Engine arm contraction mechanism for multi-rotor unmanned aerial vehicle

The invention discloses an engine arm contraction mechanism for a multi-rotor unmanned aerial vehicle. The engine arm contraction mechanism comprises a first connecting piece, a second connecting piece and a third sleeve, wherein the first connecting piece comprises a first sleeve and a first plug; the second connecting piece comprises a second sleeve, a second plug and a rotating shaft; an outer stopper of the second sleeve is spaced on the inner side of an inner stopper of the third sleeve in a closed connection state; an internal thread of the third sleeve is connected with an external thread of the first sleeve; the first plug and the second plug are inserted together. Because the first sleeve and the second sleeve are connected together through the rotating shaft and the rotating shaft is movably mounted in a slotted hole, two contraction manners of plugging/unplugging and folding can be simultaneously realized by the first sleeve and the second sleeve, and the contraction mechanism is conveniently unfol