I ran across this site a few nights ago...very well done accounting of US Army helicopter losses by type of aircraft. As you read through the UH-1 Huey portion of the site....during the Vietnam period....accident after accident shows up due to night and IIMC events. One thing to remember...lots of times the aircraft instrumentation was not operative, there was very little nav or radar available....and it was a very dark place with mountains in most parts.
www.armyaircrews.com