# SPEED, DISTANCE, AND TIME COMPUTATIONS

SPEED, DISTANCE, AND TIME COMPUTATIONS

• Speed, distance, and time are three interrelated elements. With any two of these elements, you can compute the third (missing) element.
1. The computations are
1. Speed = Distance / Time
2. Distance = Speed X Time
3. Time = Distance / Speed
1. You can use your flight computer to make the above computations.
1. Note that in any problem both the speed and distance must be in either SM or NM.
2. You can convert SM to NM or vice versa easily as explained in the preceding module.
• Determining Time Required
1. If you know the groundspeed and the distance, you can calculate the time. Time equals distance divided by groundspeed.
2. EXAMPLE: How much time will it take to fly 120 NM at a groundspeed of 100 kt.?
1. Rotate the inner scale so the Index is opposite 100 kt., or “10,” on the outer scale, as shown in the figure.
2. Locate 120 NM, or “12,” on the outer scale.
3. Under 120 on the outer scale read 72 min. on the inner scale or 1:12 on the hour scale.
3. Use your flight computer to solve these practice problems (answers are located below).
 Groundspeed Distance Time a. 80 kt. 300 NM _____ b. 95 kt. 19 NM _____ c. 105 kt. 62 NM _____ d. 120 mph 142 SM _____
1. Answers to practice problems
1. 225 min. or 3 hr. 45 min.
2. 12 min.
3. 35.5 min.
4. 71 min. or 1 hr. 11 min.
• Determining Distance
1. If you know groundspeed and time, you can determine the distance. Distance equals groundspeed multiplied by time.
2. EXAMPLE: How far will the airplane fly in 8 min. at a groundspeed of 90 kt.?
1. Rotate the inner scale so the Index is opposite 90, as shown in the figure.
2. Locate 8 on the inner scale.
3. Opposite 8 on the inner scale is 12 NM on the outer scale.
1. Use your flight computer to solve these practice problems (answers are located below).
 Groundspeed Time Distance a. 107 kt. 3 hr. 27 min. _____ b. 95 kt. 17 min. _____ c. 105 kt. 43 min. _____ d. 120 mph 1 hr. 24 min. _____
1. Answers to practice problems
1. 370 NM
2. 27 NM
3. 75 NM
4. 168 SM
• Determining Groundspeed
1. If you know the time and distance, you can determine the groundspeed. Groundspeed equals distance divided by time.
2. EXAMPLE: What is the groundspeed if the airplane takes 7 min. to go 10.5 NM?
1. Rotate the inner scale so that 10.5 on the outer scale is opposite 7 on the inner scale, as shown in the figure.
2. Locate the Index on the inner scale and read a groundspeed of 90 kt. on the outer scale.
3. Use your flight computer to solve these practice problems (answers are located below).
 Distance Time Groundspeed a. 5.5 NM 3 min. ________ b. 10 NM 6.5 min. ________ c. 15 NM 9 min. ________ d. 5 SM 4 min. ________
1. Answers to practice problems
1. 110 kt.
2. 92 kt.
3. 100 kt.
4. 75 mph