Download the PDF consolidation of Part 21 [PDF 439 KB]
This Subpart prescribes rules governing the approval of a design change.
(a) A design change may be approved by—
(1) including it in an Airworthiness Directive; or
(2) the approval of a modification; or
(3) the approval of a change to the type certificate or type acceptance certificate under Subpart D; or
(4) the issue of a supplemental type certificate under Subpart E.
(b) Design changes are acceptable to the Director if they are—
(1) described by technical data listed in Appendix D; or
(2) accepted by the issue of an airworthiness certificate.
(c) A person who is not the type certificate holder for a product and who intends to make a major modification to that product may apply to the Director for approval of the design change by the issue of a supplemental type certificate under Subpart E.
Each design change that has been approved by the Director at the time this Part comes into force is deemed to have been approved under this Part.
The organisation under which the statement of compliance for a design change was issued must undertake the continued airworthiness responsibilities required by 146.61 in respect of the change.
(a) A design change embodied on an aircraft may be accepted by the issue of an airworthiness certificate for that aircraft if —
(1) the design change is recorded in the maintenance records for the aircraft at the time of issue of the airworthiness certificate; and
(2) there is sufficient evidence that the design change meets the applicable airworthiness requirements; and
(3) there is sufficient evidence that the design change meets the applicable aircraft noise and engine emission standards specified in Appendix C.
(b) A design change accepted under this rule may only be embodied on the individual aircraft for which the airworthiness certificate has been issued.
The Director approves a modification by approving the modification’s technical data under 21.505.
