V-22 Osprey

Maintainability

The USMC plans to employ a three-level maintenance concept for the MV-22: organizational, intermediate, and depot. The USAF plans to employ a two-level concept for the CV-22: organizational and depot. Both services would employ a "power-by-the-hour" contractor logistics support (CLS) engine maintenance concept and would then conduct only organizational level (O-level) maintenance on the Allison T-406-AD-400 engines.

The V-22 design includes maintenance enhancements to meet specific maintainability, availability, and logistic supportability goals. These enhancements include: (1) a built-in test (BIT) system for fault detection and isolation; (2) the vibration, structural life, and engine diagnostic (VSLED) system; (3) extended service life dynamic components; (4) built-in work platforms; (5) single point fluid level checking and servicing; and (6) design emphasis on maintainer accessibility.

The V-22 design optimizes both existing and planned Navy and Air Force programs for collecting and utilizing maintenance data under the Automated Maintenance Environment (AME) plan. The AME concept promises to integrate, within a common shell, software programs developed for: (1) the Aviation Maintenance Event Ground Station (AMEGS); (2) the Integrated Electronic Technical Manuals (IETMS) data base; (3) the Naval Automated Logistics Command Management Information System (NALCOMIS); (4) the Air Force Integrated Maintenance Data System (IMDS); (5) parts life tracking; (6) aircraft data interface; and (7) configuration management. The goal of this approach is to provide a totally integrated technical and maintenance data management system (i.e., paperless environment) for the V-22 maintenance community.

The V-22 is designed with the maintainer in mind. Numerous features have been added that make it easier for the maintainer to reach, service, monitor and replace the Osprey's components. The on-condition design of the V-22 reduces maintenance down time, allows users to be proactive rather than reactive in maintenance planning, and reduces spares costs. With built-in work platforms, steps, handholds and 250 access openings available to the maintainer, the amount of time spent performing maintenance is reduced. The use of standard parts and tools reduces maintenance complexity, training requirements, maintenance errors, and improves aircraft availability. Avionics boxes with built-in test software give the maintainer a rapid method of fault detection and isolation. The Vibration, Structural Life, and Engine Diagnostics (VSLED) system supports aircraft maintenance diagnostic capabilities for a wide range of systems normally requiring detailed breakdown inspections at fixed time intervals. This reduces scheduled maintenance, improves aircraft availability and reduces maintenance manpower and operating costs. A central servicing station provides for servicing all hydraulic systems from the ground along with monitoring hydraulic fluid levels from a remote monitoring station. A maintenance-free battery system has an improved battery indicator, eliminating manual checkout. The Osprey's triplex fly-by-wire system eliminates extensive rigging procedures associated with cables and push-pull tubes.

The elastomeric bearings in the proprotor blades improves reliability and reduces maintenance of the proprotor hub assembly. Maintainers would have all relevant technical manuals easily available via the Interactive Electronic Technical Manuals being developed for the V-22. The system for measuring fuel quantities in the various tanks does not require calibration, thereby reducing the maintenance manpower required. Using all of these design techniques and features, as well as reliability- centered maintenance analysis, the V-22 would have a significantly lower scheduled maintenance requirements. The V-22 is essentially an on-condition aircraft. A part is removed only when there is evidence of failure or impending failure.

The maintenance concept for the V-22 is based on a Logistics Support Analysis (LSA) of the aircraft's maintainability, life-cycle cost, maintenance engineering, and logistics support requirements. The Naval Aviation Maintenance Program (NAMP), OPNAVINST 4790.2G, and Air Force Special Operations Command Instruction (AFSOCI) 21-106 provide general guidance regarding the various services' maintenance concepts. For the Navy and Marine Corps, the NAMP details three levels of maintenance (organizational, intermediate, and depot) and provides an organizational structure to collect supporting data.

The Air Force would use a two-level (organizational and depot) maintenance concept for avionics and engines. The remainder would be maintained through three levels of maintenance. During DT&E, maintenance and logistics support is the responsibility of the contractor, Bell-Boeing. During OT&E, organizational maintenance would be performed by factory trained personnel from the MOTT. The contractor would provide intermediate maintenance support.

Operating units normally perform organizational level maintenance actions on a day-to-day basis in support of its own mission. These actions are generally classified as Preventive Maintenance (PM) and Corrective Maintenance (CM). The T406-AD-400 engine would be maintained under a commercial two-level maintenance concept where the contractor (Allison Engine) provides for all aircraft maintenance beyond the organizational level at Allison repair centers. The Navy, Marine Corps, and Air Force would only be responsible for performing T406-AD-400 engine organizational level maintenance.

Preventive Maintenance consists of periodic prescribed inspections and servicing of the aircraft, systems, and subsystems as detailed in the aircraft's Maintenance Requirement Cards and Maintenance Plan. Corrective Maintenance is performed by organizational level maintenance personnel using Built-In-Test (BIT), Peculiar Support Equipment (PSE), and Common Support Equipment (CSE) to fault isolate defective Weapon Replaceable Assemblies (WRA) and Line Replaceable Units. CM includes repairs to powerplants, airframes, aircraft wiring, and connectors. Defective WRAs are forwarded to the Intermediate Maintenance Activity for repair.

Intermediate level maintenance actions are those performed in support of user activities that are beyond the capabilities of organizational level maintenance. These actions include test, repair, calibration, and modification of aeronautical equipment; repair and calibration of support equipment; and disposition of assets from stricken aircraft. Intermediate level maintenance would be performed to verify faulty WRAs and isolate to a faulty Shop Replaceable Assembly (SRA), or component, using the appropriate test equipment. The faulty SRA would be removed, repaired, and replaced, and WRA performance verified by the appropriate test equipment. Depending on the system involved, the Air Force would perform some of these maintenance tasks at the organizational, or depot level, to support the two-level maintenance concept.

Depot level maintenance actions normally require repair, major overhaul, or a complete rebuilding, manufacture, or modification of parts, assemblies, sub-assemblies, and end items beyond the capabilities of intermediate level maintenance. Naval Aviation Depot (NAVAVNDEPOT) MCAS Cherry Point, North Carolina, is planned be the depot repair site for all Marine Corps and Air Force V-22 aircraft (less engines).

In Iraq, the V-22's mission capability (MC) and full-mission capability (FMC) rates fell significantly below required levels as well as rates achieved by legacy helicopters. The V-22 MC minimum requirement is 82 percent, with an objective of 87 percent, compared with actual MC rates for the three squadrons of 68, 57 and 61 percent. This experience is not unique to Iraq deployment, as low MC rates were experienced for all MV-22 squadrons, in and out of Iraq. In comparison, the Iraq-based legacy helicopter MC rates averaged 85 percent or greater during the period of October 2007 to June 2008. Similarly, the program originally had a FMC requirement of 75 percent; but its actual rate of 6 percent in Iraq from October 2007 to April 2008 was significantly short of that, due in large part to faults in the V-22's Ice Protection System. In areas where icing conditions are more likely to be experienced, such as in Afghanistan, this may threaten mission accomplishment.

Repair parts issues and maintenance challenges affected the availability of MV-22s in Iraq. V-22 maintenance squadrons faced reliability and maintainability challenges, stemming from an immature supply chain not always responsive to the demand for repair parts and aircraft and engine parts lasting only a fraction of their projected service life. The MV-22 squadrons in Iraq made over 50 percent more supply-driven maintenance requests than the average Marine aviation squadron in Iraq. A lack of specific repair parts took place despite having an inventory intended to support 36 aircraft as opposed to the 12 aircraft deployed.