Hello All!
I am new to this mailing list and to the Europa having been asked by a
work collegue to fly and share the running costs of his Europa G-EIKY.
It is based at Insch airstrip near Aberdeen, Scotland. We are commercial
helicopter pilots and fly offshore oil support in the North Sea. I also
do a lot of gliding and have flown a couple of hundred hours on the
Falke type motorgliders with central mainwheel, outriggers and tailwheel
(familiar configuration!). I must say that I found the Europa a bit of a
handful during takeoff and landing but a delight otherwise. I suppose it
is just like the motorgliders but everything happens 4 times as fast!
Now I have got about 9 hours on it, I am reaonably happy!
It does however have a little engine problem which I have been trying to
tackle. Can I bore everybody with a lot of background and then ask a
couple of questions? BTW I was an electronic engineer before going
commercial pilot so I know a bit about that sort of thing and also have
always done my own maintenance on my cars and motorcycles and am
BGA-approved to work on motorglider engines.
The engine is a Rotax 912 with warp drive prop. It has the mod for the
cold air box/inlet on top of the cowling. I have experienced carb icing
with this mod, but the effect I am describing is not carb icing. It
starts instantly, and is generally very smooth and never misses a beat
at full power.
However in the cruise (5000 @ 120kts) it just very occasionally runs
rough for maybe half a second. Just long enough to attract attention!
You can really feel it through the pedals, especially. The other thing
is that during the mag drop checks, it is right on the limit on the left
mag and the drop difference is also right on the limit. More to the
point it is just downright rough on the left mag, but sweet as anything
on the right mag. Of course we replaced all the plugs, even though only
25 hours on the engine, but no difference. In the cruise, if I go onto
the left mag it is even more rough, although no massive rev drop, but
smooth as anything on the right mag. On the ground, on the left mag it
is perfect up to 3200 rpm and at that exact rpm the roughness comes in
suddenly and remains until nearly full throttle.
Because it was different on the 2 mags I started with the assumption
that it was something in the ignition system. I started by swapping the
following (one at a time) to the other side: Magneto switches, pickup
coils, generator coils. Nothing wrong with those. Then I swapped all the
coils over with the black boxes, and the fault changed sides, i.e.
nothing wrong with the black boxes but something wrong with the coils or
something "downstream" of them.
Having traced which 2 coils were on the faulty side, I swapped one of
them with the equivalent coil on the other side. No difference. But when
I swapped the other 2 coils, the fault changed sides so I had identified
which coil was faulty (I thought!). To check that it wasn't a fault in
the ht leads or plug caps, these were temporarily replaced with car
stuff but no difference. So I was very confident that it was the coil
itself, even though the resistances etc checked out. It must be some
vibration effect I thought. Today we fitted the new coil (costing the
owner around 150) but to my amazement no difference!
I ran through the diagnosis again but still the same conclusion that it
is something in that coil or downstream of the coil. I am now thinking
that "downsteam of the coil" could include something in the cylinder
itself!
That coil runs the rear two cyclinders' top plugs. The engine runs fine
when the bottom 2 plugs only are firing, but not when the top 2 only are
firing. Could there be some marginal mixture problem and non-uniform
distribution of the fuel within the cylinder caused by, perhaps, an air
leak? Sounds most unlikely, doesn't it, but that is what the test
results point to. (BTW the plugs all look much the same colour). Today
it was bucketing down with horizontal rain so we gave up in disgust
after lunch. I think the next step will be to swap top and bottom leads
so that the same ignition circuit is feeding the other plug, to see what
happens (will have to lengthen the upper ht leads temporarily I
suppose).
Sorry that this posting is so long!! Can I ask 2 questions:
1. Anybody got any ideas???
2. Does your Rotax 912 engine generally run noticeably rougher on one
magneto than the other during the mag checks - is the mag drop
difference near the limit? - and do you have the cold air box mod?
(answers yes or no would both be useful!)
Thankyou for persevering with this posting, any help much appreciated.
Nick Norman
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