Wow! Ooops, take #3

[Dave Nadler]

Yikes.
http://ad.easa.europa.eu/ad/2015-0052-E

[Andrzej Kobus]

On Thursday, April 2, 2015 at 4:44:59 PM UTC-4, Dave Nadler wrote:
> Yikes.
> http://ad.easa.europa.eu/ad/2015-0052-E

Wow, there are many more pure gliders now...

[Steve Leonard[_2_]]

On Thursday, April 2, 2015 at 4:16:21 PM UTC-5, Andrzej Kobus wrote:
> On Thursday, April 2, 2015 at 4:44:59 PM UTC-4, Dave Nadler wrote:
> > Yikes.
> > http://ad.easa.europa.eu/ad/2015-0052-E
>
> Wow, there are many more pure gliders now...

Hmm. Says it only applies if you have Solo 2350 c and a non foldable propeller. But in the "reason" section, it implies that all Solo 2350 C engine operation is prohibited. Don't know enough on the specific variants of the Solo 2350 to know how many this really impacts.

Also interesting is that you must inspect within 30 days and report your findings. Even if there is no issue to report, it does not remove the restriction from using the engine.

Bad news for all that are affected.

[Bill T]

It will only be a matter of time before the U.S. FAA issues an AD based on the AESA AD that will impact gliders in the US.
US owners should heed the cautions and not operate the SOLO engine.
Interesting that the AD specifically identified the previous SOLO service bulletin as not acceptable.

BillT

[[email protected]]

On Thursday, April 2, 2015 at 4:44:59 PM UTC-4, Dave Nadler wrote:
> Yikes.
> http://ad.easa.europa.eu/ad/2015-0052-E

The product information website for Solo engines shows that two models of gliders are affected: Ventus CM and the DG1000T. Other gliders with solo motors have differing model numbers.

[[email protected]]

Looking at the Solo website http://aircraft.solo-online.com/index.php it looks like the c model is very different in that it shows a belt drive while the straight 2350 shows a direct drive. It appears that the AD is only for the C model.

DVM

[[email protected]]

God doesn't like motors on sailplanes.......

[Tango Whisky]

It affects ONLY 2350C engines with non-foldable propellor. That's DG1000T in the first place (which caused the AD) and probably J'S. S-H is not concerned (and I'll use it on my Ventus cM).

[Dave Walsh]

I think it says more about the technical competence of the
engine designers; maybe God doesn't like them either?

At 02:42 03 April 2015, wrote:
>God doesn't like motors on sailplanes.......
>

[John Galloway[_1_]]

At 07:46 03 April 2015, Tango Whisky wrote:
>It affects ONLY 2350C engines with non-foldable propellor. That's
DG1000T
>in the first place (which caused the AD) and probably J'S. S-H is not
>concerned (and I'll use it on my Ventus cM).

Also the turbo Antares - or at least the prototype according to this:

https://www.youtube.com/watch?v=-mxwvd-ps2A

[Steve Leonard[_2_]]

On Friday, April 3, 2015 at 8:02:11 AM UTC-5, Dave Walsh wrote:
> I think it says more about the technical competence of the
> engine designers; maybe God doesn't like them either?
>

Well, crankshafts don't like to be loaded at their output location other than along the axis of rotation. Put a belt reduction drive on there, and you are applying load perpendicular to that. Interesting dynamics happen with a two cylinder in-line engine with this setup. It is not an easy system to design.

Steve Leonard

[Dave Nadler]

On Friday, April 3, 2015 at 9:42:40 AM UTC-4, Steve Leonard wrote:
> Well, crankshafts don't like to be loaded at their output location
> other than along the axis of rotation. Put a belt reduction drive
> on there, and you are applying load perpendicular to that.
> Interesting dynamics happen with a two cylinder in-line engine
> with this setup. It is not an easy system to design.
>
> Steve Leonard

The failure is the prop hub (receiving end of belt reduction),
not at the crankshaft. Last round was classic fatigue - nice
crystalline structure on broken part.

[Steve Leonard[_2_]]

On Friday, April 3, 2015 at 8:48:59 AM UTC-5, Dave Nadler wrote:
> On Friday, April 3, 2015 at 9:42:40 AM UTC-4, Steve Leonard wrote:
> > Well, crankshafts don't like to be loaded at their output location
> > other than along the axis of rotation. Put a belt reduction drive
> > on there, and you are applying load perpendicular to that.
> > Interesting dynamics happen with a two cylinder in-line engine
> > with this setup. It is not an easy system to design.
> >
> > Steve Leonard
>
> The failure is the prop hub (receiving end of belt reduction),
> not at the crankshaft. Last round was classic fatigue - nice
> crystalline structure on broken part.

Same sort of issue. Up and down loading on that shaft due to increasing and decreasing tension because of engine dynamics and the loading going in and out of phase with the prop being in low or high moment of inertia relative to the motion (prop horizontal, low moment of inertia relative to motion created by pushing up and down by the drive belt). Likely source of the fatigue failure. But, as stated before, these are complex systems with lots of interactions. Be interesting to know the crack propagation direction relative to the blades on the prop.

[Charlie M. (UH & 002 owner/pilot)]

On Thursday, April 2, 2015 at 4:44:59 PM UTC-4, Dave Nadler wrote:
> Yikes.
> http://ad.easa.europa.eu/ad/2015-0052-E

Sounds along the lines of this.....

http://www.bugatti100p.com/web_documents/torsionalvibration.pdf

Sorta long read (the link), but curious to see results from the new AD.

[Dave Nadler]

On Friday, April 3, 2015 at 10:44:26 AM UTC-4, Steve Leonard wrote:
> On Friday, April 3, 2015 at 8:48:59 AM UTC-5, Dave Nadler wrote:
> > On Friday, April 3, 2015 at 9:42:40 AM UTC-4, Steve Leonard wrote:
> > > Well, crankshafts don't like to be loaded at their output location
> > > other than along the axis of rotation. Put a belt reduction drive
> > > on there, and you are applying load perpendicular to that.
> > > Interesting dynamics happen with a two cylinder in-line engine
> > > with this setup. It is not an easy system to design.
> > >
> > > Steve Leonard
> >
> > The failure is the prop hub (receiving end of belt reduction),
> > not at the crankshaft. Last round was classic fatigue - nice
> > crystalline structure on broken part.
>
> Same sort of issue.

Yep.

> Up and down loading on that shaft due to increasing and decreasing
> tension because of engine dynamics and the loading going in and out
> of phase with the prop being in low or high moment of inertia relative
> to the motion (prop horizontal, low moment of inertia relative to motion
> created by pushing up and down by the drive belt). Likely source of
> the fatigue failure. But, as stated before, these are complex systems
> with lots of interactions. Be interesting to know the crack propagation
> direction relative to the blades on the prop.

Crack propagation direction wasn't obvious on the broken part I saw.
Propagation *appeared* to have started at stress points from inadequate
flange radius and/or rough machining marks.
Not my area of expertise!

See ya, Dave

[Eric Munk]

I have seen a picture of the fracture. Could be a brittle fracture, but
can't say for sure without having seen it live... I am sure Solo will be on
to it. Engine apparently was run well within operating limits, had very low
time and had the mandatory SB performed (new part failed).

[Jonathan St. Cloud]

On Friday, April 3, 2015 at 6:02:44 AM UTC-7, John Galloway wrote:
> At 07:46 03 April 2015, Tango Whisky wrote:
> >It affects ONLY 2350C engines with non-foldable propellor. That's
> DG1000T
> >in the first place (which caused the AD) and probably J'S. S-H is not
> >concerned (and I'll use it on my Ventus cM).
>
> Also the turbo Antares - or at least the prototype according to this:
>
> https://www.youtube.com/watch?v=-mxwvd-ps2A

Try buying an Antares 23, they are not even being made.

[howard banks]

On Thursday, April 2, 2015 at 2:44:59 PM UTC-6, Dave Nadler wrote:
> Yikes.
> http://ad.easa.europa.eu/ad/2015-0052-E

Based on Mr Nadler's description, failure more or less inevitable.
Too small a radius will reduce the part's fatigue limit by somewhere between one third and one half roughly speaking. A 90 degree non-radius would result in a more or less infinite reduction in the fatigue limit (which is the stress on a part below which it should have an infinite fatigue life; in the real world all sorts of things reduce this limit, as we are seeing).
Rough machining can be even more insidious. Each piece of rough machining that you can see by eye is more or less the same as an already existing early fatigue crack. Its root radius at a microscopic level is effectively infinite with a corresponding reduction in the fatigue limit. Very bad news especially when it happens at a designed in place of inherently high stress.
All they had to do was to add some hard chromium plate on any wear surface that ran around the radius and failure would have been even earlier.
Pretty basic stuff. For it to have been repeated, as seems to have happened after a known problem, amounts to extreme carelessness.

[Dave Nadler]

On Friday, April 3, 2015 at 5:25:34 PM UTC-4, howard banks wrote:
> On Thursday, April 2, 2015 at 2:44:59 PM UTC-6, Dave Nadler wrote:
> > Yikes.
> > http://ad.easa.europa.eu/ad/2015-0052-E
>
> Based on Mr Nadler's description, failure more or less inevitable.
> Too small a radius will reduce the part's fatigue limit by somewhere
> between one third and one half roughly speaking. A 90 degree non-radius
> would result in a more or less infinite reduction in the fatigue limit
> (which is the stress on a part below which it should have an infinite
> fatigue life; in the real world all sorts of things reduce this limit,
> as we are seeing).
> Rough machining can be even more insidious. Each piece of rough machining
> that you can see by eye is more or less the same as an already existing
> early fatigue crack. Its root radius at a microscopic level is effectively
> infinite with a corresponding reduction in the fatigue limit.
> Very bad news especially when it happens at a designed in place of
> inherently high stress.
> All they had to do was to add some hard chromium plate on any wear
> surface that ran around the radius and failure would have been even
> earlier.
> Pretty basic stuff. For it to have been repeated, as seems to have
> happened after a known problem, amounts to extreme carelessness.

To be clear: The failed part I examined in fall 2013 was a "take #2" part.
The part was redesigned for "take #3", "resolving" the 2013 AD.
The new "take #3" part failed, leading to the most recent AD.
I have no idea what the failure of "take #3" looks like...

It is a bit surprising that 3 iterations of this part have failed...

But it is not an easy problem!

Hope that is clear,
Best Regards, Dave

[Charlie M. (UH & 002 owner/pilot)]

On Friday, April 3, 2015 at 5:34:23 PM UTC-4, Dave Nadler wrote:
> On Friday, April 3, 2015 at 5:25:34 PM UTC-4, howard banks wrote:
> > On Thursday, April 2, 2015 at 2:44:59 PM UTC-6, Dave Nadler wrote:
> > > Yikes.
> > > http://ad.easa.europa.eu/ad/2015-0052-E
> >
> > Based on Mr Nadler's description, failure more or less inevitable.
> > Too small a radius will reduce the part's fatigue limit by somewhere
> > between one third and one half roughly speaking. A 90 degree non-radius
> > would result in a more or less infinite reduction in the fatigue limit
> > (which is the stress on a part below which it should have an infinite
> > fatigue life; in the real world all sorts of things reduce this limit,
> > as we are seeing).
> > Rough machining can be even more insidious. Each piece of rough machining
> > that you can see by eye is more or less the same as an already existing
> > early fatigue crack. Its root radius at a microscopic level is effectively
> > infinite with a corresponding reduction in the fatigue limit.
> > Very bad news especially when it happens at a designed in place of
> > inherently high stress.
> > All they had to do was to add some hard chromium plate on any wear
> > surface that ran around the radius and failure would have been even
> > earlier.
> > Pretty basic stuff. For it to have been repeated, as seems to have
> > happened after a known problem, amounts to extreme carelessness.
>
> To be clear: The failed part I examined in fall 2013 was a "take #2" part.
> The part was redesigned for "take #3", "resolving" the 2013 AD.
> The new "take #3" part failed, leading to the most recent AD.
> I have no idea what the failure of "take #3" looks like...
>
> It is a bit surprising that 3 iterations of this part have failed...
>
> But it is not an easy problem!
>
> Hope that is clear,
> Best Regards, Dave

I'm NOT an "ME", I'm a field service guy with a "ME" background (as well as spending a lot of time fixing "good enough bits" on many different types of machines.....).

My link before was to show that there are quite a few factors to consider (not that anyone here know all the facts or can direct the final decision).
Just pointing out that some failures have been hit before, thus a research can find a suitable resolution.

"Thus that ignore history are doomed to fail in the same manner"..... or close to that....

[Craig Funston]

On Thursday, April 2, 2015 at 1:44:59 PM UTC-7, Dave Nadler wrote:
> Yikes.
> http://ad.easa.europa.eu/ad/2015-0052-E

Excellent paper on torsional vibration in aviation drive trains.
www.vibrationdata.com/tutorials/torsional_vibration.pdf

Not always a simple as it appears at first.

Cheers,
Craig
7Q

[Dave Nadler]

On Friday, April 3, 2015 at 9:48:59 AM UTC-4, Dave Nadler wrote:
> The failure is the prop hub

Sorry, bad description.
The part is the axle about which the prop rotates.
It is eccentric; rotating it tensions reduction belt.

Sorry if I caused any confusion!
Best Regards, Dave