#aviation #classnotes

Understanding Time Zones

Private Pilot License (PPL) Notes

This section covers the fundamentals of time zones, their importance in aviation, and how to perform time conversions using Coordinated Universal Time (UTC).

Earth's Rotation and Time Calculation:

  1. The Earth rotates 360 degrees every 24 hours.
    1. This means it rotates at 15 degrees per hour.
  2. Longitude measurements start at the Prime Meridian in Greenwich, England.
    2. Greenwich is also the starting point for time calculations.

Time Zones:

  1. Time zones are established every 15 degrees of longitude.
    1. This results in a one-hour difference between each time zone.
  2. The contiguous United States spans from approximately 67 to 125 degrees longitude.
    2. This places the lower 48 states into four time zones:
    1. Eastern
    2. Central
    3. Mountain
    4. Pacific
  3. Example of time differences:
    1. When it's noon Central Standard Time (CST) at the 90th degree of longitude:
      1. It's 1 p.m. Eastern Standard Time (EST).
      2. It's 11 a.m. Mountain Standard Time (MST).
      3. It's 10 a.m. Pacific Standard Time (PST).

The 24-Hour Clock in Aviation:

  1. Aviation uses a 24-hour clock to avoid confusion between a.m. and p.m.
    1. Also referred to as "military time."
  2. Understanding the 24-hour clock:
    2. Afternoon hours continue counting after 12:
    1. 1 p.m. is 1300 hours.
    2. 2 p.m. is 1400 hours.
    3. 3 p.m. is 1500 hours, up to 2400 hours at midnight.
    3. Midnight is 0000 hours.
    4. Early morning hours are counted as:
    1. 1 a.m. is 0100 hours.
    2. 2 a.m. is 0200 hours, and so on.

Coordinated Universal Time (UTC):

  1. UTC is the standard time used in aviation.
    1. Previously known as Greenwich Mean Time (GMT).
    2. Also referred to as "Zulu" time by pilots.
  2. Converting local time to UTC:
    1. Add specific hours to local time based on your time zone (conversion table not provided).
  3. Example of time conversion:
    1. Departing at 10:30 a.m. Central Standard Time for a 2-hour flight to the Mountain Standard Time zone.
      1. Add 6 hours to CST to get UTC: 10:30 + 6 hours = 16:30 UTC.
      2. Add flight time to UTC: 16:30 UTC + 2 hours = 18:30 UTC.
      3. Subtract 7 hours from UTC to convert to MST: 18:30 UTC - 7 hours = 11:30 a.m. MST.

Remember, practicing time conversions makes the process easier. Understanding UTC is essential for accurate navigation and communication in aviation.