Document ID: chunk:federal_register_of_legislation:F2024C01244:reg:5:p92
Version: federal_register_of_legislation:F2024C01244
Segment Type: reg
Provision Reference: reg 5 (pt 92/225)
Character Range: 550930–553448

of 4 light units each; and

(b) 2 longitudinal lines of 6 lights each, bisecting each of the wing bars.

       (2) An AT-VASIS must consist of 10 light units arranged on one side of a runway and comprising:

(a) a single wing bar of 4 light units; and

(b) one longitudinal line of 6 lights, bisecting the wing bar.

       (3) In a T-VASIS and an AT-VASIS, the light units must be constructed and arranged in such a manner that, during an approach, the pilot of an aeroplane will:

(a) when above the correct approach slope — see an inverted white "T" pattern comprising the white wing bar lights, and 1, 2 or 3 white "fly-down" lights, the more fly-down lights being visible, the higher the pilot is above the correct approach slope; and

(b) when on the correct approach slope — see the line of white wing bar lights; and

(c) when below the correct approach slope — see a white "T" pattern comprising the white wing bar lights and 1, 2 or 3 white "fly-up" lights, the more fly-up lights being visible the lower the pilot is below the correct approach slope; and

(d) when well below the correct approach slope — see a red "T" pattern with the wing bar lights and the 3 fly-up lights showing red.

       (4) A T-VASIS and an AT-VASIS must be:

(a) located so that the light units are as shown in Figure 9.46 (1), subject to the tolerances given in Table 9.47 (5); and

       Note   The Figure shows the light unit locations for a T-VASIS; for an AT-VASIS only one side of the mirrored arrangement is present.

(b) installed so that the light units forming the wing bars, and the light units forming a fly‑down or a fly-up matched pair, appear to the pilot of an approaching aeroplane to be substantially in a horizontal line; and

(c) mounted so that the light units are as low as possible; and

(d) frangible.

9.47 Characteristics of T-VASIS light units

       (1) A T-VASIS light unit must comply with the following requirements:

(a) be suitable for both day and night operations;

(b) have a suitable intensity control which allows adjustments to be made:

 (i) to meet the prevailing conditions; and

 (ii) to avoid dazzling pilots during approach and landing;

(c) be such that the light distribution of the beam of each light unit is fan-shaped, showing light over a wide arc in azimuth in the approach direction;

(d) for the wing bar light units — produce:

 (i) a beam of white light from 1° 54' vertical angle up to 6° vertical angle; and

 (ii) a beam of red light from 0° to 1° 54' vertical angle