Vertical Obstructions ( VO )
Vertical obstructions are created by manmade ( buildings , structures ) or natural ( trees ) or other features that may encroach into the navigable airspace or radar signal transmission line of sight pathways used by the military . These obstructions can be a safety hazard to both the public and military personnel and can 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 .
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 In relation to flight operations from an airport (
obstructions are addressed through compliance Regulation ( CFR ) Title 14 Part 77 Safe , Efficient Navigable Airspace , which establishes standard requirements for objects affecting navigable air to as ( CFR ) Title 14 Part 77 compliance , this reg evaluate the potential for a vertical obstruction the airfield , the height and resulting elevation o facility , and the location of the structure or faci in question .
To determine when structures or facilities shou obstruction , ( CFR ) Title 14 Part 77 states the fol notifying the FAA :
§ 77.9 ‐ Any person / organization who inten the following construction or alterations mu Administrator of the FAA :
– Any construction or alteration exceeding level .
Any construction or alteration :
– within 20,000 feet of a public use or milita exceeds a 100:1 surface from any point on t airport with at least one runway more than
– within 10,000 feet of a public use or milita exceeds a 50:1 surface from any point on th airport with its longest runway no more tha
Background Report