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USAF Extends Phase Maintenance Interval on Lockheed Martin Block 40/42/50/52 F-1

May 23, 2000 (by Lieven Dewitte) - The U.S. Air Force recently extended the phase maintenance interval for its fleet of more than 600 Block 40/42/50/52 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. The extension essentially cuts the F-16 phase inspection workload by a third and increases the number of 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 2 percent. These savings could equate to more than $1. 5 million per year for the current USAF fleet of Blocks 40/42/50/52 aircraft.

The F-16 was originally fielded with an inspection cycle of four phases, one every 50 flight hours. The interval has been progressively increased to 100 hours, 150 hours, 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 and reliability improvements that have been incorporated in F-16 components over the years. USAF's Block 25/30/32 F-16C/D fleet has been operating at a 300-hour phase interval for a year with great success. A study on extending the phase interval to 300 flight hours is currently being conducted for USAF's Block 10/15 F-16A/B fleet and is expected to be complete soon. 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 for most of the avionics components. 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 also are 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 on one shift.