14 CFR §23.2105

1. (a)Unless otherwise prescribed, an airplane must meet the performance requirements of this subpart in—
   1. (1)Still air and standard atmospheric conditions at sea level for all airplanes; and
   2. (2)Ambient atmospheric conditions within the operating envelope for levels 1 and 2 high-speed and levels 3 and 4 airplanes.
2. (b)Unless otherwise prescribed, the applicant must develop the performance data required by this subpart for the following conditions:
   1. (1)Airport altitudes from sea level to 10,000 feet (3,048 meters); and
   2. (2)Temperatures above and below standard day temperature that are within the range of operating limitations, if those temperatures could have a negative effect on performance.
3. (c)The procedures used for determining takeoff and landing distances must be executable consistently by pilots of average skill in atmospheric conditions expected to be encountered in service.
4. (d)Performance data determined in accordance with paragraph (b) of this section must account for losses due to atmospheric conditions, cooling needs, and other demands on power sources.