1. How does an aircraft engine work? �ɻ������������������ģ�
2. The aircraft circled round over landing strip . �ɻ�����½�ܵ��Ͽն�Ȧ�ӡ�
3. This sight is a good attempt at the solution of the problems of controlling aircraft guns, and the engineering skill displayed in the design of the prototype is high. �����������ͼ������������Ŀ�����������һ���õij��ԣ�ͬʱ��ԭ�͵�������������ʦ��ʾ�˸߳��ļ��ܡ�