Narrative:

After performing extensive maintenance on a PA28-140 which included an annual inspection and the installation of a higher horsepwr engine (stc approved), a test flight was made. WX was clear, good visibility, with a thin broken stratus layer between 1100 ft and 1300 ft west of the airport -- palomar (crq). Aircraft was thoroughly checked in the run up area and no discrepancies were noted. Aircraft departed VFR on runway 24 and made left traffic, climbing out of the pattern and leveling off at 5000 ft (in class east airspace), but continuing a left pattern over the airport so that performance and reliability checks could be made on the new engine close to the airport. Tower frequency was monitored. Several circuits were made around the pattern. After a turn to the left crosswind was started, a request to the tower to descend into the pattern was initiated. At this instant a military helicopter (possibly a huey or similar size helicopter) was spotted in very close proximity to aircraft. The helicopter's position relative to aircraft appeared to be slightly to the right and maybe 40-50 ft higher at a distance of 300-400 ft converging head on. An immediate increase to the left and an immediate descent were executed. It appeared that the helicopter performed a similar maneuver, possibly climbing instead of descending. After a turn to the left downwind, now at about 4700 ft the tower inquired as to whether or not visual contact was established with the helicopter. A safe return to the airport in a left hand pattern was made following a descending right 360 degrees made from the left downwind in order to lose altitude. After a normal landing, a visit to the tower was made. It was determined that the helicopter was in contact with approach control. Type of flight (VFR or IFR) is unknown at this time so it is unknown as to whether or not he received any TA's. After discussing the matter with the 3 air traffic controllers on duty at the field and the tower supervisor, and referencing NTSB 830 which does not require any reports to be filed for an occurrence of this sort, it was determined that the best course of action based on the information was to make a report through this forum as a public service to the aviation community. Contributing factors may be: monitoring engine and flight instruments during post maintenance test flight. Traffic scan interruption as a result of attempting to maintain accurate traffic pattern legs at altitude by using ground reference points. Not monitoring approach controller frequency and requesting TA's (although not required in class east airspace). Failure or inability of approach control to issue TA to pilot of helicopter. Failure on the part of both pilots to adequately 'see and avoid.'

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Original NASA ASRS Text

Title: NMAC.

Narrative: AFTER PERFORMING EXTENSIVE MAINT ON A PA28-140 WHICH INCLUDED AN ANNUAL INSPECTION AND THE INSTALLATION OF A HIGHER HORSEPWR ENG (STC APPROVED), A TEST FLT WAS MADE. WX WAS CLR, GOOD VISIBILITY, WITH A THIN BROKEN STRATUS LAYER BTWN 1100 FT AND 1300 FT W OF THE ARPT -- PALOMAR (CRQ). ACFT WAS THOROUGHLY CHKED IN THE RUN UP AREA AND NO DISCREPANCIES WERE NOTED. ACFT DEPARTED VFR ON RWY 24 AND MADE L TFC, CLBING OUT OF THE PATTERN AND LEVELING OFF AT 5000 FT (IN CLASS E AIRSPACE), BUT CONTINUING A L PATTERN OVER THE ARPT SO THAT PERFORMANCE AND RELIABILITY CHKS COULD BE MADE ON THE NEW ENG CLOSE TO THE ARPT. TWR FREQ WAS MONITORED. SEVERAL CIRCUITS WERE MADE AROUND THE PATTERN. AFTER A TURN TO THE L XWIND WAS STARTED, A REQUEST TO THE TWR TO DSND INTO THE PATTERN WAS INITIATED. AT THIS INSTANT A MIL HELI (POSSIBLY A HUEY OR SIMILAR SIZE HELI) WAS SPOTTED IN VERY CLOSE PROX TO ACFT. THE HELI'S POS RELATIVE TO ACFT APPEARED TO BE SLIGHTLY TO THE R AND MAYBE 40-50 FT HIGHER AT A DISTANCE OF 300-400 FT CONVERGING HEAD ON. AN IMMEDIATE INCREASE TO THE L AND AN IMMEDIATE DSCNT WERE EXECUTED. IT APPEARED THAT THE HELI PERFORMED A SIMILAR MANEUVER, POSSIBLY CLBING INSTEAD OF DSNDING. AFTER A TURN TO THE L DOWNWIND, NOW AT ABOUT 4700 FT THE TWR INQUIRED AS TO WHETHER OR NOT VISUAL CONTACT WAS ESTABLISHED WITH THE HELI. A SAFE RETURN TO THE ARPT IN A L HAND PATTERN WAS MADE FOLLOWING A DSNDING R 360 DEGS MADE FROM THE L DOWNWIND IN ORDER TO LOSE ALT. AFTER A NORMAL LNDG, A VISIT TO THE TWR WAS MADE. IT WAS DETERMINED THAT THE HELI WAS IN CONTACT WITH APCH CTL. TYPE OF FLT (VFR OR IFR) IS UNKNOWN AT THIS TIME SO IT IS UNKNOWN AS TO WHETHER OR NOT HE RECEIVED ANY TA'S. AFTER DISCUSSING THE MATTER WITH THE 3 AIR TFC CTLRS ON DUTY AT THE FIELD AND THE TWR SUPVR, AND REFING NTSB 830 WHICH DOES NOT REQUIRE ANY RPTS TO BE FILED FOR AN OCCURRENCE OF THIS SORT, IT WAS DETERMINED THAT THE BEST COURSE OF ACTION BASED ON THE INFO WAS TO MAKE A RPT THROUGH THIS FORUM AS A PUBLIC SVC TO THE AVIATION COMMUNITY. CONTRIBUTING FACTORS MAY BE: MONITORING ENG AND FLT INSTS DURING POST MAINT TEST FLT. TFC SCAN INTERRUPTION AS A RESULT OF ATTEMPTING TO MAINTAIN ACCURATE TFC PATTERN LEGS AT ALT BY USING GND REF POINTS. NOT MONITORING APCH CTLR FREQ AND REQUESTING TA'S (ALTHOUGH NOT REQUIRED IN CLASS E AIRSPACE). FAILURE OR INABILITY OF APCH CTL TO ISSUE TA TO PLT OF HELI. FAILURE ON THE PART OF BOTH PLTS TO ADEQUATELY 'SEE AND AVOID.'

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.