as they approached the car park of the destination hospital two things out of the norm happened after he lowered the undercarriage , first the ladder gave up its struggle to hang on , and the top attachment broke loose , but the lower one held momentarily , fortunately stopping it from being swallowed up by the vector thrust engine ( and converting it into an airborne scrap-heap ) , but it did cause the ladder to pivot out , and then under the belly of the aircraft , from whence came a thud , a strange vibration , and finally the undercarriage light turned red oops .