heading and it needs to fly new heading 360. The turn will be 60 degrees. Since the standard rate turn is 360 degrees in 120 seconds, the plane will need 20-second standard rate turn to the left. In case of electrical instrument failure, which include turn coordinator or turn-slip indicator, the following formula will help to determine turn bank at which the turn will be made at standard rate: In order to calculate bank angle for a standard rate turn knowledge of airspeed must be known. The rule of thumb using airspeed requires that the last digit of the airspeed be dropped then add five. For example, if the airspeed is 90 knots, the bank angle would be (9+5=) 14 degrees. For 122 knots, it would be (12+5=) 17 degrees. The line of latitude is the maximum lead or lag a compass will have. The following explanations are for the northern hemisphere. For example, an aircraft flying at 45°N latitude making a turn to north from east or west maintaining a standard rate turn a pilot would need to roll out of the turn when the compass was 45 degrees plus one half of the bank angle before north. (From east to north at 90 knots 0+45+7=52) A pilot would begin to roll out to straight flight and on a heading of north when 52 degrees was read from the compass. (From west to north at 90 knots (360-45-7=308). A pilot would begin to roll the aircraft out of the bank at 308 degrees read from the compass to fly on a north heading. Making a turn towards south from west the pilot would have to roll the aircraft out of the turn when the compass was 45 degrees minus half the bank angle (from west to south at 90 knots 180-45+7=142, from east to south 180+45-7=218). From the examples we see that when turning to north from east or west the bank angle used to calculate the time to roll the plane out of the turn must begin at the greatest number of degrees or further away from north. Conversely for turns to south from east or west the bank angle is calculated to decrease the number of degrees to lead the roll out or closer to south. Generally pilots will practice making these turns using half standard rate turns. This will decrease the bank angle so that it