I am pretty sure the Chinook version flown by the Army in Nam never received an airworthiness certificate.
If you were ever in one, the leaking hydraulic lines along the inside of the body did not inspire confidence.
Properly executed, an auto rotation can be a smooth, if not firm, landing. Improperly executed it is called a crash.
Wow, thank you. My Chinook crewman buddy related an instance were a hydrol. line broke and he ordered the bird down RIGHT NOW. They and the bird survived, but my buddy had to convince the pilot that yes, indeed, the line had burst and they needed to put down right away on this field somewhere. The pilot was an ass about it for some reason.