Narrative:

The flights were to adjust autorotation RPM. I departed eastbound then asked for a climbing southeast heading to 2500 (class B 3000) where I would enter a power off 60kt glide (2000 fpm). This procedure was done 4 times (3 different aircraft) in less than an hour with each flight lasting 6 to 12 minutes. The airport has a split frequency most of the time with all helicopters and traffic north of the field on 134.6 and traffic south of the field on 118.9. The second flight was a different controller who asked me to contact approach above 2000ft for B airspace. I responded that B started at 3000 so declined to comply. On the forth flight on a east south east heading; on the helicopter frequency descending through 1500ft; a piper cherokee passed directly underneath (300 or less) westbound on the south frequency of 118.9. I inquired to the controller of the traffic who told me to switch to 118.9 for that info. Doing as directed I then had a lengthy discussion with the tower chief over the phone after landing. The piper may have had his vision blinded by the position of the sun. I do not believe he saw us. The north/helicopter controllers sometimes point out traffic to us helicopters when they are not busy with north traffic. I think the procedure should insist that helicopters operate on the south frequency whenever we are approaching or turning that direction especially when climbing above 500 ft. I calculate at my rate of descent I was about 10 to 15 seconds within impact.

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Original NASA ASRS Text

Title: Helicopter Pilot reported that while conducting maintenance checks of autorotation a NMAC with another aircraft occurred.

Narrative: The flights were to adjust autorotation RPM. I departed eastbound then asked for a climbing southeast heading to 2500 (class B 3000) where I would enter a power off 60kt glide (2000 fpm). This procedure was done 4 times (3 different aircraft) in less than an hour with each flight lasting 6 to 12 minutes. The airport has a split frequency most of the time with all helicopters and traffic north of the field on 134.6 and traffic south of the field on 118.9. The second flight was a different controller who asked me to contact Approach above 2000ft for B airspace. I responded that B started at 3000 so declined to comply. On the forth flight on a east south east heading; on the helicopter frequency descending through 1500ft; a Piper cherokee passed directly underneath (300 or less) westbound on the south frequency of 118.9. I inquired to the controller of the traffic who told me to switch to 118.9 for that info. Doing as directed I then had a lengthy discussion with the tower chief over the phone after landing. The Piper may have had his vision blinded by the position of the sun. I do not believe he saw us. The N/helicopter controllers sometimes point out traffic to us helicopters when they are not busy with north traffic. I think the procedure should insist that helicopters operate on the south frequency whenever we are approaching or turning that direction especially when climbing above 500 ft. I calculate at my rate of descent I was about 10 to 15 seconds within impact.

Data retrieved from NASA's ASRS site 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.