The word 1 blade, whose official name should be "seesaw" rotor, is a patent of Bell. Bell series helicopters are used the most, basically only in his home. The representative models are UH- 1 Huey and AH- 1 Cobra. The biggest advantages of the seesaw rotor system are simple structure, low manufacturing cost, low failure rate and convenient maintenance. Cross blade, without this name, four blades have no fixed name, and it is a single rotor system with four blades. In fact, the number of rotor blades increases with the increase of helicopter's maximum takeoff weight, such as light and small 3-4 blades, such as Squirrel 3, Bell 406, 4, Dolphin 4, medium-sized Mi -8, Mi -6, EH 10 1, CH53 6, Mi -26 8. Increasing the number of blades has three purposes. One is to reduce the force borne by each blade, thus increasing the efficiency of the whole rotor system; The second is to reduce the rotor speed; Third, mobility has improved.
Of course, the disadvantage is that the structure is complicated and the manufacturing cost is correspondingly increased. The new AH- 1Z has also been changed from the seesaw rotor system to four blades, which is in pursuit of performance improvement. Generally speaking, there are no respective advantages and disadvantages, just as a tricycle does not need to be equipped with an extra wheel, it is economical and sufficient to suit this model.
Another advantage of seesaw rotor is that it is easy to transport (air or sea). UH- 1 Because it was easy to transport during the Vietnam War, it became the most productive helicopter. Although all multi-wing helicopters now have the design of rotor folding, its folding will inevitably lead to the complexity of rotor hub design and the safety consideration of folded blades. The seesaw rotor can be placed directly along the direction of the fuselage to reduce the occupied space.