Runway System Geometric Specifications
The runway system at an
airport consists of the structural pavement, the shoulders, the blast pad, the
runway safety area, various obstruction-free surfaces, and the runway
The runway structural pavement
supports the aircraft with respect to structural load, maneuverability,
control, stability, and other operational and dimensional criteria.
The shoulder adjacent to the
edges of the structural pavement resists jet blast erosion and accommodates
maintenance and emergency equipment.
The blast pad is an area designed
to prevent erosion of the surfaces adjacent to the ends of runways due to jet
blast or propeller wash.
The runway safety area (RSA) is
an area surrounding the runway prepared or suitable for reducing the risk of damage to aircraft
in the event of an undershoot, overshoot, or excursion from the runway. ICAO
refers to an area similar to the runway safety area as the runway strip
and the runway end safety area. The runway safety area includes
the structural pavement, shoulders, blast pad, and stopway, if provided. This area
should be capable of supporting emergency and maintenance equipment as well as
providing support for aircraft.
The runway safety area
is cleared, drained, and graded and should have no potentially hazardous ruts,
humps, depressions, or other surface variations. It should be free of objects except
for objects that are required to be located in the runway safety area because
of their function. These objects are required to be constructed on frangible
mounted structures at the lowest possible height with the frangible point no
higher than 3 in above grade.
The runway object-free area (OFA)
is defined by the FAA as a two-dimensional ground area surrounding the runway
which must be clear of parked aircraft and objects other than those whose
location is fixed by function.
The runway obstacle-free zone
(OFZ) is a defined volume of airspace centered above the runway which supports
the transition between ground and airborne operations. The FAA specifies this as the airspace above a surface whose
elevation is the same as that of the
nearest point on the runway centerline and extending 200 ft beyond each end of
The inner approach obstacle-free zone,
which applies only to runways with approach lighting systems, is the airspace above
a surface centered on the extended runway centerline beginning 200 ft beyond
the runway threshold at the same elevation as the runway threshold and
extending 200 ft beyond the last light unit on the approach lighting system.
Its width is the same as the runway obstacle-free zone and it slopes upward at
the rate of 50 horizontal to 1 vertical.
The inner transitional obstacle-free
zone, which applies only to precision instrument runways, is defined by the
FAA as the volume of airspace along the sides of the runway and the inner
approach obstacle-free zone. The surface slopes at the rate of 3 horizontal to
1 vertical out from the edge of the runway obstacle-free zone and the inner
approach obstacle-free zone until it reaches a height of 150 ft above the
established airport elevation.
runway protection zone (RPZ) is an area on the ground used to enhance
the protection of people and objects near the runway approach.
*Facilities for small airplanes only.
†From end of runway;
withept,these lengthsthe begindeclaredatthestopend dist of each ASDA and both
ends of the LDA, whichever is greater.
‡For runways serving
small aircraft only; f the wingspan of the most demanding aircraft plus 20 ft
for each 1000 ft of airport elevation.
§For runways serving small aircraft with
approach speeds of less than 50 kn; increase to 250 ft for runways serving
aircraft with approach speeds greater
than 50 kn.
¶Beyond the end of each runway.