Aircraft lighting refers to the equipment used on the aircraft to illuminate the cockpit, emit light signals and illuminate the landing runway. It is divided into internal lighting and off-board lighting as well as emergency lighting. The rapid development of solid-state light source technology has brought an opportunity to improve aircraft lighting.
Background introduction
Civil aircraft lighting systems need to implement a variety of internal and external lighting functions, and strictly meet the quantitative performance requirements of airworthiness regulations. Landing lights must provide sufficient illumination on the runway to allow the pilot to obtain adequate ground information during the approach, landing, taxiing, etc. The light intensity and distribution of navigation lights and anti-collision lights must be able to identify the aircraft's contour and flight direction, provide visual reference to nearby aircraft pilots, and alert pilots to appropriate collision avoidance measures.
This kind of system is installed in the pneumatic key area of ​​the aircraft surface. The structure is complex and the space is relatively tight. It needs to consider various factors such as local shape, installation space, mechanical interface and weight. Traditional external lighting technology often uses halogen lamps with large volume, short life and high cost. The rapid development of solid-state light source technology has brought opportunities for improving external lighting.
Current situation and difficulties
Solid-state light source refers to a light source using a semiconductor electroluminescence (EL) technology such as a light-emitting diode (LED), an organic light-emitting diode ( OLED ), or a polymer light-emitting diode (PLED), which has high luminous efficiency, good color rendering, and adjustable color. The light-emitting area is small, easy to integrate, and has a long life. Among them, LED is the solid-state light source with the highest light efficiency and the most mature technical state.
At present, the external lighting of civil aircraft has adopted a large number of LEDs, and navigation lights, ice detector lights, sign lights, red light anti-collision lights, etc. have mature LED products. However, in mature aerospace lighting products, the application of LED light source is similar to that of traditional luminaires, but the traditional light source is replaced by LED, and the characteristics and advantages of LED are not fully utilized. In addition, some on-board high-power lighting equipment still do not use LED light sources, such as landing lights, taxi lights, runway cornering lights, white light anti-collision lights.
The existing landing lights, taxi lights, and runway cornering lights generally use HID lamps as the light source, and use high-pressure gas discharge to emit light, which can meet the high-brightness and high-illuminance lighting requirements, and has good anti-vibration performance. However, its life expectancy is only about 4 000 h and needs to be replaced frequently. In addition, the light source has a very long turn-on time, and a stable light output is usually achieved after 15 minutes of startup. Due to the high voltage Power Supply, the light source and the power supply cable have certain safety hazards. The large current in the cable at the moment of discharge also increases the risk of the fuel system, and the electromagnetic interference generated is large, and strict shielding measures are required. Since the power efficiency of the light source is only about 40%, most of the electrical energy is converted into thermal radiation and ultraviolet radiation, which makes the operating temperature of the luminaire high and affects other equipment and structures in the installation area.
The white light anti-collision lamp usually uses a xenon lamp as a light source, and the life of the xenon lamp is only 2 000 to 3 000 h, and the maintenance frequency is high. As a pulsed gas discharge lamp, the xenon lamp has a high ignition voltage and a large operating current, which requires high driving circuit. Large-capacity electrolytic capacitors and transformer circuits are often used, which are costly. The life of electrolytic capacitors is only about 4 000 h, which needs to be replaced frequently. The instantaneous high current caused by the gas discharge mechanism also brings problems such as electromagnetic interference and fuel hazard.
In addition, some external lighting equipment is installed in the pneumatic sensitive area. Landing lights and runway cornering lights are usually installed in the wing wing roots. Due to the influence of the leading edge slats, the installation space is tight. The left and right white light anti-collision lights and navigation lights are installed on the left and right wings. Winglets, for composite winglets, the opening of the winglet surface affects the strength of the winglet, requiring local reinforcement on the structure, increasing structural weight and cost. With the wide application of supercritical wings, the thickness of the leading edge is reduced, the installation of the luminaire is more difficult, and the structural cost required for installation is high. In addition, since the wing will be deformed during flight, if the structural bracket is not sufficiently rigid, stress will be generated in the lampshade, resulting in internal cracks and even damage, which is not conducive to the safe flight of the aircraft.
Application advantage
In the field of aircraft lighting, LED technology has great application prospects, and the use of LED lighting technology can help improve the overall performance of aircraft lighting systems. In cockpit lighting, LED light guides, ceiling lights/floods can provide high-efficiency display instruments and a low-fouling visual environment; in cabin lighting, LED floodlights, reading lights, etc. can improve the cabin Comfort, scene lighting based on the adjustable color of LED color can realize the scene of cabin lighting, providing passengers with a relaxed and pleasant environment; in external lighting, LED light source can improve the efficiency, reliability and safety of the system. Provides comfortable and effective visual information for pilots; using LED light sources in emergency lighting saves power and increases system life and reliability. In view of the inherent advantages of LED technology and the current performance gap of related products, LED products are bound to be fully used in the external lighting of civil aircraft.
At present, the external lighting of civil aircraft has been widely used LED, navigation lights, ice detector lights, sign lights, red light anti-collision lights, etc., already have mature LED products, and are applied to advanced models such as B787 and A350. However, the application of LED light sources in mature aeronautical lighting products is similar to that of traditional luminaires, except that the light source is replaced by an LED, and the characteristics and advantages of the LED are not fully utilized.
In the development of wingtip navigation lights and anti-collision lights, Goodrich has mature navigation light products and is developing LED anti-collision lamps, all of which are independent devices. The installation interface is similar to traditional lamps.
In the development of high-power, high-intensity equipment such as landing lights, taxi lights, runway corner lights, the world's major lighting equipment suppliers have carried out related research and development, and launched the corresponding LED products. In 2009, Honeywell introduced its combined LED landing lights, which were assembled using LED arrays.The combined LED landing lights are far superior to the existing HID technology in terms of life, reliability, and maintainability. The specific performance comparison is shown in Table 1 below. Through the comparison of the parameters in the table, LED-based lighting equipment has been greatly improved in terms of working life, flight cycle, start-up time, stroboscopic work, line safety and reliability.
The development trend of solid-state lighting equipment has the characteristics of increasing power, gradually improving light efficiency, and gradually improving power efficiency. In the design method of high-power solid-state lighting equipment, the application of integrated modular design technology is more and more extensive, which further improves the reliability and maintainability of the equipment.
In the existing civil aircraft lighting system, high-power landing lights, taxi lights, runway cornering lights, white light anti-collision lights, etc. are not using solid-state light sources. The performance of the external lighting system directly affects the pilot's visual capabilities and aircraft safety. Airworthiness regulations and related industry standards have clear performance requirements for landing lights and anti-collision lights. Although the prior art can meet the airworthiness performance requirements to a certain extent, the use of conventional light sources brings many problems to the system level integration. As mentioned above, the use of conventional light sources results in short system life, tight installation space, high maintenance frequency, poor electromagnetic compatibility, and long start-up time.
Solid-state light source technology brings an opportunity to improve system performance and integration advantages. From the research results, it can be seen that all major aviation lighting system suppliers have fully transferred to high-power solid-state light source application technology, and developed a high-power combination with initial prototypes. LED landing lights. Although the technology has not been applied to mature models, based on the inherent advantages of solid-state light sources and technological development potential, and its significant advantages in system integration, it is expected that the technology will be widely used in the next generation of civil aircraft.
Conclusion
According to the current state of the art and the development trend at home and abroad, high-power solid-state lighting technology can significantly improve the overall performance of off-board lighting. Integrated landing lights and wingtip navigation anti-collision lights have great performance advantages over traditional technologies, and can effectively solve the interface definition, maintenance and installation problems of the prior art. The application of solid-state light source technology will greatly improve the integration convenience of the wing landing lights and wingtip navigation anti-collision lights, and optimize the local layout according to the characteristics of the aircraft shape, effectively reducing the influence on the shape and structure. Solid-state lighting integrated design technology helps improve overall system performance and aircraft performance, reducing operating and maintenance costs.
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