Question: An American twin-engine attack helicopter that was developed for the United States Marine Corps as part of the H-1 upgrade program is also called what when based on the ICAO phonetic alphabet pronunciation of it's variant letter? 
Sentence (from "Bell AH-1Z Viper"): The Bell AH-1Z Viper is an American twin-engine attack helicopter, based on the AH-1W SuperCobra, that was developed for the United States Marine Corps as part of the H-1 upgrade program.
Relevant evidence: Yes