Narrative:

It was my first solo IFR flight after earning my instrument rating; and I was excited to fly up through a low cloud layer on my own. I set up and filed my IFR flight plan; pre-flighted the plane; a cessna 172; strapped myself into the pilot's seat and started the engine. When I radioed ZZZ departure clearance to activate my flight plan to ZZZ and receive departure clearance; I was given...depart via departure; cleared to 10;000; then as filed.I looked at my departure procedure and saw two pages. [Page] one specified I fly runway heading with vectors. The other [page] specified a climbing left turn to the VOR; thence as filed.in my excitement; I wondered which of the two I should use; and chose what I thought would be the safest as well as the quickest; not remembering that in any uncertainty I could always ask; and did not think to look closer at the fine print. On takeoff from runway xxr; I dutifully began my climbing (nearly 180-degree) left turn to intercept the VOR; just as I was entering the 800-AGL ceiling of clouds.before I had turned more than about 30 degrees; tower called me to direct me to fly runway heading until further notice; and to call them via phone after I landed. I wondered why; but did as directed for what turned out to be a safe; otherwise uneventful flight.when I called the number tower had given me; they explained that I had departed from the [standard instrument] departure procedure. I told them what I had thought I was doing; and they informed me kindly that the runway heading with subsequent vectors from departure control was the correct selection; that I could have caused an accident had I been in heavy traffic; but that no harm was done this time.as soon as I could; I spoke to an experienced flight instructor about the incident with a question about which page of the procedure was correct and why. The instructor chuckled and told me the turning maneuver I had chosen was the lost communications procedure. To use that one; I would have needed to have changed my transponder to 7600.this is something I should have known.the error; thankfully an uneventful error; drilled that lessen into my memory in a way that I doubt I will forget again. To avoid such mistakes in the future; I know I can take extra time to review procedures until I understand them fully; and to ask questions when I do not.

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Original NASA ASRS Text

Title: C172 pilot reported that he misunderstood the instrument departure clearance.

Narrative: It was my first solo IFR flight after earning my Instrument Rating; and I was excited to fly up through a low cloud layer on my own. I set up and filed my IFR flight plan; pre-flighted the plane; a Cessna 172; strapped myself into the pilot's seat and started the engine. When I radioed ZZZ Departure Clearance to activate my flight plan to ZZZ and receive departure clearance; I was given...depart via Departure; cleared to 10;000; then as filed.I looked at my Departure procedure and saw two pages. [Page] one specified I fly runway heading with vectors. The other [page] specified a climbing left turn to the VOR; thence as filed.In my excitement; I wondered which of the two I should use; and chose what I thought would be the safest as well as the quickest; not remembering that in any uncertainty I could always ask; and did not think to look closer at the fine print. On takeoff from Runway XXR; I dutifully began my climbing (nearly 180-degree) left turn to intercept the VOR; just as I was entering the 800-AGL ceiling of clouds.Before I had turned more than about 30 degrees; Tower called me to direct me to fly runway heading until further notice; and to call them via phone after I landed. I wondered why; but did as directed for what turned out to be a safe; otherwise uneventful flight.When I called the number Tower had given me; they explained that I had departed from the [Standard Instrument] Departure procedure. I told them what I had thought I was doing; and they informed me kindly that the runway heading with subsequent vectors from departure control was the correct selection; that I could have caused an accident had I been in heavy traffic; but that no harm was done this time.As soon as I could; I spoke to an experienced Flight Instructor about the incident with a question about which page of the procedure was correct and why. The instructor chuckled and told me the turning maneuver I had chosen was the lost communications procedure. To use that one; I would have needed to have changed my transponder to 7600.This is something I should have known.The error; thankfully an uneventful error; drilled that lessen into my memory in a way that I doubt I will forget again. To avoid such mistakes in the future; I know I can take extra time to review procedures until I understand them fully; and to ask questions when I do not.

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.