PURPOSE.

a. This Advisory Circular (AC) publishes needed changes to the existing AC material. Additionally, there is incorporation of previously approved AC material and non-technical editorial changes to various sections.

b. The change number and the date of the changed material are shown at the top of each page. The vertical lines in the outside margin indicate the beginning and end of each change. Pages that have different page numbers, but no text changes, will retain the previous heading information.

c. This AC does not change regulatory requirements and does not authorize changes in, or deviations from, regulatory requirements. This AC establishes an acceptable means, but not the only means, of compliance. Since the guidance material presented in this AC is not regulatory, terms having a mandatory definition, such as "shall" and "must," etc., as used in this AC, apply either to the reiteration of a regulation itself, or to an applicant who chooses to follow a prescribed method of compliance without deviation.