another Autoflight gearbox failure - this time after 34 hrs

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wsimpso1

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Thanks for the detailed explanation, Billsky.
I discussed the idea of demanding a new gearbox with Bill, but he felt the gears looked fine and at least this way we know what we have and can fix it. Another gearbox would be an unknown that might have other screwups inside it that we don't know about.

Bill tried to explain to me in layman's terms what happened, and I gathered the machinist who put in the bearing didn't understand how to take into account the position of the bearings that had already been installed when placing the new one. He just put the case in the CNC machine and ran the program to place that bearing.

Would the gear tooth damage be something that would be visually apparent?

Jim
Inspection. This is a big topic. Consult anything you can find on visual inspection of gears, splines, bearings, etc. Usually this sort of thing requires both training and experience.

I will tell you that if find any bad signs, you and your repair guy have a discussion ahead of you. You clean the gears, shafts, and bearings with a solvent, dry them, then examine every gear tooth face, spline tooth face, bearing race and bearing roller under magnification and with good light over your shoulder. If you find any evidence of contact along edges of these surfaces, the part was edge loaded and may have a short lifetime. The parts it was in contact with are equally suspect. If you find surfaces that appear to have lost any material or appears to have fines embedded in the surfaces, it will have a short lifetime indeed. But I can not tell you that a part you find nothing wrong with will live well and long... No inspection like this will tell if the rest of the parts lost only a little of their life or some big fraction.

Billski
 

pantdino

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A prop strike often results in hidden damage.
I was concerned about that too. Inspection supposedly was OK. My understanding is that a hollow composite prop decreases that risk because it just shatters rather than torquing anything.
 

pantdino

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Inspection. This is a big topic. Consult anything you can find on visual inspection of gears, splines, bearings, etc. Usually this sort of thing requires both training and experience.

I will tell you that if find any bad signs, you and your repair guy have a discussion ahead of you. You clean the gears, shafts, and bearings with a solvent, dry them, then examine every gear tooth face, spline tooth face, bearing race and bearing roller under magnification and with good light over your shoulder. If you find any evidence of contact along edges of these surfaces, the part was edge loaded and may have a short lifetime. The parts it was in contact with are equally suspect. If you find surfaces that appear to have lost any material or appears to have fines embedded in the surfaces, it will have a short lifetime indeed. But I can not tell you that a part you find nothing wrong with will live well and long... No inspection like this will tell if the rest of the parts lost only a little of their life or some big fraction.

Billski
I get the feeling Titan won't be around much longer, so at this point I don't really have any choice but to see how this gearbox does. My only other alternative would be to order a new gearbox with the different bearing from Autoflight in New Zealand and wait who knows how long for it to be delivered.
 

BBerson

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I was concerned about that too. Inspection supposedly was OK. My understanding is that a hollow composite prop decreases that risk because it just shatters rather than torquing anything.
The manufacturer is not expected to warranty after a prop strike. Warranty is void after damage unless the factory did the repair for a fee.
For example guidance read the Continental Engine service bulletin regarding minor prop strike. Shattered prop is a major strike. The insurance company normally would have bought a new gear box and engine after a prop strike, in my opinion. Anything less than that and it is at risk of the owner or the unsuspecting salvage buyer.
 
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wsimpso1

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In a gear box, with this situation, why would the PSRU all of a sudden fail at 34 hours? Would it not have been a progressive failure starting at hour number one?
Yes. With a bearing located out of position, the damage would have started with the first turn of the prop under power.

How do you know how much off the bearing was? By the time it was noted, it would have been well on the way to destruction, with no real and reliable way to get an accurate measurement.
It sounds like the gearbox was still functioning, but the accumulation of fines from the bearing that was tearing up was beginning to stick a control valve in the governor. Prior to outright failure, which would have trashed much of the box, you have the incipient failure phase, with the box contaminated with fines - wear particles - from the bearing that is tearing up. I would expect that the bore that the bearing outer race was pressed into was still fine, and easily measured for size and position.

Billski
 

TXFlyGuy

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The manufacturer is not expected to warranty after a prop strike. Warranty is void after damage unless the factory did the repair for a fee.
For example guidance read the Continental Engine service bulletin regarding minor prop strike. Shattered prop is a major strike. The insurance company normally would have bought a new gear box and engine after a prop strike, in my opinion. Anything less than that and it is at risk of the owner or the unsuspecting salvage buyer.
The prop strike occurred with a factory employee in the cockpit, with the plane in the factory hangar, after a factory mechanic had performed work on the engine and throttle linkage.

Now who is responsible for the damage? And it was major...shattering the propeller, with propeller parts becoming airborne and taking out the leading edge of one wing.

This easily could have been a fatal accident.
 

TXFlyGuy

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I get the feeling Titan won't be around much longer, so at this point I don't really have any choice but to see how this gearbox does. My only other alternative would be to order a new gearbox with the different bearing from Autoflight in New Zealand and wait who knows how long for it to be delivered.
Normal lead time for Autoflight New Zealand is 12 to 36 months. It took us over two years to get our PSRU.
 

wsimpso1

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The previous owner seized an engine and had a prop strike, both with this gearbox? Ugh. Did the engine seize while running? Or did it refuse to turn after being shut down? A seize that stops a running engine is little better than a prop strike. Add in the prop strike, and yeah, no manufacturer of the PSRU would cover it. But a bearing bore out of position 0.015" IS a manufacturing problem. Did Titan mod the case for the roller bearing or did AutoFlight supply it that way? Reuse of the suspect PSRU should be Titan's problem.

This box has had a hard life, including one or two sudden stoppages. In addition to looking at EVERY PART with strong light and magnification for irregularities, abrasive wear and embedded particles, I would also have a dye penetrant check of aluminum parts, either dye penetration or mag particle check of all steel parts, and check for radial runout of shafts.

If it were mine, I would be re-thinking a new box. Maybe from someone else.

Billski
 

TXFlyGuy

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The previous owner seized an engine and had a prop strike, both with this gearbox? Ugh. Did the engine seize while running? Or did it refuse to turn after being shut down? A seize that stops a running engine is little better than a prop strike. Add in the prop strike, and yeah, no manufacturer of the PSRU would cover it. But a bearing bore out of position 0.015" IS a manufacturing problem. Did Titan mod the case for the roller bearing or did AutoFlight supply it that way? Reuse of the suspect PSRU should be Titan's problem.

This box has had a hard life, including one or two sudden stoppages. In addition to looking at EVERY PART with strong light and magnification for irregularities, abrasive wear and embedded particles, I would also have a dye penetrant check of aluminum parts, either dye penetration or mag particle check of all steel parts, and check for radial runout of shafts.

If it were mine, I would be re-thinking a new box. Maybe from someone else.

Billski
No, not the previous owner. All of this took place under the direct supervision of Titan, and/or it's employees.
 

proppastie

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fines from the bearing that was tearing up was beginning to stick a control valve in the governor.
the prop governor in my plane has a screen that one looks at for metal if there is metal anywhere in the combined oil stream....Now the slowdown of the prop because of a governor problem could be because of a clogged screen......or as you say the metal got past the screen in which case I think the prop is suspect along with the governor.
 

BBerson

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I am confused. The OP said it was an old gearbox, made in NZ, I presume. But somehow is angry that the airframe company is responsible after a factory incident?
Which factory made the .015" error?
 

wsimpso1

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No, not the previous owner. All of this took place under the direct supervision of Titan, and/or it's employees.
I have read the whole thread pretty carefully. If Titan was not the seller, were they brokering the sale? Either way it looks pretty sour with Titan in the middle of it.
 

wsimpso1

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the prop governor in my plane has a screen that one looks at for metal if there is metal anywhere in the combined oil stream....Now the slowdown of the prop because of a governor problem could be because of a clogged screen......or as you say the metal got past the screen in which case I think the prop is suspect along with the governor.
The screen is in there to keep a single piece of trash from blocking flow completely. Common source is built in debris - a manufacturing chip, dirt in a component, that sort of thing. If you find wear chips on the inlet screen, the wear has usually become pretty big. The initial pieces of wear metal will be really tiny and pass right through the screen or other filter. Enough of these really fine pieces will silt up a control valve without ever clogging a filter. As wear progresses and the particles increase in size, single particles will fit in the valve clearance between valve and bore. Both silting and bigger particles can cause the control valve to be sticky and overshoot both ways around the intended control point. If the prop was hunting around the intended rpm, I expect a sticky valve from contamination. Hunting above or below the intended rpm, other stuff is likely: Reduced flow; Silting that restricts valve stroke; and a bunch of other lower likelihood things.

The sparkly oil is a dead giveaway that there were a lot of tiny pieces through the box, and why I would need really good proof that nothing is wrong with any one part.

Billski
 

TXFlyGuy

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I have read the whole thread pretty carefully. If Titan was not the seller, were they brokering the sale? Either way it looks pretty sour with Titan in the middle of it.
The current owner bought the T-51 from another builder, and it had (I think) a Rotax engine.

It was then flown to Titan for numerous upgrades, including PSRU and LS3 engine. And that is when all of the fun began.
 

Vigilant1

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The current owner bought the T-51 from another builder, and it had (I think) a Rotax engine.

It was then flown to Titan for numerous upgrades, including PSRU and LS3 engine. And that is when all of the fun began.
And Titan installed the engine/PSRU that had experienced a prop strike and a separate seizure into that airframe ?
 

pantdino

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The previous owner seized an engine and had a prop strike, both with this gearbox? Ugh. Did the engine seize while running? Or did it refuse to turn after being shut down? A seize that stops a running engine is little better than a prop strike. Add in the prop strike, and yeah, no manufacturer of the PSRU would cover it. But a bearing bore out of position 0.015" IS a manufacturing problem. Did Titan mod the case for the roller bearing or did AutoFlight supply it that way? Reuse of the suspect PSRU should be Titan's problem.

This box has had a hard life, including one or two sudden stoppages. In addition to looking at EVERY PART with strong light and magnification for irregularities, abrasive wear and embedded particles, I would also have a dye penetrant check of aluminum parts, either dye penetration or mag particle check of all steel parts, and check for radial runout of shafts.

If it were mine, I would be re-thinking a new box. Maybe from someone else.

Billski
There was no previous owner of this gearbox. The plane had a Rotax engine and was purchased by a dealer, who took it to Titan in November 2016 to upgrade it to an LS3 powered plane, which involves a lot of stregthening of the fuselage, gear, etc. While it was there the plane was started under full power in a crowded hangar, trashing another plane and shredding the prop and damaging the leading edge of the right wing on this one.

The engine would begin to misfire after 30 minutes of flying and they couldn't diagnose the problem until it blew up-- 2 holes in the crankcase per their pilot.

So this was a brand new gearbox installed in 2018. Now it sounds like it's history, never having left the Titan factory.

Sounds like I need to file an insurance claim and get a new box. I bought this plane in July 2018 and still haven't flown in it.

I'm not a happy camper
 

TFF

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Definitely not the owners fault. Does Titan run naked with insurance like Robinson Helicopters? They seem to acknowledge it was in their care, but not their fault.
 

Vigilant1

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Sounds like I need to file an insurance claim and get a new box. I bought this plane in July 2018 and still haven't flown in it.
You've got insurance that covers mechanical failures? Normally you have to go to the trouble of flying and crashing a plane in this condition to file an insurance claim.

I hate to say this, I suspect you need a lawyer, and it sounds like you shouldn't wait.
 
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