Bluey

I have to agree with many of the sentiments here. This is an example of a case where activating a plb would have been of great benefit to all involved. I for one would not want to put my family through the pain of wondering whether I was safe after skipping my report in time by such a long interval.

Thanks for the advice Mike.

Glad to hear they are ok too. I fly into the Oaks regularly. I may well have met the pilot. This would probably have been a Jabiru as they are all big fans of the Jab over at the Oaks. I am a bit surprised that a plb was not activated as having to walk that far for help is far too risky to attempt in remote areas. It seems to me as though one was not being carried. Not sure why you would risk it in this day and age???

Thanks Mcguyver, I might have to take you up on that offer. :-)

Thanks for all the advice, it is very reassuring to read about all your experiences. I am yet to cut open the filter. Do you need a special tool to open up the filter as some have suggested? I am waiting for someone to do it for me for this reason. I would much prefer to do it myself.

Thanks Maj, I was thinking the same thing. It was mostly sludge with some metal filings. I did work the engine harder since the last service and I think an oil change more regularly is warranted in the future. From memory, the previous change which was also at about 90hrs showed quite a clean plug.

It is always a rotax filter and I change it at every oil change.

it is out of the motor just in front of the gearbox (912 UL). Looking at the totax manual, it states that an accumulation of less than 3mm is ok. The largest clumps and it was very patchy with all that dark oil around the plug were no more than 1mm in height. Certainly not like the unacceptable levels depicted in the rotax maintenance manual. Either way, my next oil change will be closer to the 50hr mark than at 90hrs like this one.

I'm using shell vsx 4 and always use premium unleaded (95 octane). The motor has 486hrs and the images look a little worse than it did in the flesh.

images of magnetic plug Here they are...

Images of magnetic plug Looks like I'll have to shrink the images before I can post them.

Not sure what happened to the images attached to this post. I'll have to have another go at attaching them when I get home.

Did an oil change this morning after 90hrs in about 4 months. Had a look at the magnetic plug and it seemed a little furrier than the last time I did an oil change. Will be cutting open the oil filter and inspecting that too very soon.

Interesting read.

I am going to continue testing with the analogue gauge to see if the initial results are repeated under different conditions (ie longer periods between flights). I especially want to know how the pressure at start up behaves when the engine has sat idle for around a week. So far my initial tests were after 2.5 days resting and those results clearly indincated no problem with oil pressure. I will report back if future results indicate a problem.

That's a good idea. Will have to look into that.

Thanks everyone, I tried having both units plugged into the same sender unit and the result was higher than normal pressures on the analogue gauge and an open circuit on the skydat. This makes sense as the reduced current going to each unit would result in a larger than normal indicated pressure. The analogue unit coped much better than the skydat as it seemed to take most of the load and so the indicated pressure was around 1 bar higher than expected. The skydat just didn't get enough current and so went open circuit. It would be great to be able to have both working normally as I think a backup analogue pressure gauge is required especially after the issues I and others have had. This whole exercise has cost me more than $300 that could have been better spent had an analogue unit been fitted in the first place. My advice to anyone with oil pressure issues is: Before you do anything, bypass the skydat with either a multimeter as stated by davidh or obtain a cheap analogue unit as I have done. The only problem with the analogue unit is you need to either hook it up to the trike power supply in order to get an effective earth or earth the sender unit to an external 12v supply (something I haven't yet tried but should work provided you can secure the earth to the outside of the sender unit using a clamp). Speaking to a repco dealer today, it turns out that a vdo sender unit is available with two indipendent outputs but it may be too large to fit in the space for the sender unit on the 912. Also quite expensive from what I was told (> $400).

The oil pressure gauge installed is the one recomended by Bert floods for the vdo unit installed on the 912. The pressures it indicated on warm up were very steady and in the ball park of the skydat system.

After a quick connection of the analogue unit in place of the lead to the skydat, I can confirm that oil pressure on the analogue unit rose as soon as the engine fired up without delay. This after more than three days of sitting idle. Normally after this length of time a delay of around 10 seconds would have been seen on the skydat. So what have I learnt from this is that the issue lies somewhere between the vdo sender unit and the skydat. most likely it is an issue with the skydat itself. We tested it a number of times with the engine warm and the same occurred, no delay. With the skydat connected, a small delay was noted but this is not unusual with a warmed engine. Bottom line, I don't trust the skydat.

As far as the sender unit is concerned this is with the new sender unit already installed.

I just picked up an analogue vdo unit and will install it this afternoon to see what is going on. I do more than 200hrs per year so and generally fly for more than 1hr at a time so the oil gets well used during each flight. It doesn't sit around for long between each flight.

David, where exactly do you hook up the multimeter to get readings? I know one connection (+ve) goes to the VDO sender unit but what about the earth. Exactly where is the earth? (excuse my ignorance).

I forgot to mention that even at the longer service interval, very little oil is consumed by the engine.

At oil changes the oil is dark but I have been assured by a number of experienced people as well as airborne themselves that oil changes need only be done every 100hrs. The rotax manual quotes 100hrly services. I have been told that 50hr services are overservicing the engine. I can understand why people do it though. It is an aircraft after all. I was very reluctant to increase the service interval. On another note, a check of my oil filter residue should reveal if any damage is being done to the engine internals and hence confirm whether the pressure issues are a problem or not.

All oil and filters have been changed within the allotted 100hrly service intervals. Usually services have been performed around the 50 - 60 hr mark. The last service was done at 90hrs. I know many people do services strictly every 50hrs but according to both airborne and rotax that is not necessary if not running on avgas. I am curently at 80hrs since the last service and will now do it to check for particles in the oil filter. I use shell advance vsx 4 oil and only ever use genuine rotax oil filters. It is only my last two services that have gone more than 50hrs. The engine is now at 479hrs. I am beginning to wonder about what possible engine damage may have been done if these oil readings are real????