Imaginary Surfaces ( Figure 4 )
Federal Aviation Regulations , Part 77 specifies a series of imaginary height restriction surfaces surrounding an airfield . The imaginary surfaces of an active runway are used to define the required airspace that must remain free of vertical obstructions in the vicinity of aviation operations to optimize safe flight operations . Structures should not exceed these heights to protect the navigable airspace associated with the airfield , the safety of pilots and people , and the land use on the ground . This is especially important in the clear zone and the approach‐departure surfaces . Figure 4 illustrates the outermost extent of the imaginary surfaces at Travis AFB . For a complete technical explanation of the imaginary and transitional surfaces for Travis AFB , see Chapter 5 , Compatibility Assessment ( Section 5.23 Vertical Obstructions ) of the Background Report .
The Department of Defense Unified Facilities Criteria 3‐260‐01 , Airfield and Heliport Planning and Design , establishes airspace imaginary surfaces associated with assault landing zones located at Travis AFB .
Airfield Accident Potential Zones ( Figure 4 )
In addition to the assessment of imaginary surfaces , the second element of the airfield safety analysis is the assessment of Accident Potential Zones ( APZs ). For a complete technical explanation of the APZs for Travis AFB , see Chapter 5 , Compatibility Assessment ( Section 5.21 Safety ) of the Background Report .
There are typically three safety zones that extend from each end of a runway : Clear Zone ( CZ ), APZ I , and APZ II . These safety zones are illustrated on Figure 4 . The CZ for the runway measures 3,000 feet wide by 3,000 feet long . This is the area that has the highest potential of an aircraft incident . It is recommended that no development occur in the CZ unless it is a use that is needed for safe operations of aircraft .
The APZ I is an area beginning at the end of eac and a length of 5,000 feet . The APZ II is an area each APZ I and is 3,000 feet wide by 7,000 feet potential for accidents and therefore have less recommendations .
There are two smaller safety zones associated w the CZ and the APZ‐LZ . The landing zone CZ beg landing zone , which starts at an inner width wh each side of the centerline and tapers out to a w side of the centerline . The landing zone CZ exte the extended assault strip centerline . The APZbegins at the far end of the CZ and extends out the centerline for 2,500 feet along the extended
Aircraft Noise Contours ( Figure 4 )
Aircraft noise is produced from flight operation landings , touch‐and‐go operations ) and engine engine run‐up is a maintenance procedure perf for proper engine performance . The Air Force c impact the local community by calculating an av measured as a day‐night average sound level ( D uses the DOD NOISEMAP program to produce n noise exposure levels from aircraft operations ; of aircraft at Travis AFB .
The contour lines developed in the model range 80 dB DNL and increase in increments of five dB loudest contour line computed and the 60 dB D has been determined to be a reliable measure o aircraft noise and has become a standard metri impacts .
Travis AFB Sustainability Study Report