Rule of three (aeronautics)
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In aviation, the rule of three or "3:1 rule of descent" is a rule of thumb that 3 nautical miles (5.6 km) of travel should be allowed for every 1,000 feet (300 m) of descent.[1][2] For example, a descent from flight level 350 would require approximately 35x3=105 nautical miles. This would have to be adjusted for headwind or tailwind,[1] and also to allow for deceleration time.
Alternatively, David P. Davies gives the rule as 300 feet of descent required for each nautical mile of distance.[3]: 176
Large aircraft approaching to land normally use a 3 degree approach path.[4] This is equivalent to 3.14 nautical miles per 1000 ft of descent. If exactly 3 nmi are allowed per 1000 ft of descent, the glide path will be 3.14 degrees.
See also
References
- ^ a b Instrument Procedures Handbook (IPH) AA-H-8083-16B. Federal Aviation Administration. 2017. pp. 3–6.
- ^ "Top 10 rules of thumb". Plane and Pilot Magazine. 2006-01-01. Retrieved 5 November 2012.
- ISBN 0903083019.
- ^ Dillman, Donald R. (February 1990). Swing Low Sweet Chariot. The MAC Flyer. p. 10. Retrieved 20 June 2022.