8KCAB Fitting LED tail light

Big Ed

Big Ed

N50247 - '79 Super D
Joined
Jul 20, 2020
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Tampa, FL
Finally bit the bullet and ordered a WAT Orion LED tail light to replace my ancient Grimes. The model I ordered is listed by WAT as direct replacement for the Grimes model I had, and the Decathlon is on the AML, so I assumed it would be more or less "drop in". Not so much.

The mounting ring on the trailing edge of the rudder is too small. Looks like I will have to remove a substantial amount of material to widen the hole enough to fit the new light post. Enough that my IA is concerned about weakening the structure of that part of the rudder.

Has anyone else done this install on a Bellanca-era aircraft?

Photos to follow when I go to the hangar later today.
 
I put one on my 1973 Bellanca Viking and on a 1974 (1975) Citabra... the metal cup is really pretty thick.
Just go slow with a sharp file and you'll be fine. Don't forget to seal the light/mount with a dab of silicone.

Chris
 
Had the same problem trying to fit a Uavionix TailBeacon. The hole in the rudder nav light ring was about 0.050" too small.

After making almost no progress with a half-round file, I used an air-powered die grinder with a 1" expanding rubber arbor with a slide-on abrasive cylinder. It removed material fairly well but the cutter rapidly heated the metal. After each 20 seconds of cutting, I'd apply a wet cloth to cool the ring before it got hot enough to melt the fabric. Afterwards , I dangled a magnet on a wire in the bottom of the rudder to fish out some of the chips. It was a noisy, tedious, and frustrating project but got the job done ok.
 
Chatted with Chad about it yesterday. They stopped installing tail Nav lights when they went to the wingtip lights that have white and colored Nav lights. The factory ring/cup is indeed smaller than industry standard. They found that out when they tried to install a few of the TailBeacons.

He said the people he talked to all just removed material from the ring, as discussed here. However the factory did not tell them to do that, and takes no position on it.

I'm in a bit of a quandary because my IA is not comfortable allowing me to remove material from the ring, due to its structural role. Telling him a lot of people on the internet did it is not going to persuade him.

We will look closer at how much material needs to be removed and take some measurements. Maybe that will make him more comfortable with it.

He thinks there are LED nav lights that will fit. I can't find any others. Only thing I found would be the AeroLED Polaris drop in bulb. Anyone know another alternative?

Also, since the STC AML lists 8KCAB, shouldn't there be instructions somewhere documenting installation procedure?
 
We used a sharp hole saw. Took two minutes. Put lots of masking tape in there, let it cool between ten second pokes, use a drop of cutting fluid, and above all don't go too far or you will cut fabric. Battery powered drill is enough.

Typed this yesterday - no idea why it didn't get posted. Also no idea why your IA thinks that trailing edge is highly stressed - note how thick that stamping is with respect to those thin steel ribs. Sometimes the bottom rib just rusts away unbeknownst, and Decathlons do not fall out of the sky when it fails.
 
Bob Turner said:
We used a sharp hole saw. Took two minutes. Put lots of masking tape in there, let it cool between ten second pokes, use a drop of cutting fluid, and above all don't go too far or you will cut fabric. Battery powered drill is enough.

Typed this yesterday - no idea why it didn't get posted. Also no idea why your IA thinks that trailing edge is highly stressed - note how thick that stamping is with respect to those thin steel ribs. Sometimes the bottom rib just rusts away unbeknownst, and Decathlons do not fall out of the sky when it fails.
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I am depending on him to sign off on a massive 337 rebuilding the aircraft from the ground up, so I am not in a position to argue over small points.

Fortunately the cover is off, so we can get a real good look at it. Will post pics tonight.
 
You could always make a new one and weld it in - that’s what we did with J3 rudders. They may make stampings ready to weld.
 
Bob Turner said:
You could always make a new one and weld it in - that’s what we did with J3 rudders. They may make stampings ready to weld.
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Already powder coated and ready to start laying fabric, so that's would be a step backwards. I think my fallback option would be the drop in LED bulb replacement, which is now PMA.
 
Ed,

Finish the airplane with the old light fixture in there and let someone else ream out the ring for whatever you want to put in there. It'll be a simpler log entry and most other people won't mind the process to get it in there. IMHO
 
Not to be a wise guy, weather you grind it, cut it or weld in a new section it still breaks or damages the powder coating and will leave exposed metal that needs sealed if your worried about the coating correct. Now is the best time to do this modification and then re coat. Also probably least expensive and easiest to repairing if something goes wrong.

my vote is installing now and then after all is done there’s no “I wish I’d have done that”

ps this is looking goooood!
 
I've done several with a bur bit. As an IA, I understand yours, and his positions.

Another option is Aveo Engineering. Their tech data says the stem is .906.

I do not like their epoxy embedded lights. They craze in just a few years. The manufacture says that its normal, and that one can polish the lights every couple weeks. but they will eventually craze, crack and turn yellow. Also, I have replaced 3 sets of these lights that were less than 8 yrs old because the internal circuit would short, get extremely hot, and make smoke before the breaker would pop. All on cubs. Not a good feeling on a fabric covered plane.

That said, they seem to no longer offer that same tail light, and this new (to me) light appears to not be of the epoxy embedded style. I would be willing to try it.

LEDs require cooling, and I believe (know) that the epoxy embedded lights did not allow sufficient cooling for the circuit.
 
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