Development of Aircraft Maintenance Program (AMP)

Introduction

The Airworthiness of an aircraft is maintained by the Operator by developing their own Approved Aircraft Maintenance Program (AMP). The AMP is developed by the CAMO Engineering department of an operator and is considered to be the primary reference for airworthiness management. The AMP has to be available for every aircraft the operator owns and it needs to be consulted with regards to every maintenance action to be performed.

The AMP includes the scheduled tasks, interval requirements for derivative or newly type -certificated (TC) aircraft and powerplants, and certification maintenance requirements.

When a new aircraft is designed and developed, the Aviation Authority such as FAA, Manufacturer and various participants from the industry form group known as Maintenance Steering Group (MSG). This group conducts several meetings in order to determine the scope and frequency of aircraft maintenance tasks and inspections to be performed. The information collected during the MSG meetings is provided to another group known as Maintenance Review Board (MRB) group. Then, the MRB will issue their final recommendations to the manufacturer on how an aircraft should be maintained using the Maintenance Review Board Report (MRBR). The manufacturer then publishes this information in Maintenance Planning Documents (MPD) to be provided to the customer. For small and private aircraft owners the AMP is developed using the published manufacturer documents. However, for commercial operators the MRB and MPD recommendations will be used to develop the Aircraft Maintenance Program (AMP), this document is then approved by the subsequent local aviation authority.

Why is the AMP Developed?

The Aircraft Maintenance Program is an essential document to be developed by the subsequent operator in order to keep the aircraft in airworthy condition throughout its life span. The AMP has to be developed as the MPD is a generic document issued by the aircraft manufacturer and applies to several aircraft in the worldwide fleet. The MPD also doesn’t comprise the local authority requirements. Moreover, the MPD man-hours mentioned don’t consider the following key points:

1.????Non-routine work such as repair, troubleshooting, shop overhaul.

2.????Preparatory work such as aircraft cleaning, positioning work stands, connecting ground power carts.

4.????One-time actions, e.g. degreasing, stripping, painting.

5.????Embodiment of modifications, cabin (galley, lavatory, furnishings) refurbishment.

6.????Non-productive time, e.g. shift change, set-up of tools, waiting for sealant or paint drying.

7.????Planning and establishment of procedures. ?

Hence, the AMP is developed by the Engineering department of the Operator according to its resources such as manpower, tools, equipment, capabilities, etc. in order to keep the aircraft in airworthy condition.

What does an Approved Maintenance Program comprise of?

The AMP is the primary source of reference for aircraft maintenance scheduling, planning and all maintenance tasks needed to ensure the aircraft is in airworthy condition, hence below contents are present in the AMP:

1.????Distribution list (to all concerned persons).

2.????Summary of changes.

3.????Abbreviations.

4.????Airworthiness limitation.

5.????Aircraft and APU utilization ratio - flight hour to flight cycle ratio and flight hour per year -which the AMP developed depending on it ().

6.????All applicable modifications.

7.????A list (in the form of a long table) of all maintenance tasks which need to be performed on an aircraft from time to time. And repairs need periodic inspection.In other words, based on the AMP an airworthiness engineer knows exactly what tasks need to be performed after an aircraft reaches a certain point in life, be it calculated based on calendar age, flight hours of flight cycles. How to group the maintenance tasks? - I will make a complete article about this important topic -

8.????Airworthiness Directives ADs status.

9.????Service Bulletin SBs status.

10.?Reliability Control Board RCB recommendations.

11.?Certification Maintenance Requirements (CMR).

12.?System Equipment Maintenance Requirements (SEMR).

13.?ETOPS Configuration, Maintenance and Procedures (CMP).

14.?Fuel Airworthiness Limitations.

15.?Maintenance escalations rules.

16.?Life Limited Parts /Time Change Items.

17.?Local authority maintenance requirements for airworthiness.

18.?Structure program.

19.?Corrosion Prevention program.

20.?Engine Monitoring program.

21.?Sampling program.

22.?Aircraft Utilization Limitation / Limit Of Validity (LOV)

23.?Cat II/Cat III landing capabilities, Reduced Vertical Separation Minima (RVSM) capabilities and Extended Twin Engine Operations (ETOPS / EDTO) are inherent functions of the basic design standard of the aircraft. Scheduled tasks necessary for these operations have been considered in the development of the AMP. Operators should comply with National Requirements as applicable.

Key Reference Documents Needed to Develop AMP

The following documents are used to develop the Approved Maintenance Program:

1.????Maintenance Planning Document (MPD)

2.????Aircraft AD Status – The approved AMP must include all the applicable tasks which have to be performed on the aircraft. This includes all the applicable and repeat inspections required by the AD’s.

3.????Aircraft modification status – There are few tasks for which the applicability depends on the aircraft modification status. The mod status is needed as some tasks may depend on the “pre-mod” and “post-mod” status.

4.????Aircraft SB Status – All the Service bulletin approved by the operator must be included in the AMP.

5.????Local Authority Requirements

6.????Recommendations based on the operators Reliability Program – The technical author can shorten interval for some maintenance tasks based on the recommendations of the reliability reports. The local aviation authority must be convinced prior to amending the AMP.

How does the AMP change with time?

The Approved maintenance program keeps changing during the entire life span of the aircraft. The AMP has to be changed at least twice a year and the review and implication of relevant changes is performed by the NAA. So why does the AMP change so frequently?

Remember, the AMP is developed using several reference documents. Well, they also keep changing frequently, hence the AMP has to be amended appropriately. The several reasons as to why the AMP changes is mentioned below:

1.????The source documents (MPD) being revised on frequent basis forces the operator to revise the AMP frequently.

2.????The aircraft has been modified and new airworthiness directives, service bulletins have been issued on it. Hence, the AMP has to be amended accordingly.

3.????The operator’s reliability program continues to work and brings in new reliability data. This data should be regularly analyzed and proper conclusions should be drawn with respect to aircraft maintenance and airworthiness. This is why there is a requirement to analyze the effectiveness of an AMP at least twice a year.

The CAMO director and personnel must be convinced that the AMP indeed “foresees” aircraft damage and provides appropriate maintenance tasks at appropriate intervals, and have to regularly revise/amend / re issue.

Types of Maintenance Task Intervals:

1.????Daily Checks – This check comprises of oil level check. The oil level on the aircraft engine has to be checked between 15 to 30 minutes after engine shutdown to obtain precise reading.

2.????48 Hour Checks – This check is to be performed every 48 hours depending on the airline operation specifications. This check includes more detailed tasks compared to the daily check. Tasks include checking the condition on tires, GVI of key airframe zones such as fuselage, wings etc. Replenishment of engine oil, hydraulics, APU etc.

3.????Hourly limit tasks – These tasks are determined during the MSG analysis. This approach is used for aircraft flight controls, engines, systems, etc.

4.????Operating cycle limit tasks – Other aircraft systems are maintained using scheduled operating cycles they have endured. Some components such as Landing gear have maintenance tasks defined with cycle intervals. Moreover, other components such as engine (LP, HP impeller, blades), airframe structures that are subject to cyclic stresses have cycle-influenced tasks.