Blue Christmas....O-300 accessory gears damaged by Mag

Fearless Tower

Fearless Tower

Touchdown! Greaser!
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Fearless Tower
Got a bad news phone call today from a friend of mine who is an A&P IA in the Fort Worth area.

Background: Last week I was finally able to fit into my schedule the time to move my 170 from San Diego to Norfolk. Made it about half-way....to just east of Plainview, TX and then diverted to Mineral Wells (friend has a hangar there) after loosing the right mag and had to fly commerical home.

Turns out the right mag was loose (had quite a bit of play when turning the prop by hand). Pulled the mag and a whole tooth was missing. We haven't found the piece inside, but the borecsope today confirmed that the accessory gears were badly damaged inside.

So.....looks like the engine is coming off. No idea what this is going to cost, but I suspect it won't be pretty:mad2:

Any guesses how much this is going to cost?
 
Fearless Tower said:
Got a bad news phone call today from a friend of mine who is an A&P IA in the Fort Worth area.

Background: Last week I was finally able to fit into my schedule the time to move my 170 from San Diego to Norfolk. Made it about half-way....to just east of Plainview, TX and then diverted to Mineral Wells (friend has a hangar there) after loosing the right mag and had to fly commerical home.

Turns out the right mag was loose (had quite a bit of play when turning the prop by hand). Pulled the mag and a whole tooth was missing. We haven't found the piece inside, but the borecsope today confirmed that the accessory gears were badly damaged inside.

So.....looks like the engine is coming off. No idea what this is going to cost, but I suspect it won't be pretty:mad2:

Any guesses how much this is going to cost?
Click to expand...

Whoa ,,, hold on ,,,, why would you pull the whole engine to change gears? strip the accessory case and pull it, there is no way the debris can get out of the accessory case and back into the oil system.

Pull the screens and see what you have there. don't panic this is fixable with out a whole overhaul
 
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Tom-D said:
Whoa ,,, hold on ,,,, why would you pull the whole engine to change gears? strip the accessory case and pull it, there is no way the debris can get out of the accessory case and back into the oil system.
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Tom,

Can you pull the accessory case apart without taking the engine off the mounts? Looks pretty tight back there between the back of the engine and the firewall.
 
Fearless Tower said:
Tom,

Can you pull the accessory case apart without taking the engine off the mounts? Looks pretty tight back there between the back of the engine and the firewall.
Click to expand...
Yes you can. it's a bit-h but it can be done with out tearing the engine down.
 
Tom-D said:
Yes you can. it's a bit-h but it can be done with out tearing the engine down.
Click to expand...
Thanks for the info....I'll see if we can pull that one off.

Any idea why the mag would suddenly become loose? I suspect it came loose and the extra play is what caused the tooth to shear off.

The mag was last removed when I did the first annual over a year ago. Took it off and did an IRAN then re-installed. I flew the airplane around 75 hrs since then. The shop that did my last annual (a month ago) said they didn't touch the mags.
 
I'll be in town until Jan 24 if you need a ride to MW or whatever.

Fearless Tower said:
Thanks for the info....I'll see if we can pull that one off.

Any idea why the mag would suddenly become loose? I suspect it came loose and the extra play is what caused the tooth to shear off.

The mag was last removed when I did the first annual over a year ago. Took it off and did an IRAN then re-installed. I flew the airplane around 75 hrs since then. The shop that did my last annual (a month ago) said they didn't touch the mags.
Click to expand...
 
Fearless Tower said:
Got a bad news phone call today from a friend of mine who is an A&P IA in the Fort Worth area.

Background: Last week I was finally able to fit into my schedule the time to move my 170 from San Diego to Norfolk. Made it about half-way....to just east of Plainview, TX and then diverted to Mineral Wells (friend has a hangar there) after loosing the right mag and had to fly commerical home.

Turns out the right mag was loose (had quite a bit of play when turning the prop by hand). Pulled the mag and a whole tooth was missing. We haven't found the piece inside, but the borecsope today confirmed that the accessory gears were badly damaged inside.

So.....looks like the engine is coming off. No idea what this is going to cost, but I suspect it won't be pretty:mad2:

Any guesses how much this is going to cost?
Click to expand...

Depends on his rate and the damage done, I'll rough it at a low of $5k and a high of $13k by the time it's headed home.
 
Fearless Tower said:
Pulled the mag and a whole tooth was missing. We haven't found the piece inside, but the borecsope today confirmed that the accessory gears were badly damaged inside.....

Any guesses how much this is going to cost?
Click to expand...

There is ALOT of metal shaving, pieces, chunks that have traveled through out the motor.... IMHO.... A teardown is prudent..:sad:
 
N801BH said:
There is ALOT of metal shaving, pieces, chunks that have traveled through out the motor.... IMHO.... A teardown is prudent..:sad:
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0-200 and 0-300 can't happen.

the heavy particles stay in the sump, the oil movement isn't fast enough to pull them out and all oil goes thru the screens.
any damage that can occur will be in the oil pump, and that will come off with the accessory case.
 
Fearless Tower said:
Any idea why the mag would suddenly become loose? I suspect it came loose and the extra play is what caused the tooth to shear off.
Click to expand...

most likely happened the other way around. I'd check the mag hold down studs for being pulled out. that is one hell of a big force that is generated when you try to run a gear tooth thru the gear train. it would generate a force side ways to the mag and try to tear it off the engine.
 
Some pictures of the gears we are talking about.

Notice there is a partition between the gear case and the oil pick up area of the lower portion of the accessory case, this is to keep the gear failures out of the sump. all debris will stay in this area.
 

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Tom-D said:
0-200 and 0-300 can't happen.

the heavy particles stay in the sump, the oil movement isn't fast enough to pull them out and all oil goes thru the screens.
any damage that can occur will be in the oil pump, and that will come off with the accessory case.
Click to expand...

I hope so. For FT's sake...:confused:
 
N801BH said:
I hope so. For FT's sake...:confused:
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There are reasons for pulling it and doing the overhaul, but I have not seen the reason here.

How old is the engine, are these gears the ones that came new with the engine?

are the thru case studs loose now ?

several inspections should be completed before they make a decision.
 
Tom-D said:
There are reasons for pulling it and doing the overhaul, but I have not seen the reason here.

How old is the engine, are these gears the ones that came new with the engine?

are the thru case studs loose now ?

several inspections should be completed before they make a decision.
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I'll have to dig up the logs to see how old the engine itself is. It has been around 360 SMOH. I would bet that the gears are original to the engine, but I could be wrong.

Sounds like we have few more things to check.
 
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