A cessna TR182 pilot reports an near midair collision with another cessna in the sbp traffic pattern...

Attributes
ACN	359356
Time
Date	199701
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sbp
State Reference	CA
Altitude	msl bound lower : 1800 msl bound upper : 1800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sbp
Operator	general aviation : personal
Make Model Name	Skylane 182/RG Turbo Skylane/RG
Operating Under FAR Part	Part 91
Flight Phase	cruise other other
Route In Use	arrival other
Flight Plan	VFR
Aircraft 2
Make Model Name	Cessna Aircraft Undifferentiated or Other Model
Operating Under FAR Part	other : unknown
Flight Phase	climbout : initial
Route In Use	departure other
Person 1
Affiliation	Other
Function	flight crew : single pilot
ASRS Report	359356
Person 2
Affiliation	government : faa
Function	controller : local oversight : supervisor
Qualification	controller : non radar
Events
Anomaly	conflict : nmac
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 100 vertical : 0
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

The problem began with my reporting my position incorrectly when initiating my call to tower at 9 mi out. I said I was southwest when I was really south of the airport. Tower instructed me to make a downwind to runway 29. I descended in order to make a 45 degree entry to downwind. Tower reported that the cessna which had just taken off and was on crosswind would be departing downwind. I had the cessna in sight and, expecting him to turn downwind, told tower I'd turn in behind him. The cessna never did turn downwind, however, and continued to climb out on crosswind. We came very close to colliding on the extended crosswind. I made a steep right bank evasive maneuver to avoid hitting him. Had I reported my position to tower correctly to begin with, I probably would have received a straight-in and this whole situation would have been avoided. As I watched the conflict develop, I should have been aggressively on the radio to tower to clarify the other plane's intentions, rather than assuming the cessna would turn. The other plane should have gotten on the radio when he changed his mind about his departure. Had he announced his intention of continuing west for departure, rather than making the downwind departure, I would have turned downwind earlier and avoided the near miss. Tower claimed it never saw me due to my reporting my original position incorrectly. Tower didn't talk to the departing plane or me about the conflict as it developed.

Original NASA ASRS Text

Title: A CESSNA TR182 PLT RPTS AN NMAC WITH ANOTHER CESSNA IN THE SBP TFC PATTERN.

Narrative: THE PROB BEGAN WITH MY RPTING MY POS INCORRECTLY WHEN INITIATING MY CALL TO TWR AT 9 MI OUT. I SAID I WAS SW WHEN I WAS REALLY S OF THE ARPT. TWR INSTRUCTED ME TO MAKE A DOWNWIND TO RWY 29. I DSNDED IN ORDER TO MAKE A 45 DEG ENTRY TO DOWNWIND. TWR RPTED THAT THE CESSNA WHICH HAD JUST TAKEN OFF AND WAS ON XWIND WOULD BE DEPARTING DOWNWIND. I HAD THE CESSNA IN SIGHT AND, EXPECTING HIM TO TURN DOWNWIND, TOLD TWR I'D TURN IN BEHIND HIM. THE CESSNA NEVER DID TURN DOWNWIND, HOWEVER, AND CONTINUED TO CLB OUT ON XWIND. WE CAME VERY CLOSE TO COLLIDING ON THE EXTENDED XWIND. I MADE A STEEP R BANK EVASIVE MANEUVER TO AVOID HITTING HIM. HAD I RPTED MY POS TO TWR CORRECTLY TO BEGIN WITH, I PROBABLY WOULD HAVE RECEIVED A STRAIGHT-IN AND THIS WHOLE SIT WOULD HAVE BEEN AVOIDED. AS I WATCHED THE CONFLICT DEVELOP, I SHOULD HAVE BEEN AGGRESSIVELY ON THE RADIO TO TWR TO CLARIFY THE OTHER PLANE'S INTENTIONS, RATHER THAN ASSUMING THE CESSNA WOULD TURN. THE OTHER PLANE SHOULD HAVE GOTTEN ON THE RADIO WHEN HE CHANGED HIS MIND ABOUT HIS DEP. HAD HE ANNOUNCED HIS INTENTION OF CONTINUING W FOR DEP, RATHER THAN MAKING THE DOWNWIND DEP, I WOULD HAVE TURNED DOWNWIND EARLIER AND AVOIDED THE NEAR MISS. TWR CLAIMED IT NEVER SAW ME DUE TO MY RPTING MY ORIGINAL POS INCORRECTLY. TWR DIDN'T TALK TO THE DEPARTING PLANE OR ME ABOUT THE CONFLICT AS IT DEVELOPED.

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.