WASHINGTON -- The Army is about 19 percent complete with a retrofit of strap pack "mega-nuts" that connect Apache helicopter rotor heads to their air frame and keep the blades from spinning off during flight.Maj. Gen. Douglas M. Gabram, commander, U.S. Army Aviation and Missile Command, said the retrofit of all Apaches should be complete by the 3rd quarter of 2019.In the meantime, "fail-safe collars" are being installed on the remaining Apaches, he said, during an expeditionary sustainment panel Wednesday at the Association of the U.S. Army's "hot topics" aviation forum.SAFETY CONCERNEight strap pack nuts connect the rotor blades on an Apache to the air frame. However, a safety concern arose earlier this year that severe weather and salt in coastal areas might corrode the original nuts to the point where they crack under stress.In February, AMCOM issued guidance that required rigorous pre- and post-flight inspections of the strap pack nuts on all Apache helicopters. Technicians were instructed to use borescopes for the inspections. Further, the Army temporarily halted the delivery of new AH-64E Apache helicopters.Gabram said the good news is "we have a materiel solution and we're fielding it. We are fielding the mega-nut."ENTERPRISE SOLUTIONThe solution came about through teaming with industry and the "whole aviation enterprise," Gabram said.Two battalions per month are now being refitted, and he said it's not an easy process."We're doing major surgery on every one of our main rotor heads … Why: to reduce the burden on the Soldier, because we don't want to borescope this thing for the rest of our life, every day. Two: to restore confidence and trust … with this aircraft, between aviator and ground."JUST IN TIME?With repair parts in general, the Army has been operating for 15 years under a "just in time" logistics delivery model, eliminating huge stockpiles, Gabram said. This may not be good enough when facing near-peer adversaries in the future, he surmised.If the U.S. Army faced a near-peer competitor -- in addition to its commitments in Iraq and Afghanistan -- he estimated the demand for spare parts would go up by 50 percent. More stock on hand would be needed."We want 90 days stock on the shelf, based on average monthly demand," Gabram said, adding that no back orders should be greater than 30 days. "That's our metric. That's what we're going to fight for, and that costs resources, that costs prioritization.""So 'just in time' is effective in our LMP, logistics modernization program ... but we need some strategic depth based on this near-peer threat," he said."What keeps me up at night is stock on hand in some key readiness drivers."EXPEDITIONARY SUSTAINMENTAviation units have not really been required to handle expeditionary sustainment in the past 18 years, said Command Sgt. Maj. Jason D. Huff, senior aviation NCO with the observer coach/trainers at the National Training Center, Fort Irwin, California.Army units have been operating in theaters where large sustainment support areas are set up to handle rotational forces, Huff said. When aviation task forces are pulled away from combat aviation brigades, units struggle to determine their correct authorized stockage list and prescribed load list.Units sometimes come to the National Training Center at Fort Irwin, California, without enough spare parts, Huff said, and when ordered parts don't arrive in time, aircraft are often grounded for multiple days."As you're moving around the battlefield at 72 to 96 hours … you end up leaving a trail of aircraft behind that need security," he said.The flip side is that other units don't understand what they need, and bring "entirely too much" with them. Then they can't maneuver without help from external assets, and that reduces their ability to survive, Huff said.