Airframe is the body from drone. At the moment we are just learning to fly a drone, want to buy a drone as powerful as anything, it is definitely going to be a collision/crash. Just look at the news about friends who buy expensive but a goodly drone nabrak building. Therefore, at the moment we are just learning to fly drones, we need to choose which airframe drones which have a light but tough. If weight is difficult flight suit. And if it's not tough, the airframe could be torn/ruptured at the time of the collision or crash/fall.
Because we have been sure a collision/crash time just learning, we must mastiin the safety of propeller at the time of the collision/crash. Right fit again flying, spinning propeller with very high speed. If the propeller is not protected, then the time of the collision/crash, the propeller can break because it hit the goods/building/plant/soil at high speed round. If the propeller is broken at a time when drones in the air again, so sure that drones will fall because of the loss of lift (Elevator). So choose drones which have a protective propeller. If possible, the protector of the propeller should be strong but flexible. Strong to protect the propeller. Flexible protective order that propellernya itself is not damaged when the collision.