The other safety issues are common with other powered model categories. Hand-starting very powerful engines, with very sharp propellers, can be quite hazardous. An electric starter can be used, but can have negative effects on the engines due to engines not being designed to take that kind of force pushing the crank shaft back. One such method is the "back-bump" method, where the engine is choked and flipped through with no battery attached to create favorable starting conditions. Once prepared, all that is necessary is to rock the engine backwards so that it coasts up to compression, and if done correctly, starts forwards. This provides time to move the hand out of the way and the fingers are not in contact with the propeller or spinner when the engine starts. Care must be taken even choking the engine as modern engines with their accurate piston/cylinder fit can "bump" or even start without the battery attached. Once the propeller is rotating, extreme care must be taken when preparing for flight and adjusting the engine. A starting accident frequently results in a small cut to the finger, but once the engine is at full speed any injury that is encountered is likely to be quite severe.