DA40 pilot reported a near midair collision during take off from a non-towered airport.

Attributes
ACN	1543409
Time
Date	201805
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	DA40 Diamond Star
Operating Under FAR Part	Part 91
Flight Phase	Takeoff
Route In Use	None
Flight Plan	VFR
Aircraft 2
Make Model Name	Robinson R22
Operating Under FAR Part	Part 91
Flight Phase	Landing
Route In Use	None
Flight Plan	VFR
Person 1
Function	Single Pilot Pilot Flying
Qualification	Flight Crew Private
Experience	Flight Crew Last 90 Days 5 Flight Crew Total 61 Flight Crew Type 61
Events
Anomaly	Conflict NMAC Deviation - Procedural Published Material / Policy Inflight Event / Encounter Weather / Turbulence
Miss Distance	Vertical 10

Narrative:

While I was finishing up the run up; my instructor notified me that I should find another route because of a thunderstorm rolling into my original destination. While taxiing to the 360 check; I was feeling pretty stressed since there was a lot of things going on in my mind. I was thinking about how I should go to my new destination and after that I checked for any traffic while doing the 360. I did not see anything so I checked my ads-B but I did not see anything. I must have missed the helicopter on the ads-B. I went to the hold short for runway 35 and I looked both ways and it looked like I was clear so I announced that I was taking the runway for take-off. As soon as I got onto the runway; all of my attention went into my plane but I heard a helicopter call and I thought they said parallel for runway 35 since that is what they always did while I was in the pattern. It turned out they did a landing on 35 which I've never encountered. When I started to take off; it looked like they were doing a parallel which confirmed what I thought I heard; so I went with the take-off but when I checked again about 1000 feet off the ground; they were under me so I tried to climb as fast as I could.

Original NASA ASRS Text

Title: DA40 pilot reported a NMAC during take off from a non-towered airport.

Narrative: While I was finishing up the run up; my instructor notified me that I should find another route because of a thunderstorm rolling into my original destination. While taxiing to the 360 check; I was feeling pretty stressed since there was a lot of things going on in my mind. I was thinking about how I should go to my new destination and after that I checked for any traffic while doing the 360. I did not see anything so I checked my ADS-B but I did not see anything. I must have missed the helicopter on the ADS-B. I went to the hold short for Runway 35 and I looked both ways and it looked like I was clear so I announced that I was taking the runway for take-off. As soon as I got onto the runway; all of my attention went into my plane but I heard a helicopter call and I thought they said parallel for Runway 35 since that is what they always did while I was in the pattern. It turned out they did a landing on 35 which I've never encountered. When I started to take off; it looked like they were doing a parallel which confirmed what I thought I heard; so I went with the take-off but when I checked again about 1000 feet off the ground; they were under me so I tried to climb as fast as I could.

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.