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AA.I.D.K8FAA-S-ACS-11A · Nov 2023Knowledge

Best range and best endurance.

ACS element text (the applicant demonstrates understanding of)

Best range and best endurance.

Bottom line

Range is about flying distance, while endurance is about flying time. Maximum range is obtained at maximum lift/drag ratio (L/DMAX), which occurs at a particular AOA for a given aircraft configuration. Maximum endurance is obtained at the point of minimum power required, since this requires the lowest fuel flow for steady, level flight.

Key numbers

Key numbers for Best range and best endurance.
NumberWhat it means
99 percent of absolute maximum specific rangeLRC range
1 percent of range traded for 3 to 5 percent higher cruise speedLRC trade

FAA references

  1. PHAK ch. 11 (p. 11-9) — FAA-H-8083-25C (2023)
  2. PHAK ch. 11 (p. 11-10) — FAA-H-8083-25C (2023)
  3. RMH ch. 3 (p. 3-4) — FAA-H-8083-2A
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