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# NAV 16

Version 1. - May 2006

2000

5

1

# A

= 2000 divided by 5 multiplied by 1 = 400 feet (in one minute) ie 400 ft/min

To calculate rate of descent using distance left to fly and wind speed, more steps are required. You still need to end up with an answer in feet per minute, and to find this you need to know how many feet you need to descend in how many minutes.

Question: You are flying at 3,200ft AMSL, and you want to land at a point 2 miles ahead where the ground level is 200ft AMSL. What rate of descent will be required to achieve this if the wind speed is 12 knots?

Step 1: How many feet? You must descend from 3,200AMSL to 200AMSL. The distance to descend is therefore 3,200 minus 200 = 3,000 feet.

Step 2: How many minutes? You are travelling at 12 knots (12 miles in one hour), and you can travel 2 miles. Set up the square to calculate the time.

(miles)

(minutes)

12

60

# A

= 2 divided by 12 multiplied by 60 = 10 minutes

Step 3: Set up the square again to calculate the descent rate required to drop 3000 feet in 10 minutes. (You may not need the square for this one.)

(feet)

(minutes)

3000

10

# A

= 3000 divided by 10 multiplied by 1 = 300 feet (per minute).

## © Australian Ballooning Federation Inc

ABF Pilot Training Manual Part 8

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