Narrative:

My flight took me down napa valley followed by some stations near davis and up towards woodland. Before the flight; special emphasis was made of tfrs as the fires were growing quite rapidly. Some of the stations were inside the tfr and were not flown. After refueling in napa; I headed east; south of the tfr; towards the central valley at 3;000 ft.; thinking that I would remain under any IMC density smoke. There were several factors for choosing 3;000 ft. And eventually 3;500ft.: 1) it kept me above the local terrain; 2) it kept me out of the travis AFB class D. Another factor which affected my choice of altitude was the radio situation. The aircraft I was flying uses a handheld radio and the spare batteries were not charged upon arrival at the aircraft. I felt the need to conserve the battery life for returning to the home airport so I minimized transmissions. As I kept moving east; visibility began dropping to what seemed like 4 sm as the ground was visible roughly 4 miles away. Instead of returning towards napa; where there was less smoke; I continued east then northeast to my photo mission location. Throughout this time I was losing reference to the horizon as the smoke became quite thick; IMC conditions; I had to recall my instrument training to maintain direction and altitude although the aircraft was poorly equipped to handle IMC. I tried climbing above the smoke to no avail [to] 8;500 ft.; as some photo stations were around 6;000 ft. I had reason to attempt to climb above the smoke. Recognizing that the photo mission was unable to be completed; I focused solely on returning to my home base. By this point; the original tfr of concern was expanded significantly and another tfr had popped up near my home airport. Eventually; I descended below the smoke; 5;000 ft.; as I was making my way north along the eastern edge of the tfr. If an occurrence like this were to happen again; I would return to the nearest VFR airport; in this case napa; and plan out the next part of the flight; along with this plan; I would utilize the radio to gather information from local facilities about smoke conditions: talk with travis.

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Original NASA ASRS Text

Title: Small aircraft Pilot reported encountering IMC due to heavy some due to forest fires.

Narrative: My flight took me down Napa Valley followed by some stations near Davis and up towards Woodland. Before the flight; special emphasis was made of TFRs as the fires were growing quite rapidly. Some of the stations were inside the TFR and were not flown. After refueling in Napa; I headed east; south of the TFR; towards the central valley at 3;000 ft.; thinking that I would remain under any IMC density smoke. There were several factors for choosing 3;000 ft. and eventually 3;500ft.: 1) It kept me above the local terrain; 2) It kept me out of the Travis AFB Class D. Another factor which affected my choice of altitude was the radio situation. The aircraft I was flying uses a handheld radio and the spare batteries were not charged upon arrival at the aircraft. I felt the need to conserve the battery life for returning to the home airport so I minimized transmissions. As I kept moving east; visibility began dropping to what seemed like 4 sm as the ground was visible roughly 4 miles away. Instead of returning towards Napa; where there was less smoke; I continued east then northeast to my photo mission location. Throughout this time I was losing reference to the horizon as the smoke became quite thick; IMC Conditions; I had to recall my instrument training to maintain direction and altitude although the aircraft was poorly equipped to handle IMC. I tried climbing above the smoke to no avail [to] 8;500 ft.; as some photo stations were around 6;000 ft. I had reason to attempt to climb above the smoke. Recognizing that the photo mission was unable to be completed; I focused solely on returning to my home base. By this point; the original TFR of concern was expanded significantly and another TFR had popped up near my home airport. Eventually; I descended below the smoke; 5;000 ft.; as I was making my way north along the eastern edge of the TFR. If an occurrence like this were to happen again; I would return to the nearest VFR airport; in this case Napa; and plan out the next part of the flight; along with this plan; I would utilize the radio to gather information from local facilities about smoke conditions: talk with Travis.

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.