L46 Ultra High Intensity LED Lighting
LED Wingtip Taxi Light HID Wingtip Taxi Light
Malibu Aerospace has developed an LED Taxi Light system for the Malibu, Mirage and Meridian. This system utilizes ultra high intensity LEDs that output over 100 Lumens per watt for bright light and high efficiency. They also retain nearly all of their luminosity after 50,000 hours of operation for extreme long life and continued high performance. In comparison, the standard Halogen light has an output of 10 Lumens per watt and the HID upgrades average about 80 Lumens per watt. This means that the Halogen light puts out 350 Lumens and consumes 1.3 amps, the HID light puts out 2800 Lumens and consumes 1.3 amps and the LED puts out 2,000 Lumens and consumes 1.0 amps. Now you may realize that the HID is actually producing more Lumen's than the LED, but this is where optics come into play.
LED Wingtip Taxi Light HID Wingtip Taxi Light
The semi-parabolic reflector that both the Halogen and HID lights use is extremely inefficient at projecting the light any distance without losing much of its focus. On the other hand, the optics that we have chosen to use with the LEDs is a total internal reflection lens that is extremely efficient and projects 97% of the light output within a 4° beam with a perfectly round pattern. The last factor to consider is color temperature, which gives you visible light that is within a range that the human eye can efficiently use. The Halogen light typically puts out a "warm" white light of around 3,000°K, HID lights can vary widely, but the HID light upgrade we tested was around 3,400°K, while the LED lights are between 5,000-6,000°K, which is much closer to natural daylight and is easier for the human eyes to see.
Degrading HID Light and Reflector
With all of the light output, power consumption, lens efficiency and color temperature factors in play, we also have the reality of degradation over time. With the Halogen bulb, it isn't much of an issue since the bulb simply fails rather than degrades. With the HID, over time, the color will shift as the purity of the metallic oxide compounds and the Xenon gases degrade after many on/off cycles, but worst of all is the reflector itself, which often times gets so hot that the aluminized coating literally peels off and the light efficiency degrades terribly. The LEDs are rated for degradation over tens of thousands of hours and over the life of your airplane the degradation will be negligible and the optics are also designed with no reflective applications to degrade.
Our testing has shown that with a Phillips DL-2001 light meter, the LED lights are projecting 434 footcandles peak at a five foot distance and 415 footcandles average over a one foot test area while the HID light projected only 357 footcandles peak and 270 footcandles average over the same one foot area. The same test at eight feet showed the LED lights projecting 185 footcandles peak and 175 footcandles average with the HID projecting 175 footcandles peak and only 120 footcandles average in the same conditions. What this shows is that the LED lighting is over 45% brighter and more consistent and the HID has a much more irregular "hot-spot" beam pattern. If you are not familiar with what footcandles are and what these numbers mean; a footcandle is...
footcandle, fc: It is the illuminance on a surface one square foot in area on which there is a uniformly distruibuted flux of one lumen, or the illuminance produced on a surface all points of which are at a distance of one foot from a directionally uniform point source of one candela.
2-3fc is adequate for public spaces with dark surroundings
5-10fc is for simple orientation for short times
10-20fc is for working spaces where visual tasks are occasionally performed
20-50fc is for performance of visual tasks of high contrast or large size
50-100fc is for performance of visual tasks of medium contrast or small size
100-200fc is for performance of visual tasks of low contrast and very small size
200-500fc is for performance of visual tasks of low contrast and very small size over a prolonged period
500-1000 is for performance of very prolonged and exacting visual tasks
Additional outdoor testing at night with a Malibu Aerospace L46T LED light in the left wingtip and a LoPresti Boom-Beam HID light in the right wingtip has shown that over longer distance, the LED light is far superior. Measurements taken at 25 feet shows an average of 19 footcandles over a 4'x4' area for the LED light and only 12 footcandles over the same 4'x4' area for the HID light. At 50 feet, the LED measured an average of 5 footcandles over an 8'x8' area and the HID measured only 3.5 footcandles over the same area. Also, the consistency of the LED light was very good over the measured area, while the HID had very small spots that were bright, and very large areas that were much dimmer.
We took a series of photos with the camera set manually to give us the same exposures for both lights and the difference that the camera shows is dramatic. Here you can see that at the same distance, it is much easier to see the person standing 150 feet in front of the plane, as well as the ground in the area, which can help in missing obstructions on the ramp such as parking cones, taxiway markers, or other objects that can cause a prop strike.