DG1000T Solo 2350C Engine A.D.

[NG]

Yet another A.D. prohibiting the use of the DG1000T engine in the United States kicked in on May 29th 2015. This is the 3rd failure resulting in a third A.D. prohibiting the use of the engine, due to repeated propeller departure (as in breaking off). The current A.D. mandates immediate propeller shaft testing, while at the same time banning starting the engine, due to recurring propeller shaft fractures. Now a third consecutive season banning the use of the engine has passed.

If you are in the process of ordering or considering a new DG1000T, I personally would recommend giving it some closer consideration. In my opinion, the glider is unparalleled in performance, handling, fit and finish. However, the Solo 2350C 2 stroke engine and integration into the aircraft, speaks for itself. The engine in my experience is finicky regarding gasoline type, has high vibration, has high part failure, has poor service support from Solo,and has had the unnerving problem of propeller departure for the last three gliding seasons. To be honest, I have had weed whacker engines that are more reliable and easier to care for.

Now, even in the face of the 3rd proposed propeller shaft fix, a new problem with the engine mounts has apparently developed due to new vibration issues caused by the proposed fix. Part of the proposed fix involves replacing the metallic mounting hub which attaches the propeller to the propeller shaft with a rubber hub. A rubber hub, are you kidding me. Save your money (and lots of it) and buy something else.

NG
N918FC
DG1000T

[Tango Whisky]

I can't comment on the integration of the Silo 2350C into the DG, but the engine itself as it is integrated into my Ventus cM is absolutely reliable if I look back on my last 10 years flying the glider.

[Ventus_a]

Yet another A.D. prohibiting the use of the DG1000T engine in the United States kicked in on May 29th 2015. This is the 3rd failure resulting in a third A.D. prohibiting the use of the engine, due to repeated propeller departure (as in breaking off). The current A.D. mandates immediate propeller shaft testing, while at the same time banning starting the engine, due to recurring propeller shaft fractures. Now a third consecutive season banning the use of the engine has passed.

If you are in the process of ordering or considering a new DG1000T, I personally would recommend giving it some closer consideration. In my opinion, the glider is unparalleled in performance, handling, fit and finish. However, the Solo 2350C 2 stroke engine and integration into the aircraft, speaks for itself. The engine in my experience is finicky regarding gasoline type, has high vibration, has high part failure, has poor service support from Solo,and has had the unnerving problem of propeller departure for the last three gliding seasons. To be honest, I have had weed whacker engines that are more reliable and easier to care for.

Now, even in the face of the 3rd proposed propeller shaft fix, a new problem with the engine mounts has apparently developed due to new vibration issues caused by the proposed fix. Part of the proposed fix involves replacing the metallic mounting hub which attaches the propeller to the propeller shaft with a rubber hub. A rubber hub, are you kidding me. Save your money (and lots of it) and buy something else.

NG
N918FC
DG1000T

It reminds me of all the problems they had with the BD-5 propshaft. In that case part of the cure in the end, if I recall correctly, was to go to a shaft with more torsional flexibility. Numerous efforts to fix the problem with stiffer and stronger shafts all failed.

Having said all that it's hard to have engine problems if you don't have one

[danlj]

Agree. I have a Ventus Cm, too, with the Solo 2350B engine. Solo don't make the prop! In 15 years, it's never failed to start except once when the plugs were gapped wrong.

[NG]

Apparently another variant of the 2350C or the Solo 2350C has recently developed a vibration problem in another aircraft type. DG has recently posted the following message regarding the delay in resolution of the current problem with the DG1000T Solo 2350C as follows: "The complexity of the whole problem is also reflected in the fact that a defective vibration behavior at the propeller shaft has also been found by another manufacturer, and also in this case, extensive tests and measurements are necessary". The full statement can be found @:
http://www.dg-flugzeugbau.de/index.php?id=1349&tx_ttnews%5Btt_news%5D=306&cHash=12e753b242eed326665097dbe7ab3ed3
So you may want to make sure that this is not an issue with the Ventus CM. It is unclear from the DG post because the "another manufacturer" is not specified.

That said, I think it is hard to make an argument for reliability of the engine when 3 consecutive airworthiness directives by EASA and the FAA have emergently banned the use of the engine over 3 consecutive gliding seasons. In my opinion, the levity of propeller departure, either on the ground or in the air, should not be diminished by arguing that your engines have always started. That is not the point.

In fact our Solo 2350C has NEVER failed to start. The issue we have had with it is that it won't stop when the ignition is turned off. Our IA/A&P who is highly experienced, has not been able to solve the problem. Not stopping would not even be that serious of a problem but the engine has attempted to stow itself on multiple occasions, while still running. This is a recognized problem and resulted in DG service note No. 73-11 which states the following regarding a "run-on" situation: "If this happens the engine will retract further and propeller stopper will collide with the rotating propeller." Which it has. This is an unsavory situation either in flight or on the ground.

[Bengt Aronsson[_3_]]

I think the significant difference is that the Ventus cM does not have a
rigid propeller, but a foldable 2 blade Technoflug prop. This installation
has been in use in 100+ gliders since 25 years without propellershaft
problems, I think this is one of the SLG's with least trouble.. Also the
2350D has the same prop shaft part number, but installed with the 5 blade
foldable turbo propeller, these also have no problems. The newer
installations in DG1000T and Antares18T uses a conventional rigid
propeller, so I suspect the problem is that the prop has much higher
inertia in the "bending" plane of the propshaft.
I don't know which the other aircraft type is, but my bet is the Antares..
If they'd just known about all these ongoing problems, they should have
shifted to the Ventus prop..


At 16:42 24 September 2015, NG wrote:
>
>Apparently another variant of the 2350C or the Solo 2350C has recently
>deve=
>loped a vibration problem in another aircraft type. DG has recently
posted
>=
>the following message regarding the delay in resolution of the current
>prob=
>lem with the DG1000T Solo 2350C as follows: "The complexity of the whole
>p=
>roblem is also reflected in the fact that a defective vibration behavior
>at=
> the propeller shaft has also been found by another manufacturer, and
also
>=
>in this case, extensive tests and measurements are necessary". The full
>st=
>atement can be found @:
>http://www.dg-flugzeugbau.de/index.php?id=3D1349&tx_ttnews%5Btt_news%5D=3D3=
>06&cHash=3D12e753b242eed326665097dbe7ab3ed3
>So you may want to make sure that this is not an issue with the Ventus
CM.
>=
> It is unclear from the DG post because the "another manufacturer" is not
>s=
>pecified.
>
>That said, I think it is hard to make an argument for reliability of the
>en=
>gine when 3 consecutive airworthiness directives by EASA and the FAA have
>e=
>mergently banned the use of the engine over 3 consecutive gliding
seasons.
>=
> In my opinion, the levity of propeller departure, either on the ground
or
>=
>in the air, should not be diminished by arguing that your engines have
>alwa=
>ys started. That is not the point. =20
>
>In fact our Solo 2350C has NEVER failed to start. The issue we have had
>wi=
>th it is that it won't stop when the ignition is turned off. Our IA/A&P
>wh=
>o is highly experienced, has not been able to solve the problem. Not
>stopp=
>ing would not even be that serious of a problem but the engine has
>attempte=
>d to stow itself on multiple occasions, while still running. This is a
>rec=
>ognized problem and resulted in DG service note No. 73-11 which states
the
>=
>following regarding a "run-on" situation: "If this happens the engine
>will=
> retract further and propeller stopper will collide with the rotating
>prope=
>ller." Which it has. This is an unsavory situation either in flight or
>on=
> the ground. =20
>

[[email protected]]

On Thursday, September 24, 2015 at 10:42:18 AM UTC-6, NG wrote:

>
> In fact our Solo 2350C has NEVER failed to start. The issue we have had with it is that it won't stop when the ignition is turned off.

This is a feature of 2-strokes which have been run at full throttle. Since every cylinder fires every shaft rotation there isn't time for hot carbon deposits in the combustion chambers to cool below auto-ignition temperature before the next compression stroke. Consequently, the engine can run as a glow-plug engine after the spark has been turned off.

I recall amusing myself with a small 2-stroke motorcycle by switching off the ignition and letting the engine run on until a large throttle change caused it to quit.

[[email protected]]

In this statement, DG is referring to Antares gliders with 2-stroke engine installation. Lange Aviation is also using the Solo 2350C engine, combined with a larger propeller. So they are also affected by the AD. However, the propeller and engine mounting are not the same as in the DG1001T, leading to a different vibration level.

[NG]

Bill, thanks for the run on comments. Chris thanks for the clarification about who else is affected.

Bengt, my guess is, and I am not an engineer, that you are correct. The more flexible prop interactions in other types are placing less of a bending moment on the shaft. Additionally, the current prop shaft is already at risk because it has a half round radius cut in it circumferentially, which apparently has been a point of failure. Steve Leonard et.al. have discussed these issue in depth in other threads, related to the first group of failures.

The rubber prop attachment apparently is an attempt to make this situation more like the types (Ventus CM) which are not showing failure.

Regardless, I still stand by my original statements which I think are self apparent.

[Charlie Papa[_2_]]

As for the run-on problems, I have been for 10 years using iridium spark plugs, which have a fine needle that gets hot enough that carbon cannot form there.

My Solo 2350 is in a Discus 2cT, and has performed flawlessly. The five blade asymmetrical seems weird, but is said to reduce noise and vibration.

[NG]

Chris. Apparently the Solo Engine problems are not just isolated to the DG1000T and Antares turbo. In the past the Duo Discus T which also incorporates the Solo engine and a variant propeller drive, also has had propeller hub cracking problems resulting in 2 separate FAA ADs. In 2007 AD 2006-25-14 called for daily pre-flight inspection of the propeller hub with a "10X magnifying glass" for cracks and mandatory return to the manufacturer if cracks were found. This was followed by another more recent AD in 2013, AD 2013-24-16, requiting inspection revisions for further issues with the same propeller hub, AD 2013-24-16. I contacted the U.S. dealer to try and find more about this history and possible similar issues with no reply.

I received a private notice from a party in the U.K. who stated that he had replaced his Duo T propeller hub no less than 3 times. In addition he states that a recent propeller departure in a Duo T resulted in entry into the fuselage with aileron linkage disruption which is currently being investigated by the U.K. authority.

So there you have it. More than 8 years of recurrent propeller hub and shaft failures, involving 5 airworthiness directives, spanning 3 different manufacturers, in addition to Solo the engine type certificate holder.