Narrative:

Tyr is a nonradar environment. When inbound to LOM (initial fix) approach said 'maintain 3500' until established, cleared ILS 13 approach, contact the tower at the OM'. There was later some question as to whether the approach controller said OM inbound, but both the first officer and myself understood the communication as described above. At the OM the first officer contacted tyr tower stating'...with you at the OM'. The tower responded 'clear to land'. This would be unusual in most cases, but our company operates frequently out of this airport and occasionally is issued unusual clrncs. I believe the entire conflict could have been avoided by using the more correct phraseology 'OM outbnd', but considering the short rest of the previous night, WX deviations and holding, etc. The deviation from more standard phraseology went unnoticed. Apparently the tower then told approach we were landing assured as apparently approach then cleared another aircraft (of same type) for the ILS approach, 'cross the OM at or after...' thus setting up a timed approach from a holding fix. As we were on tower frequency and the other aircraft was on approach frequency we were unaware of this conflict of airspace. Our first indication of the problem was when tower asked us our altitude and told us to 'descend immediately'. There were a number of contributing factors in this situation. Fatigue, abnormal procedures due to WX and aircraft saturation of a relatively small airspace, the focus upon details required to deal with unusual or abnormal situations, and a basic lack of clear communication due to casual or informal radio phraseology.

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Original NASA ASRS Text

Title: ACR REPORTER MISINTERP ATC INSTRUCTIONS AND CONTACTED TWR AT THE OUTER MARKER OUTBND RATHER THAN OUTER MARKER INBND. CONFLICT OCCURRED WITH ANOTHER ACFT ALSO MAKING AN APCH AT NON RADAR ARPT.

Narrative: TYR IS A NONRADAR ENVIRONMENT. WHEN INBND TO LOM (INITIAL FIX) APCH SAID 'MAINTAIN 3500' UNTIL ESTABLISHED, CLRED ILS 13 APCH, CONTACT THE TWR AT THE OM'. THERE WAS LATER SOME QUESTION AS TO WHETHER THE APCH CTLR SAID OM INBND, BUT BOTH THE F/O AND MYSELF UNDERSTOOD THE COM AS DESCRIBED ABOVE. AT THE OM THE F/O CONTACTED TYR TWR STATING'...WITH YOU AT THE OM'. THE TWR RESPONDED 'CLR TO LAND'. THIS WOULD BE UNUSUAL IN MOST CASES, BUT OUR COMPANY OPERATES FREQUENTLY OUT OF THIS ARPT AND OCCASIONALLY IS ISSUED UNUSUAL CLRNCS. I BELIEVE THE ENTIRE CONFLICT COULD HAVE BEEN AVOIDED BY USING THE MORE CORRECT PHRASEOLOGY 'OM OUTBND', BUT CONSIDERING THE SHORT REST OF THE PREVIOUS NIGHT, WX DEVIATIONS AND HOLDING, ETC. THE DEVIATION FROM MORE STANDARD PHRASEOLOGY WENT UNNOTICED. APPARENTLY THE TWR THEN TOLD APCH WE WERE LNDG ASSURED AS APPARENTLY APCH THEN CLRED ANOTHER ACFT (OF SAME TYPE) FOR THE ILS APCH, 'CROSS THE OM AT OR AFTER...' THUS SETTING UP A TIMED APCH FROM A HOLDING FIX. AS WE WERE ON TWR FREQ AND THE OTHER ACFT WAS ON APCH FREQ WE WERE UNAWARE OF THIS CONFLICT OF AIRSPACE. OUR FIRST INDICATION OF THE PROB WAS WHEN TWR ASKED US OUR ALT AND TOLD US TO 'DSND IMMEDIATELY'. THERE WERE A NUMBER OF CONTRIBUTING FACTORS IN THIS SITUATION. FATIGUE, ABNORMAL PROCS DUE TO WX AND ACFT SATURATION OF A RELATIVELY SMALL AIRSPACE, THE FOCUS UPON DETAILS REQUIRED TO DEAL WITH UNUSUAL OR ABNORMAL SITUATIONS, AND A BASIC LACK OF CLR COM DUE TO CASUAL OR INFORMAL RADIO PHRASEOLOGY.

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.