Arcus vs. competing products... ASG32Mi, DG500, HpH304MTS

[rianmonnahan]

Hi all,

I have been admitted to this group on the understanding I would lauch a debate about the relative merits of the Arcus M (v2) vs. competing products in the same class - motorized 20m sailplanes.

I am personally interested in the debate since I am slowly going down the path of purchasing one of these gliders. I haved owned a number of sailplanes both pure and sustainers. 

Right now I own a JS1C and JS3 both with jet sustainers. I'm thinking of selling one of these gliders and replacing it with a full fledges self-launcher. And I want a two seater.

Thanks in advance for your input. 

[Chester Fitchett]

For the altitude I launch at (as high as 5000' ASL), the rotary engine used on the Schleicher gliders is not an option.

DG500/DG1000 - I solo'd and licensed on a DG1000.  Nice glider, but much heavier on the controls than an Arcus.  Also, I think Flaps are a necessity.

Twin Shark - never flown one, but seems to check the same boxes as the Arcus.  As a starting point (Arcus vs. Twin Shark), I would consider price, and the relative financial health of Schempp vs. HPH.

I continue to love my Arcus, but a self-launcher is a mechanical contraption that requires ongoing care and maintenance.  Well worth it, IMHO.

[rianmonnahan]

Hi Chester,

Indeed, the financial viability of the company  is a serious issue. It's an issue when you order and an on-going issue during the time of ownership. Still, it's somewhat hard to guage as most of these companies are closely held concerns. I recall questionning myself about the political stability in South Africa when I bought my JS gliders. 

As for power, it's too bad Wankel never developped a more powerful version of the rotary for Schleicher. The relatively low output of the current model seems to plague the AS line's heavier ships. Yet, it is far quieter, smoother than the Solo/Binder motors albeit more complicated to manage. I guess 5000 AMSL is in feet. Unless you are flying off the Tibetan plateau, the figure cannot be in meters. ;)

[Mark B]

I'm sure the three flapped 20m gliders are all great to fly and have near identical performance.

I was considering a DG before the Arcus was announced, now I would not consider the DG. The gliding operation at Denbigh in the UK had a DG1001M and an Arcus - I heard they very much preferred the Arcus, and this year they got rid of the DG and acquired a second Arcus, the new one being the first Arcus M 20 in the country.

Having had a rotary before my Arcus (ASH 26E), I think the advantages and disadvantages balance out, and the extra HP of the Solo (68 for the Arcus injection version, 62 for the Shark non injection) versus the rotary (57) is the over-riding factor. I use a bigger headset in the Arcus because of the higher noise level, but the simpler and quicker warm up and cool down is more significant. I am not bothered about the level of automation - I never found the start up or shut down of the ASH confusing so I don't think the automation of the Arcus is a significant advantage - just a little bit more to go wrong (and I have had more than one prop position sensor issue). I have had failures with both engine systems, I don't think I can say which has been more unreliable for me, let alone on a statistically significant basis.

For weak UK days I would like the lower empty weight of the Shark.

A key issue for me would be who is going to maintain the glider and what they have more experience of.

Mark Burton

Arcus M s/no 24

[Bill Tugnett]

We've just had the engine seize in our Arcus M (#132). The engine is the fuel injected Solo 2625-02i, it's 5 years old & has approx 42 hrs TTIS. After strip down the engineer advised the seizure occurred at the rear cylinder big end bearing. Rather than repair, his recommendation is that we purchase a new engine block. Has anyone experienced this & if so, do you have a suggestion as to the cause. Thanks

Bill Tugnett,  Bathurst,  Australia

[Chester Fitchett]

Ouch.  When did it seize?  On the ground?  Launching?

I had a snowmobile (2 stroke) years ago.  The oil was injected during operation, rather than doing pre-mix.  Engine seized several times, until we switched to pre-mixing oil with the gas.  Which tells me the issue was lack of oil in the gas.  Any chance you missed adding the 2-stroke oil?

A concern in North America is ethanol mixed with the gas, which I'm told reduces the lubricity of the gas/oil mixture.  So I test for ethanol and try to buy gas without it.

Please keep us informed, I'm curious what a new engine costs...

Chester s/n 173

[Bill Tugnett]

In our case, the seizure occurred during launch at ~2000' agl. The engine was developing full power until just prior to seizing, when the revs dropped off followed by a sudden stop. We're are certain that we had the oil mix right (we've always used 50:1 ethanol free Premium unleaded mogas 98 RON / Castrol 2T / TTS). Reflecting on this - we had noticed that when starting the engine for ~ 7 - 8 launches prior, the engine seemed to start & run on one cylinder for 5 - 10 seconds before the second cylinder caught, after which the engine ran & warmed up smoothly. I'm wondering if the rear cylinder fuel injector was not operating initially, resulting in a lack of lubrication? Regards,  Bill

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[Aldo Cernezzi]

Dear all,

I'm not at all surprised by this short report. I must say that my direct experience as an Arcus M owner (s/n 37) was satisfactory, no major failures of the engine and only a small series of radiator, exhaust, ignition coils failures, all easily fixed at the airport.

However I have seen a significant number of these engines lying on the workshop desk with catastrophic internal failures generally unseen in modern engines, especially the injected variants as seen on the Arcus, Quintus and DG1001, even at very low total hours (single, or lower double, digit!).

In most of these cases, I was told that the engine manufacturer strongly suggested replacing the whole engine. I know of only one case where replacement parts (big-end or crankshaft bearings, mainly) have been made available for local repair by trusted operators. Generally, the failure of the bearings leads to damage of the block and/or crankshaft, making an all new engine the preferred solution.

Lubrication comes to my mind as well as the root cause. Unless it's a case of questionable quality control by the producer of the bearings.

In my consideration, the e-injection system MAY be able to partialize the fuel flow more efficiently than carbs, for a cleaner combustion. This MAY find confirmation in the relative cleanliness of the tail fin, when compared with other engine installations such as EB and HpH. Less fuel equates to less oil, in our case.

As a side note, on my DG800b, the EGT probes consistently indicate very high combustion temperatures upon throttle reduction, which I was prompted to apply for the sake of "being kind towards the engine". I got to above 800 °C! Looks to me like the air/fuel intake gets way too lean.

In conclusion, on the Arcus and any similar engine, I decided for the following deviations from prescribed procedures:

. Very moderate (150-200 rpm) throttle reduction during climb, if any.

. Cool-down at no less than 4500 rpm.

. During cool-down, apply full throttle for 1s every 20s (this should activate a rich mixture and therefore inject more fuel than for a rich air/fuel ratio.

. Mixing oil to gasoline with no less than 2.5% ratio.

. Hand rotating the propeller after each flight, getting a memory of normal sounds and trying to notice any changes in these sounds.

I'd recommend each owner to notify these engine failures to the technical authorities for the appropriate actions to take place.

all the best landings,

Aldo Cernezzi

www.voloavela.it

[Thomas Jobs]

Hi all,

We fly an Arcus with serial nr 140 (2016) and first year, after approx 2 hours engine time, we had an engine seizure. Engine replaced by SH. We never got an explanation what caused the seizure, but I guess a bearing failure (after landing a lot of noise from engine when hand cranking the propeller). As you might remember an AD was published in December 2016, mandating installing an updated firmware for the engine. 

I support Aldo recommendations above, except power reduction during climb. Air/Fuel mixture is cooling/lubricating a two stroke engine.....correct or wrong? Cant tell, but a lot of experienced engineers recommend full throttle....

We always fly fully loaded (800kg) and use 4000 rpm for cooling down. It give a zero climb and is therefore perfect when participating in competition and you have to stay below an altitude.

Brgds /Thomas