total electrical failure

[mooniac15u]

Isn't that circuit protected by a circuit breaker?

[rpcc]

Looks to be worth some professional investigation - it bought the farm to save something much more expensive from the same fate.

[carusoam]

If Piloto is right, there is another melted piece nearby...

The shunt used to be a straight piece between the two bolts.  It softened and deformed before melting in half... it had a small amount of resistance to it, so it could provide a voltage drop with the current.  The current must have been huge to get that hot.

look to see if hot metal drips landed on anything below the shunt.

Something drained more than 60amps through the shunt and off to ground somewhere... this is the first important thing to find.

PP ideas only,

Best regards,

-a-

[mooneyflyfast]

On 3/28/2017 at 1:39 AM, carusoam said:

If Piloto is right, there is another melted piece nearby...

The shunt used to be a straight piece between the two bolts.  It softened and deformed before melting in half... it had a small amount of resistance to it, so it could provide a voltage drop with the current.  The current must have been huge to get that hot.

look to see if hot metal drips landed on anything below the shunt.

Something drained more than 60amps through the shunt and off to ground somewhere... this is the first important thing to find.

PP ideas only,

Best regards,

-a-

 

On 3/28/2017 at 1:39 AM, carusoam said:

If Piloto is right, there is another melted piece nearby...

The shunt used to be a straight piece between the two bolts.  It softened and deformed before melting 

-a-

Actually the new one is arched like that too--part of the design.

[mooneyflyfast]

Update. Replaced the shunt and found that the ammeter was damaged beyond repair. Replaced with an Electronics International digital unit--has to be calibrated to the shunt.. Have flown it 4 hours and all is well. We never found any cause for the failed shunt. 

[mooneyflyfast]

Update. After 15 or 20 hours the same thing happened again. Fortunately I was on approach into KHRL where there is a great radio shop (Gulf Avionics- Don Wiles). Don found two buried wires downstream of the shunt -a no 10 and a number 6 that had chaffed through he insullation exposing the conductors. Everyone knew the shunt was a sympton, not the cause. It took Don to find the underlying problem. Hopefully this will not happen again. 

[Brandontwalker]

Glad you now have a proper fix in place.  I had an electrical failure two years ago.  Mine was in VMC, but on a moonless night.  As a result, I now restrict my night flying to around 100nm, or less, from home.  May be silly, but flying with just an ipad for navigation and the flashlight on an iPhone to illuminate the panel is a real gut check.  I also had to figure out how to activate the runway lights.  I was sure glad to have some old tech on board at the time so I could select the frequency on the manual dials of the KX170b.  I then moved the landing gear selector to the down position.  My thought was that it would put load on the system and prevent the failed regulator from frying everything.  I then had my wife reset the buss breaker.  Immediately que lights for the runway, wait for green on the gear and then pull the buss breaker.  It was a no flap, no landing light landing and probably one of my best.  If I was unable to que the lights, plan B was to call approach control at the neighboring Class C via cell phone and make an emergency landing where I knew I had plenty of lights and 10,000 ft of runway.  Fortunately, I was able to save myself a mound of paperwork.

Edited July 18, 2017 by Brandontwalker

[LANCECASPER]

4 hours ago, Brandontwalker said:

. . . If I was unable to que the lights, plan B was to call approach control at the neighboring Class C via cell phone and make an emergency landing where I knew I had plenty of lights and 10,000 ft of runway.  Fortunately, I was able to save myself a mound of paperwork.

Declaring an emergency usually equals no paperwork and gets you top priority and handling. Not declaring an emergency and then having an incident or accident is what usually ends up in a mound of paperwork.

[carusoam]

Great photos.

The melted missing aluminum is impressive!

Glad you found it.  Thanks for the follow-up.

Best regards,

-a-

[RLCarter]

@mooneyflyfast sounds like you fly into KHRL frequently, I live in Harlingen and hangar at Weslaco so if ever need anything down here I'd be glad to help if I can. Don replaced the amp in my audio panel a few months back, have known him since the late 70's and is the go to guy for Radio/Avionics work. PM me next time your going to be down here and I'll buy lunch.

[Mooneymite]

18 hours ago, LANCECASPER said:

Declaring an emergency usually equals no paperwork....

Sometimes it percipitates an investigation by your local Feds....

 

[LANCECASPER]

13 minutes ago, Mooneymite said:

Sometimes it percipitates an investigation by your local Feds....

Thanks for sharing that. I hope this is a rare isolated case where an over-zealous FSDO guy had nothing better to do. Sometimes people feel the need to justify their existence. Thankfully the case closed without any other problems.

 

[mooneyflyfast]

3 hours ago, RLCarter said:

@mooneyflyfast sounds like you fly into KHRL frequently, I live in Harlingen and hangar at Weslaco so if ever need anything down here I'd be glad to help if I can. Don replaced the amp in my audio panel a few months back, have known him since the late 70's and is the go to guy for Radio/Avionics work. PM me next time your going to be down here and I'll buy lunch.

Thanks R.L.  I'll do that.. we have a weekend place and a boat at Arroyo city so we try to get down there every couple of weeks. Keep an airport car at Gulf Avation.. I go back a long way with Don too.. He is a great guy.