Picture yourself in the cockpit counting on your eyeballs to keep you clear of thunderstorms. Theres a buildup ahead and youve got to ask for a diversion. But how many degrees? You dont have a pretty cockpit display with the weather today, so youll be estimating.You can get a good estimate just using your binocular vision. Hold a raised finger at arms length and sight across that finger first with only one eye and then the other eye. Your finger displaces about 10 degrees. So if you put your raised finger between you and the storm with your right eye only and then look with only your left eye, the new position of your finger shows where a 10-degree turn to the right would take the airplane. In this way, you can measure 10-degree chucks of heading change against the view outside-and then confidently ask ATC for 30 right.
Pilots can estimate angular diversions, such as for thunderstorms, by using binocular vision with a raised finger or pencil as a visual marker.
The basic method involves observing the marker's displacement by alternately closing one eye, representing roughly a 10-degree change.
Accuracy can be significantly enhanced by calculating the precise distance to hold the marker, derived from one's interpupillary distance (PD) multiplied by 5.67.
Once this specific distance is learned, pilots can confidently measure and request precise heading changes from air traffic control without modern cockpit weather displays.
Picture yourself in the cockpit counting on your eyeballs to keep you clear of thunderstorms. There’s a buildup ahead and you’ve got to ask for a diversion. But how many degrees? You don’t have a pretty cockpit display with the weather today, so you’ll be estimating.
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