What does 'acclimatized' mean, and why does it change my maximum FDP?

Acclimatized is defined in CARs 700.01 as describing a flight crew member “whose biorhythm is aligned with local time.” In practical terms, your body clock is aligned with the local day and night where you’re acclimatized.

Why it matters

The 700.28 maximum-FDP tables use the start time of your flight duty period at the location where you’re acclimatized. That may not be the same as the local time where your FDP actually begins (AC 700-047 § 4.19(5)).

• Acclimatized to where the FDP begins → use the local start time.
• Not acclimatized → convert the start time to the local time at the location where you’re acclimatized, and use that time in the FDP table.

That conversion can move your start time into a different row of the FDP table and therefore change your maximum FDP. For example, a 07:00 report in Toronto while still acclimatized to Calgary is treated as a 05:00 start for the purposes of the table.

When you count as acclimatized

An air operator may assume you’re acclimatized to your home-base time zone unless previous duty has acclimatized you to a different time zone. Only duty can acclimatize you to another time zone — for example, operating or positioning to a new time zone and remaining there long enough to become acclimatized. A trip to another time zone followed by a return to your starting location the next day does not normally change where you’re acclimatized (AC 700-047 § 4.23).

CARs 700.28(5) provides three ways to determine acclimatization:

• Less than 4 hours’ difference: you’re considered acclimatized after the required rest periods have been provided and you’ve spent 72 hours in the same time zone.
• 4 hours’ difference or more: you’re considered acclimatized after the required rest periods have been provided and you’ve spent 96 hours in the same time zone.
• Daily adjustment: you may adjust your acclimatized time by 1 hour toward the new time zone for every 24 hours spent there.

That last method means your acclimatized time can progressively move toward the new time zone rather than remaining fixed at your original time zone until the 72- or 96-hour threshold is reached (CARs 700.28(5); AC 700-047 §§ 4.23–4.26).

For the purposes of these rules, CARs 700.28(7) treats the Canadian time zones as Pacific, Mountain, Central, Eastern and Atlantic, with the Atlantic time zone including Newfoundland and Labrador.

A note on other operations

The medical evacuation flight rules in the CARs 700.100 series use their own flight-time, FDP and rest provisions. Operations under Subpart 702 (Aerial Work) are also subject to different requirements. If either applies to your operation, check the applicable provisions directly rather than assuming the 700.28 acclimatization rules apply.

See also: Maximum Flight Duty Period (700.28) · FDP calculator