Narrative:

I decided to take a student to fly out to practice area to practice some approaches and hover work. We took off after pre-flight; VFR condition with 6000 ceiling and 10 SM vis; wind was 050 at 6; temp 48; dew point 40; relative humidity rate 73% at ZZZ at the time we took off [approximately one hour before sunset]. I was wearing winter clothes but not the student; we both wore the life vest though. After about 50 minutes flight; I demonstrated an approach to the student then gave him control to take off; at 300 AGL before turning crosswind; I looked around for traffic and noticed fog/low clouds approaching us from the east; I said to the student the weather just turned bad; we have to return to the airport; and the next second visibility around us just dropped drastically. I took over the control from the student and turned towards the airport; about 1 minute later the visibility dropped to about 1 mile and I made a precaution landing to an empty field; 4NM southeast of the airport. I didn't make the call to [advise the] tower in flight or report the precautionary landing due to the landing itself was pretty stressful as I was trying to confirm nobody was on the field and watch out for poles and wires in the low visibility. I called the tower after we shut down the helicopter. Based on the taf report published [six hours earlier]; there was going to be temporary drizzle and mist; with ceiling drop to 2500 and visibility drop to 4~5 SM. I decided to go out of the airport anyway. Thought the 7 NM distance would allow us to return in case the weather turns bad; which turned out to be the cause of us flying into that dangerous situation way below my personal minimums. It's a VFR trainer R-22 without attitude indicator or any gyro instrument.

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Original NASA ASRS Text

Title: R22 Flight Instructor reported a precautionary off field land due to unanticipated contact with instrument weather conditions while operating a VFR helicopter.

Narrative: I decided to take a student to fly out to practice area to practice some approaches and hover work. We took off after pre-flight; VFR condition with 6000 ceiling and 10 SM Vis; wind was 050 at 6; temp 48; dew point 40; relative humidity rate 73% at ZZZ at the time we took off [approximately one hour before sunset]. I was wearing winter clothes but not the student; we both wore the life vest though. After about 50 minutes flight; I demonstrated an approach to the student then gave him control to take off; at 300 AGL before turning crosswind; I looked around for traffic and noticed fog/low clouds approaching us from the east; I said to the student the weather just turned bad; we have to return to the airport; and the next second visibility around us just dropped drastically. I took over the control from the student and turned towards the airport; about 1 minute later the visibility dropped to about 1 mile and I made a precaution landing to an empty field; 4NM southeast of the airport. I didn't make the call to [advise the] tower in flight or report the precautionary landing due to the landing itself was pretty stressful as I was trying to confirm nobody was on the field and watch out for poles and wires in the low visibility. I called the tower after we shut down the helicopter. Based on the TAF report published [six hours earlier]; there was going to be temporary drizzle and mist; with ceiling drop to 2500 and VIS drop to 4~5 SM. I decided to go out of the airport anyway. Thought the 7 NM distance would allow us to return in case the weather turns bad; which turned out to be the cause of us flying into that dangerous situation way below my personal minimums. It's a VFR trainer R-22 without attitude indicator or any gyro instrument.

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.