ENR 5.4 Air Navigation Obstacles

1.. General

  1. The Daily Digital Obstacle File describes all known obstacles of interest to aviation users in the United ­States, with limited coverage of the Pacific, the Caribbean, Canada, and Mexico. The obstacles are assigned ­unique numerical identifiers, accuracy codes, and are listed in order by state: https://www.faa.gov/air_traffic/­flight_info/aeronav/digital_products/DailyDOF/.
  2. Additional information regarding Obstacle Construction Notices:
    https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/ObstConstrNotices/.

2.. Obstructions to Flight

  1. Many structures exist that could significantly affect the safety of your flight when operating below 500 feet ­above ground level (AGL), and particularly below 200 feet AGL. While 14 CFR section 91.119 allows flight ­below 500 feet AGL when over sparsely populated areas or open water, such operations involve increased safety ­risks. At and below 200 feet AGL there are numerous power lines, antenna towers, etc., that are not marked and ­lighted and/or charted as obstructions and, therefore, may not be seen in time to avoid a collision. Notices to ­Airmen (NOTAMs) are issued on those lighted structures experiencing temporary light outages. However, some ­time may pass before the FAA is notified of these outages, and the NOTAM issued, thus pilot vigilance is ­imperative. Additionally, new obstructions may not be on current charts because the information was not ­received prior to the FAA publishing the chart.
  2. Extreme caution should be exercised when flying less than 2,000 feet AGL because of numerous skeletal ­structures, such as radio and television antenna towers, that exceed 1,000 feet AGL with some extending higher ­than 2,000 feet AGL. Most skeletal structures are supported by guy wires which are very difficult to see in good ­weather and can be invisible at dusk or during periods of reduced visibility. These wires can extend about 1,500 ­feet horizontally from a structure; therefore, all skeletal structures should be avoided horizontally by at least ­2,000 feet.