15 / 20

A helicopter descends from 3500 ft to 1500 ft with an average TAS of 160 kt and a headwind component of 15 kt. If the descend flight-path gradient is 5%, calculate the required time and rate of descent.

  • A

    2 minutes and 46 seconds; 725 fpm

  • B

    2 minutes 46 seconds; 800 ft/min

  • C

    3 minutes 30 seconds; 725 ft/min

  • D

    3 minutes 30 seconds; 800 ft/min

Rate of descent (ROD) is a vertical speed and represents the rate of decrease of the vertical height per unit of time, usually expressed in feet per minute (fpm).

Descend flight-path gradient is defined as the ratio of the loss of altitude to horizontal distance expressed as a percentage.

1. The helicopter descends from 3500 ft to 1500 ft, thus the Height difference is: 3500 ft - 1500 ft = 2000 ft.

2. The helicopter descends with a headwind component of 15 kt, thus its Groundspeed will be: 160 kt - 15 kt = 145 kt.

3. The Rate of Descend in feet per minute is: ROD = G/S (kt) x Gradient of Descend (%) = 145 kt x 5% = 725 fpm.

4. Thus, the flight time during the descent is: Height difference / Rate of Descend = 2000 ft / 725 fpm = 2.76 min or 2 minutes and 46 seconds.

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.

  • Greece
    2
Keyboard Shortcut Use Keyboard Shortcuts