14 CFR 65.75: Knowledge requirements.

(a) Except as specified in paragraph (c) of this section, each applicant for a mechanic certificate or rating must, after meeting the applicable experience requirements of § 65.77, pass a written test, appropriate to the rating sought, which includes the aeronautical knowledge subject areas contained in the Aviation Mechanic General, Airframe, and Powerplant Airman Certification Standards (incorporated by reference, see § 65.23), as appropriate to the rating sought.

(b) The applicant must pass each section of the test before applying for the oral and practical tests prescribed by § 65.79. A report of the written test is sent to the applicant.

(c) An applicant for a mechanic certificate or rating may take the mechanic general written test prior to meeting the applicable experience requirements of § 65.77, provided the applicant presents an authenticated document from a certificated aviation maintenance technician school that demonstrates satisfactory completion of the general portion of the school's curriculum and specifies the completion date.

(d) An applicant is eligible to take a practical test for a mechanic certificate or rating under this part with an expired written test report in accordance with § 61.40 of this chapter.