Visibility Reminder

These days visibility has not been great, so I made sure to revisit key points here in Guatemala.

Visual meteorological conditions (VMC) at the La Aurora Airport require a cloud ceiling of at least 1,500 ft and visibility of at least 5,000 meters.

The METAR is a good start. Considering the below…

MGGT 061200Z 16003KT 1000 FG OVC002 15/15 Q1025 A3027 APCH CLSD

Overcast or cloud ceiling at 200 ft and 1000 meters of visibility, so definitely Visual Meteorological Conditions (IMC). I always have to remind myself that visibility in METAR reports is provided in meters (if not otherwise stated). That must be the only data provided in meters. Cloud altitudes are stated in ft above ground. Knowing La Aurora is at 4952 ft altitude this seems pretty obvious. For less obvious situations, it is important to remember. FEW018 at La Aurora represents clouds at 1800 ft above ground or roughly 6,800 ft indicated altitude.

The best way to determine visual conditions remains taking a look. The visibility panoramic picture can help… The “El Reformador” tower is 3700 meters looking north to end of the runway 02. If you can see the tower, good. But you will need a little bit more visibility. If the mountains to the east are not hidden by clouds and you can spot the antennas, you have almost 6000 meters visibility. From a minimums perspective, it is visual. No need to say that your go/no-go decision needs much more considerations.

Good visibility everyone!

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3 Responses to Visibility Reminder

  1. admin says:

    Something to add…. The Guatemala visibility limit is conveniently provided in meters, same as a METAR report. In the Unites States visual visibility limits are provided in statue miles (who came up with that?). In most cases the visibility limit in the US is 3 SM. Well, the conversion factor from statue miles to meters is 1.6 and 3 statue miles therefore equals 4800 meters. Thats pretty close to 5000 meters right? Why not use 5000 meters across the board? As a memory aid, the maximum visibility that can fit the 4 digit code is 9999 meters. That number is used to show 10 kilometers or more. 5000 is right in the middle, easy enough to remember.

  2. Oscar says:

    Alex, very good points. However, in this area, where you have mountains, volcanos, etc. all around the field, you have to be extra careful. Specially if you don’t know the area. Also this time of the year haze is a real factor that complicates things even further.

    • admin says:

      Agreed. Personal limits are a different story and should be adapted to knowlegde of the area, experience, currency and many more factors.

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