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Given:

ILS GP angle: 3.5 deg
GS: 150 kt

What is the approximate rate of descent?

  • A

    900 ft/min

  • B

    700 ft/min

  • C

    800 ft/min

  • D

    1000 ft/min

Convert speed from kts/ hr to feet per minute
1 kt = 6080 feet
Speed per minute = 150 x 6080 / 60 = 15200 ft / min

Rule 1:60
Descent rate = 15200 x 3.5 / 60 = 886 ft / min

Tan 3.5˚ = Descent rate per minute / ground speed per minute
Descent rate per minute = Tan 3.5˚ x ground speed per minute
Descent rate per minute = 0.0611 x 15200 = 929 ft / min

Closest answer: 900 ft / min

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