Engine failure

[hen...@holmkristensen.dk]

We have had yet annoter bad engine failure in our Arcus M.

Normal takeoff run, but loss of power at an elevation of approx. 150 m.
Able to land at airfield.

Found total loss of compression on the front cylinder.

When viewing through borescope it can be seen that a part of the piston is missing at the exhaust port location.

When turning the propeller it can also be felt that likely a roller in a main bearing

is broken.

This breakdown is occurring after only 91 hours after last rebuild, where we also had a total failure after most likely a top piston rod bearing broke, and sent metal parts through the engine.

The last breakdown occurred after only 83 hours total.

Br 
Henrik 

Arcus no 58

  

[b.aronsson]

Hi Henrik,

On my club's Arcus M (s/n 41), at last year annual inspection I discovered an unnormal play in the piston bearing system. Almost since new I have performed the check called CCBCT (Conrod Clearance Bearing Test) that is required on the Rotax engines by their SB505-010R1 also on the Arcus' engine.

From the normal about 0,05 mm I had 0,30 on the front cylinder, and after a consultation with Emmerich at Solo I dismounted the heads, cylinders and pistons. The fault was wear on the piston pin, the bearing seemed to have rotated properly so far, and no other defects was found. I think this was discovered shortly before a failure that could have been similar to yours.

I changed the pisons, piston pins and -bearings, and the engine was back to normal again.

This happened at 126 h engine time, of which 71 h was on the old ignition mapping (changed by TN 4600-6).

Many years back I asked mr Emmerich about this testing method, and he said it was not reliable enouch as a proper test, due to the use of caged piston pin bearing, and I suppose you can get slight difference in the measurement depending on the bearing roller positions.

After that, I also asked why they still use caged bearings, as the modification to cageless solved most of this type of overload problem in the Rotax engines, but I never got an answer for that..

I decided for myself that it was a good method to get early indication of problems, and belive that saved a failure like yours.

Best regards

Bengt Aronsson

Falbygdens Flygklubb, Sweden

Arcus M s/n 41

[Arcusdriver Andreas]

Welcome to the club...Did you check https://groups.google.com/g/schempp-hirth-arcus/c/iERrbG8v7Pc/m/j9UAPSpuAQAJ

It was as well the front cylinder. 77h engine hours only :-(.

SH contacted me afterwards but with no helpful outcome. 

I hope your Arcus is self-launched up in the air again.

Best regards

Andreas

S/N 114

[hen...@holmkristensen.dk]

Hi

This failure occured because the gasket in one of the air intake ports failed.

The mixture was then very leanon that cylinder. 

It overheated and caused the breakdown. 

The cylinder top was melted at the exhaust port location 

Br

Henrik

Arcus no 58