§ 256.3 - Criteria.

(a) General. The Air Installations Compatible Use Zone for each military air installation shall consist of (1) land areas upon which certain uses may obstruct the airspace or otherwise be hazardous to aircraft operations, and (2) land areas which are exposed to the health, safety or welfare hazards of aircraft operations.

(b) Height of obstructions. The land area and height standards defined in AFM 86-8,1NavFac P-272 and P-80,1 and TM 5-803-4 1 will be used for purposes of height restriction criteria.

(c) Accident potential—(1) General. (i) Areas immediately beyond the ends of runways and along primary flight paths are subject to more aircraft accidents than other areas. For this reason, these areas should remain undeveloped, or if developed should be only sparsely developed in order to limit, as much as possible, the adverse effects of a possible aircraft accident.

(ii) DoD fixed wing runways are separated into two types for the purpose of defining accident potential areas. Class A runways are those restricted to light aircraft (See § 256.6) and which do not have the potential for development for heavy or high performance aircraft use or for which no foreseeable requirement for such use exists. Typically these runways have less than 10% of their operations involving Class B aircraft (§ 256.6) and are less than 8000 feet long. Class B runways are all other fixed wing runways.

(iii) The following descriptions of Accident Potential Zones are guidelines only. Their strict application would result in increasing the safety of the general public but would not provide complete protection against the effects of aircraft accidents. Such a degree of protection is probably impossible to achieve. Local situations may differ significantly from the assumptions and data upon which these guidelines are based and require individual study. Where it is desirable to restrict the density of development of an area, it is not usually possible to state that one density is safe and another is not. Safety is a relative term and the objective should be the realization of the greatest degree of safety that can be reasonably attained.

(2) Accident potential and clear zones (See § 256.7). (i) The area immediately beyond the end of a runway is the “Clear Zone”, an area which possesses a high potential for accidents, and has traditionally been acquired by the Government in fee and kept clear of obstructions to flight.

(ii) Accident Potential Zone I (APZ I) is the area beyond the clear zone which possesses a significant potential for accidents.

(iii) Accident Potential Zone II (APZ II) is an area beyond APZ I having a measurable potential for accidents.

(iv) Modifications to APZs I and II will be considered if:

(A) The runway is infrequently used.

(B) The prevailing wind conditions are such that a large percentage (i.e., over 80 percent) of the operations are in one direction.

(C) Most aircraft do not overfly the APZs as defined herein during normal flight operations (modifications may be made to alter these zones and adjust them to conform to the line of flight).

(D) Local accident history indicates consideration of different areas.

(E) Other unusual conditions exist.

(v) The takeoff safety zone for VFR rotary-wing facilities will be used for the clear zone; the remainder of the approach-departure zone will be used as APZ I.

(vi) Land use compatibility with clear zones and APZs is shown in § 256.8.

(d) Noise—(1) General. Noise exposure is described in various ways. In 1964, the Department of Defense began using the Composite Noise Rating (CNR) system to describe aircraft noise. Several years ago the Noise Exposure Forecast (NEF) system began to replace CNR. In August 1974, the Environment Protection Agency notified all Federal agencies of intent to implement the Day-Night Average Sound Level (Ldn) noise descriptor, and this was subsequently adopted by the DoD. This Ldn system will be used for air installations. Where AICUZ studies have been published using the CNR of NEF systems or where studies have progressed to the point that a change in the descriptor system is impractical or uneconomical, such studies may be published and continued in use. However, in such cases, data necessary for conversion to Ldn should be collected and studies should be revised as soon as time and budgetary considerations permit. However, if State or local laws require some other noise descriptor, it may be used in lieu of Ldn.

(2) Noise Zones. (i) As a minimum, contours for Ldn 65, 70, 75 and 80 shall be plotted on maps as part of AICUZ studies.

(ii) See § 256.10 for a further discussion of Ldn use and conversion to Ldn from previously used systems.