Technical data

Product Specification

HIF-2121/R5 CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 965-1176-601 REV: D SHEET 78

245' AGL

400' AGL

700' AGL

2.45NM 4NM 12NM 15NM

FIG-6.3.1.3-5: TCF ALERT AREA VIEWED ALONG RUNWAY TRACK

The Runway Field Clearance Floor (RFCF) alert envelope is a circular band centered over the selected runway but unlike the

radio altitude based TCF envelope, the RFCF envelope only extends 5 NM past the end of the runway. The bias factor

(where the protection starts) is equal to the TCF bias factor (k) plus an additional offset proportional to the Geometric

Altitude Figure Of Merit (FOM). Figure 6.3.1.3-6 illustrates the shape of the alert envelope. This feature provides improved

alerting for cases where the runway is at a high elevation compared to the terrain below the approach path. In these cases the

radio altitude may be large enough to inhibit normal TCF operation, but the aircraft could actually be below the runway

elevation.

Field clearance (height above runway) is determined by subtracting the elevation of the selected destination runway from the

current altitude (MSL).

(1.5 + Krf) nm

Minimum Runway Field Clearance, ft

RFCF Ceiling (300 ft above field)

Krf

RFCF

Alert Area

Krf = (Position Error + Runway Data Quality +

Geometric Altitude FOM/200)

For example, if position error = .13, Runway Data

Quality = 0.3125, Geo Alt FOM = 100 ft, then;

Krf = 0.13 + 0.3125 + 100/200 = 0.94 NM

Runway

End

Field

Elevation

5.0 nm

(Outer Limit)

(No Lower Limit)

FIGURE 6.3.1.3-6: RFCF ALERT AREA