The confederates might not have been successful with a helicopter, but they did make a missile. If memory serves me, the confederate missile used alcohol for fuel, was launched at Washington, but impacted in a vacant lot on the city outskirts after a 15 or 20 mile flight. Additionally, the explosives failed to detonate.
They also had a somewhat successful submarine, the Hunley which is credited with the first sinking of a ship (USS Housatonic) by a sub.
Unfortunately for the Hunley they didn't realize the effect the explosion would have on the sub. It is speculated the entire crew was killed instantly by the concussion. When the sub was raised in 2000 all hands were still at their stations. What sunk the Hunley