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Alternator drive gear failure


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We’re pulling a TSIO520NB out of a Cessna 414A due to large amounts of metal in the oil filter.  This is the same engine used in Rocket conversions and the same alternator drive used in Acclaims and Ovations.  We found that three of the four gear bolts and two lock plates are missing, ground up and sucked through the oil system.

We discovered it when we pulled the alternator.  If I recall this happened to a Rocket owner here on MS before.  If your alternator is off, it would be a good idea to inspect the bolts and lock plates.

Clarence

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I just had to send my IO550(g) from my Ovation 1 back to the overhauler after only 60 hours as a result of an improperly aligned alternator to crank drive gear. It was making metal and chewing up the coupling. Luckily, I caught it early by seeing very small amounts of orange coupling material in the oil filter. The overhaul shop agreed to IRAN it as a result. These designs are great when they work properly but all my research suggests to not go over the 500 hours prior to inspection. 

 

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  • 2 months later...
On 2/26/2020 at 12:38 PM, MarkD34M said:

I just had to send my IO550(g) from my Ovation 1 back to the overhauler after only 60 hours as a result of an improperly aligned alternator to crank drive gear. It was making metal and chewing up the coupling. Luckily, I caught it early by seeing very small amounts of orange coupling material in the oil filter. The overhaul shop agreed to IRAN it as a result. These designs are great when they work properly but all my research suggests to not go over the 500 hours prior to inspection. 

 

After reading these posts and not finding any reference to alternator overhaul and/or inspection in my log books (1380TT),  I decided to have my Eagle's  alternator sent out for inspection.  I also wanted my mechanic to  visually inspect the gears and bolts,  which he found them to be OK.  The bearings and brushes were replaced by the overhaul shop.   

A few days ago, I heard from another pilot that a low time io-550 had the alternator gear failure and the engine is shot.   All four bolts were sheared off.  I asked my mechanic if this is an installation problem or bad luck or poor workman ship at the engine shop?  His only comment was that this was a rare event and now he hears about it more frequently.   This not an aging fleet issue since it happened on two or more low time engines. 

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  • 1 year later...
On 2/26/2020 at 3:38 PM, MarkD34M said:

I just had to send my IO550(g) from my Ovation 1 back to the overhauler after only 60 hours as a result of an improperly aligned alternator to crank drive gear. It was making metal and chewing up the coupling. Luckily, I caught it early by seeing very small amounts of orange coupling material in the oil filter. The overhaul shop agreed to IRAN it as a result. These designs are great when they work properly but all my research suggests to not go over the 500 hours prior to inspection. 

 

@M20Doc

Is there a way to identify if it was indeed improper installation?  Could improper installation cause a brand new alternator to seize within about 10 hours, thus causing a chain reaction tearing up the elastomer coupler?

Edited by Browncbr1
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1 hour ago, Browncbr1 said:

@M20Doc

Is there a way to identify if it was indeed improper installation?  Could improper installation cause a brand new alternator to seize within about 10 hours, thus causing a chain reaction tearing up the elastomer coupler?

Continental is pretty specific about installation of the drive coupling, proper torquing of the nut and installation of the cotter pin.  I don’t know if over or under torquing the nut could lead to the alternator seizing.  

The one I posted above was the actual gear retaining bolts and lock plates failing, not the drive coupling.

Id suspect something in the alternator bearings.

Clarence

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1 hour ago, Will.iam said:

Is this applicable to TSIO-360MB engines as well and need to check the bolts / plates / alternator every 500 hours? Or is this only affecting the 550 series engines?

This only affects the larger engines, which have a front mounted gear drive alternator. There is a recommended 500 hour inspection interval for the alternator, drive coupling, and gears to head off the issue noted by the OP. 

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On 2/26/2020 at 10:32 AM, Fritz Kaiser said:

Hello ,

my IO550 in a '95 O1  lost all 4 screws.

Here you can see , how the gears looks like after droping into the enginecase.

It seems, that continental has a problem to secure the screws in a proper way.

Here the link:

Fritz

In looking at that original alternator drive coupling Fritz, the cotter pin is installed incorrectly and not in compliance with Continental SB 11-3

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

After managing a fleet of C-402's and having similar problems I am of the opinion that most the problems are at the coupler level. When you get the engine speed varying, along with the load on the alternator shifting that coupling is taking a beating and it transfers onto the crank gear if the coupler is the least bit suspect. If the crank gear is not installed correctly and the coupler is not optimal, trouble is assured. For this reason, I replace the coupler every 500 hours. It is impossible IMHO to accurately assess the coupler in the field in accordance with SB 11-3 paragraph 3 and I really can't see how the rebuilt units can be rebuilt and hold to tolerances because there is too much stretching on the cup removing and inserting a new elastomer unit . For that reason, I just bite the bullet and replace them at 500 hours with a new unit. Since I have been doing that....zero problems with big bore Continentals.

 

 

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On 2/25/2020 at 5:45 PM, M20Doc said:

We’re pulling a TSIO520NB out of a Cessna 414A due to large amounts of metal in the oil filter.  This is the same engine used in Rocket conversions and the same alternator drive used in Acclaims and Ovations.  We found that three of the four gear bolts and two lock plates are missing, ground up and sucked through the oil system.

We discovered it when we pulled the alternator.  If I recall this happened to a Rocket owner here on MS before.  If your alternator is off, it would be a good idea to inspect the bolts and lock plates.

Clarence

71450593-E12E-49F0-AC95-452AA389C90C.jpeg

C0E53E43-E117-4068-B1E9-5A12FE8F63D3.jpeg

59B95540-9D77-456C-B584-105E121D3B0A.jpeg

DBEE43A1-E5EB-4D64-9FF2-655D3E2B0A76.jpeg

Yes, 

I was the Rocket owner. The lock plates were not bent over when engine was assembled by Continental. It failed at 80 hours. Continental paid Rocket to R&R the engine so they could fix it. The gear came loose and destroyed the alternator sending FOD into the engine. 
 I was IFR above a solid cloud deck just out of Jackson Hole for Spokane. 

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On 5/27/2021 at 5:04 PM, Will.iam said:

Is this applicable to TSIO-360MB engines as well and need to check the bolts / plates / alternator every 500 hours? Or is this only affecting the 550 series engines?

It’s not quite the same drive as the “Permold” series engine.  The gears are still bolted to the camshaft and crankshaft.  The drive coupling is much smaller, but equally prone to failure.

Clarence

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