Sean Conlin Legal Interpretation 2000

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US. Department

of lranspo'tation Federal Aviation Administration FEB2 2.000 Mr. Sean Conlin Quality Assurance Pan American Airways Corp.

14 Aviation Avenue

Portsmouth, NH 03801

Dear Mr. Conlin:

preceding 24 calendar months."

800 Independence Ave., SW.

Washington. DC. 20591

I am responding to your letter dated September 15, 1999, to the Office of the Chief Counsel, Federal Aviation Administration (FAA), regarding the meaning of "within the You state in your letter that two interpretations exist within the industry regarding the meaning of "24 calendar months." One interpretation is that it means two years, e.g. January 15, 1997, to January 15, 1999. The second interpretation is that it means "24 unit months," e.g. regardless of the day in January 1997, to January 31, 1999. You state that your local Flight Standards District Office (FSDO) believes the second interpretation, 24 unit months, to be correct. You ask this office to confirm this before you change your policy.

The term "24 calendar months" as used throughout the Federal Aviation Regulations (14 CFR) means "24 unit months" if you define "unit months" as beginning on the first of the month and ending on the last day of the month. The term "24 months" means two years, from date to date. These terms are further discussed below. If you are required to comply with a regulation under 14 CFR "within the preceding 24 calendar months," you have from the beginning of the 24th calendar month before the month in which you are required to comply. For example, section 91.411 (14 CFR section 91.411) requires certain altimeter system and altitude reporting equipment tests and inspections to have been accomplished "within the preceding

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24 months" before a person may operate an airplane or helicopter in controlled airspace under IFR. Therefore, if you want to operate an airplane in controlled airspace under IFR on January 15, 2000, you must have, since January 1, 1998, met the requirements of section 91.411(a). If you are required to comply with a regulation under 14 CFR "24 calendar months after or from," you have until the end of the 24th month after the month in which the time began to run. For example, section 61.19 (14 CFR section 61.19) provides an expiration date for a student pilot certificate of 24 calendar months from the month in which the student pilot certificate is issued. Therefore, if you obtain a student pilot certificate on January 2, 2000, it expires on January 31, 2002.

Please note that an additional "grace calendar month" may be provided to a person for purposes of complying with a particular section under 14 CFR (e.g. 14 CFR section 61.58(g)).

If you are required to comply with a regulation under 14 CFR "within the preceding 24 months" or "24 months after or from," you have from two years before the date you are required to comply or two years after the date the time began to run, respectively. For example, if a regulation under 14 CFR requires you to meet certain requirements "within the preceding 24 months" before you can operate an aircraft, then you must have accomplished the requirements with the two years before the date you want to operate the aircraft. Therefore, if you want to operate an aircraft on January 19, 2000, you would have to have met the requirements within the period of time starting on January 19, 1998.

I hope this satisfactorily answers your question.

Sincerely,

M. ro)(

*onald P. Byrne Assistant Chief Counsel Regulation Division