It Couldn't Happen---But It Did

[donkaye]

I drove to the airport to update my databases today, G500 TXi, GTN 750Xi, GTN650Xi.  I setup Database Concierge for database transfer to the GTN 750Xi and started the transfer in the usual manner. About 30 seconds into the transfer it happened.

A lot of thought went into my panel design.  I included everything available at the time to make flying as safe and enjoyable as possible.  This included both passive and active traffic, dual certified GPSs, Stormscope , the best engine monitor available in my opinion, dual ADSB, along with XM weather and audio.  Later I added the latest in GA Autopilots, an AOA and the LHS callout system.  The plane came with dual batteries and dual alternators.  I stayed with one manufacturer to simplify interface issues as much as practical.  So the airplane is all electric.  Gone are the dual vacuum pumps with all their failure modes.  What could possibly go wrong with such a setup?

Thirty seconds into the database update, with a small flash and a small spark hitting the floor, total and complete electrical failure.  Everything went out.  Multiple GPSs, multiple comms, dual batteries, dual alternators, stormscope, dual ADSB --irrelevant.  Nothing.

To save battery during updates I disable the engine monitor and G5.  Had I had the G5 on, that would have gone to battery.  In fact I did turn on the G5 after the fact and it did come on in battery mode, so had I been IMC, while I would have lost all comms, I still could have remained right side up,  The AP in LVL mode wouldn't have worked.

In thinking about what I have available as other backups, the Aera 760 and iPad could be used for Navigation and obtaining comm frequencies for use with my handheld receiver.  The GDL 52 would give me ADSB traffic, weather and SXM weather.  I'd have no ADSB Out.  My avionics tech talked me out of a switch to plug in the handheld in a comm antenna, but now I'm going to insist he put one in.

I was comfortably on the ground in the hangar when this happened.  It probably would have happened on the next flight just as I took off.  Not a pleasant thought.  

The idea that I have a single point of failure that can cause all this havoc is troubling.  As of now, I don't know the cause.  Trying to get someone over here to track down the issue is my next problem.

 

[hubcap]

Very sobering. Thankfully it happened when it did.

[N201MKTurbo]

I have a friend who was flying freight dogs at night for a while. One dark and stormy night he decided to see if he could fly the whole flight with just an IPad and stratus. He turned down all the panel lights so all he could see was the IPad. 
 

He said it was real easy. Easier than the built in stuff.

[N201MKTurbo]

What ever happened to partial panel IFR? We used to practice flying with just an altimeter, airspeed, turn coordinator, whiskey compass and one VOR needle. I’m pretty good at it.

[Hank]

3 hours ago, N201MKTurbo said:

What ever happened to partial panel IFR? We used to practice flying with just an altimeter, airspeed, turn coordinator, whiskey compass and one VOR needle. I’m pretty good at it.

He ain't got them no more, leastways not without electricity. The batteries are s'posed to make 'em work, but looks like not this time.

Glad it happened on the ground, Don. What took out my electrical system in flight was a component [unidentifiable due to complete annihilation] on the circuit board that's part of the cockpit lighting dimmer circuit. 

Good luck with the repairs! Hope it's fairly straightforward. 

[Ragsf15e]

One thing I’ve thought about if I ever get to redesign my avionics architecture is putting in a switch to directly connect a radio and possibly the audio panel to the battery.  So something similar to a “clearance” or “emer” switch found on some other models (Pa-46T has an “emer”).  In its normal mode, the switch would leave everything on avionics buss power, but in emer, it would give you 1 radio.

I’m confident in my multiple battery powered ADIs staying on, and I can navigate and probably even fly a poor man’s approach with an ipad or phone, but it would be so much better to be able to talk to ATC.  I realize you could have a spectacular failure that even negates this, but then you should have a handheld and be ready to be 90% comm out.

[ArtVandelay]

I would have the second battery/alternator isolated, and each would have its own avionics bus, com2/nav2 would be on the second bus, and you could have emergency cross connect switch.

[jlunseth]

Man, that hurts. Sorry Don. I have been going more and more electric/electronic as well, but I have reached the point where I think I should stop for just the reason you discovered. My aircraft has a single point of failure in the alternator, and I have experienced the joy of having it fail in the air (not in IMC) and having to fly with the Master off. Absolutely everything in the panel is dark, including the engine monitor, except maybe analog altitude and airspeed. I have been thinking about removing the vacuum pump, which currently just drives a backup AI. I would add a backup alternator on the accessory pad in place of the vacuum pump. But the problem that would leave me with is exactly what you experienced, a failure of the electrical system would take out everything. I have lost a GPS that burned out one day when the second comm had been removed temporarily for repairs. Got to fly back into my Class D home airport during an air show and land with light signals with everyone on the ground and watching. I have lost the alternator as I said. There is a message in there somewhere. When we put all those electronics together one by one we are still building a system and the system itself may be the problem. I think I just decided to stick with the vacuum pump backup AI and be happy I have it.

[mike_elliott]

oh, that sux Don. Your panel was well thought out from safety/redundancy point and your dual buss platform an excellent choice to bring up to the era of modern avionics and their inherent reliability over the fine swiss watch steam gauge system. As you correctly say, glad it happened on the ground and more importantly, not in the air and potentially an in flight fire. Let us know what caused that "spark" and of course Trey and Joe Steward would most definitely want to be kept in the loop. Nothing that money cant cure at this point. and there is a letter that doesnt have to be written. 

[Ned Gravel]

Don:  

Ouch!  I know where you are coming from.  When I was doing my IFR in my E-model, I lost everything during a practice approach into one of our local dromes.  I was still mostly vacuum driven in those days but, this happened more than once and the faults were turned out to be, in order, a faulty regulator, a faulty generator and some not-very-good wiring.

Today, I have an alternator, a Zeftronics regulator, a Concorde battery, a Skytec starter and a correctly installed avionics bus (that was not there when I bought the aircraft).  The panel is also much different, but this summer, going to and from Oshkosh, I lost everything again.  The first time was on departure from Wayne County and I declared an emergency with Ute holding the breaker in and landed at Ypsilanti.  The second time was during the run up on the way home from Saginaw, MI.  Flew home VFR because engaging pitot head was causing the generator breaker to trip.  It turned out to be the main generator breaker (50 amps) on the right side of the panel.  It was giving up the ghost and took quite some time to troubleshoot.

Good luck on figuring out the cause.  Once that is done, I have every confidence that the Don Kaye logic machine will easily determine an appropriate solution. 

 

 

[toto]

25 minutes ago, jlunseth said:

Absolutely everything in the panel is dark, including the engine monitor, except maybe analog altitude and airspeed. I have been thinking about removing the vacuum pump, which currently just drives a backup AI. I would add a backup alternator on the accessory pad in place of the vacuum pump. But the problem that would leave me with is exactly what you experienced, a failure of the electrical system would take out everything.

Yep. Attitude information is everything when a glass panel goes dark. We need either a spinning gyro or a battery-powered AHRS.

Don has been an advocate of the Aera 760 as a portable backup, and one of the key features of the Aera 760 is a built-in AHRS with an attitude display. 

Too many of us are flying around with an iPad “backup” that will have no attitude information in the event of a power loss, and I hope that we appreciate how significant that is. 

In my flying career, I have had two alternator failures in IMC and a third at night, and having a vacuum attitude indicator was crucial to a successful outcome. Today, IMC for me means having an attitude indicator that isn’t dependent on the ship’s electrical power (whether that’s a separate battery or a vacuum). 

A takeaway from this thread is that despite careful planning, anything can fail, and may fail in unexpected ways at inopportune times. We have to make sure that we enter IMC with an independent attitude source (vacuum or battery). An Aera 760 (1.5 AMU) or a Dynon D3 Pocket Panel (0.8 AMU) is pretty cheap insurance when the lights go out. 

[Marauder]

What ever happened to partial panel IFR? We used to practice flying with just an altimeter, airspeed, turn coordinator, whiskey compass and one VOR needle. I’m pretty good at it.

It all went away when these things started showing up in panels. The issue for us single alternator, single battery guys is the loss of the alternator means you have a small finite amount of time before the Nav/Com driving the battery powered backup goes offline.




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[carusoam]

It is well known…. 
 

The big guy upstairs only gives us challenges that he knows… we can handle….  

The measurement of our skill sets is really easy…. Don gets all the huge WTF kind of challenges….  
 

By  comparison… I get a fuel drip from the sump valve kind of challenges….   

 

To have a spark hit the floor, knocking out all of the power…

Has got to be really somewhat unique…

Like a piece of metal falling onto the shunt… sparks fly, metal melts, fuses blow…

 

We have seen this before around here.

+1 for a decent portable nav com with spare batteries…

+1 for a battery powered back-up AI… panel mounted, always on…

 

Good luck with the next steps Don!

 

Who gets the hardest electrical challenges…

1) Skilled CFII….

2) Long term owner of a Long Body…

3) Huge fan of fully integrated electronics…

4) Electrical Engineer….

 

Best regards,

-a-

[hais]

1. What is the emergency bus? I thought that was an electrically independent second power bus. Is it only only connecting the 2nd alternator to the same bus?

2. The G5 would have saved the day. More concerning is the spark starting a fire. Did the breakers performed flawlessly? 

[carusoam]

1 hour ago, hais said:

1. What is the emergency bus? I thought that was an electrically independent second power bus. Is it only only connecting the 2nd alternator to the same bus?

2. The G5 would have saved the day. More concerning is the spark starting a fire. Did the breakers performed flawlessly? 

Busses available to the long body…

1) Main bus

2) Avionics bus

3) Emergency bus

In a normal expected emergency situation all the busses may get cut… for electric power reduction…. Common for a dead alternator…

Leaving the Emergency power Bus on, to power the critical items for flight…

Without an E-bus… we get to turn stuff off individually….  Which can get challenging in modern planes with an out of direct sight avionics shelf….

 

What doesn’t get covered… abnormal failure that may cause unexpected results…

An example of an abnormal failure for two bus applications…. Is the failure of the avionics relay…. In the open position…

In Europe (non-FAA)…. A third relay is used for emergency power to the avionics bus… (really smart for flight in IMC)

 

Expect… Each bus gets its own CB…. In case the bus gets grounded….

If Don’s Bus CBs didn’t open…  there isn’t much back there that is upstream of the busses….  

1) Main supply wires…

2) Amp meter…

3) Inline Fuses….

4) Shunt that is somewhat protected from stuff falling on it… but open to attack by something that really wants to get in there….

PP thoughts only… not an electronics guru… checking the details of the electrical drawings were not done for this post…  fuzzy PP memories only…

Best regards,

-a-

 

[hais]

3 hours ago, carusoam said:

Busses available to the long body…

1) Main bus

2) Avionics bus

3) Emergency bus

In a normal expected emergency situation all the busses may get cut… for electric power reduction…. Common for a dead alternator…

Leaving the Emergency power Bus on, to power the critical items for flight…

Without an E-bus… we get to turn stuff off individually….  Which can get challenging in modern planes with an out of direct sight avionics shelf….

 

What doesn’t get covered… abnormal failure that may cause unexpected results…

An example of an abnormal failure for two bus applications…. Is the failure of the avionics relay…. In the open position…

In Europe (non-FAA)…. A third relay is used for emergency power to the avionics bus… (really smart for flight in IMC)

 

Expect… Each bus gets its own CB…. In case the bus gets grounded….

If Don’s Bus CBs didn’t open…  there isn’t much back there that is upstream of the busses….  

1) Main supply wires…

2) Amp meter…

3) Inline Fuses….

4) Shunt that is somewhat protected from stuff falling on it… but open to attack by something that really wants to get in there….

PP thoughts only… not an electronics guru… checking the details of the electrical drawings were not done for this post…  fuzzy PP memories only…

Best regards,

-a-

 

Thanks. So only one avionics bus, unlike the SR22 system 

[carusoam]

Note for Hais…

Unfortunately, I’m unfamiliar with what the SR22 has….

 

Best regards,

-a-

[hais]

6 minutes ago, carusoam said:

Note for Hais…

Unfortunately, I’m unfamiliar with what the SR22 has….

 

Best regards,

-a-

Don't worry, I'm not considering defecting 

Here's a simplified diagram - the NAVs and COMs are on different buses 

SR22T G5 Electrical Diagram.pdf

[carusoam]

Way cool Hais!

I need to work on my bus terminology…

Emergency bus…. Has been changed to Essential Bus…

To better represent what it does…. 
 

Both can be called the E-bus this way….
 

 

Best regards,

-a-

[Scottknoll]

A few days ago, I was studying the electrical schematic to try to understand this. The AFM leaves a lot to be desired as to how this works.

Someone please correct me if this is incorrect. My understanding in our Ovation is that under normal conditions the entire electrical system is powered by the main alternator or the selected battery (1 or 2 via the Batt Switch through the 70A Batt CB), usually both together. The 20A Bat SBY CB has no connection to the Battery in normal ops.

In the case of a main alternator failure, activating the EMERG BUS switch enables the SBY Alt and connects the battery to the 20A SBY BUS BAT CB. Nothing is de-powered at this point.

In this state, the battery has two connections to the bus. One via the 70A main CB, and one to the limited set of items via the 20A CB. There is a diode between the two buses.

The 70A Battery CB and main alternator can power the entire system, but the 20A SBY BUS BAT CB and Standby Alternator can only send power to the items on the EMERG BUS. The diode separates the two.

The B&C flight manual supplement then has you pull the 70A Bat CB (Load Shedding). At this point power can only flow to the EMERG bus items via the 20A SBY BUS BAT CB and the SBY ALT.

Additionally, the SBY alternator sends power via the Emerg Alt Bus CB to the Pitot Heat, Ice Light, and TKS, if equipped.

So it’s normally a single bus system, but can be split and power just one side of the “dual” bus system in emergency mode.

This is just my understanding of the electrical schematic and may be flawed, possibly severely. I do enjoy trying to learn these systems though

[carusoam]

Let’s invite somebody that knows more details…. About two alternator systems in Mooneys… @M20Doc (electrical question, two batteries, two alternators, three busses… How does the system know….  )

 

 

The output of the two alternators is usually handled by a dual alternator VR…

One can be set lower so it provides most of the charge…. Until it can’t keep up… or gets turned off…

 

PP thoughts only…

Best regards,

-a-

[Pinecone]

Hmm, maybe to start thinking about two separate busses for avionics.  Put a nav/com and AI on each.  Maybe even a battery back up on one (lower load one).  Extra avionics master relays as mentioned.  I wonder if there is a way to set up dual alternators to keep one able to power a single bus if something takes out the main bus.  Just thinking out loud.

And the port to connect a handheld to one of the Com antennas is a very good thing.

FYI, Stratus and Sentry have AHRS as well.  As well as the ADSB In.  So that gives you a backup versus the Aera 760.

[toto]

1 hour ago, Pinecone said:

FYI, Stratus and Sentry have AHRS as well.  As well as the ADSB In.  So that gives you a backup versus the Aera 760.

Indeed. There are several different options for external AHRS sources. But Aera 760 and the Dynon D3 are two examples of display devices with built-in AHRS. 

No knock on the external sources, but using this approach means ensuring two charged batteries and two devices in your flight bag that are properly set up and working during preflight. 

[N231BN]

Mooney could have designed their electrical system like a mulit-engine turboprop or jet and have dual independent buses but it would have added a lot of unnecessary cost and weight.

One item that should be added to all of these airplanes is an emergency avionics master. It is just a simple 30a CB switch that bypasses the avionics relay. I understand that the relays are designed to be fail-safe but there are multiple possible failure modes.

Another option: I installed new avionics in one of the DC-3s I'm involved in, one of the requirements for installing Garmin GTNs in a large aircraft is that they be powered by independent buses. While adding the second bus I added a selector switch to allow it to be powered by the hot battery bus.

One of the failure modes with a hydromatic feathering propeller is the feathering pump relay can weld closed. The only solution if that happens in-flight is to shut off all the power to the airplane. If that would happen in this airplane, I can bring back the audio panel, number two GTN, and transponder. The co-pilot's gyros are vacuum powered so you have a complete functioning panel with both generators and the battery disconnected.

If you did split the avionics bus in a Mooney it wouldn't be too difficult to add a properly sized and fused wire back to the battery to give it an "emergency power" option.

[Pinecone]

2 hours ago, toto said:

Indeed. There are several different options for external AHRS sources. But Aera 760 and the Dynon D3 are two examples of display devices with built-in AHRS. 

No knock on the external sources, but using this approach means ensuring two charged batteries and two devices in your flight bag that are properly set up and working during preflight. 

True.  But since I already have one, maybe two, iPads, it is really one more device.   The Stratus 3 can be hooked up to power via USB cable, then will revert to batteries of there is a loss of power.

The question starts to be, how far down the rabbit hole do you want to go?

How about this, a separate line from battery to an essential avionics bus, separate to the line to the Master.  That way if the line that feeds everything goes poof, you have a back up for an AI, Nav, and Com.