121.179—Airplanes: Reciprocating engine-powered: En route limitations: All engines operating.
(a)
No person operating a reciprocating engine powered airplane may take off that airplane at a weight, allowing for normal consumption of fuel and oil, that does not allow a rate of climb (in feet per minute), with all engines operating, of at least 6.90 V
So (that is, the number of feet per minute is obtained by multiplying the number of knots by 6.90) at an altitude of at least 1,000 feet above the highest ground or obstruction within ten miles of each side of the intended track.
(b)
This section does not apply to airplanes certificated under part 4a of the Civil Air Regulations.
(c)
This section does not apply to large nontransport category airplanes operated under § 121.173(c).