TB 55-1500-337-24
Section I. INTRODUCTION
1.
Purpose. This bulletin shall direct implementation of the Phase Maintenance System. In addition, this bulletin has
the following objectives:
a.
Describes the Phase Maintenance System.
b.
Explains Inspection Requirements.
c. Provides Changeover Instructions.
d. Provides Transfer Instructions.
2.
Scope. This bulletin explains phase maintenance and provides direction in areas not covered by the applicable
aircraft Phase Maintenance Checklist Technical Manual.
3.
Arrangement. This bulletin consists of four sections and one appendix. Sections I and II consist of the introduction
and guidance for the Phase Maintenance System.
Section III provides Phase Maintenance approach to optimizing preventive maintenance.
Section IV provides changeover instructions.
Section II. IMPLEMENTATION OF PHASE MAINTENANCE SYSTEM
4.
Receipt of Technical Bulletin and Maintenance Checklists. This Technical Bulletin is being distributed worldwide
and covers all types of Army aircraft. As Phase Maintenance Checklists for various types of Army aircraft are developed
or revised, * they will also be distributed worldwide. Upon receiving this Technical Bulletin and the applicable Phase
Maintenance Checklists, aviation activities are hereby directed to immediately begin changeover to the Phase
Maintenance System on all assigned aircraft covered by these checklists.
Section III. PHASE MAINTENANCE SYSTEM
5.
Name Designation. In keeping with technical language most often used in industry and the armed forces, the Army
has decided to identify the phase inspection system as Phase Maintenance. Therefore, the expression Phase
Maintenance shall be used regularly in this bulletin, the applicable checklists and other Army documents covering Army
aviation maintenance.
6.
Phase Maintenance Cycle.
a.
Phase Maintenance of aircraft is a system of scheduled maintenance. The interval between phase
inspections is assigned a flight hour value for the type aircraft (i.e., UH-1H, 150 flight hours; CH-47C, 200 flight hours,
etc.).
b.
A phase maintenance cycle is also assigned a flight hour value for the type aircraft (i.e., UH-1H, 900 flight
hours; CH-47C, 800 flight hours, etc.). The number of phase inspections per cycle is determined by dividing the flight
hours in one cycle by the flight hours in one phase (i.e., UH-1H, 6 phases; CH-47C, 4 phases, etc.).
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