Here is the full list of all 29 Choppa achievements.
The base game contains 27 achievements, and there is 1 DLC pack containing 2 achievements.
Unlock Hot Air Balloon
Unlock the AK-84 RED CAMO chopper.
Unlock Prehistoric Chopper
Unlock GOLDEN BOY chopper.
Save a person without using the ladder.
Unlock UFO.
Do a somersault.
Unlock the AK-84 APALACHEE chopper.
Unlock Desert Chine
Unlock the VH-84 CHINE chopper.
Unlock Steam Choppa
Unlock Classic Choppa
Unlock the BLUE FALCON chopper.
Unlock the RESCUE chopper.
Unlock a new chopper.
Collect 1000 coins.
Fully upgrade a chopper.
Grab a person mid-air.
Save a person from drowning.
Save 5 people.
Witness a human getting burned
Neutralize a seagull
Pass stage 15 on oil-rig level.
Pass stage 10 on oil rig level.
Unlock the Santa's Sled Choppa
Stay alive for 1 minute in survival mode
Stay alive for 2 minutes in survival
Unlock the FULL-TIME UFO chopper
Unlock the VACUUM chopper