日本の航空法で定める区分は2種類。
| 設計の変更の区分 | 設計の変更の内容 |
| 小変更 | 重量、強度、動力装置の機能、飛行性その他航空機の耐空性に重大な影響を及ぼさない変更 |
| 大変更 | 小変更以外の変更 |
EASAのType Design Changeの区分も同様に以下の通り。
| minor change | 質量、バランス、構造強度、信頼性、動作特性、騒音、燃料排気、排気ガス、または製品の耐空性に影響を与えるその他の特性に相当な影響を与えない変更。 |
| major change | minor change以外の変更 |
21.A.91 Classification of changes in type design
Changes in type design are classified as minor and major. A ‘minor change’ is one that has no appreciable effect on the mass, balance, structural strength, reliability, operational characteristics, noise, fuel venting, exhaust emission, or other characteristics affecting the airworthiness of the product.
Without prejudice to point 21.A.19, all other changes are ‘major changes’ under this Subpart. Major and minor changes shall be approved in accordance with points 21.A.95 or 21.A.97 as appropriate, and shall be adequately identified.
classifications to the level of design change – substantial, signifi cant, and not significant.
GM 21.A.101
Significant change
– A change to the type-certificate significant to the extent that it changes at the product level one or more of the following: general configuration, principles of construction, or the assumptions used for certification,but not to the extent to be considered a substantial change. The significance of the change must be considered in the context of all previous relevant design changes and all related revisions to the certification specifications of the applicable airworthiness code. Not all product level changes are significant.
Substantial change
– A change which is so extensive that a substantially complete investigation of compliance with the applicable type-certification basis is required, and consequently a new type certificate, in accordance with 21.A.19.
輸入航空機については、さらに以下の分類となる。設計国の当局が当該設計変更について承認を行っていることが前提。
| a. 航空局の承認が必要な設計変更 | (1) 主要な大変更 | 飛行規程の限界事項の変更に係るもの |
| ICAのALSの変更に係るもの | ||
| TCDSの変更に係るもの | ||
| MMEL&CDLの変更に係るもの | ||
| CBの変更に係るもの | ||
| MoCの変更に係るもの | ||
| Significant Changeに該当するもの | ||
| (2) 航空局指定項目 | TC取得時のJCAB認証項目に影響のある設計の変更 | |
| 騒音及び排出物の基準に該当する設計変更 | ||
| 客室仕様の重大な変更 | ||
| b. 航空局への通知が必要な設計変更 | a.又はc.のいずれにも該当しない設計変更。 | |
| c. 航空局への通知が不要な設計変更 | 小変更に相当するもの | |
サーキュラー No.1-001 (96, 113), No.7-001 (191)