Narrative:

I, the instructor, was with a student pilot in an archer iv holding short of runway 27 at isla grande airport in puerto rico. The airport control tower was still closed, and we were announcing ourselves on CTAF. So, we thought we were talking on CTAF, until we heard another aircraft taxiing into position on runway 9 when we were already on runway 27 numbers. I took control of the communication and stated that we were on runway 27. The other aircraft started the roll down runway 9 and took off, without ever acknowledging our announcement. It was then that I realized that the communication #1 and communication #2 selector switch was in the wrong position. It seems to me that the other aircraft did not see us, for had it seen us, it would not have entered runway 9 and taken off while we were on the other end of the runway, which was runway 27. The other aircraft took off in a short distance and passed above us well above our position, which was runway 27 numbers. Contributing factor was my failure to check that the student was transmitting in proper frequency.

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Original NASA ASRS Text

Title: PA28 ON WRONG FREQ DURING CTAF PROCS, ENTERS RWY AND IS OVERFLOWN BY DEP, FROM OPPOSITE END OF RWY AT SAN JUAN, PR.

Narrative: I, THE INSTRUCTOR, WAS WITH A STUDENT PLT IN AN ARCHER IV HOLDING SHORT OF RWY 27 AT ISLA GRANDE ARPT IN PUERTO RICO. THE ARPT CTL TWR WAS STILL CLOSED, AND WE WERE ANNOUNCING OURSELVES ON CTAF. SO, WE THOUGHT WE WERE TALKING ON CTAF, UNTIL WE HEARD ANOTHER ACFT TAXIING INTO POS ON RWY 9 WHEN WE WERE ALREADY ON RWY 27 NUMBERS. I TOOK CTL OF THE COM AND STATED THAT WE WERE ON RWY 27. THE OTHER ACFT STARTED THE ROLL DOWN RWY 9 AND TOOK OFF, WITHOUT EVER ACKNOWLEDGING OUR ANNOUNCEMENT. IT WAS THEN THAT I REALIZED THAT THE COM #1 AND COM #2 SELECTOR SWITCH WAS IN THE WRONG POS. IT SEEMS TO ME THAT THE OTHER ACFT DID NOT SEE US, FOR HAD IT SEEN US, IT WOULD NOT HAVE ENTERED RWY 9 AND TAKEN OFF WHILE WE WERE ON THE OTHER END OF THE RWY, WHICH WAS RWY 27. THE OTHER ACFT TOOK OFF IN A SHORT DISTANCE AND PASSED ABOVE US WELL ABOVE OUR POS, WHICH WAS RWY 27 NUMBERS. CONTRIBUTING FACTOR WAS MY FAILURE TO CHK THAT THE STUDENT WAS XMITTING IN PROPER FREQ.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.