Landing Light Performance

Any DA62 related topics

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bdbogle
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Re: Landing Light Performance

Post by bdbogle »

Just got my DA42 out of annual and had some other maintenance performed to include the installation of new XeVision bulbs and ballasts. MUCH better performance. Highly recommended. I can actually see the runway better on approach and had a tower see our lights at 4+ nm from the field. Attached is a pic on a taxiway. Granted, the phone does compensate rather well for low light visibility, but it is much better. Looking at them on the ground was almost too hard to look at...kind of light trying to look at the sun.
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neema
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Re: Landing Light Performance

Post by neema »

Good to see. did you install the 50w ballasts?
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Re: Landing Light Performance

Post by XeVision »

neema wrote: Mon Feb 27, 2023 12:50 am Good to see. did you install the 50w ballasts?
Yes they did install 50 Watt ballasts as well as new bulbs, since the bulbs loose output over the hundreds or thousand + hours of use over the years.
Last edited by XeVision on Mon Feb 27, 2023 7:49 pm, edited 1 time in total.
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Re: Landing Light Performance

Post by XeVision »

The terms and metrics for comparing Landing and Taxi lighting performance are as follows:

Candela - cd (“Candle Power - CP” - a Legacy term “officially obsoleted” in 1948). The word Power is never included as part of the term Candela, Candela is a “stand alone” term. Adding the word power is redundant to its meaning. Both cd and CP measure the same specific performance characteristics, even though Candle Power (actually Center Beam Candle Power) has been effectively replaced by Candela in the professional lighting industry gradually over the years since 1948.
The Candle Power (CBCP) metric 1 = 0.981 Candela cd - Thus a Candela is ever so slightly more powerful than the old Candle Power metric. For the purposes of comparison they can be considered equal. The cd metric only measures the brightest part (hot spot) of the beam and is an indicator of how far the beam can reach downrange, in terms of useful illumination for the human eye. This metric alone though can be deceiving without knowing the beam size as well. A laser beam will have a very high cd number but is so narrow to be useless for our discussed purposes here. Note: MOST Landing and Taxiing LED units currently on the market dim to about half their claimed (rated) Candela outputs within 5-10 minutes of being powered on. Even worse performance if located in a hot cowling and already hot when turned on, ie. turned on once in the pattern after a long flight. They dim as they heat up. You could cook an egg on the backs of some of them after 10 minutes or so of use, about 200 degrees F. Just imagine how much hotter the junction temps are of the individual LED’s and the control electronics inside, typically on the same PCB (printed circuit board).

Beam Angle - the industry standard for beam angle claims is typically by determining where the cd value has dropped to 1/2 of its Peak value. As an example, if the cd value rating were 200,000 cd, the beam angle would be determined based on where the cd level drops to 100,000 cd. Some manufacturers will also measure down to 10% intensity as well, so 20,000 cd in this example. In that rarely used 10% based case, it should be noted in the beam angle specifications. With a very powerful Light source the 10% value can be meaningful to beam angle claims, for moderate or dim light sources it’s mostly meaningless.
The 1/2 intensity boundary will typically be used for the beam angle measurements and specs., both horizontal and vertical, if not a round shaped beam pattern. Note: some specifications provide a half beam angle measurement rather than full width beam angle, if so it is stated that way. A full beam angle is from one edge of the beam to the other opposite side. The half beam is only measuring from the center to one side. This measurement can be doubled to provide the full beam angle dimension.

Lumens - The total amount of visible light emanating from a light source, this often does not take into account the light lost from optical inefficiencies of lenses and reflector components as part of an optical assembly. Just using the light source manufacturers specs (LED’s or a bulb) and ignoring the measurement of whats actually coming out the front of the complete lighting fixture is often misleading. This precise Lumens measurement is made using a large globe shaped enclosure called an integrating sphere. This testing can be done for the individual light sources or the completed fixture, it can also be done over a time period to determine any dimming as the unit reaches a relatively stable operating temperature. This dimming doesn’t really affect HID output but can have a dramatic halving of claimed output with in 5-10 minutes of use for LED’s. This effect mostly for LED Landing and or Taxi lighting units, most having poor or inadequate thermal management characteristics to maintain anything remotely close to full starting output. In order to optimize the effectiveness of the lumens for Landing or taxiing purposes parabolic optics are used with HID and LED’s to focus the light in useful areas, not wasted as scattered light. The usefulness of gauging performance based on Lumens is totally dependent on the size, shape, type and quality of the optics being used. This would also include the multiple TIR’s used with each individual LED surface mounted chip.

LUX - A unit of measurement that takes into account distance performance from the light source. Lux can be used to determine the useful “throw” or projected distance of a light source. An example 0.20 LUX is approximately the maximum amount of light from a full moon at night on a perfectly clear no haze (dust or humidity), 1 LUX is needed to comfortably read a newspaper. 1/2 LUX is really the useful limit of distant illumination for timely piloting visual recognition use.
The definition of lux 1 Lux (one) is equal to 1 lumen per square meter. Again the amount of light needed to comfortably read a newspaper. As you get closer to the light source the Lux value climbs dramatically.
There are very easy to use calculators (google it) to convert Candela or CP to Lux at any given distances you want to determine. I would say looking for 1 Lux and 1/2 Lux are the most meaningful to determine useful landing light performance distances once you have the cd value. If you have the Lux reading value at an established distance you can also back calculate Candela.

As they say “knowledge is power” in making optimal performance and informed purchasing decisions. There is so much Lighting misinformation out there, in aviation lighting marketing, articles and forums etc… I felt the need to put this together.
Hope you find it useful as a reference going forward.

Dan Blumel
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Re: Landing Light Performance

Post by MikeMeadows »

Flew a DA62 on Sunday night that just had the taxi and landing light ballasts upgraded to 50 watts. Huge difference and well worth it.

Shop that did it said the hardest part was removing the front seats. Ballasts just a drop in replacement (4 bolts) from the old ones.

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Re: Landing Light Performance

Post by MackAttack »

I just ordered the upgraded ballasts for my DA62 and will have them installed when the plane is in for service … will provide a PIREP afterwards.
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Re: Landing Light Performance

Post by dant »

MOST Landing and Taxiing LED units currently on the market dim to about half their claimed (rated) Candela outputs within 5-10 minutes of being powered on.
Is this true for all types of lights? i.e. HID/LED/etc
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Re: Landing Light Performance

Post by XeVision »

Old incandescent or halogen bulbs NO !!!. Most (not all) LED Landing or Taxiing lights do this dimming as they warm up, both by themselves as the junction temp goes up so does the internal resistance but they can still thermal runaway and self destruct. Because of this all the manufacturers gradually pull the LED power back for warranty prevention purposes, causing this ~50% over 5-10 minutes dimming. Note: not true for LED strobes because they are only on momentarily as they strobe, never getting hot.
We at XeVision make both LED landing and taxi lighting that DOES NOT DIM, we use active cooling to effectively eliminate this dimming problem and offer substantially higher outputs than all others.
HID's only dim gradually over many hundreds to 1 thousand hours of use. They don't dim as they warm up, in fact they get brighter over the first minute they are turned on and maintain this intensity.
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Re: Landing Light Performance

Post by XeVision »

See the earlier top of page 2 of this thread for 2 comparison graphs, one graph of ours and one about our competition for LED's. It covers the thermal performance over time, it was produced by Whelen (WAT). The first 5-15 minutes are most noteworthy.
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Re: Landing Light Performance

Post by MackAttack »

FWIW, I had my first night landing in my 62 last night. Strictly speaking, it was near the end of civil twilight but it was dark enough that I needed the lights and certainly needed them to taxi. I was disappointed in how poorly they light the runway/taxiway environment. It wasn’t dangerously dim or anything, just dimmer than I’m used to on other aircraft. I have ordered the upgraded ballasts and I think they arrive today (but they won’t get installed for a bit). Won’t be as much of an issue as we head into summer but I’m hoping to get them installed when a MX opportunity presents itself …
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