UFC 3-535-01
17 November 2005
12-3.1.3
Determine the Runway Reference Point (RRP) based on runway gradient,
as shown in Figure 12-6, establishing the RRP where the elevation of the lens center of
the light units coincides with the elevation of the runway centerline. The method
provides a direct solution, based on two equations and two unknowns, when the grade
of the runway is relatively uniform. The RRP is based on the PAPI light beam, where the
elevation of the lens center of the PAPI light units intercept the ground elevation along
the runway centerline (within tolerance). Case 4 in Figure 12-6 provides an iteration
method for locating the RRP when the runway grade varies significantly through the first
approximately 450 meters (1,500 feet).
12-3.1.4
Adjust the location of the PAPI for cross slope or other factors, as
required. Several examples of how the location of the RRP or location of the PAPI might
be adjusted are presented below. Stay within allowable tolerances and other
dimensional requirements of paragraph 12-3.2. See Figure 12-7 for guidance on
tolerances and adjustments if PAPI can not be located at the RRP.
12-3.1.4.1 Where the terrain drops off rapidly near the approach threshold and
severe turbulence is typically experienced, it would be beneficial to locate the RRP and
PAPI farther from the threshold if sufficient runway length is available. In this case
consider using the maximum TCH allowed by tolerance in determining the RRP.
12-3.1.4.2 On shorter runways, the RRP and PAPI may be located nearer the
threshold to provide the maximum amount of runway for braking after landing. In this
case consider using a lower TCH as allowed by tolerance in determining the RRP.
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