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alternator failure modes

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Wed Jul 05, 2006 3:30 pm Post subject: alternator failure modes

I have had several people write to me to tell me that they have never  

seen an alternator turn into a grenade. Neither have I. I was just  

listing that is a *possible* scenario, as in, "I suppose this might  

happen." I think it unlikely but I do think that things like broken  

brackets, having the alternator seize, and who knows what happens if  

both happen at once.



The key point is that there are mechanical failure modes, not just  

electrical failure modes. When the alternator stops producing power  

it is not just an electrical problem. If one were to fly for a longer  

period of time something bad could happen that would make the  

situation much worse.



I still hold that it is a good idea to land and check things out even  

if you have a backup alternator or lots of battery capacity.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

brinker(at)cox-internet.c
Guest

Posted: Wed Jul 05, 2006 3:50 pm Post subject: alternator failure modes

Yep it's not like we can coast to the side of the road when we have a 

major problem. Better safe than sorry. And hey we might even make a friend 

at our non scheduled destination. If there's one thing I've noticed in my 

relatively short flying experiences is that airport folks are generally 

friendly and willing to help.



Randy



---

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FLYaDIVE(at)aol.com
Guest

Posted: Thu Jul 06, 2006 4:41 am Post subject: alternator failure modes

In a message dated 7/5/06 7:53:06 PM Eastern Daylight Time, 

brinker(at)cox-internet.com writes:



 	  Quote: 	
		    If there's one thing I've noticed in my 

  relatively short flying experiences is that airport folks are generally 

  friendly and willing to help.

  

  Randy

=================
	


Yup, as long as you keep away from the FBO's.

And look for the EAA types.



Barry

"Chop'd Liver"

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FLYaDIVE(at)aol.com
Guest

Posted: Fri Jul 07, 2006 11:07 am Post subject: alternator failure modes

In a message dated 7/5/06 7:32:46 PM Eastern Daylight Time, 

brian-yak(at)lloyd.com writes:



 	  Quote: 	
		   I have had several people write to me to tell me that they have never  

  seen an alternator turn into a grenade. Neither have I. I was just  

  listing that is a *possible* scenario, as in, "I suppose this might  

  happen." I think it unlikely but I do think that things like broken  

  brackets, having the alternator seize, and who knows what happens if  

  both happen at once.

============================
	


Brian:

 

When you say grenade, are you saying totally blown apart with the case 

breaking into pieces?



I have done two alternators jobs that have had what I would call catastrophic 

failures.  

The first had the through bolts come out and the alternator bells separated.  

This caused the rotor to violently wobble and destroy the stator.  Basic 

cause - Plane owner went to his buddy to have an annual done.  Cost of Annual: One 

bottle of Jonnie Walker Black.  I do not know at what point the bottle was 

consumed.

Second was a failure of the alternator's end bell (sheave end) where the 

bearing is pressed in.  The voltage output failed and the rotor just started to 

wobble off center.  Basic cause - The alternator was installed off center.  The 

sheave was not aligned with the gear tooth ring.



I would not cal lit a grenade, but close.



Barry

"Chop'd Liver"

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Fri Jul 07, 2006 11:53 am Post subject: alternator failure modes

On Jul 7, 2006, at 3:04 PM, FLYaDIVE(at)aol.com wrote:

 	  Quote: 	

 In a message dated 7/5/06 7:32:46 PM Eastern Daylight Time,

 brian-yak(at)lloyd.com writes:

> I have had several people write to me to tell me that they have never

>  seen an alternator turn into a grenade. Neither have I. I was just

>  listing that is a *possible* scenario, as in, "I suppose this might

>  happen." I think it unlikely but I do think that things like broken

>  brackets, having the alternator seize, and who knows what happens if

>  both happen at once.

 ============================

 Brian:

 When you say grenade, are you saying totally blown apart with the case

 breaking into pieces?

Yes, that was the picture I had in my mind but really, any failure  

where the energy in the rotor causes catastrophic failure of the  

case. It could be just breaking off the mounting ears, bells  

separating, etc.

 	  Quote: 	

 I have done two alternators jobs that have had what I would call  

 catastrophic

 failures.

 The first had the through bolts come out and the alternator bells  

 separated.

 This caused the rotor to violently wobble and destroy the stator.   

 Basic

 cause - Plane owner went to his buddy to have an annual done.  Cost  

 of Annual: One

 bottle of Jonnie Walker Black.  I do not know at what point the  

 bottle was

 consumed.

Usually pre-inspection. That ensures that the signature appears in  

the logbook regardless of the condition of the airplane.

 	  Quote: 	
		   Second was a failure of the alternator's end bell (sheave end)  

 where the

 bearing is pressed in.  The voltage output failed and the rotor  

 just started to

 wobble off center.  Basic cause - The alternator was installed off  

 center.  The

 sheave was not aligned with the gear tooth ring.

 I would not cal lit a grenade, but close.

That is pretty much what I was thinking. I could see the rotor  

suddenly seizing because a bearing failed and the rotor jams with the  

case or the stator. The sudden stoppage along with the additional  

torque being applied by the belt could cause some or all of the  

alternator to do the grand tour of the cowling. I can see that doing  

damage to the carb, fuel injection servo, linkages, exhaust, airbox,  

or other bits down there under the engine. I don't think it likely to  

hole the case of the engine but weird stuff happens. OTOH, there is a  

lot more mass in an alternator than in a piston or connecting rod. It  

would not be a pretty sight.

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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George W Braly

Joined: 09 Jan 2006
Posts: 15

Posted: Sat Jul 08, 2006 4:45 am Post subject: alternator failure modes

I have had an alternator turn into a hunk of  twisted junk due to a

failed bearing.



--

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