The U.S. Army's most popular aircraft is continuing to evolve. The aircraft in question is the Raven, which weighs less than five pounds, and is a UAV used mainly by combat troops. Infantry companies and platoons regularly use them to get a look at what's over the hill, or behind surrounding buildings. Recent improvements include a "fail safe" mode, where a Raven that has lost contact with its operator, will immediately head for where it was launched from. There is now a location beacon, so that if one crashed over the hill, it can be quickly found. The latest improvements...