Whelen Parmetheus Lens Failure

[Marauder]

In the 27 years I have owned my F, I have replaced my landing light once. That was to change a 24 year old incandescent bulb with a Whelen LED. Flew last night and was cleaning the bugs off of the plane and noticed this:
 

 
There is no indication of a stone being thrown on it (the crack appears to have started behind the lip of the light housing). I know that since the first day I owned it, I saw some fogging behind the lens and saw this on a few other planes with this bulb , so I thought this was normal.
 
Any ideas on what caused this? I will be calling Whelen to find out of the lens can be replaced only.

 
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[DXB]

56 minutes ago, Marauder said:

In the 27 years I have owned my F, I have replaced my landing light once. That was to change a 24 year old incandescent bulb with a Whelen LED. Flew last night and was cleaning the bugs off of the plane and noticed this:
 

 
There is no indication of a stone being thrown on it (the crack appears to have started behind the lip of the light housing). I know that since the first day I owned it, I saw some fogging behind the lens and saw this on a few other planes with this bulb , so I thought this was normal.
 
Any ideas on what caused this? I will be calling Whelen to find out of the lens can be replaced only.

 
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I wonder if the vibration got to it finally. Curious to hear what Whelen says - I have the same bulb and it has always had H2O condense behind the lens like you describe.  If the moisture behind the lens was not a problem then a crack might not be either. 

[Marauder]

I wonder if the vibration got to it finally. Curious to hear what Whelen says - I have the same bulb and it has always had H2O condense behind the lens like you describe.  If the moisture behind the lens was not a problem then a crack might not be either. 

I spoke to Whelen technical support this afternoon. Didn’t have a reason for the failure but didn’t seemed surprised either. He said they were a “wear and tear” item. Provided part numbers for both the PAR 36 & 46 replacement lens.

PAR 46 is 01-0471577-00
PAR 36 is 01-0471486-00

He said that Aircraft Spruce should carry them.


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[jaylw314]

Is there no plexiglass light cover on that light housing?

[Marauder]

Is there no plexiglass light cover on that light housing?

I think the part you see cracked in my photo is the plexiglass light cover. If you look closely at the picture you can see where the screws would be driven in from the inside of the light.

I’ll know more when we get it out for repair.


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[jaylw314]

1 minute ago, Marauder said:

 

I think the part you see cracked in my photo is the plexiglass light cover. If you look closely at the picture you can see where the screws would be driven in from the inside of the light.

I’ll know more when we get it out for repair.


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Oh, no I meant to ask if the light sits behind a plexiglass shield?  My cowl landing light has an acrylic shield that that gets installed in front of the landing light.

[Marauder]

Oh, no I meant to ask if the light sits behind a plexiglass shield?  My cowl landing light has an acrylic shield that that gets installed in front of the landing light.

Nope. I’ve seen those on the Js but my F doesn’t have one.


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[Yetti]

I would say stress crack from improper installation.   The square bump on the lens should line up with the notch in the alum ring.   If it was installed lined up when  originally installed, then it has been bouncing around.   You can get a tractor light to go with your tractor mags that says Wheelen on it and you won't be as mad when if/when it breaks because you did not pay as much.   Looks like you got another split in the top right of the pic. 

https://www.amazon.com/Whelen-Engineering-PAR-46-Super-LED-Replacement/dp/B009LQG5S0/ref=sr_1_1?s=automotive&ie=UTF8&qid=1531225126&sr=1-1&keywords=whelen+par+46

 

I would probably run it till it impacted light output.

[Marauder]

3 hours ago, Yetti said:

I would say stress crack from improper installation.   The square bump on the lens should line up with the notch in the alum ring.   If it was installed lined up when  originally installed, then it has been bouncing around.   You can get a tractor light to go with your tractor mags that says Wheelen on it and you won't be as mad when if/when it breaks because you did not pay as much.   Looks like you got another split in the top right of the pic. 

https://www.amazon.com/Whelen-Engineering-PAR-46-Super-LED-Replacement/dp/B009LQG5S0/ref=sr_1_1?s=automotive&ie=UTF8&qid=1531225126&sr=1-1&keywords=whelen+par+46

 

I would probably run it till it impacted light output.

Good eye. That does look like another crack on top. I will be going to the airport tonight and will closer at it.

[bradp]

I’ve got three little rectangles of baffle seal material RTVd in front of my Whelen LED to prevent vibration being transferred to the  light.  Try that with next R&R. 

[carusoam]

Expect a stress crack to be a possible idea...

If taking it out... See if there is anything like bumps on the mounting surface... things that wouldn’t bother the old glass bulb.

Is there any alignment bumps or anything like that back there?

Does Whelen give mounting advice on how to avoid stress cracks?  Like use of a rubber grommet/spacer or something like that?

PP thoughts only...

Best regards,

-a-

[Hank]

It's not as much of a closeup, but this is what mine looks like. The four bumps on the face are half behind the trim ring, while yours are all inside it and not working as standoffs.

Do you need a closer-up like you posted? This was right after install in Spring '14.

[Marauder]

It's not as much of a closeup, but this is what mine looks like. The four bumps on the face are half behind the trim ring, while yours are all inside it and not working as standoffs.

Do you need a closer-up like you posted? This was right after install in Spring '14.

I think the picture is big enough to see the details. Based on what I am seeing, the orientation is pretty close to what mine.

I think mine is a PAR46. Is that what your LED is?


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[Hank]

5 minutes ago, Marauder said:

I think the picture is big enough to see the details. Based on what I am seeing, the orientation is pretty close to what mine.

I think mine is a PAR46. Is that what your LED is?

Yes, it's PAR 46 too. But the fit of the ring is different, almost like yours has a larger diameter opening, making the ring rest against the face of the lens instead of the four little standoffs molded into it, which is where mine touches.