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NAV 12


Version 1. - May 2006

Standard pressure setting (1013.2 hPa) is used by all aircraft above a specified altitude (10,000ft in Australia), to allow long-distance flights to be made without resetting the altimeter frequently. The procedures for using this are given in VFG pages 70-71 (and see Altimeter Settings in the FRP notes in this manual).

Time and date

Time is written using the 24 hour clock, the first two figures being the hour and the last two the minutes, starting at 0000 (midnight) and onwards through 0001 and 0002 etc, ending at one minute to midnight (2359) and then back to 0000 again. 1315 is therefore 1.15pm.


04 13




month day



Time and date can be combined as a 6, 8 or 10 figure group. 10.35am on the 13th of April 2002 is shown as 0204131035,

ie, from greatest to least

An 8-figure group simply omits the year (the current year is assumed). A 6-figure group omits the year and month (the current year and month are assumed).

Co-ordinated Universal Time (UTC) is calculated from zero longitude at Greenwich, and was previously called Greenwich Mean Time. UTC can also be abbreviated as Z in meteorological messages. Aviation information and forecasts are given in UTC unless shown otherwise, so you must be able to convert UTC to local time and vice versa.

Local standard time sectors in Australia are Western, Central and Eastern Standard Time (UTC plus 8, 9.5, and 10 hours respectively). So 0200Z plus 9.5 hours equals 1130CST (often spoken as 'eleven-thirty local').


Daylight is defined as the period from first light (the beginning of morning civil twilight) until last light (the end of evening civil twilight). Night is the rest of the time. Balloons may fly between first light and last light provided there is sufficient visibility (see below).

First light and last light for any location can be calculated from the tables printed in AIP or VFG, given the date and the latitude and longitude of the location. You calculate the time for the precise location, then adjust this to UTC, then to local standard time. See explanation and examples in AIP, VFG or the Trevor Thom book – you must be able to do this calculation.

© Australian Ballooning Federation Inc

ABF Pilot Training Manual Part 8

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