In aircraft maintenance, the Aircraft Maintenance Program (AMP) and Last Done/Next Due (LDND) records are critical tools for ensuring compliance, airworthiness, and operational efficiency. While the AMP defines maintenance tasks, thresholds, and intervals, the LDND is the actionable record that tracks these tasks against the actual status of the aircraft and its components.
AMP and LDND: Breaking Down the Roles
AMP (Aircraft Maintenance Program) is a structured guideline that specifies:
Tasks: What needs to be inspected, repaired, or replaced (e.g., “Overhaul fuel pumps every 5 years”).
Thresholds: The initial limits for completing tasks (e.g., 5,000 flight hours, 3,000 cycles, or 5 calendar years).
Intervals: The repetition frequency after the initial task (e.g., every 500 cycles).
LDND (Last Done/Next Due) is a database or record system that operationalizes the AMP by tracking:
Last Done: When a task was last completed for a specific component (e.g., a fuel pump overhaul done at 4,800 flight hours).
Next Due: When the task is next required, calculated based on the current flight hours, cycles, or calendar date (e.g., next overhaul at 9,800 flight hours).
The AMP provides high-level maintenance tasks, but the LDND applies these to individual components installed on the aircraft. For example:
Fuel Pumps:
The AMP might state “Overhaul every 5 years.” The LDND must track:
Location of each pump on the aircraft.
Serial numbers to differentiate between multiple pumps.
Last Done dates for each pump’s overhaul.
Next Due dates specific to each pump’s unique maintenance history.
Engines and LLPs:
The AMP outlines limits for Life-Limited Parts (LLPs), such as turbine blades or fan discs. The LDND tracks:
Each LLP by serial number.
Remaining life based on operating cycles or hours.
Next replacement or inspection thresholds.
Lease and Asset Management:
During lease returns, LDND records are crucial for proving compliance with maintenance requirements.
Accurate records prevent disputes and costly penalties.
Managing Complexity:
With multiple identical components on an aircraft (e.g., fuel pumps, engines, or avionics), the LDND ensures that tasks are not generalized but applied correctly to each serial-numbered part.
Challenges and Interdependencies
Changing a part number installed can affect status regarding service bulletin or AD applicability – one high level part such as an engine can contain multiple sub components such as sensors or pumps.
Reconfigurations or line maintenance can see existing parts location moved and while not replaced the location has altered
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