The troubled V-22 Osprey aircraft program is in trouble again, as the test aircraft were grounded for two weeks so that hydraulic problems could be fixed. Engineers and mechanics who have worked on, or with, the V-22 report that the aircraft is simply too complicated for military, and perhaps even commercial, use. The V-22s cost $90 million each and are to replace aging heavy helicopters used by the marines. The aircraft can carry 24 combat troops 350 kilometers about twice as fast as a helicopter. Thus special operations troops are also interested. But durability and reliability are critical characteristics for combat aircraft and the V-22 may prove to be lacking in this department.