Lecture 2.9

2.3.4. Exterior lights

2.3.4.1. Overview Exterior Lights

There are a variety of exterior lighting systems. These include position, landing, taxi, anti-collision and wing inspection lights.

The exterior lighting system fulfils various functions:

• illuminating the runway and taxiway

• illuminating the wing leading edges and engine air intakes

• indicating the aircraft position and direction

• reducing collision risk in flight and on ground.

Figure 1: Exterior Lights of a commercial Aircraft

An overview of the exterior lighting arrangement on a large passenger aircraft is illustrated in Fig. 2. Exterior lighting is used for:

• logo illumination

• landing/taxiing

^• wing illumination

^• anti-collision/navigation.

White flashing strobe lights are installed in each wing tip leading edge and one in the tailcone, facing rearward. When anticollision strobe lights and anticolli-sion beacon lights flash, a timing system controls them in order to flash alternately in a synchronized fashion.

Red flashing anticollision beacon lights are installed: one on the lower and one on the upper fuselage at the aircraft center line.

Runway turn off lights illuminate the lateral areas of the runway. They are installed on the nose landing gear.

A fixed landing light is installed on each wing.

Take- off and taxi lights are installed on the nose landing gear in a fixed position. All lights go off automatically when the landing gear is retracted.

Wing and engine scan lights are installed on each side of the fuselage to enable the flight crew to visually detect ice on engine air intakes and leading edges.

Navigation lights give an external visual indication of the position of the aircraft and its direction of flight.

Logo Lights are installed on the horizontal stabilizer to illuminate the company logo.

Figure 2 Exterior lights (large transport aircraft)

A fixed Take Off Light and a Retractable Landing Light is shown on following figures.

Figure 3: Fixed Lights installed at Nose Landing Gear

Figure 4: Retractable Landing Light

Position lights are used to indicate the position of an aircraft during night operations. If pilots can identify the position of another aircraft from its position lights, they may safely navigate around that aircraft, hence position lights are often referred to as navigation lights. One or more position lights must be located on each wing tip and the tail of the aircraft. The right wing tip must have a green coloured light, the left a red light and the tail must have a white light. These lights are required on any aircraft certified for night flight.

In commercial aircrafts a dual system gives the possibility to select the second system if one bulb has failed. Bulb replacement can be done at convenient time.

Figure 5: Position Lights

Anti-collision light are found in two basic styles. Older aircraft were originally equipped with rotating beacons either on top of the vertical stabilizer or on top or bottom of the fuselage. Newer systems utilize solid state electronics to create a flashing- or strobe-type light. The rotating beacon system typically contained a stationary light bulb and a rotating reflector covered by a red glass lens.

Figure 6: Position Lights Dual System

Figure 7: Rotating Beacon Light

The strobe light has an extremely bright flash produced by a Xenon tube which requires approximately 400 Volts. The high voltage is produced by the strobe power supply which uses a capacitor charging system to achieve this high voltage.

Modern aircraft are required to have 3 white strobe lights. One on each wing and one at the tail. Coordinated flashing of the strobe lights and the anticollision lights is controlled by a synchronisation connection between the power supply units.

Be careful, the voltage to the xenon flash tube assy is dangerous.

Figure 8: Flashing Beacon Light

Figure 9: Flashing Strobe Light

Figure 10: Strobe Light System