Narrative:

I was in vny surface area and I was transitioning in a northeast direction into whp airspace. Whp tower was closed at the time so I broadcast on 135.0 that I was 1 mi south of the I-5 freeway and I was going to proceed northbound across the airport. An aircraft broadcast that he was left downwind. I don't recall if he broadcast his tail number. After his broadcast, I broadcast that I did not see him. A short time later, I broadcast that I was northbound crossing the approach end of runway 12 at 1400 ft. I continued nebound and approximately 15 seconds later, I observed a low wind, single engine airplane traveling swbound at approximately 1300 ft. He was approximately 300 ft east of my course. He did not broadcast that he was flying a modified pattern nor did he broadcast that he had turned to his base leg. If he continued on his route he would have crossed the runway 12 centerline approximately 200-400 yards north of the threshold. I do not know if the aircraft landed at the airport or left the area. I did not hear any other broadcasts from him. Although I did not see the airplane when it was left downwind, I had no intention of crossing the left downwind route. If the other pilot had broadcast his turn to base leg I may have been able to visually acquire his position. If the other pilot had broadcast that he intended to deviate from the established pattern I would have avoided the area. Instead he did not fly over the 118 freeway for his base leg. He was well inside the pattern on his base leg. The other pilot never acknowledged my broadcasts or indicated if he saw me.

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Original NASA ASRS Text

Title: NMAC BTWN A GOV HELI TRANSITIONING NBOUND THROUGH THE BASE LEG AREA OF THE RWY AT 400 FT AGL AND AN SMA LOW WING ON A CLOSE-IN BASE LEG TO THE RWY TO WHICH THE RPTR WAS XING THROUGH.

Narrative: I WAS IN VNY SURFACE AREA AND I WAS TRANSITIONING IN A NE DIRECTION INTO WHP AIRSPACE. WHP TWR WAS CLOSED AT THE TIME SO I BROADCAST ON 135.0 THAT I WAS 1 MI S OF THE I-5 FREEWAY AND I WAS GOING TO PROCEED NBOUND ACROSS THE ARPT. AN ACFT BROADCAST THAT HE WAS L DOWNWIND. I DON'T RECALL IF HE BROADCAST HIS TAIL NUMBER. AFTER HIS BROADCAST, I BROADCAST THAT I DID NOT SEE HIM. A SHORT TIME LATER, I BROADCAST THAT I WAS NBOUND XING THE APCH END OF RWY 12 AT 1400 FT. I CONTINUED NEBOUND AND APPROX 15 SECONDS LATER, I OBSERVED A LOW WIND, SINGLE ENG AIRPLANE TRAVELING SWBOUND AT APPROX 1300 FT. HE WAS APPROX 300 FT E OF MY COURSE. HE DID NOT BROADCAST THAT HE WAS FLYING A MODIFIED PATTERN NOR DID HE BROADCAST THAT HE HAD TURNED TO HIS BASE LEG. IF HE CONTINUED ON HIS RTE HE WOULD HAVE CROSSED THE RWY 12 CTRLINE APPROX 200-400 YARDS N OF THE THRESHOLD. I DO NOT KNOW IF THE ACFT LANDED AT THE ARPT OR LEFT THE AREA. I DID NOT HEAR ANY OTHER BROADCASTS FROM HIM. ALTHOUGH I DID NOT SEE THE AIRPLANE WHEN IT WAS L DOWNWIND, I HAD NO INTENTION OF XING THE L DOWNWIND RTE. IF THE OTHER PLT HAD BROADCAST HIS TURN TO BASE LEG I MAY HAVE BEEN ABLE TO VISUALLY ACQUIRE HIS POS. IF THE OTHER PLT HAD BROADCAST THAT HE INTENDED TO DEVIATE FROM THE ESTABLISHED PATTERN I WOULD HAVE AVOIDED THE AREA. INSTEAD HE DID NOT FLY OVER THE 118 FREEWAY FOR HIS BASE LEG. HE WAS WELL INSIDE THE PATTERN ON HIS BASE LEG. THE OTHER PLT NEVER ACKNOWLEDGED MY BROADCASTS OR INDICATED IF HE SAW ME.

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.