6 cylinder surprise

[GolfWhiskeyHotel]

I follow this forum at irregular intervals , but given the latest news re: Jabiru Gen 4 , I thought "I wonder what everybody is saying".  So I came for a look.  Now I know what everyone is saying . NOTHING.  Not one post?  But People are being told

"Your engine will require a new crankshaft" , please join the queue.  Has no-one anything to say?   I hear that 3 or 4 hundred engines are involved. Worldwide.  Seems to me to be a postworthy subject wouldn't you think?

My aircraft is not involved of course, being a J160 with 912uls engine. (coming up to its third year and MARAP yet to be completed) . Happy Hours in the sky................ Geoff

[turboplanner]

4 minutes ago, GolfWhiskeyHotel said:

I follow this forum at irregular intervals , but given the latest news re: Jabiru Gen 4 , I thought "I wonder what everybody is saying".  So I came for a look.  Now I know what everyone is saying . NOTHING.  Not one post?  But People are being told

"Your engine will require a new crankshaft" , please join the queue.  Has no-one anything to say?   I hear that 3 or 4 hundred engines are involved. Worldwide.  Seems to me to be a postworthy subject wouldn't you think?

My aircraft is not involved of course, being a J160 with 912uls engine. (coming up to its third year and MARAP yet to be completed) . Happy Hours in the sky................ Geoff

Depends whether it's a recall or not. If it is and Jabiru are paying for the changeover, that's quite normal for Australia, and should be commended.

[onetrack]

It appears the recall is being managed very well, with the 6 cyl engines most at risk being repaired first, and the remaining engines dealt with as time and ability permits. As the new crankshafts are being supplied at no cost to owners, I would think this was a very worthy and laudable exercise.

Remember, Jabiru still have an aircraft manufacturing operation to support and keep in production - replacing faulty crankshafts is something that must be managed, so it doesn't interfere excessively with the manufacturing side of the business.

 

The 6 cyl engines affected were built April 2017 and June 2024.

 

Jabiru announces SB re crankshaft replacement - https://www.australianflying.com.au/recreational/jabiru-issues-service-bulletin-for-crankshafts#:~:text=Jabiru Aircraft last week issued,April 2017 and June 2024.

 

Edited Sunday at 12:20 PM by onetrack

[Red]

Detail is important ..Quote

" no component cost to the customer."    Removal of engine, complete strip of engine and rebuild with new crank plus any transport costs involved in shipping parts/engines aint gonna be cheap.

[BrendAn]

this video paul cherna has on facebook shows what he considers the problem with jab cranks.

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[Red]

Facebook, can't see it.

Does he post elsewhere?

[facthunter]

jabiru say it's variations in the heat treatment and replacement will be from solid billet fully machined. Engines are OK to 150 Hours so get in touch and schedule the work  prior  to reaching 150 Hours.   Existing warrantees are extended to

 cover this. Nev

[BrendAn]

18 minutes ago, Red said:

Facebook, can't see it.

Does he post elsewhere?

no . you need a facebook account unfortunately

[BrendAn]

18 minutes ago, facthunter said:

jabiru say it's variations in the heat treatment and replacement will be from solid billet fully machined. Engines are OK to 150 Hours so get in touch and schedule the work  prior  to reaching 150 Hours.   Existing warrantees are extended to

 cover this. Nev

there is not much support for the crank snout and they often use long extensions to mount the props.  cherna believes the cranks would be fine if they had more substantial support behind the prop. 

[facthunter]

Depends on where they are breaking wouldn't it? Its one of the few AERO Engines with a Mainbearing on each throw.  Nev

[BrendAn]

11 minutes ago, facthunter said:

Depends on where they are breaking wouldn't it? Its one of the few AERO Engines with a Mainbearing on each throw.  Nev

They are breaking at the first crank web behind the front bearing.

He showed one in the video.

Edited Monday at 06:47 AM by BrendAn

[facthunter]

That is the Normal place to break.  I think it's where the UL's normally DO as well. . Torsional vibration can do that. Having a flywheel on the other end  and more mainbearings aggravates it. Might need dynamic Balance weights. You can't feel torsional vibration.  IF a prop extension was doing that you would feel it. Nev

[Thruster88]

I would not call any crankshaft breakage normal. As Paul points out in his vid, the front bearing is very short, the standard prop extension is too long. The crank is not properly supported.   

[dlegg]

2 hours ago, Thruster88 said:

I would not call any crankshaft breakage normal. As Paul points out in his vid, the front bearing is very short, the standard prop extension is too long. The crank is not properly supported.   

You would also have to think that if the crank support was inadequate then the crank case itself would fail. That doesn't seem to be the case, nor does a crankshaft breakage history.

[onetrack]

It appears the crankshaft design has been fine, up until this particular batch - so the problem is in the batch of crankshafts, not in the crankshaft design.

[facthunter]

That is the Jabiru assessment of it... When considering the forces applying, you have to consider the larger order as being more significant. Potentially it's harmonics.. There will be a bad rpm SOMEWHERE on any engine.   IF there's been a fault with SOME crankshafts and is Known that is a Quality control issue so fix that anyhow.. Gyroscopic forces broke Crankshafts in Croppy C-180's Pivoting on one wheel at High engine RPM.    Nev

[Blueadventures]

14 hours ago, onetrack said:

It appears the crankshaft design has been fine, up until this particular batch - so the problem is in the batch of crankshafts, not in the crankshaft design.

Not sure, but is is connected to were billet now forged?

[onetrack]

It appears so - but the reverse is the case - were forged, now billet. The article says "Jabiru has now reverted to machining crankshafts from imported (solid) billets". The suspect crankshafts were forged.

 

It's a curious decision, because I was always under the impression forged crankshafts were superior, with a better grain flow in the metal, leading to improved strength and durability and better resistance to cracking.

 

Crankshafts machined from solid billets mean the metal grain is cut and discontinuous, caused by the machining, and as a result are generally regarded as weaker.

 

I would suspect the faulty forged crankshafts have been produced from a substandard metal that either failed to meet specifications, or it contained internal flaws - or it was heat-treated and tempered improperly.

 

I would opine that Jabiru have taken over direct control of the crankshaft manufacturing, possibly doing the machining in-house, whereas previously, it's likely the forging was outsourced and therefore less ability for Jabiru to keep control of product quality. Ongoing and constant checks are very necessary in repeated production, as errors can creep in, resulting in large-scale disasters.

 

Even robotic manufacturing is not immune, someone has to keep a watch on the robotics parameters to ensure they don't move from their settings.

[BrendAn]

4 hours ago, facthunter said:

That is the Jabiru assessment of it... When considering the forces applying, you have to consider the larger order as being more significant. Potentially it's harmonics.. There will be a bad rpm SOMEWHERE on any engine.   IF there's been a fault with SOME crankshafts and is Known that is a Quality control issue so fix that anyhow.. Gyroscopic forces broke Crankshafts in Croppy C-180's Pivoting on one wheel at High engine RPM.    Nev

So you would think a crank snout with more bearing area and getting rid of the long extension should fix the problem .

I know when I got my 2200 I thought the prop was a long way from the crankcase.

 

[BrendAn]

19 minutes ago, onetrack said:

It appears so - but the reverse is the case - were forged, now billet. The article says "Jabiru has now reverted to machining crankshafts from imported (solid) billets". The suspect crankshafts were forged.

 

It's a curious decision, because I was always under the impression forged crankshafts were superior, with a better grain flow in the metal, leading to improved strength and durability and better resistance to cracking.

 

Crankshafts machined from solid billets mean the metal grain is cut and discontinuous, caused by the machining, and as a result are generally regarded as weaker.

 

I would suspect the faulty forged crankshafts have been produced from a substandard metal that either failed to meet specifications, or it contained internal flaws - or it was heat-treated and tempered improperly.

 

I would opine that Jabiru have taken over direct control of the crankshaft manufacturing, possibly doing the machining in-house, whereas previously, it's likely the forging was outsourced and therefore less ability for Jabiru to keep control of product quality. Ongoing and constant checks are very necessary in repeated production, as errors can creep in, resulting in large-scale disasters.

 

Even robotic manufacturing is not immune, someone has to keep a watch on the robotics parameters to ensure they don't move from their settings.

Did you watch that video link. It makes sense.

[facthunter]

it's  Extremely Difficult to forge something like a six throw crank shaft with seven Main Bearings.  The grain flow you refer to is not ideal  either in that application as it is in a poppet valve where you an extrude the shape and jump it up to thickness it. Plenty of racing car shafts are from billet  and the get a more balanced result as well.  Aero shafts are often nitrided  where stress reliving is achieved at the same time as surface hardening..  Crack testing is done new and  at every rebuild.  There is NO non destructive test for Metal fatigue.  At some stage the Part should be discarded, "Lifed" or it was built far too heavy to be on a plane. .Nev

[Garfly]

On 28/04/2025 at 3:58 PM, Red said:

Facebook, can't see it.

Does he post elsewhere?

I presume this is it:

 

 

[BrendAn]

39 minutes ago, Garfly said:

I presume this is it:

 

 

That's it. I didn't think to look on YouTube.

[Blueadventures]

7 hours ago, onetrack said:

It appears so - but the reverse is the case - were forged, now billet. The article says "Jabiru has now reverted to machining crankshafts from imported (solid) billets". The suspect crankshafts were forged.

 

It's a curious decision, because I was always under the impression forged crankshafts were superior, with a better grain flow in the metal, leading to improved strength and durability and better resistance to cracking.

 

Crankshafts machined from solid billets mean the metal grain is cut and discontinuous, caused by the machining, and as a result are generally regarded as weaker.

 

I would suspect the faulty forged crankshafts have been produced from a substandard metal that either failed to meet specifications, or it contained internal flaws - or it was heat-treated and tempered improperly.

 

I would opine that Jabiru have taken over direct control of the crankshaft manufacturing, possibly doing the machining in-house, whereas previously, it's likely the forging was outsourced and therefore less ability for Jabiru to keep control of product quality. Ongoing and constant checks are very necessary in repeated production, as errors can creep in, resulting in large-scale disasters.

 

Even robotic manufacturing is not immune, someone has to keep a watch on the robotics parameters to ensure they don't move from their settings.

The early billet one Paul is working on in his shop has a cracked crank and the recall is on the newer ones which have a forged crankshaft.  

[BrendAn]

1 minute ago, Blueadventures said:

The early billet one Paul is working on in his shop has a cracked crank and the recall is on the newer ones which have a forged crankshaft.  

true, but what he says about adding a crank snout and increasing the bearing area has to help. 

the jabiru prop extension is probably fine until there is a slight imbalance from prop damage and wear.