Lamp for gear indicator window in floor

[Pooldoc]

I have a 1975 M20F and will be opening the belly (with an A&P) to inspect/service the switch that indicates the gear position. When I'm down there, I want to replace the bulb that illuminates the background of the gear indicator window in the floor. I want to be ready, so I need to know the bulb specs in order to not lose any flying time. Also, is there an LED substitute so I won't have to replace it again in the near future? 

Thanks again for your help,

Larry

[Vance Harral]

Larry, I doubt your bulb is actually burned out.  That light doesn't illuminate until/unless the down limit switch we've been discussing closes.  I suspect the same thing that's causing your gear warning problems is also causing the bulb;to not illuminate.

 

If you do need a new bulb, it's a GE 330, which is very common and inexpensive (like two bucks).  You can get them from Aircraft Spruce, Chief, etc, and maybe even your local auto parts store.  That's if your maintenance shop doesn't already stock them, which is likely given how common a bulb it is.

 

We've never replaced our gear indicator floor window bulb, and it has worked for over 10 years.  I'm sure there's some LED equivalent that would work, but I wouldn't bother with it.

[Vance Harral]

One other thing... unless you have the one-piece belly mod, the panel you remove to access the limit switch isn't the same one you remove to get to the gear indicator bulb.  Again, suggest you resolve any issues with the limit switch first before fooling with the bulb.

[carusoam]

In some Mooney's there are 24v bulbs lighting the 12V gear indicator...

This is a note to let you know what to look for if you find an odd 24v bulb where you expect a 12v one to be...

Best regards,

-a-

[DonMuncy]

+1 on the 24v bulb. My 231 had a 24 volt bulb which was so dim it was worthless. I, er my hangar elf, changed it to a 12v and it works fine. I think the listing of the 24v in a 12v system was simply an error.

[NotarPilot]

This should be the light you seek.  

 

http://www.aircraftspruce.com/catalog/elpages/marketled.php?clickkey=277416

 

They work from 5-28V DC or AC and are bi polar.  They are not PMA'd but may fall under the FAA legal interpretation of a standard part.  Apparently there is an FAA letter of interpretation from 1997 that covers this definition but I can't seem to find it.  Anyone know where it might be found?

[NotarPilot]

I think I found some guidance regarding standard parts.  The link to the entire document is provided below.

 

A part manufactured in complete compliance with an established industry or U.S. Government specification which includes design, manufacturing, test and acceptance criteria, and uniform identification requirements; or for a type of part which the Administrator has found demonstrates conformity based solely on meeting performance criteria, is in complete compliance with an established industry or U.S. Government specification which contains performance criteria, test and acceptance criteria, and uniform identification requirements. The specification must include all information necessary to produce and conform the part and be published so that any party may manufacture the part. Examples include, but are not limited to, National Aerospace Standard (NAS), Army-Navy Aeronautical Standard (AN), Society of Automotive Engineers (SAE), SAE Sematec, Joint Electron Device Engineering Council, Joint Electron Tube Engineering Council, and American National Standards Institute (ANSI).

 

https://www.faa.gov/aircraft/safety/programs/sups/standard_parts/media/standard_parts.pdf

[Andy95W]

I think I found some guidance regarding standard parts.  The link to the entire document is provided below.

 

A part manufactured in complete compliance with an established industry or U.S. Government specification which includes design, manufacturing, test and acceptance criteria, and uniform identification requirements; or for a type of part which the Administrator has found demonstrates conformity based solely on meeting performance criteria, is in complete compliance with an established industry or U.S. Government specification which contains performance criteria, test and acceptance criteria, and uniform identification requirements. The specification must include all information necessary to produce and conform the part and be published so that any party may manufacture the part. Examples include, but are not limited to, National Aerospace Standard (NAS), Army-Navy Aeronautical Standard (AN), Society of Automotive Engineers (SAE), SAE Sematec, Joint Electron Device Engineering Council, Joint Electron Tube Engineering Council, and American National Standards Institute (ANSI).

 

https://www.faa.gov/aircraft/safety/programs/sups/standard_parts/media/standard_parts.pdf

Looks great, but I think there will always be IA's who will say no. From the FAA document:

"substituting standard parts would require a demonstration of acceptability in accordance with part 43."

If you jump through the hoops and "show acceptability", you may as well have just PMA'ed the part. Probably better to not tell anyone, or find an IA who is either pretty casual or doesn't dig too deep.

[Guest]

This should be the light you seek.  

 

http://www.aircraftspruce.com/catalog/elpages/marketled.php?clickkey=277416

 

They work from 5-28V DC or AC and are bi polar.  They are not PMA'd but may fall under the FAA legal interpretation of a standard part.  Apparently there is an FAA letter of interpretation from 1997 that covers this definition but I can't seem to find it.  Anyone know where it might be found?

I'm not sure we should be discussing "bi" "polar" in this thread, unless of course you mean the metal illness, not the other "bi"

Clarence