How world distances change
If you are in the SuperFunGuy's Quizzes loop, you will probably have seen a couple of questions regarding distances across the world, but are you aware that the distances can change?
When I first joined British Airways, the distance from Heathrow to JFK New York was 3,456 miles a really simple number to remember, even for me.
At that time the runway numbers were designated as 10 and 28. Meaning that Heading east you would take off on a runway heading of 100 degrees (10).
Taking off to the west you would be heading at 280 degrees(28).
Then, one day, the runways were re-designated to 09 and 27. Nobody had dug them up and re-laid them, it was a purely natural phenomena.
Thousands of feet below the earth's crust is a a mass of molten iron sloshing around.
Compasses point to magnetic north to be able to work. They detect where the greatest mass of iron is and point there. Of course molten iron is mobile, which also means magnetic north is not stationary.
This phenomena has various names, magnetic drift, polar drift, polar wandering are a few, but they and others, all mean the same thing.
Aeroplanes have to rely on compasses to be able arrive at the correct spot on the globe, therefore, they have to be calibrated regularly.
~ Importance of Aircraft Compass Calibration
Calibration of an aircraft compass is crucial for accurate navigation. It ensures that the compass aligns with true magnetic north, eliminating errors caused by magnetic interference from onboard systems. Regular calibration is essential for compliance with aviation standards and safe flight operations.
~ Compass Calibration Process
Steps for Calibration
• Preparation: Ensure the aircraft is in an open area away from metallic objects that could interfere with the compass.
• Compass Swing:
• Align the aircraft to known headings: North, South, East, and West.
• Record the indicated heading and note any deviation errors.
• Use the following formulas to calculate corrections:
• North/South Correction = ½ [N error - S error]
• East/West Correction = ½ [W error - E error]
• Adjustment: Make necessary adjustments using deviation cards or adjustment screws based on the recorded errors.
~ Tools and Equipment
• Calibration Devices: Use specialized compass calibration equipment for precise adjustments.
• Reference Compass: A sight compass can be used to compare readings during the calibration process.
~ Frequency of Calibration
Calibration should be performed:
• After any maintenance affecting the compass system.
• When operating in a new geographic area that may impact magnetic alignment.
• At intervals recommended by the aircraft manufacturer.
Regular calibration helps maintain the accuracy and reliability of the aircraft's navigation systems, ensuring safe and efficient flight operations.
Getting back to the Heathrow to JFK journey mentioned above, with the new runway designations came a new calculated distance of 3,451 miles. Overnight it became a shorter journey, however, there was no reduction in ticket price!
When I first joined British Airways, the distance from Heathrow to JFK New York was 3,456 miles a really simple number to remember, even for me.
At that time the runway numbers were designated as 10 and 28. Meaning that Heading east you would take off on a runway heading of 100 degrees (10).
Taking off to the west you would be heading at 280 degrees(28).
Then, one day, the runways were re-designated to 09 and 27. Nobody had dug them up and re-laid them, it was a purely natural phenomena.
Thousands of feet below the earth's crust is a a mass of molten iron sloshing around.
Compasses point to magnetic north to be able to work. They detect where the greatest mass of iron is and point there. Of course molten iron is mobile, which also means magnetic north is not stationary.
This phenomena has various names, magnetic drift, polar drift, polar wandering are a few, but they and others, all mean the same thing.
Aeroplanes have to rely on compasses to be able arrive at the correct spot on the globe, therefore, they have to be calibrated regularly.
~ Importance of Aircraft Compass Calibration
Calibration of an aircraft compass is crucial for accurate navigation. It ensures that the compass aligns with true magnetic north, eliminating errors caused by magnetic interference from onboard systems. Regular calibration is essential for compliance with aviation standards and safe flight operations.
~ Compass Calibration Process
Steps for Calibration
• Preparation: Ensure the aircraft is in an open area away from metallic objects that could interfere with the compass.
• Compass Swing:
• Align the aircraft to known headings: North, South, East, and West.
• Record the indicated heading and note any deviation errors.
• Use the following formulas to calculate corrections:
• North/South Correction = ½ [N error - S error]
• East/West Correction = ½ [W error - E error]
• Adjustment: Make necessary adjustments using deviation cards or adjustment screws based on the recorded errors.
~ Tools and Equipment
• Calibration Devices: Use specialized compass calibration equipment for precise adjustments.
• Reference Compass: A sight compass can be used to compare readings during the calibration process.
~ Frequency of Calibration
Calibration should be performed:
• After any maintenance affecting the compass system.
• When operating in a new geographic area that may impact magnetic alignment.
• At intervals recommended by the aircraft manufacturer.
Regular calibration helps maintain the accuracy and reliability of the aircraft's navigation systems, ensuring safe and efficient flight operations.
Getting back to the Heathrow to JFK journey mentioned above, with the new runway designations came a new calculated distance of 3,451 miles. Overnight it became a shorter journey, however, there was no reduction in ticket price!
