS AT THE SAME ALT. I IMMEDIATELY CALLED THE TFC IN SIGHT AND THAT I WOULD MAINTAIN VISUAL SEPARATION FROM THE TFC AND MAINTAIN 2000 FT; AS HE HAD INSTRUCTED. THE B737 CONTINUED ITS CLB TO THE NE AND EVENTUALLY RECEIVED CLRNC BACK ON COURSE DIRECT TO CRP. I CONTINUED NBOUND AND RECEIVED A CLRNC TO NGP. UPON LNDG AT NGP; I FOUND OUT THAT THE B737 HAD JUST TAKEN OFF FROM RWY 13 AND THAT WAS THE REASON FOR THE TWR INSTRUCTIONS OF 'FLY RWY HDG.' WE DO NOT HAVE TCASII IN OUR ACFT AND I DON'T KNOW EXACTLY HOW CLOSE WE CAME BECAUSE WE DIDN'T SEE THE TFC UNTIL VALLEY APCH RPTED IT. CONTRIBUTING FACTORS: 1) FAILURE TO COMPLY WITH THE PROPER DEP INSTRUCTIONS; IE; THOSE GIVEN BY TWR. 2) POOR COM ON MY PART FOR NOT CLARIFYING THE INSTRUCTIONS AS SOON AS THEY WERE GIVEN. 3) POOR BAL OF INSTRUCTION AND SAFETY ON MY PART FOR LETTING THE STUDENT DELAY TOO LONG IN CONTACTING VALLEY APCH. 4) POOR SITUATIONAL AWARENESS ON MY PART FOR NOT REALIZING THAT TWR HAD CLRED THE B737 FOR TKOF ON RWY 13 AFTER MY TOUCH-AND-GO ON RWY 17R. 5) POOR 'SEE AND AVOID' DOCTRINE ON MY PART. 6) INSTRUCTIONS GIVEN BY TWR THAT CONFLICTED WITH THOSE GIVEN BY VALLEY APCH. 7) SIMULTANEOUS USE OF XING RWYS (RWY 17R AND RWY 13) WITH ACFT DEPARTING TO THE SAME GENERAL DIRECTION (NE). LESSONS LEARNED: 1) THE MOST RECENT INSTRUCTIONS SUPERSEDE ANY PREVIOUSLY GIVEN INSTRUCTIONS. 2) IF THERE IS A CONFLICT OF INSTRUCTIONS; FOLLOW THE MOST RECENT INSTRUCTIONS WHILE YOU ATTEMPT TO CLARIFY AND CLARIFY ASAP. 3) THERE ARE TIMES TO ALLOW A STUDENT TO LEARN HOW TO TALK ON THE RADIO; BUT NEVER COMPROMISE SAFETY; ESPECIALLY IF THERE IS A CONFLICT OF INSTRUCTIONS. 4) WE CAN'T EMPHASIZE ENOUGH THE IMPORTANCE OF A GOOD 'SEE AND AVOID' DOCTRINE. INCLUDING THE OBSERVER. WE ALWAYS CLR IN THE DIRECTION OF THE TURN; EVEN WHEN ON AN IFR CLRNC AND THIS IS A PERFECT EXAMPLE OF WHY. 5) THIS IS A PERFECT EXAMPLE OF A SEEMINGLY SMALL BREAKDOWN IN CREW RESOURCE MGMNT; SPECIFICALLY SITUATIONAL AWARENESS AND COM; WHICH NEARLY COST SEVERAL LIVES AND 2 PERFECTLY GOOD ACFT.