Mooney Ovation2 alternator failure and Standby failure

[pk911]

Hi guys,
today I was on a trip home from southern France to Germany. IFR FL090, clouds from 2000 to 6000 and complete fog below for about 300nm.
Suddenly the generator lamp flashes and the display reports -8 ampere. My generator obviously stopped working. I pushed the standby generator, the indication changed to +6 then +3 amperes and everthing seemed good.

NOW, never touch a running system! I switched standby off and alternator switch off and alternator switch on again. Nothing happend. Then I returned back to the standby alternator again and NOTHING happend! It has stoped working too!

I communicated with ATC switched of nearly everything beside transponder and my handheld radio and shoot an approach 1 hour later in a fog free area and returned home VFR with remaining battery power. 2 good batteries!

Does anybody have an idea what caused two alternators to stop working?

Thanks, Peter

[LANCECASPER]

If your standby alternator is the B & C 20 amp alternator did you make sure that you only had essential items on? Your Mooney is a 2004, is it a DX or GX (G1000)?

Good job getting it down safely! Again the value of two good airworthy batteries! The second one isn't just back there for ballast. Having it made all of the difference and turned it into almost a non-event, even though I'm sure it didn't feel that way at the time.

[pk911]

My Mooney is a 2004 Ovation 2 DX.

Yes, the second battery is worth every penny! I used both on way home today. Two good batteries can save lives.

And, yes it's a 20 amp alternator and I didn't pull the fuse! But when switched on the first time the voltage was 30V and indicated load of 2 amps.

[ilovecornfields]

@Jerry 5TJ previously posted a graph here showing the propeller RPM vs. standby alternator output. On my plane if I turn off all the external lights, the standby alternator will run everything at 2300 (except pitot heat and TKS). If I want both of those on as well I have to increase the RPM or I show a discharge on the ammeter. Did you check if you blew a circuit breaker when you switched the standby alternator on and off?

[carusoam]

@Dale…

Similar discussion….  And PK911’s is actual….

Also inviting @M20Doc (report of dual alternator failure, in IMC….  Good to have two batteries!)

 

Yikes!

+1 for never touch a good working system! 
 

Great pirep PK911!

Thanks for sharing the details.

 

Lets see if there is a special procedure for starting the back-up alternator…. Like supply it power so it’s magnets work… when shutting everything down, it may have lost power too… not noticeable until after it wasn’t supplying its own power….

Best regards,

-a-

 

 

[MatthiasArnold]

Somewhat triggered by your report, I checked the behavior of my O2 GX's electrical system (generator & standby generator) on ground (first) and in the air (second) today.
It worked like described in the POH:

• Turning ALT switch off -> whole systems runs on the selected battery
• Engaging standby alternator and monitoring the AMPS on the MFD's engine page
  • With many loads engaged (G1000, pitot heat, A/P) I had to increase prop RPM to >2400 to balance the system load (no discharge on battery)
  • The way I read the POH further load can be shed (only systems on the emergency bus stay operative) once you pull the battery CB (did not try this in flight)
• Turning standby alternator off -> whole systems runs on the selected battery
• Turning ALT switch on -> whole systems runs on the main alternator

Don't know what went wrong (technically) in your case..
However, you handled & resolved it very good.

Best regards,
Matthias

[pk911]

19 hours ago, ilovecornfields said:

@Jerry 5TJ previously posted a graph here showing the propeller RPM vs. standby alternator output. On my plane if I turn off all the external lights, the standby alternator will run everything at 2300 (except pitot heat and TKS). If I want both of those on as well I have to increase the RPM or I show a discharge on the ammeter. Did you check if you blew a circuit breaker when you switched the standby alternator on and off?

Thanks for the details. Yes, I checked the circuit breakers, before first pushing Alternate Bus and after the 1st attempt to get the main alternator back. They were all in.

After not getting any alternator back to work I pulled some breakers to redurce battery load.

[pk911]

10 hours ago, carusoam said:

@Dale…

Similar discussion….  And PK911’s is actual….

Also inviting @M20Doc (report of dual alternator failure, in IMC….  Good to have two batteries!)

 

Yikes!

+1 for never touch a good working system! 
 

Great pirep PK911!

Thanks for sharing the details.

 

Lets see if there is a special procedure for starting the back-up alternator…. Like supply it power so it’s magnets work… when shutting everything down, it may have lost power too… not noticeable until after it wasn’t supplying its own power….

Best regards,

-a-

 

 

Thank you!
Please look at my answer to Jerry 5TJ. When trying to get the standby working again, all breakers are in.
ALL the 70 amp bus selector, too. Maybe this caused some trouble. But some members go with the standby and nearly full equipment.

I wonder if the main alternator switch must be OFF before the standby alternator can be put in work?
You hit the point with your question concerning a special procedure for starting the back-up alternator! POH says nothing special.

Best regards from Germany!
Peter

[pk911]

3 hours ago, MatthiasArnold said:

Somewhat triggered by your report, I checked the behavior of my O2 GX's electrical system (generator & standby generator) on ground (first) and in the air (second) today.
It worked like described in the POH:

• Turning ALT switch off -> whole systems runs on the selected battery
• Engaging standby alternator and monitoring the AMPS on the MFD's engine page
  • With many loads engaged (G1000, pitot heat, A/P) I had to increase prop RPM to >2400 to balance the system load (no discharge on battery)
  • The way I read the POH further load can be shed (only systems on the emergency bus stay operative) once you pull the battery CB (did not try this in flight)
• Turning standby alternator off -> whole systems runs on the selected battery
• Turning ALT switch on -> whole systems runs on the main alternator

Don't know what went wrong (technically) in your case..
However, you handled & resolved it very good.

Best regards,
Matthias

Thank you Matthias,

I use the standard POH ground procedure every time I depart IFR. In this case everyting worked well on the ground and even after the main alternator failure in the air.

Switching back and trying to bring the main alternator back to life without success and then back to standby alternator killed the system.

I have to find out why!

I plan to examine the airplane with my shop next Monday and keep you all informed.

Have a nice day!
Peter

[pk911]

Does anybody have a detailed cabeling layout of the Ovation 2 DX? I wonder how main alternator and standby alternator get voltage for delivering power. Maybe same source? Maybe without a dividing diode?

Thanks in advance!
Peter

[carusoam]

17 hours ago, pk911 said:

Does anybody have a detailed cabeling layout of the Ovation 2 DX? I wonder how main alternator and standby alternator get voltage for delivering power. Maybe same source? Maybe without a dividing diode?

Thanks in advance!
Peter

Somebody posted manuals for the Eagle today….

Otherwise, they are available through Mooney and the MSC network…

Often @M20Doc has this kind of knowledge… (dual alternator question…)

Best regards,

-a-

[pk911]

4 hours ago, carusoam said:

Somebody posted manuals for the Eagle today….

Otherwise, they are available through Mooney and the MSC network…

Often @M20Doc has this kind of knowledge… (dual alternator question…)

Best regards,

-a-

Thanks a lot!

Best regards and nice weekend!

[pk911]

On 1/18/2022 at 5:47 PM, pk911 said:

Hi guys,
today I was on a trip home from southern France to Germany. IFR FL090, clouds from 2000 to 6000 and complete fog below for about 300nm.
Suddenly the generator lamp flashes and the display reports -8 ampere. My generator obviously stopped working. I pushed the standby generator, the indication changed to +6 then +3 amperes and everthing seemed good.

NOW, never touch a running system! I switched standby off and alternator switch off and alternator switch on again. Nothing happend. Then I returned back to the standby alternator again and NOTHING happend! It has stoped working too!

I communicated with ATC switched of nearly everything beside transponder and my handheld radio and shoot an approach 1 hour later in a fog free area and returned home VFR with remaining battery power. 2 good batteries!

Does anybody have an idea what caused two alternators to stop working?

Thanks, Peter

Hello everybody,

now after nearly one month some updates to the alternators mystery:

Main alternator field voltage check on F1 positive but without current flow. Coals?
The main alternator was VERY difficult to remove. Two bolts above no problem, one left down a catastrophe. The Continental guys must have dwarf hands...
After removal and sending to a special repair shop they detected both coals were down to the metal and scratched the alternators axis. So the alternator has to be replaced.
The alternator had about 1200 hours without service. Continental recommends service every 500 h. It's worth doing so! See first 3 pics below!

The 20A standby alternator from B&C was very easy to remove. Just 4 screws. Shear Coupling was broken. A $42 item, that can decide over your life! This part should be replaced after a certain amount of time. Mine was still original and broke after 18 years! See pic 4. B&C is very cooperative! Top specialists and very quick delivery! Super perfect! Thank you TJ!

My shop will going to install the alternators in the upcoming days.

In future I will have a closer look at my subsystems and will prompt more actively my maintenance shop for such details. These can decide about your life.

Fly save and have fun
Peter

[Mufflerbearing]

Excellent information!  Thank you for the update.  Next annual, I'll take a look at my contacts.  Once they hit the armature, the alternator is done. 

One question I have is why did the secondary alternator die?  You said that the shear pin sheared.  This would tell me that there may have been a load on the alternator that the shear pin couldn't handle.  Was this the case?

[GeeBee]

Make sure your shop reads and heeds the Continental service bulletin on installation of the drive coupler cotter key. A failure to do it right can result in engine failure. As to the coupler, personally, I install a new one every 500 hours and I only buy new, not rebuilt. It is internal to your engine and too critical of a component to not get right.

https://www.aircraftspruce.com/catalog/pdf/avl-9610-sb.pdf

 

[pk911]

On 2/20/2022 at 11:56 PM, Mufflerbearing said:

Excellent information!  Thank you for the update.  Next annual, I'll take a look at my contacts.  Once they hit the armature, the alternator is done. 

One question I have is why did the secondary alternator die?  You said that the shear pin sheared.  This would tell me that there may have been a load on the alternator that the shear pin couldn't handle.  Was this the case?

The shear coupling was simply to old. These couplings become brittle (and fracture prematurely) given the effects of age and environment.

It hasn't anything to do with the load in my opinion. If load is to high you will see negative load that is taken from the batteries. That should be avoided. 
The shear coupling can handle the full draw from the alternator.

So I will mine replace every 10 years now. It was 17 years when broken.

[pk911]

On 2/21/2022 at 1:52 PM, GeeBee said:

Make sure your shop reads and heeds the Continental service bulletin on installation of the drive coupler cotter key. A failure to do it right can result in engine failure. As to the coupler, personally, I install a new one every 500 hours and I only buy new, not rebuilt. It is internal to your engine and too critical of a component to not get right.

https://www.aircraftspruce.com/catalog/pdf/avl-9610-sb.pdf

 

Thank you! Good advice, I will check availability of the coupler in Germany.

Mine has 17 years and 1200 hours now. This part was inspected last week and found satisfactory by the shop.

[GeeBee]

That is a lot of time on a coupler.

 

[carusoam]

Great details and pics pk!

Thanks for sharing all of the details!

Best regards,

-a-