Narrative:

Small aircraft Y operated by a flight school on a training flight. Small aircraft X called in as a flight of 2 and was told to enter base. Small aircraft Y on the downwind was sequencing behind the flight of 2. On final the second aircraft of the flight (a biplane) began to s- turn for spacing without telling the tower. An aircraft for departure began a long narrative of what he wanted to do. The biplane made a tight 360 degree turn on final and turned back to final beneath small aircraft Y which had climbed and turned to avoid collision. The departure request didn't even end until after the 360 was completed. The small aircraft Y pilot voiced his displeasure over the event and landed after flying around the pattern. The biplane landed without further incident and was instructed to call the tower. At that time he gave his call sign, which was the first time it was aired. Corrective actions seemed, at the time, impossible. The frequency was blocked by another transmitter and the call sign of the offending aircraft was unknown. In retrospect, it is likely the tower transmitter would have overridden the other radio and small aircraft Y could have been warned earlier. The biplane pilot was told over the phone not to call in as a flight if he couldn't fly as a flight, and to make a normal pattern if he had to go around.

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Original NASA ASRS Text

Title: SMA X FLT OF 2 (BI-PLANE). BI-PLANE NONADHERENCE TO ATC CLRNC MADE UNAUTHORIZED 360 TURN ON FINAL APCH HAD NMAC WITH SMA Y SEQUENCED TO FOLLOW. PLTDEV.

Narrative: SMA Y OPERATED BY A FLT SCHOOL ON A TRAINING FLT. SMA X CALLED IN AS A FLT OF 2 AND WAS TOLD TO ENTER BASE. SMA Y ON THE DOWNWIND WAS SEQUENCING BEHIND THE FLT OF 2. ON FINAL THE SECOND ACFT OF THE FLT (A BIPLANE) BEGAN TO S- TURN FOR SPACING WITHOUT TELLING THE TWR. AN ACFT FOR DEP BEGAN A LONG NARRATIVE OF WHAT HE WANTED TO DO. THE BIPLANE MADE A TIGHT 360 DEG TURN ON FINAL AND TURNED BACK TO FINAL BENEATH SMA Y WHICH HAD CLBED AND TURNED TO AVOID COLLISION. THE DEP REQUEST DIDN'T EVEN END UNTIL AFTER THE 360 WAS COMPLETED. THE SMA Y PLT VOICED HIS DISPLEASURE OVER THE EVENT AND LANDED AFTER FLYING AROUND THE PATTERN. THE BIPLANE LANDED WITHOUT FURTHER INCIDENT AND WAS INSTRUCTED TO CALL THE TWR. AT THAT TIME HE GAVE HIS CALL SIGN, WHICH WAS THE FIRST TIME IT WAS AIRED. CORRECTIVE ACTIONS SEEMED, AT THE TIME, IMPOSSIBLE. THE FREQ WAS BLOCKED BY ANOTHER XMITTER AND THE CALL SIGN OF THE OFFENDING ACFT WAS UNKNOWN. IN RETROSPECT, IT IS LIKELY THE TWR XMITTER WOULD HAVE OVERRIDDEN THE OTHER RADIO AND SMA Y COULD HAVE BEEN WARNED EARLIER. THE BIPLANE PLT WAS TOLD OVER THE PHONE NOT TO CALL IN AS A FLT IF HE COULDN'T FLY AS A FLT, AND TO MAKE A NORMAL PATTERN IF HE HAD TO GAR.

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.