Narrative:

There were 3 of us in the cockpit including 1 non-pilot. We were heading northbound along the san francisco peninsula just north of the osi VOR. Approaching osi VOR the controller gave us a TA which from my best recollection did not include a relative position. We acknowledged but apparently idented the wrong traffic. A few moments later a large airliner passed behind us at a distance that appeared to be less than 1 mi although he was about 500 ft lower than us. This traffic caught us by surprise and by the time we queried the controller about the traffic it had quickly passed behind us from left to right. This traffic was not a factor but left us somewhat uneasy. This uneasy feeling we each had played a significant role in the event which would follow a few moments later. At about the same time, all 3 of us looked off to the 9 O'clock position and saw 2 landing lights which appeared to be a single large aircraft approaching at a very rapid rate. I quickly asked the controller if he had our traffic at our 9 O'clock position. In response he asked, 'which one?' I replied, 'the one at our 9 O'clock position and closing rapidly.' the controller did not respond immediately so we decided that there was not enough time and space to wait any longer and took evasive action. We banked to the right and pulled the throttle to idle in an attempt to avoid what appeared to be an imminent collision course. We then returned to level flight to see that the perceived aircraft was still approaching from the same direction and was now much closer. After another brief moment we realized that what we were looking at was the landing lights of 2 separate aircraft approaching from the west and that we were experiencing a visual illusion. It was not until the aircraft finally got close enough to see the position lights that we were able to distinguish 1 aircraft from the other. At this time the controller asked us to depart the class B airspace and we complied. Some contributing factors are: 1) our failure to properly identify the previous traffic causing us to feel uncomfortable with the traffic separation. 2) there was little or no moonlight that night to provide any other visual references. It was very dark. 3) our view to the west was over the pacific ocean and as a result there were no surface lights or surface features to provide a reference to the horizon. (There was no visible horizon in the direction from which the traffic was coming.) 4) all 3 persons in the aircraft thought they saw the same thing which reinforced the belief that this was 1 aircraft instead of 2. 5) the controller did not make it clear that there were 2 aircraft approaching from the west. I think that the best way to avoid this situation in the future is to increase the awareness of the contributing factors to visual illusions.

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Original NASA ASRS Text

Title: PLT AND INSTRUCTOR PLT IN A PA28-181 NIGHT OP PERFORM AN EVASIVE MANEUVER WHEN THEY BELIEVE THAT THE 2 DISTANT ACR ACFT WITH LIGHTS ON ARE 1 ACFT IN A RAPID CLOSURE EVENT. CTLR ASKS THEM TO LEAVE THE CLASS B AIRSPACE.

Narrative: THERE WERE 3 OF US IN THE COCKPIT INCLUDING 1 NON-PLT. WE WERE HDG NBOUND ALONG THE SAN FRANCISCO PENINSULA JUST N OF THE OSI VOR. APCHING OSI VOR THE CTLR GAVE US A TA WHICH FROM MY BEST RECOLLECTION DID NOT INCLUDE A RELATIVE POS. WE ACKNOWLEDGED BUT APPARENTLY IDENTED THE WRONG TFC. A FEW MOMENTS LATER A LARGE AIRLINER PASSED BEHIND US AT A DISTANCE THAT APPEARED TO BE LESS THAN 1 MI ALTHOUGH HE WAS ABOUT 500 FT LOWER THAN US. THIS TFC CAUGHT US BY SURPRISE AND BY THE TIME WE QUERIED THE CTLR ABOUT THE TFC IT HAD QUICKLY PASSED BEHIND US FROM L TO R. THIS TFC WAS NOT A FACTOR BUT LEFT US SOMEWHAT UNEASY. THIS UNEASY FEELING WE EACH HAD PLAYED A SIGNIFICANT ROLE IN THE EVENT WHICH WOULD FOLLOW A FEW MOMENTS LATER. AT ABOUT THE SAME TIME, ALL 3 OF US LOOKED OFF TO THE 9 O'CLOCK POS AND SAW 2 LNDG LIGHTS WHICH APPEARED TO BE A SINGLE LARGE ACFT APCHING AT A VERY RAPID RATE. I QUICKLY ASKED THE CTLR IF HE HAD OUR TFC AT OUR 9 O'CLOCK POS. IN RESPONSE HE ASKED, 'WHICH ONE?' I REPLIED, 'THE ONE AT OUR 9 O'CLOCK POS AND CLOSING RAPIDLY.' THE CTLR DID NOT RESPOND IMMEDIATELY SO WE DECIDED THAT THERE WAS NOT ENOUGH TIME AND SPACE TO WAIT ANY LONGER AND TOOK EVASIVE ACTION. WE BANKED TO THE R AND PULLED THE THROTTLE TO IDLE IN AN ATTEMPT TO AVOID WHAT APPEARED TO BE AN IMMINENT COLLISION COURSE. WE THEN RETURNED TO LEVEL FLT TO SEE THAT THE PERCEIVED ACFT WAS STILL APCHING FROM THE SAME DIRECTION AND WAS NOW MUCH CLOSER. AFTER ANOTHER BRIEF MOMENT WE REALIZED THAT WHAT WE WERE LOOKING AT WAS THE LNDG LIGHTS OF 2 SEPARATE ACFT APCHING FROM THE W AND THAT WE WERE EXPERIENCING A VISUAL ILLUSION. IT WAS NOT UNTIL THE ACFT FINALLY GOT CLOSE ENOUGH TO SEE THE POS LIGHTS THAT WE WERE ABLE TO DISTINGUISH 1 ACFT FROM THE OTHER. AT THIS TIME THE CTLR ASKED US TO DEPART THE CLASS B AIRSPACE AND WE COMPLIED. SOME CONTRIBUTING FACTORS ARE: 1) OUR FAILURE TO PROPERLY IDENT THE PREVIOUS TFC CAUSING US TO FEEL UNCOMFORTABLE WITH THE TFC SEPARATION. 2) THERE WAS LITTLE OR NO MOONLIGHT THAT NIGHT TO PROVIDE ANY OTHER VISUAL REFS. IT WAS VERY DARK. 3) OUR VIEW TO THE W WAS OVER THE PACIFIC OCEAN AND AS A RESULT THERE WERE NO SURFACE LIGHTS OR SURFACE FEATURES TO PROVIDE A REF TO THE HORIZON. (THERE WAS NO VISIBLE HORIZON IN THE DIRECTION FROM WHICH THE TFC WAS COMING.) 4) ALL 3 PERSONS IN THE ACFT THOUGHT THEY SAW THE SAME THING WHICH REINFORCED THE BELIEF THAT THIS WAS 1 ACFT INSTEAD OF 2. 5) THE CTLR DID NOT MAKE IT CLR THAT THERE WERE 2 ACFT APCHING FROM THE W. I THINK THAT THE BEST WAY TO AVOID THIS SIT IN THE FUTURE IS TO INCREASE THE AWARENESS OF THE CONTRIBUTING FACTORS TO VISUAL ILLUSIONS.

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.