The Central Oregon Emergency Information Network says the pilot and a passenger were killed in the crash about 2 pm (local time) today about a mile south of Madras Municipal Airport.
Authorities did not identify the victims.
Jefferson County Sheriff Jim Adkin says the crash started a brushfire on a cliff.
Campers have been gathering at the airport for tomorrow's eclipse.
About 200,000 people are expected in the area that's considered a prime viewing spot as the moon completely blots out the sun.