Leeway is the leeward motion of a vessel due to wind only. It may be expressed as distance, speed, or angular difference between course steered and course through the water. A northerly wind causes a 3° leeway. Leeway is an error that must be ADDED or SUBTRACTED depending on the kind of question you are asked.
LEEWAY
Here are two sample problems using leeway:
1. You desire to make good 152° T. The magnetic compass deviation is 4° E, the variation is 5° E, and the gyro error is 3° E. A southwesterly wind produces a 4° leeway. Which course would you steer (psc) and (pgc) to make good the true course?
A.137 psc B.141 psc C.143 psc D.147 psc
T 152
V 5E
M 147
D 4E
C 143 psc
CE 9E
T 152
GE 3E
PGC 149
ANSWER "D"
NOTE: When the question asked "what course to steer", then do whatever it takes to crab into the wind. The wind is hitting you on the starboard side so you would crab to the right to get into the wind. In this case the leeway is added on to your course to steer. If the wind was Northeasterly you would have subtracted it from our course to steer. Don't forget the rule ADD WESTERLY AND SUBTRACT EASTERLY. I also like to draw a picture so I can visualize the problem better.
2. Your vessel is steering 195° per standard magnetic compass. Variation for the area is 13° W, the deviation is 4° E, and the gyro error is 3 E. The wind is from the west-southwest, producing a 2° leeway. Which true coure are making good?
A.178T B.180T C.182T D.184T
T 186
V 13W
M 199
D 4E
C 195
CE 9W
T 186
GE 3E
PGC 183
ANSWER "D"
NOTE: When the question asked for "what course are you making good" then let the wind push you don't crab into the wind. The wind is hitting you on the starboard side, it would push you to the left, so the direction would get smaller, and you would subtract the leeway. If the wind was southeasterly, you would have to add the leeway.
