Engine Problems Lycoming IO360 - Robin DR 500

I support this view, cooling the mags is just extending a bit the final life of an otherwise sick Slick . Basically up to 100 degrees C should be OK for mags with healthy components and I mean the coil and capacitor, no other parts are heat critical – and no repairer will make a difference, they just cannot look into these . An oven test is about the only test to diagnose a bit the momentary condition but does not say much about life expectancy of said parts. Mag troubles are quite familiar but you will not find many crashes due to mag failures as there are two of them , one alive for the rest of the fight and you typically find out before next start – hopefully – that all is not well. Again, adapt a habit of doing a mag test AFTER landing for diagnosing sick coils and capacitor in hot condition. The cold before – takeoff mag test only shows up bad spark plugs or ht leads. Vic

That’s a great bit of debugging!

However I still think there is something dramatically wrong going on (with the mags) because planes aren’t crashing all over the world. Countless Lyco engines of this type and/or with these mags fly both high up and low down. In particular, and notwithstanding that your type is overall very rare, the bulk of the Robin fleet is in France where it spends most of its time close to sea level and southern France gets pretty warm in the summer.

It looks like the mags are just faulty; probably some mistake made by a dodgy maintenance/overhaul shop on both of them. Maybe a bad batch of capacitors (condensers)? This sort of thing is possible. All kinds of weird things do happen; you would be amazed at some of the stories I have heard.

I would buy new ones from somewhere completely different (the USA, probably) together with a new ignition harness.

We had this behaviour severeval times: fuel caps clogged, fuel shutoff valve halve closed etc.
Number one was in a cessna 182 with Conti IO550 conversion. Engine running perfect, but after halve traffic pattern severe power loss was coming up. Short story: fuel cock was in OFF position. The fuel was sucked backwards to the return line!!! After returning to BOTH position everything was fine. But this conclusion comes up after immediate landing and some brain storming. BTW an AD was arriving at the same time regarding desgn of fuel cock. The OFF position was eliminated then.

Hallo, have you checked it personnally? Otherwise check it again. Disconnect breather and vent lines, blow it with pressurised air in opposite direction. Engine run on the ground is not sufficient.

Hallo, have you checked it personnally? Otherwise check it again. Disconnect breather and vent lines, blow it with pressurised air in opposite direction. Engine run on the ground is not sufficient.

Willi66 wrote:

The system works perfect until the engine sucks more fuel than is replaced by fresh air.

The OP stated, that the engine was tested independent of the aircraft’s fuel system with no change in behaviour.

Hi folks,
Have you checked the vent lines of the tanks in detail? On DR400 airframes these lines coming out of the fuselage down under approx 50cm aft of trailing edge of the wing and are made of a very small plastic tube. The inner diameter fits perfect to insects and other debris/
The system works perfect until the engine sucks more fuel than is replaced by fresh air. Depending on the remaining diameter of opening of vent lines it will work more or less.

There has to be something really major going on here. It cannot be a small difference in airflow. Planes would be falling out of the sky all the time.

I reckon it is what happens quite often: the maintenance company says X has been changed, but it hasn’t actually been changed.

And to spend 100k €… not even an aircraft owner could be that stupid, surely. The whole Robin is not likely to be worth that much. It cannot be flown in the present state, with a weird problem in the propulsion which could bring it down anytime.

Or somebody is winding somebody up