Spiral dive 嘅成因除左唔夠lift 之外，其實human factors 都係一個好重要嘅因素，因為人嘅感官其實有好多限制~
Spiral dive 嘅出現就係同人嘅 Vestibular System 有關~
Vestibular system 係負責我地嘅spatial orientation (空間感)，gaze stability (睇野嘅穩定性)，同埋 balance(平衡)。大致上 vestibular system 可以分成兩個部份，1. Otolith organs, 2. Semicircular canals
Otolith organs 嘅作用係感受linear acceleration; semicircular canals 嘅作用係感受angular acceleration，佢地提供比我地大腦嘅info 未必一定係啱嘅。而呢個錯嘅info 就係令graveyard spiral 出現嘅human factor ~
跟住落嚟就比個例子同大家解釋下點解spiral dive 同 vestibular system 有關啦~
一個長時間嘅 coordinated constant-rate turn 有機會令到機師覺得自己唔係轉緊彎，原因係所有嘅dynamic changes in angular acceleration & linear motion 隨住轉彎嘅時間愈黎愈長而消失，導致Vestibular System 比左個同實際情況唔相符嘅資訊我地，呢個時候機師就會好自然就會扭個control yoke，令架飛機bank 得更多，同時間飛機嘅lift 都會因為bank angle 增加而減少 ，如果機師決定pull back 個control yoke 去gain lift 就只會tighten 個turn，最後進入spiral dive 嘅狀態~~