IATA Aircraft Lease Guidance

Guidance Material and Best Practices for Aircraft Leases
Annex VI: Modifications Guidelines
Aircraft Model :
All models
Applicability : EASA and FAA environment
1. Introduction
During the lifetime of an aircraft, various modifications are implemented with the intention to change or
upgrade specific functions or systems of the aircraft. During a transfer of aircraft the Lessor often requires a
consolidated file showing compliance with the applicable regulations and the lease agreement of all
modifications performed. However, this does exclude modifications performed at component level. This annex
provides guidelines for the airline on how to create a modification compliance file. The term modification file
is commonly used to describe two separate files:
●
●
The EOs and SBs file
STCs
2. Regulatory Basis
2.1 EASA Procedures
EASA regulations applicable to modifications can be found Part M (M.A 304, 305, 708, 710) and Part 21. In
addition, EASA has published GM and AMC, which provide additional insights into the regulatory
requirements of the modification process.
EASA distinguishes between major and minor for any changes made to the type design of the aircraft. The
determination for major or minor modifications needs to be performed by an organization holding the EASA
design organization approval (DOA), or directly by EASA.
There are different levels of EASA DOA authorizations. For example, a basic DOA allows the holder to classify
major or minor modification, and approve minor modifications only. A TC/STC holder with an EASA DOA can
approve both major and minor modifications.
The process to determine if a change is major or minor is illustrated in Figure 10. The first criteria for the
selection of a major or minor modification is the appreciable effect on weight, balance, structural strength,
reliability, and operational characteristics of the aircraft. If the proposed modification has an impact on one of
these factors, the modification should be classified as major. If this is not the case a second step of
considerations needs to be taken in order to determine the classification of the modification. During this step,
the impact of the modification on the certification basis, Type Certificate, previous performed compliance
demonstration, and the need for reassessment of this compliance data is reviewed. Also, if the modification is
part of an AD, or introduces or affects a function where failure is catastrophic or hazardous, it will be
classified as major. The major classification for modifications linked to an AD may be re-classified as minor
96 4 th Edition 2017