Gyroplane pilot reported an near midair collision with another aircraft while in the pattern.

Narrative:

Experimental gyroplane departed ZZZ on the west taxiway 15. Gyroplanes and ultralights at ZZZ use the west taxiway with a pattern to the west in order to avoid faster fixed wing traffic whose patterns are on the east side of the airport. After takeoff; in order to clear for traffic; gyroplane made a right 270 [degree] turn to the east. Since this particular gyroplane is piloted from the right seat a 270 [degree] turn enables the pilot to better view traffic over the runway as a left turn directly over the runway turns toward the blind side. There were at least 3 other fixed wing aircraft in the pattern at the time.after having passed over the center of the runway; at 400-500 ft.; headed 060 (90 degrees from the runway); at about 1/4 to 1/2 mile from the runway and climbing through about 600-700 ft. A cessna type aircraft passed directly under the gyroplane from the opposite direction. Gyroplane pilot didn't see the cessna until it was just directly front of and below the gyroplane. Gyroplane pilot was looking up and down (right & left) the downwind leg where other aircraft are expected to be seen and did not see the cessna until about 2 seconds before it passed underneath the gyroplane. The cessna; heading westerly; passed directly under the gyroplane. Gyroplanes at spb usually stay between 600-800 ft. While passing under the fixed wing traffic pattern (which is at 1100 ft.).

Original NASA ASRS Text

Title: Gyroplane pilot reported an NMAC with another aircraft while in the pattern.

Narrative: Experimental Gyroplane departed ZZZ on the west Taxiway 15. Gyroplanes and ultralights at ZZZ use the west taxiway with a pattern to the west in order to avoid faster fixed wing traffic whose patterns are on the east side of the airport. After takeoff; in order to clear for traffic; Gyroplane made a right 270 [degree] turn to the east. Since this particular Gyroplane is piloted from the right seat a 270 [degree] turn enables the pilot to better view traffic over the runway as a left turn directly over the runway turns toward the blind side. There were at least 3 other fixed wing aircraft in the pattern at the time.After having passed over the center of the runway; at 400-500 ft.; headed 060 (90 degrees from the runway); at about 1/4 to 1/2 mile from the runway and climbing through about 600-700 ft. a Cessna type aircraft passed directly under the Gyroplane from the opposite direction. Gyroplane pilot didn't see the Cessna until it was just directly front of and below the Gyroplane. Gyroplane pilot was looking up and down (right & left) the downwind leg where other aircraft are expected to be seen and did not see the Cessna until about 2 seconds before it passed underneath the Gyroplane. The Cessna; heading westerly; passed directly under the Gyroplane. Gyroplanes at SPB usually stay between 600-800 ft. while passing under the fixed wing traffic pattern (which is at 1100 ft.).

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.

Attributes
ACN	1674678
Time
Date	201908
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Ultralight
Operating Under FAR Part	Part 91
Flight Phase	Initial Climb
Flight Plan	None
Aircraft 2
Make Model Name	Cessna Aircraft Undifferentiated or Other Model
Flight Phase	Descent Landing Final Approach
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Instrument Flight Crew Commercial Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 20 Flight Crew Total 1464 Flight Crew Type 162
Events
Anomaly	Conflict NMAC Deviation - Procedural Published Material / Policy
Miss Distance	Horizontal 0 Vertical 100