forced landing-smoke in the cockpit

[Jerrytex]

I had a forced landing today due to smoke in the cockpit. Fortuanetly I was nearby the airport and landed safely after shutting down all the electrical. After removing the foam donuts that my butt cut out of the seat pads, I started troubleshooting. I found that one of the wires from the coils/alternator where it goes into the regulator was fried. Is there a way to test the Ducati regulator? Any ideas on what is going on? I heard a loud squealing in my headset when the smoke got real thick so I wonder if the problem is in the alternator part or in the regulator. Any help is appreciated. Now I am going to have a stiff drink.

Jerry

3025

3026

3027

[Dorsal]

Glad you made it down safely, looks like possibly a problem with the crimp? Do you have signs of extreme heat anywhere else?

[Jerrytex]

That's the weird part, it is only burnt on the end where it plugs in. I know that loose connections will do strange things, but this connection seems tight and clean. It would seem that if the Regulator all of a sudden switched to ground, it would have burned the entire wire not just an inch. After I landed, I turned everything on and it worked. Even ran the engine at idle and the wire didn't burn further. I am tempted to cut off the damaged part, solder a new end on and try again but it took 10 hours in phase one for this problem to surface. I don't want make it a habit of emergency landings!

[kmach]

Hi,
my experience with regulators is , if they burn out it is real noticeable. the back of them melt.

They don't do anything once burnt and you will not have any charging , but this is just my experience on one regulator.

From your pictures it looks like a loose connection, though, as you said it seemed tight. I think the same as you, repair the wire, ensure it is connected good , and retry.

[cap01]

jerry , do you have a crowbar installed in the system ?

[Jerrytex]

Not sure what a crow bar is? I am thinking about putting a switch between the "alternator" outputs and the regulator. That way I can turn off the output before the regulator in case I run into this again. I have a Hot box but it hooks in after the regulator. It's strange that there is no fuse or safeguard before the regulator. Maybe that's what the crow bar is? I am a pretty mechanical person and experience is pointing towards a bad connection but...damn, all that smoke was a little spooky especially for a new pilot like me. I would like to do everything possible to make sure I have whatever is wrong fixed before I continue on.

[cap01]

a crowbar is a overvoltage protection . a relay is installed in one of the coil leads of the alternator with a c/b controlling it . when the crowbar senses an overvoltage it will short the c/b to ground , causing the relay to open ,effectively turning off the alternator.
there are a lot of people that arent big fans of the vinyl automotive type terminals and splices . the pidg terminals and splilces are the only way to go ,along with an amp or other high quality crimper .

[Dave Holl]

It could have also been a high resistance in the crimp rather than a poor spade connection at the regulator.
Still a scary moment well handled!
Only other thing worth checking is have you done a total load analysis to ensure you are not drawing to much current normally?

[Dave S]

Jerry,

I concur with the other members commenting on a possible high resistance connection. Its not burned at the end of the connector and it is not burned further back up the wire.

I copied the 3rd image and magnified it as best I could - although the resolution isn't real good at that point - it appears that several strands are cut and turned out on the right edge of the burned spot - if that is not an illusion of the photo - the reduced current carrying capacity of the wire connection could account for a hot spot with everything else being normal.

It can happen where some strands are accidentally cut off or damaged in the stripping process; or, strands cracking off due to vibration; or a crimp that has loosened up, or some of the strands did not get captured within the crimp etc. - any one of which can reduce the current carrying capacity of the wire and cause a local hot spot - as it heats up resistance increases with greater heat developing and the vicious cycle proceeds till enough heat is developed to raise some smoke.

Sometimes a bum connection can be found before smoking the cabin by frequently checking all connections visually from time to time in the wring-out period.

If a person carefully picks apart the insulation and connection - I bet you will be able to detect a fault of some kind which may have caused your smoke problem.

Also goes to show you that keeping your head is what it takes to manage the emergency and avoid any unnecessary problems - just because a person has some smoke doesn't mean you can't handle the aircraft - you dealt with it well. :)

FYI - a friend of mine had an electrolytic condenser on an old certified airplane explode under the panel with a loud bang and much smoke on the takeoff run:eek: - a quick abort, shutdown and fairly expedient departure from the aircraft followed - although it was an impressive attention getter - the likelyhood of a real fire was pretty remote and never occurred - but you don't know that at the time.

I bet you will figure this one out soon.:)

Sincerely,

Dave S

[Monocock]

Glad it ended safely.

[Jerrytex]

Thanks everyone for the input. When this happened, all that was on was the radio and intercom so no big load. However, up until this day, I have done mostly touch and goes, stalls, etc. so the engine never ran for more than 10-15 minutes or so a full throttle. This day I was out messing around a river so I was at 5500 rpm for over 20-30 minutes so the alternator was putting out full power longer than any other time. I am kind of wondering if this gave the bad connection enough time to to get enough resistance to melt the insulation?

I think my game plan now is to re-do the connector. I think I am going to solder them to make sure the connection is good. This part of the electrical was done by another builder so I didn't have any input other than checking it to make sure it was right according to the manual.

The one thing I noticed now is it seems there should be a switch to turn the output from the alternator off. Kind of like a "crow bar" but something I could turn off in case this happens. I always thought that when the master is turned off, it shut all the electrical off but now I realize this is not the case since the alternator is still powering the regulator. After I saw the smoke, I shut the master off and reduced my rpm. The smoke subsided and most blew out during my 2000 fpm slip to the runway. The crazy thing is, in theory, turning the master off did not stop the alternator output so the wire should have continued to burn. I am wondering if reducing the throttle thus reducing the alternator output is what stopped the smoke? Has anyone put a switch in? If that is not a option, is the crow bar just a circuit breaker that I could buy at an auto parts store? I guess a panel mounted C/B would essentially be a switch. If this ever happened again, I could kill the master and pull the breaker. This might be a better option?

[Dorsal]

Shutting the master off should remove the load from the Alt, the load at the time of your event may have been charging the Batt. The only place I have seen a switch recommended is after the regulator to disconnect it from the system if it looses it's cookies (also what a crowbar can do). The Alt will not put out much current if there is no load on the Regulator.

[Jerrytex]

Interesting. That makes sense. I guess with the load turned off there really would be no need to put switches in.

[szicree]

A good crimp is preferred over solder. A soldered joint creates a stress riser at the place where the solder stops. With vibration the wire will break at this location.

[Dave Holl]

My advice for what its worth would be to crimp the connection but get a proper AMP crimper not a cheap crimper from the auto suppliers, if I was more local you could borrow mine?
Not sure on your wiring but standard practice would be to have a generator field switch this should kill the gen/alternator output when operated!

[War Eagle]

On my plane I installed a solid state switch panel.

It included a generator field switch for shutting down the output of the Rotax generator just in case you experienced generator related electrical problems in flight. It allows you to keep any needed electrical instruments (and electrical fuel pump) powered up because you don't have to shut down the master.

The generator field switch is connected to pin C on the voltage regulator. When this switch is shut off your generator output is killed.

There is a start up and shut down procedure that I follow to make sure the Generator field is turned off after landing and turned on before taxi and take off.

I concer with others that is very wise to have this feature wired into your electrical system.

[Av8r_Sed]

On my 582 installation I have a relay wired in to cut out the lighting coil input to the rectifier. This way I can run purely off of battery or switch in the rectifier circuit. Works fine in ground tests but I'm not flying yet and don't have any long runs on it.

-- Paul S

[Jerrytex]

After speaking to many people, including a tech a popular Rotax repair facility, I am pretty sure it was a bad connection. In fact the tech told me he has seen this same thing several times and actually solders the ends of the wires to the spade connector leaving the crimp to maintain the strain relief on the wire. I have made this repair and will see what the outcome is. I feel pretty sure that it's fixed. When I cut the old connection out, I was able to see the wires moving under the old crimp. I bought a good pair of ratchet crimpers and recrimped all the connections that I could get to. Thanks again for all the input.