Flap indicator light replacement

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CFIDave
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Re: Flap indicator light replacement

Post by CFIDave »

Here is the LED bulb info again for anyone who wants to order it.

The Diamond part number: 461K_02_2801_WS (Single-LED T4.6-28V/1mA white)

The LEDs list for about $18 apiece vs. about $5 for the older incandescent bulbs.
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Chris B
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Re: Flap indicator light replacement

Post by Chris B »

CFIDave wrote:Here is the LED bulb info again for anyone who wants to order it.

The Diamond part number: 461K_02_2801_WS (Single-LED T4.6-28V/1mA white)

The LEDs list for about $18 apiece vs. about $5 for the older incandescent bulbs.
This is by far the easiest route.

But if you are handy with a soldering iron, there is always DIY: link

Chris
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Re: Flap indicator light replacement

Post by CFIDave »

One more important note (taken from the Canadian L360 DA42 parts list):

NOTE: If this LED lamp is installed, the same P/N LED lamp must be installed in all four places on the Landing Gear Panel. Mixing of bulbs and LEDs are not permitted.

I imagine that this same note would also apply to the flap bulbs on either the DA40 or DA42, i.e., don't mix bulbs.
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Steve
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Re: Flap indicator light replacement

Post by Steve »

For the landing gear indicator bulbs, LED replacement makes sense. Not so much for the flap indicator ones. After all, you can always look out at the wing to check on the flap position. As one data point, I'm at 13+ years on the original flap indicator bulbs...

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Re: Flap indicator light replacement

Post by rwtucker »

CFIDave wrote:One more important note (taken from the Canadian L360 DA42 parts list):
NOTE: If this LED lamp is installed, the same P/N LED lamp must be installed in all four places on the Landing Gear Panel. Mixing of bulbs and LEDs are not permitted.
I imagine that this same note would also apply to the flap bulbs on either the DA40 or DA42, i.e., don't mix bulbs.
Wonder why? LEDs and incandescent bulbs exist happily in parallel in many circuits. From an electrical point of view, the lamps will draw different currents but, since they are in parallel and since the circuit was designed to handle the higher combined load of the incandescent bulbs, this requirement would seem unnecessary except that theoretical bulb life/replacement would differ. I can think of one or two possible explanations, but they require different assumptions on the wiring.
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Re: Flap indicator light replacement

Post by Chris B »

rwtucker wrote:Wonder why? LEDs and incandescent bulbs exist happily in parallel in many circuits.
Hi Robert -

I suspect that this is due to the differences in how they handle dimming. One type could be at wildly different brightness than the other.

Chris
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Re: Flap indicator light replacement

Post by carym »

CFIDave wrote:One more important note (taken from the Canadian L360 DA42 parts list):

NOTE: If this LED lamp is installed, the same P/N LED lamp must be installed in all four places on the Landing Gear Panel. Mixing of bulbs and LEDs are not permitted.

I imagine that this same note would also apply to the flap bulbs on either the DA40 or DA42, i.e., don't mix bulbs.
Wow, even the DA42 L360 allows LED's, but not DA42's with Thielert Engines. I'm beginning to feel persecuted. I think it is time for me to write to Customer Service and see if that was on purpose or just an error of oversight.
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Re: Flap indicator light replacement

Post by Rich »

rwtucker wrote: Wonder why? LEDs and incandescent bulbs exist happily in parallel in many circuits. From an electrical point of view, the lamps will draw different currents but, since they are in parallel and since the circuit was designed to handle the higher combined load of the incandescent bulbs, this requirement would seem unnecessary except that theoretical bulb life/replacement would differ. I can think of one or two possible explanations, but they require different assumptions on the wiring.
But not all. One example is the stop/tail light arrangement on my motorcycle. This consisted of 2 1157 incandescent bulbs. I replaced them with two equivalent LED replacements. At the point I replaced the first one, I turned the bike on and the LED came on, but not the remaining incandescent. Pulled the LED back out and the 1157 worked fine. Replaced both and both LEDs work fine. I still haven't figured this out but have confirmed with others this is exactly what happens.
Last edited by Rich on Sat Jan 03, 2015 2:59 am, edited 1 time in total.
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Re: Flap indicator light replacement

Post by rwtucker »

Chris B wrote:
rwtucker wrote:Wonder why? LEDs and incandescent bulbs exist happily in parallel in many circuits.
Hi Robert - I suspect that this is due to the differences in how they handle dimming. One type could be at wildly different brightness than the other. -- Chris
Great point! As a lowly DA40 driver, I haven't had the opportunity to fly a DA42 at night. (On my bucket list.) I thought the gear lights would be excluded from the dimming circuit given how much such circuits add to the failure equation. Given that thay are dimmed, you are spot on; the range of useful illumination for the typical LED (any illumination, really) is compressed to the upper end of the voltage range. They will be below their threshold voltage when the incandescents still have quite a bit of range left.
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Re: Flap indicator light replacement

Post by Chris B »

rwtucker wrote:... the range of useful illumination for the typical LED (any illumination, really) is compressed to the upper end of the voltage range. They will be below their threshold voltage when the incandescents still have quite a bit of range left.
Hi Robert -

FWIW, I think this depends on how the LED is set-up. LED brightness is controlled by current, not voltage. And after the LED gets to "full" brightness, more current has little impact. Until the magic smoke escapes. ;)

So depending on the particular LED and the resistor values used to target a specific drive current, the sensitive part of the current/luminosity curve could be anywhere. One potential issue with LEDs designed for 12V operation is that in a 24V aircraft, the LED won't dim - at all - until the control is set to nearly-off. By then all of the other lights on the circuit will be invisible...

Chris
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