Narrative:

Upon arrival into class D airspace, transition from approach and being handed over to teb tower, aircraft #2 reported '1 mi out' to teb tower. Tower response was. '1 mi out from where?' aircraft #2 said 'airport.' the tower gave landing clearance to aircraft for runway 19, aircraft #2 requested runway 24. Tower cleared aircraft #2 to land on runway 24. After entering downwind from circling approach, aircraft #1 configured for landing runway 19 at 1500 ft pattern altitude. While turning base leg at 1500 ft, starting descent from pattern altitude, a yellow TCASII target with no mode south (altitude tag) appeared at the 12 O'clock position, less than 1 mi. I maintained 1400 ft and increased rate of turn. The aircraft #2 went underneath us at 100 ft. We reported an near midair collision to teb tower (aircraft #1) and continued on visual approach to runway 19. While on final to runway 19 (aircraft #1), aircraft #2 being on a very steep approach to runway 24, dove towards the runway increasing rate of descent and ground speed. Monitoring closure rates of the 2 aircraft on intersecting runways, separation deteriorated. It was determined by aircraft #1 that there was inadequate separation between the 2 landing aircraft and aircraft #1 initiated a go around at 50-100 ft AGL. There was no input or communication from the tower during the convergence. Many sequential events happened: 1) aircraft #2 apparently entered class D airspace without permission. 2) aircraft #2 gave incorrect position. 3) aircraft #2 was at wrong pattern altitude. 4) aircraft #2 had no mode south. 5) teb tower was not diligent in maintaining separation.

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Original NASA ASRS Text

Title: F900 CREW HAD AN NMAC IN PATTERN AND A GAR ON SHORT FINAL.

Narrative: UPON ARR INTO CLASS D AIRSPACE, TRANSITION FROM APCH AND BEING HANDED OVER TO TEB TWR, ACFT #2 RPTED '1 MI OUT' TO TEB TWR. TWR RESPONSE WAS. '1 MI OUT FROM WHERE?' ACFT #2 SAID 'ARPT.' THE TWR GAVE LNDG CLRNC TO ACFT FOR RWY 19, ACFT #2 REQUESTED RWY 24. TWR CLRED ACFT #2 TO LAND ON RWY 24. AFTER ENTERING DOWNWIND FROM CIRCLING APCH, ACFT #1 CONFIGURED FOR LNDG RWY 19 AT 1500 FT PATTERN ALT. WHILE TURNING BASE LEG AT 1500 FT, STARTING DSCNT FROM PATTERN ALT, A YELLOW TCASII TARGET WITH NO MODE S (ALT TAG) APPEARED AT THE 12 O'CLOCK POS, LESS THAN 1 MI. I MAINTAINED 1400 FT AND INCREASED RATE OF TURN. THE ACFT #2 WENT UNDERNEATH US AT 100 FT. WE RPTED AN NMAC TO TEB TWR (ACFT #1) AND CONTINUED ON VISUAL APCH TO RWY 19. WHILE ON FINAL TO RWY 19 (ACFT #1), ACFT #2 BEING ON A VERY STEEP APCH TO RWY 24, DOVE TOWARDS THE RWY INCREASING RATE OF DSCNT AND GND SPD. MONITORING CLOSURE RATES OF THE 2 ACFT ON INTERSECTING RWYS, SEPARATION DETERIORATED. IT WAS DETERMINED BY ACFT #1 THAT THERE WAS INADEQUATE SEPARATION BTWN THE 2 LNDG ACFT AND ACFT #1 INITIATED A GAR AT 50-100 FT AGL. THERE WAS NO INPUT OR COM FROM THE TWR DURING THE CONVERGENCE. MANY SEQUENTIAL EVENTS HAPPENED: 1) ACFT #2 APPARENTLY ENTERED CLASS D AIRSPACE WITHOUT PERMISSION. 2) ACFT #2 GAVE INCORRECT POS. 3) ACFT #2 WAS AT WRONG PATTERN ALT. 4) ACFT #2 HAD NO MODE S. 5) TEB TWR WAS NOT DILIGENT IN MAINTAINING SEPARATION.

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.