LANDING STRIP. Includes the landing area, endzones, shoulders, and cleared areas.REVETMENT. A protective pen usually made byexcavating into the side of a hill or by constructing earth,timber, sandbag, or masonry traverse around thehardstands. Such pens provide protection against bombfragments from high-altitude bombing but provide littleprotection against ground strafing. They may actuallydraw this type of fire if they are not well concealed.RUNWAY. That portion of the landing strip, usuallypaved, that is used for the landing and takeoff of aircraft.SHOULDER. The graded and stabilized areaadjacent to the runway or taxiway. Although it is madecapable of supporting aircraft and auxiliary equipment(such as crash trucks) in emergencies, its principalfunction is to facilitate surface drainage.TAXIWAY. A specially prepared area over whichaircraft may taxi to and from the landing area.TRANSITION SURFACE. A sloping planesurface (about 1 foot rise to 7 feet run) at the edge of alanding strip. Its function is to provide lateral safetyclearances for planes that accidental] y run off the strip.(See fig. 3-15.)PLANNING AN AIRFIELDPlanning for aviation facilities requires specialconsideration of the type of aircraft to beaccommodated; physical conditions of the site,including weather conditions, terrain, soil, andavailability y of construction materials; safety factors,such as approach zone obstructions and traffic control;the provision for expansion; and defense. Underwartime conditions, tactical considerations are alsorequired. All of these factors affect the number,orientation, and dimensions of runways, taxiways,aprons, hardstands, hangars, and other facilities.SUBBASE AND BASE COURSEPavements (including the surface and underlyingcourses) may be divided into two classes—rigid andflexible. The wearing surface of a rigid pavement isconstructed of portland cement concrete. Its flexuralstrength enables it to act as abeam and allows it to bridgeover minor irregularities in the base or subgrade uponwhich it rests. All other pavements are classified asflexible. Any distortion or displacement in the subgradeof a flexible pavement is reflected in the base course andupward into the surface course. These courses tend toconform to the same shape under traffic. Flexiblepavements are used almost exclusively in the theater ofFigure 3-17.-Typical pavements using stabilized layers.operations for road and airfield construction since theyadapt to nearly all situations and can be built by anyconstruction battalion unit in the Naval ConstructionForce (NCF).FLEXIBLE PAVEMENT STRUCTUREA typical flexible pavement is constructed as shownin figure 3-16, which also defines the parts or layers ofpavement. All layers shown in the figure are not presentin every flexible pavement. For example, a two-layerstructure consists of a compacted subgrade and a basecourse only. Figure 3-17 shows a typical flexiblepavement using stabilized layers. (The word pavement,when used by itself, refers only to the leveling, binder,and surface course, whereas flexible pavement refers tothe entire pavement structure from the subgrade up.)The use of flexible pavements on airfields must belimited to paved areas not subjected to detrimentaleffects of jet fuel spillage and jet blast. In fact, their useis prohibited in areas where these effects are severe.3-17
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