Narrative:

While on a right downwind visual approach to runway 29 at 1100 ft AGL, I had a descend RA. The trigger aircraft was never in sight, but was most likely a military T2. The traffic pattern was full and my flight was #3 to follow a PA28 on final. The trigger aircraft was seen to fly through the final from left base to the right downwind on TCASII. Observing the target closure, I accelerated (from the tower requested minimum approach speed) in an attempt to avoid conflict. The target matched my speed and altitude changes exactly through the TA. The descend RA occurred at 1100 ft AGL (not including the tall antenna farm). At 200 ft separation 900 ft AGL, the 'descend' RA changed to a level 'monitor vertical speed' RA. The egpws never triggered. On base the trigger aircraft triggered another TA. The T2 was observed clearing runway 29 shortly after my aircraft. At no time did tower issue an advisory, which may have been due to distrs by other small aircraft in the full pattern. The thought that a military training flight would perform an unannounced unauthorized intercept and formation flight in a traffic pattern is unacceptable! Yet the evidence points to that conclusion. The T2 was the only aircraft in the pattern that could match the LJ60 performance. A visual confirmation could not be made due to the target being in the 5 O'clock position blind spot. If for some reason it was a false RA (unlikely!), then a descent RA at 1100 ft AGL was highly dangerous. Luckily enough, the WX was cavu. Few pilots would be comfortable with a 1000-1500 ft FPM descent 1100 ft AGL, especially considering the LJ60 10000 FPM climb capability on a cold day.

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Original NASA ASRS Text

Title: LJ60 AND MIL T2 HAD AN NMAC IN BED CLASS D.

Narrative: WHILE ON A R DOWNWIND VISUAL APCH TO RWY 29 AT 1100 FT AGL, I HAD A DSND RA. THE TRIGGER ACFT WAS NEVER IN SIGHT, BUT WAS MOST LIKELY A MIL T2. THE TFC PATTERN WAS FULL AND MY FLT WAS #3 TO FOLLOW A PA28 ON FINAL. THE TRIGGER ACFT WAS SEEN TO FLY THROUGH THE FINAL FROM L BASE TO THE R DOWNWIND ON TCASII. OBSERVING THE TARGET CLOSURE, I ACCELERATED (FROM THE TWR REQUESTED MINIMUM APCH SPD) IN AN ATTEMPT TO AVOID CONFLICT. THE TARGET MATCHED MY SPD AND ALT CHANGES EXACTLY THROUGH THE TA. THE DSND RA OCCURRED AT 1100 FT AGL (NOT INCLUDING THE TALL ANTENNA FARM). AT 200 FT SEPARATION 900 FT AGL, THE 'DSND' RA CHANGED TO A LEVEL 'MONITOR VERT SPD' RA. THE EGPWS NEVER TRIGGERED. ON BASE THE TRIGGER ACFT TRIGGERED ANOTHER TA. THE T2 WAS OBSERVED CLRING RWY 29 SHORTLY AFTER MY ACFT. AT NO TIME DID TWR ISSUE AN ADVISORY, WHICH MAY HAVE BEEN DUE TO DISTRS BY OTHER SMALL ACFT IN THE FULL PATTERN. THE THOUGHT THAT A MIL TRAINING FLT WOULD PERFORM AN UNANNOUNCED UNAUTH INTERCEPT AND FORMATION FLT IN A TFC PATTERN IS UNACCEPTABLE! YET THE EVIDENCE POINTS TO THAT CONCLUSION. THE T2 WAS THE ONLY ACFT IN THE PATTERN THAT COULD MATCH THE LJ60 PERFORMANCE. A VISUAL CONFIRMATION COULD NOT BE MADE DUE TO THE TARGET BEING IN THE 5 O'CLOCK POS BLIND SPOT. IF FOR SOME REASON IT WAS A FALSE RA (UNLIKELY!), THEN A DSCNT RA AT 1100 FT AGL WAS HIGHLY DANGEROUS. LUCKILY ENOUGH, THE WX WAS CAVU. FEW PLTS WOULD BE COMFORTABLE WITH A 1000-1500 FT FPM DSCNT 1100 FT AGL, ESPECIALLY CONSIDERING THE LJ60 10000 FPM CLB CAPABILITY ON A COLD DAY.

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.