Narrative:

Departed from ZZZ enroute to sar case. During the taxi call to ground; the pm requested VFR northwest from the outer-ramp with [the ATIS]. We were given takeoff own risk from outer ramp; early right turn out approved. We exercised the early right option; PF (PIC) cleared the aircraft right along the shoreline and called for level-off checks when level at 500ft; pm performed level off checks. We continued along the shoreline; approaching the extended centerline of runway 4R and noticed a previously unseen GA fixed wing aircraft on short final to runway 4R. They passed below our helicopter with approximately 300ft separation. We received no TCAS alerts or indications that another aircraft was within 6 NM of them on TCAS. Also; in monitoring tower freq; pm and PF didn't hear any other traffic calls that would them to believe any other aircraft was in contact with tower or operating within class D airspace. After passing through the extended centerline; PF queried tower regarding another aircraft in close proximity to our flight; the other aircraft (callsign unknown) responded that it was 'quite a surprise'. Tower apologized for the incident; noting that they thought we were departing to the south. After returning from sar; PIC immediately contacted unit flight safety officer and gave him the details. At his direction; PIC contacted tower via landline identified himself and asked to speak to the supervisor regarding the incident. Once again; the tower controller stated he was sorry; noting that he thought our flight was departing to the south; not the northwest.

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Original NASA ASRS Text

Title: A military helicopter flying a search and rescue mission reported departing an airport VFR with an early right departure turn clearance and had a near miss with an aircraft on short final.

Narrative: Departed from ZZZ enroute to SAR case. During the taxi call to Ground; the PM requested VFR Northwest from the outer-ramp with [the ATIS]. We were given Takeoff own risk from outer ramp; early right turn out approved. We exercised the early right option; PF (PIC) cleared the aircraft right along the shoreline and called for Level-Off Checks when level at 500ft; PM performed level off checks. We continued along the shoreline; approaching the extended centerline of RWY 4R and noticed a previously unseen GA Fixed Wing Aircraft on short final to RWY 4R. They passed below our helicopter with approximately 300ft separation. We received no TCAS alerts or indications that another aircraft was within 6 NM of them on TCAS. Also; in monitoring Tower Freq; PM and PF didn't hear any other traffic calls that would them to believe any other aircraft was in contact with Tower or operating within Class D airspace. After passing through the extended centerline; PF queried tower regarding another aircraft in close proximity to our flight; the other aircraft (callsign unknown) responded that it was 'quite a surprise'. Tower apologized for the incident; noting that they thought we were departing to the South. After returning from SAR; PIC immediately contacted Unit Flight Safety Officer and gave him the details. At his direction; PIC contacted Tower via landline identified himself and asked to speak to the Supervisor regarding the incident. Once again; the tower controller stated he was sorry; noting that he thought our flight was departing to the South; not the Northwest.

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.