Major Type Design Changes

FAR 21.97 — Major Type Design Changes

FAR 21.97 explains what an applicant must submit and show to gain FAA approval for a major change to an aircraft's type design, including engine configurations.

In Plain English

FAR 21.97 sets the requirements an applicant must meet when seeking FAA approval of a major change in type design. A type design defines the certificated configuration of an aircraft, engine, or propeller, so any major change to it must be formally approved before the product can be produced or operated under that certificate.

To get approval, the applicant must:

Provide substantiating data and the descriptive data needed to incorporate the change into the type design.
Show that the change and any affected areas comply with the applicable airworthiness requirements of this subchapter, and give the FAA the means used to demonstrate that compliance.
Submit a statement certifying compliance with the applicable requirements.

For aircraft engines, the approval applies only to the specific engine configuration that was changed — unless the applicant identifies other configurations of the same engine type in the descriptive data and shows the change is compatible with those configurations. This matters operationally because it ensures modifications don't compromise certificated safety standards across an engine family.

Regulation Text

14 CFR § 21.97

§ 21.97 Approval of major changes in type design. (a) An applicant for approval of a major change in type design must— (1) Provide substantiating data and necessary descriptive data for inclusion in the type design; (2) Show that the change and areas affected by the change comply with the applicable requirements of this subchapter, and provide the FAA the means by which such compliance has been shown; and (3) Provide a statement certifying that the applicant has complied with the applicable requirements. (b) Approval of a major change in the type design of an aircraft engine is limited to the specific engine configuration upon which the change is made unless the applicant identifies in the necessary descriptive data for inclusion in the type design the other configurations of the same engine type for which approval is requested and shows that the change is compatible with the other configurations. [Amdt. 21-40, 39 FR 35459, Oct. 1, 1974, as amended by Amdt. 21-92, 74 FR 53387, Oct. 16, 2009; Amdt. 21-96, 77 FR 71695, Dec. 4, 2012]

Oral Exam Questions a DPE Might Ask

Q1What must an applicant provide to obtain FAA approval of a major change in type design?

Per FAR 21.97, the applicant must provide substantiating and descriptive data for inclusion in the type design, show that the change and affected areas comply with applicable requirements (and how compliance was shown), and provide a statement certifying compliance.

Q2If a major change is made to an aircraft engine, does the approval automatically apply to other configurations of that engine type?

No. Under FAR 21.97(b), approval is limited to the specific engine configuration changed, unless the applicant identifies the other configurations in the descriptive data and shows the change is compatible with them.

Q3What is the purpose of the certifying statement required under FAR 21.97?

FAR 21.97(a)(3) requires the applicant to certify that they have complied with the applicable requirements, giving the FAA a formal declaration of compliance to support approval of the major design change.

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Related Sections in Part 21

§ 21.1

Certification Procedures

§ 21.101

Type Certificate Changes