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TB20 landing gear indicator lamps

During the Landing phase- call out: three Green! No only two!
Which wheel? nose wheel. Stress, action. All the procedure carefully done. Happy landing!
The reason was the cable shoe at the bulb. Badly crimped.
Corrosion is a unpleasant appearance and a permanent companion.
In order to be on the safe site I soldered all of the 3 cable shoes of the green bulbs.

Berlin, Germany

Ah yes another Socata subassembly made in this advanced DGAC 145 approved factory

deep in the Pyrenees And this is an exclusive photo of the company owner, on the date (roughly 2001) Socata decided to stop piston production

Anyway

Crimping
Crimping

If you are going to crimp, make sure the cable is properly supported. That should be done anyway, but crimped joints tolerate crappy wiring for a few more years than soldered joints

I have wondered about those lamps. If one fails, you have a really big problem! They should really be LEDs, but if you just put in normal 24V LEDs you lose the “night” mode; they emit almost the same light. The avionics backlight dimming system is tweaked for normal bulbs and just putting in 24V LEDs like this

(those are not the exact style) they are too bright on the Night mode. I have tried it. However, the gear selector lamp assembly has its own Night mode switch, so tweaking that part would not affect the other instruments.

It’s a really stupid design, widely used in GA. You are just one lamp failure away from needing to re-upholster the pilot seat.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

It’s a really stupid design, widely used in GA. You are just one lamp failure away from needing to re-upholster the pilot seat.

The PA28R and PA32R have a clever design where you can replace the lamps from the front of the panel. Action #2 if you don’t get three greens is to swap the lamp which is not lit with one of the other ones. This would not have helped Thomas, of course.

(Action #1 is to check if the instrument panel lights are on and turn them off if they are. The instrument panel light switch also dims the landing gear lights enough that they are difficult to see in daylight.)

ESKC (Uppsala/Sundbro), Sweden

I think the Socata ones are front-removable, though I am not sure. The way it is supposed to work is that the lens comes off (with a special tool) and then you pull the lamp out (with another tool which is basically a rubber tube).

The way the heatshrink sleeving was applied

would totally prevent the lampholder being extracted.

Has anyone else had to deal with these lamps?

Administrator
Shoreham EGKA, United Kingdom

It wasn’t possible to pull out the lamp. The heat shrink doesn’t go through the hole.
I had to cut and then pulled it out. But it was very easy to disassemble this Unit.

Berlin, Germany

It looks like this is a G1 TB20 on which various panel mods were done. As a result you ended up with a simple rectangular plate held by four screws, which gives you good access to that area.

The GTs don’t have this removable plate so the only way is from behind, and extract the whole module with the gear lamps and switch, which is very difficult.

Administrator
Shoreham EGKA, United Kingdom

Isn’t there a recommendation against soldering in airplanes? Something to do with vibrations bending the cable at the solder, leading to quicker fatigue vs crimping.

Switzerland

Not a general recommendation as such AFAICS (I know specific IMs or MMs call for crimping and specific tools) but see the two links above.

Administrator
Shoreham EGKA, United Kingdom

Regarding to cable connection.Yes, vibration. A soldered free running cable at the end of solder joint could be problem.
But all the connection must be fixed by cable tie. By the way we have a lot of solder Connections in our planes.
Sometimes it is easier to find out a cable break than a bad crimp-connection.

Berlin, Germany

Airborne_Again wrote:

The PA28R and PA32R have a clever design where you can replace the lamps from the front of the panel. Action #2 if you don’t get three greens is to swap the lamp which is not lit with one of the other ones. This would not have helped Thomas, of course.

Adding a little lamp test button would be much more clever than forcing pilots to switch lamps while flying a busy traffic pattern, IMHO. The TB20 already has an annunciater test button but apparently it isn’t connected to the gear indicator lamps. (Good to know. I was under the impression that it is but only ever have pressed it while on the ground.)

EDQH, Germany
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