A helicopter” is the correct usage, in case of telling about hour (time) “an hour” is the correct usage. “A” & “An” are defined as indefinite articles in English Grammar, both of them serves the same purpose. read more
The correct expression is “A helicopter”, because A is used before a word starting with a consonant and An is used before a word starting with a vowel; h is a consonant. But it is not that simple, actually. We don’t say “It’s been a honour”. read more
correct: a helicopter. explanation: an is only used when the word after begins with a vowel: a e i o u. correct: a helicopter. explanation: an is only used when the word after begins with a vowel: a e i o u. read more