Vertical Obstructions ( VO )
Vertical obstructions are created by buildings , trees , structures , or other features that may encroach into the navigable airspace or line of sight radar signal transmission pathways used by the military . These obstructions can be a safety hazard to both the public and military personnel and potentially impact military readiness .
Vertical obstructions can compromise the value of low‐level flight training by limiting the areas where such training can occur . These obstructions can include a range of items from man‐made , such as telephone poles , utility transmission towers , and radio antennas , to natural , such as tall trees and land features . Vertical obstructions can also interfere with radar transmissions , compromising the integrity of data transmission between the transmitter and receiver . Though most critical near the transmitter , the geographic area impacting the transmissions , or radar viewshed , can be broad depending on the distance between the transmitter and receivers .
Key Terms
Imaginary Surfaces . The term imaginary surface refers to the areas surrounding a heliport or airfield that must be kept clear of objects that might pose a safety threat to aviation activities . A man‐made or natural object that projects above an imaginary surface is an obstruction .
Frangible Structures . Construction above the ground surface that will collapse or shatter upon impact .
Vertical Obstructions . Vertical obstructions are objects or structures that exceed a specified height above ground level and extend into airspace . Vertical obstructions may be created by buildings , trees , structures , or other features that are of greater height than , and encroach into , the navigable airspace used for military operations ( aircraft approach‐departure surfaces , transitional surfaces , as well as military training or flight routes ). These can present a safety hazard to both the public and military personnel and potentially impact military readiness .
Technical Background
Vertical obstructions can compromise the value limiting the areas where such training can occu include a range of items from man‐made , such antennae , to natural , such as tall trees and land
In relation to flight operations from an airport ( obstructions are addressed through compliance Title 14 Part 77 , which establishes standards an for objects affecting navigable airspace . Comm compliance , this regulation provides details to e vertical obstruction based on the elevation of th resulting elevation of the new structure or facil structure or facility in relation to the airfield in q
To determine when structures or facilities shou obstruction , Part 77 states the following require
§ 77.9 ‐ Any person / organization who intend following construction or alterations must n of the FAA :
– Any construction or alteration exceeding level .
Any construction or alteration :
– within 20,000 feet of a public use or milita a 100:1 surface from any point on the runw at least one runway more than 3,200 feet .
– within 10,000 feet of a public use or milita a 50:1 surface from any point on the runwa longest runway no more than 3,200 feet .
– within 5,000 feet of a public use heliport 25:1 surface .
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