Each aircraft shall begin changeover to the phase system immediately upon receiving Phase Maintenance
System Checklists and this technical bulletin.
The changeover time period is the time interval between completion of the last periodic inspection and the
time when the first phase inspection is due. During this interval, services only will be performed instead of complete
intermediate inspections. Services consist of lubrications, taking oil samples for analysis, changing filters are required
and avionics and armaments servicing. Special inspections contained in the -23 technical manual will be performed as
required at the specified intervals.
The first phase maintenance inspection, Phase No. 1, is due after a number of flying hours equal to the
interval between phases have elapsed since the last periodic inspection. (Example: For the AH-lS aircraft, the initial
Phase No. 1 inspection is due 150 flying hours after the last periodic inspection.) In addition to meeting the requirements
of all tasks in the Phase Maintenance Checklist, each aircraft shall be given a complete safety of flight inspection.
Safety of flight inspection shall consist of meeting all critical inspection requirements of the complete Phase Maintenance
System, including daily and all phases. Each critical inspection requirement is printed in bold type in the Daily and Phase
Maintenance Checklists. Special inspection requirements will also be accomplished.
Items due for maintenance before being scheduled on the Phase Maintenance Checklist need special
attention. To prevent exceeding the intervals required by the Phase Maintenance System, maintain the item at the first
maintenance phase. Then future maintenance shall be as scheduled in the checklist. Time intervals between
maintenance of some items change when going from the old PMI/PMP System to the Phase Maintenance System. In
such a case, time interval between maintenance actions during the changeover time period shall be as required by the
Phase Maintenance System.
Changeover is complete and the aircraft is on Phase Maintenance when the following actions have been
(1) All tasks in new Phase Maintenance Checklist.
(2) Safety of flight inspection.
(3) All required special inspections.
(4) All additional items required to avoid exceeding the allowable time intervals.
Changeover Instructions for Phase Maintenance Interval Change.
Changeover instructions in this technical bulletin cover Army aircraft. When previously established aircraft
phase maintenance intervals are changed, these instructions shall apply.
Changeover to the new phase maintenance interval will be accomplished at the next scheduled phase
inspection under the old phase time interval. Transition to the new phase inspection interval is accomplished by
performing a complete phase inspection