Narrative:

The occurrence that I would like to describe is a conflict between 2 cessna 172's on the downwind leg of the traffic pattern for napa county airport's runway 18R. Although I was safely on the ground, I feel my descriptions may have something to add that may be beneficial in future research. On the day of the conflict, I was on ground control taxiing out as the 2 aircraft were coming back in and I could hear their excitement over the radio. Both aircraft taxied over to the maintenance hangar. I could hear the controller instructing both pilots to phone the tower at their next possible opportunity. Later that afternoon I talked with a student of mine who was in the pattern at the time. He said he was abeam the numbers of runway 18R beginning his descent for landing procedures, when he heard the commotion on downwind over the radio. He could not see them ahead of him so he continued with his approach. On short final he was told to 'go missed approach,' which he correctly interpreted as the same as 'go around.' he was more concerned with controling his own aircraft so he could not remember the exact words between the 2 172's, or between the airplanes and the control tower, if there were any. I also work as an a&P mechanic so I have looked at the damage to both aircraft. The yellow 172 was hit on the left wingtip and down by the wing strut support (very minimal damage). The blue 172 has damage to the right horizontal stabilizer and elevator, probably requiring replacement of both. The elevator still moves freely and a safe landing was completed by both pilots. From an instructor's point of view, I have had contact with the pilot of the blue 172. He is a local pilot known by many at the airport. I flew with him a while back (I believe it was last summer) for his biennial flight review. I remember him doing a fine job of controling the aircraft, but I did ask him to come back for a second appointment as we were not able to cover all of the areas I felt we should in 1 meeting. I can recall he had a weak area in flight logbook documentation and radio procedures. It has been my past experience that logbooks can be a touchy area with some pilots. They view it as almost an invasion of privacy (similar to looking through someone's checkbook was one analogy I was told). To help the pilot with his radio procedures I even provided him with some crib sheets to help organize his radio work. Hopefully my instruction was of benefit to him as I do stress emergency procedures and traffic pattern operations during my biennials. Such an occurrence as these 2 172's had, could obviously have been prevented by proper collision avoidance techniques as well as better coordination with the control tower as to the location of other aircraft.

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Original NASA ASRS Text

Title: OBSERVER RPT REGARDING A MIDAIR COLLISION BTWN 2 C172 ACFT IN ATA.

Narrative: THE OCCURRENCE THAT I WOULD LIKE TO DESCRIBE IS A CONFLICT BTWN 2 CESSNA 172'S ON THE DOWNWIND LEG OF THE TFC PATTERN FOR NAPA COUNTY ARPT'S RWY 18R. ALTHOUGH I WAS SAFELY ON THE GND, I FEEL MY DESCRIPTIONS MAY HAVE SOMETHING TO ADD THAT MAY BE BENEFICIAL IN FUTURE RESEARCH. ON THE DAY OF THE CONFLICT, I WAS ON GND CTL TAXIING OUT AS THE 2 ACFT WERE COMING BACK IN AND I COULD HEAR THEIR EXCITEMENT OVER THE RADIO. BOTH ACFT TAXIED OVER TO THE MAINT HANGAR. I COULD HEAR THE CTLR INSTRUCTING BOTH PLTS TO PHONE THE TWR AT THEIR NEXT POSSIBLE OPPORTUNITY. LATER THAT AFTERNOON I TALKED WITH A STUDENT OF MINE WHO WAS IN THE PATTERN AT THE TIME. HE SAID HE WAS ABEAM THE NUMBERS OF RWY 18R BEGINNING HIS DSCNT FOR LNDG PROCS, WHEN HE HEARD THE COMMOTION ON DOWNWIND OVER THE RADIO. HE COULD NOT SEE THEM AHEAD OF HIM SO HE CONTINUED WITH HIS APCH. ON SHORT FINAL HE WAS TOLD TO 'GO MISSED APCH,' WHICH HE CORRECTLY INTERPRETED AS THE SAME AS 'GAR.' HE WAS MORE CONCERNED WITH CTLING HIS OWN ACFT SO HE COULD NOT REMEMBER THE EXACT WORDS BTWN THE 2 172'S, OR BTWN THE AIRPLANES AND THE CTL TWR, IF THERE WERE ANY. I ALSO WORK AS AN A&P MECH SO I HAVE LOOKED AT THE DAMAGE TO BOTH ACFT. THE YELLOW 172 WAS HIT ON THE L WINGTIP AND DOWN BY THE WING STRUT SUPPORT (VERY MINIMAL DAMAGE). THE BLUE 172 HAS DAMAGE TO THE R HORIZ STABILIZER AND ELEVATOR, PROBABLY REQUIRING REPLACEMENT OF BOTH. THE ELEVATOR STILL MOVES FREELY AND A SAFE LNDG WAS COMPLETED BY BOTH PLTS. FROM AN INSTRUCTOR'S POINT OF VIEW, I HAVE HAD CONTACT WITH THE PLT OF THE BLUE 172. HE IS A LCL PLT KNOWN BY MANY AT THE ARPT. I FLEW WITH HIM A WHILE BACK (I BELIEVE IT WAS LAST SUMMER) FOR HIS BIENNIAL FLT REVIEW. I REMEMBER HIM DOING A FINE JOB OF CTLING THE ACFT, BUT I DID ASK HIM TO COME BACK FOR A SECOND APPOINTMENT AS WE WERE NOT ABLE TO COVER ALL OF THE AREAS I FELT WE SHOULD IN 1 MEETING. I CAN RECALL HE HAD A WEAK AREA IN FLT LOGBOOK DOCUMENTATION AND RADIO PROCS. IT HAS BEEN MY PAST EXPERIENCE THAT LOGBOOKS CAN BE A TOUCHY AREA WITH SOME PLTS. THEY VIEW IT AS ALMOST AN INVASION OF PRIVACY (SIMILAR TO LOOKING THROUGH SOMEONE'S CHECKBOOK WAS ONE ANALOGY I WAS TOLD). TO HELP THE PLT WITH HIS RADIO PROCS I EVEN PROVIDED HIM WITH SOME CRIB SHEETS TO HELP ORGANIZE HIS RADIO WORK. HOPEFULLY MY INSTRUCTION WAS OF BENEFIT TO HIM AS I DO STRESS EMER PROCS AND TFC PATTERN OPS DURING MY BIENNIALS. SUCH AN OCCURRENCE AS THESE 2 172'S HAD, COULD OBVIOUSLY HAVE BEEN PREVENTED BY PROPER COLLISION AVOIDANCE TECHNIQUES AS WELL AS BETTER COORD WITH THE CTL TWR AS TO THE LOCATION OF OTHER ACFT.

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.