SAS,
To help you catch up:
- the 53 and 64 are tradional helicopters with 60's performance and abysmal safety records
- the 67 ended up scattered across a field in England due to poor maneuverability and/or pilot error
- the Cheyenne was an expensive failure with design flaws many related to the rotor
As for the Piasecki, this is a joke going nowhere.