“小折刀”是据传由诺斯罗普·格鲁门秘密研制中的新技术隐身攻击机的一个形象的绰号。因为该机机翼的变掠角（折叠）原理就像我们日常所用的折叠刀。它很可能是美国航空界在新世纪打造的又一个军用航空产品的亮点新闻 “Pocket Knife” is nicknamed as an image of the stealth attack aircraft of the new technology, which was secretly crafted by Northrop Grumman. Because the aircraft wing sweep angle (folding) principle is like our daily use folding knife. It is likely to be another highlight of the U.S. aviation community’s military aviation product built in the new century