May 17, 1999 (by Lieven Dewitte) - The U.S. Air Force recently extended the phase maintenance interval for its fleet of over 600 block 25, 30 and 32 F-16C/Ds, indicating increasing reliability of the aircraft as the fleet matures. The F-16 phase maintenance interval has been extended from a two-phase, 200-flight hour interval to a single-phase, 300-flight hour interval. This essentially cuts the F-16 phase inspection requirements by a third. This means fewer aircraft out of service and more aircraft on the flight line available for operational training or combat missions. This change will reduce the total base level maintenance man hours required to support these aircraft by two percent. This savings could equate to over $1. 5 million per year for the current USAF fleet of Block 25/30/32 aircraft.
Most of these aircraft are assigned to Air Force Reserve and Air National Guard squadrons. Most international air forces operating F-16s follow the USAF's lead in these decisions. The F-16 was originally fielded with an inspection cycle of four phases, one every 50 flight hours. This has been periodically increased to 100 hours, 150hours, then 200 hours. These increases were based on extensive analysis of aircraft maintenance data.
"Two facts of maturation have permitted these increases - increasing knowledge of the aircraft that permits less conservatism in inspection frequency, and the reliability improvements that have been incorporated in F-16 components over the years, " said Gill. A similar study (on extending the phase interval to 300 flight hours) is currently being conducted on USAF's Block 40/50 fleet. This study will be completed in June of this year, and indications are that the extension will be recommended and implemented.
A similar 300-hour study of the USAF's Block 10/15 F-16A/B fleet has just begun and will be completed in June 2000. The F-16 uses the standard three-level maintenance concept consisting of organizational maintenance (flight line), intermediate (base-level back shop component repair) and depot (at military depots or contractor production facilities). The aircraft's avionics reliability has allowed a two-level maintenance concept to be adopted. The F-16 airframe is designed so that no depot inspections are required over its long, 8, 000-flight hour service life, a unique feature for military aircraft.
An aircraft goes through phase inspection at its home or deployed base. This includes inspecting the airframe and aircraft systems, replacing certain consumable items and fixing any discrepancies discovered. For convenience, special one-time base level inspections and parts changes are also performed at this time. For active duty operations, an F-16 phase inspection (including fixes and upgrades) normally takes about a week using a 10-person crew.