Date: 201507
Local time of day: 0601-1200
Location: PAO.Airport, CA
Flight conditions: VMC
Weather elements / visibility: 20
Light: Daylight
Aircraft: Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Operator: Personal
Operating under: Part 91
Flight plan: VFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class D PAO
ATC / advisory: Tower PAO
Second aircraft: Cessna Aircraft Undifferentiated or Other Model
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Private
Human factors: Distraction; Confusion; Communication Breakdown; Situational Awareness; Workload; Time Pressure
Anomaly: ATC Issue All Types; Conflict NMAC; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Contributing factors: Airport; Airspace Structure; Environment - Non Weather Related; Human Factors; Procedure
Primary problem: Procedure

Narrative: I flew my privately owned aircraft from my home base to PAO. I flew direct VPLEX (to remain clear of San Jose Class C). I contacted NORCAL Approach near Salinas (SNS) and began a descent prior to passing west of VPLEX to remain below the outer rings of SFO Class B.From VPLEX; my flight plan called for a right turn prior to VPSLA; which would position me for a right crosswind or left downwind entry to Runway 31. ATIS Information was current at the time; and I advised NORCAL that I had picked up ATIS. Approximately 8 miles out; NORCAL advised me to turn inbound direct PAO and change to tower frequency. While this would give me less time to descend to pattern altitude and slow to desired speed for the pattern; I assumed that the direction was intended to provide separation so I complied without hesitation.It is possible that during this time; I unintentionally descended below noise abatement guidelines and possibly below pattern altitude before I realized I was too low. Upon contacting tower; I was advised to enter L downwind for Runway 31. I turned left; then nearly 180 to the right (to a heading of 130) to join the left downwind. I was immediately directed to make a 360 to the right; then rejoin the left downwind. At about this time I realized I was slightly below pattern altitude; so I added power in the turn to climb back to proper altitude. The tower controller thanked me for the 360 and called my base turn. Immediately upon turning left base; the controller directed an immediate climb; then a turn to final. As I turned to final; I saw a Cessna (or other high wing) passing below and nearby my position; approximately 300 feet below me. I judge my altitude to have been approximately 800 feet at the time of the turn to final. The controller thanked me for the climb; and I landed uneventfully.It was very busy at PAO and I had a hard time seeing the field from more than two miles away; although I knew from studying the sectional and other maps where to look. I do not fault the controller for the close proximity to the Cessna; but believe I followed his directions promptly and accurately. I would sincerely like to learn from the incident; so would appreciate feedback/analysis when available.




Synopsis: A pilot approached the San Francisco Bay Area from the South intending to land at PAO. They were vectored to the airport by NCT; but once nearing the PAO pattern he had difficulty seeing the airport; entering the pattern; maintaining altitude. Turning final for Runway 31 they had a NMAC.