Douglas A-1 (later AD-1) Skyraider, for those (like me) unfamiliar with the slang term "Spad", which I always thought referred to a First World War French fighter aircraft! For an example of the latter, see picture #3980.
You are correct with the nickname. The US Forces got around to using prop-driven aircraft as helicopter escorts and COIN (counter-insurgency) aircraft in Vietnam. The other nickname was "Sandy"
Added by Peter Langsdale on 10 April 2010.