The Propeller Spear is one of several uniques in Crimson Desert that can be a worthwhile addition to your arsenal. You can use the weapon as is, or you can use it to get the Kuku Propeller Spear (an upgraded version with better stats).
However, it all begins with finding the base version.
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Propeller Spear location in Crimson Desert
The Propeller Spear is located in the Aeronautical Research Base. This POI can be found in the southeast of Delesyia, in one of the guard towers. To identify the correct guard tower, you need to reach the marked location on the image below.

The correct tower will have an active chimney. Once you’ve found the tower, you can make your way to finding the weapon.
How to find the Propeller Spear in Crimson Desert
Take the stairs of the tower, and you’ll eventually reach a room packed with cannons and cannonballs. The weapon can be found on a weapons rack around a nearby pillar.

As a special ability, the Propeller Spear can generate a wind wave that moves in the forward direction and knocks back the targeted foe. You can use this ability after charging it up to five times, but there’s a five-second cooldown.
Since the Propeller Spear has fixed durability, it will break if you use it as a main weapon. Hence, it’s best to use it for making the Kuku Propeller Spear. The upgraded versions do more damage, can store more charges, and the cooldown is shorter. While you’ll still need the blueprint and a few other materials, the upgrade is the best way to use the Propeller Spear.