Time/Speed/Distance.


Ok let’s take a look on some easy techniques for simplifying problems with multiple equations involved such as in the time, speed, and distance problem.
First remember that there will be only four variables in the formula, and the interviewer will need to give you three of them.
The four variables are wind, distance, time, and true airspeed.
The basic time-speed-distance formula is this.
(GS) X (Time) = (Distance)
Remember every 30 knots equals 5 miles/minute or 60 knots equals 1mile/minute.
So if you have a speed of 480 knots, you travel 8 miles/minute.
Ground Speed Knots
Miles per minute
60
1
90
1.5
120
2
150
2.5
180
3
210
3.5
240
4
270
4.5
300
5
330
5.5
360
6
390
6.5
420
7
450
7.5
480
8
510
8.5
540
9


No wind factor involved, if it’s not given to you, you can assume it to be zero.
If you are given TAS, and want to find the Ground speed, you use this formula.
TAS plus/minus Wind = GS

Ok let’s practice this with some examples.
KTAS
WIND
TIME
DISTANCE
240
60 TW
?
200 NM
280
70 HW
10 MIN
?
150
0
?
5 NM
?
0
4 MIN
20 NM
420
60 TW
?
400 NM
?
0
2 MIN
14 NM
?
0
1.5 hr
600 NM
500
0
45 MIN
?
?
0
40 MIN
340 NM

Calculate the examples and fill in the blanks.
Here it is good to use the technique of converting the ground speed to miles per minute to make the problem solving easier during the interview.
It is important to keep it as simple as possible since you probably not are allowed to use calculator or, pen and paper.
When you are given the ground speed or can figure it out from the true airspeeds and winds, convert it to nautical miles per minute.
Example 350 knots GS= 360 divided by 60 = 6 miles per minute
You can then more easily multiply these nautical miles per minute by the number of minutes to get the distance traveled.  10 @ 6 nmpm = 60 miles
Or you can divide the distance by the nautical miles per minute to figure the number of minutes
90 miles @ 6nmpm = 15 minutes


Here are the answers from the previous task.
KTAS
WIND
TIME
DISTANCE
240
60 TW
40 MIN
200 NM
280
70 HW
10 MIN
35 NM
150
0
2 MIN
5 NM
300
0
4 MIN
20 NM
420
60 TW
50 MIN
400 NM
420
0
2 MIN
14 NM
400
0
1.5 HR
600 NM
500
0
45 MIN
375 NM
510
0
40 MIN
340 NM

Notice that the last three problems are easier to solve using an approach of proportions.
1,5 hour is three segments of 0,5 hour, and that 600 NM is three segments of 200 NM, then you realize that you travel 200 NM per half hour or 400 NM per hour = 400 knots ground speed.