Oil Pressure issues with 912

[Bluey]

Hi all:

 

Just did some flying this morning and noticed at one point during the flight that my oil pressure dropped to zero for a few seconds. This was noticed when the warning light suddenly came on. The oil pressure restored itself in a matter of seconds but I was of course concerned and started looking around for a possible forced landing. This never eventuated and a safe landing at YWOL followed soon after. I must add that my oil pressures have been a bit variable lately usually between 2.8 and 3.6 (in cruise) which I thought a little unusual. Also, at start up, I have been seeing zero oil pressure reading for a number of seconds when the skydat is first switched on and the engine is cold. typically after a week or so of no flying. I have spoken to a few people about this and they say that it is most likely the oil pressure sender unit as these are commonly failing. The engine now has 430hours and I have already had two unrelated failed EGt probes. Anyone have any experiences similar to this?

 

Regards: Bluey

 

 

[Guest JeffC]

Hi Bluey,

 

Faulty sender was the cause of a similar situation with my ULS in cruise and at idle on approach, although pressure at start was high (as you'd expect). They are not expensive so replacement as a fault-find is a reasonable option. Suck eggs stuff but check; electrical connections at sender and behind skydat, wires for chaffing, temp OK?

 

Cheers,

 

Jeff

 

 

[Bluey]

Yes, the engines other vitals are all normal and not at all variable like the oil pressure readings are.

 

 

[HEON]

Senders seem to have limited life, especially the batch(s) that came from India. Currently using European ones...cost more but seem to last longer.

 

This is PROBABLY the problem. Buy one and change to see if it is. Will not be money wasted as you will need one sometime.

 

 

[Bluey]

Lets say for the sake of argument that it is the oil pump. Would this lead to a zero oil pressure reading if it suddenly failed during flight? It doesn't seem logical to me that a failed pump would cause a zero pressure. Wouldn't a failed pump lead to a non zero pressure especially if there is no loss in oil and then a climbing oil temperature as cooling would no longer be effective due to a lack of oil circulation?

 

Bluey

 

 

[alf jessup]

Lets say for the sake of argument that it is the oil pump. Would this lead to a zero oil pressure reading if it suddenly failed during flight? It doesn't seem logical to me that a failed pump would cause a zero pressure. Wouldn't a failed pump lead to a non zero pressure especially if there is no loss in oil and then a climbing oil temperature as cooling would no longer be effective due to a lack of oil circulation?Bluey

Bluey,

 

Put 1/2 a doz beers on a dickie sender mate, mines done it and so has a mates.

 

Replacement VDO sender i got from Floods was not much chop either as it didnt last all that long either.

 

If you got a mate a WOL with a 912 trike ease your mind and borrow his sender for 8 mins (1 min to undo it and 7 mins for a circut only to see it all good again) and you can then go buy the cascade light for me:big_grin:;)

 

Cheers

 

Alf

 

 

[alf jessup]

Senders seem to have limited life, especially the batch(s) that came from India. Currently using European ones...cost more but seem to last longer.This is PROBABLY the problem. Buy one and change to see if it is. Will not be money wasted as you will need one sometime.

Heon,

 

Where did you get you European ones from, have you an address or website for these as i couldnt find anything overseas when i looked a few years back when i needed one after my dissapointment with the replacement VDO one from Floods.

 

Cheers

 

Alf

 

 

[cscotthendry]

Lets say for the sake of argument that it is the oil pump. Would this lead to a zero oil pressure reading if it suddenly failed during flight? It doesn't seem logical to me that a failed pump would cause a zero pressure. Wouldn't a failed pump lead to a non zero pressure especially if there is no loss in oil and then a climbing oil temperature as cooling would no longer be effective due to a lack of oil circulation?Bluey

Bluey:

You don't even want to go there about a failed oil pump in flight. If the pump failed, the pressure might well go to zero instantly, followed by an engine out (read seizure) very shortly thereafter. Oil flow in a high stress engine situation is critical. Don't bet your life on it, spend the $$ and get a new sender if there's any question at all.

 

 

[HEON]

European one supplied via Richard Eacott SE Qld Rotax rep. Not sure but think via Flood's.

 

 

[Bluey]

Yep, I will be calling Bert Floods tomorrow and organising a replacement sender unit. Flew this morning and as expected there was no low pressure warning at start up since I flew yesterday. Start up pressure is around 5. For the first 90 minutes of flying, oil pressure was very stable at around 3.7 which is what I've seen on other 912's. However, for the last 1 hour of flying it started to vary again. Got as low as 2.5 for a brief moment before settling at around 3.1. I monitored temps carefully and they remained very steady while the oil pressure varied.

 

Has anyone heard of an oil pump failure on a 912 before as the few people in the know I have spoken to say they cannot ever recall such a failure?

 

Bluey.

 

 

[Bluey]

I forgot to mention that the pressure variations in flight are usually very slow. But the low pressure warnings I often get at start up usually go from zero to above 4 in only a couple of seconds once its starts to go up. It could be at zero for around 10 seconds or more on start up though because my start up procedure is to start the engine with the skydat off then turn it on immediately once engine is started. I am using the shell VSX 4 oil. I have heard from Bert Floods that aeroshell plus 4 has had pressure issues in the past but am not aware of any details of these issues.

 

Bluey

 

 

[Guest rocketdriver]

Bluey

 

I'm no expert, but I remember similar symptomns in some of the older cars I ran in my youth ...... It sounds as if the internal oil galleries are draining down when the engine is stationary for a while, and then its taking a long time to refil them. Is the oil fresh? Also your bottom end bearings may have excessive clearances or perhaps the oil pressure valve is not seating properly .... could also be a worn oil pump or a leaking internal pipe fitting ...... In any case, I would be a little concerned about a 10 second delay in the oil pressure coming up as this will promote wear to the bearings, valve gear and bores.

 

Regards

 

Martin

 

 

[Bluey]

oil change was done 37hrs ago. Will run some tests with the skydat on before start up to see how long oil pressures take to reach normal levels. I will also try hand cranking the prop more to see if this changes anything. I recently turned the engine off in flight and then back on again with skydat on and a warning light flashed for a few seconds when the engine roared back to life. I wonder what the delay is between real oil pressure and the skydat registering it on the display?

 

Bluey.

 

 

[Guest Maj Millard]

Another common fault can simply be a rattling push-on connector to the sender, if that's the type you have. Easily fixed with a dob of silicon on the connector to stabilize it, then go and put a dob on all the other push-on connectors, for super stable readings.

 

I have also seen the odd oil pressure sender go bad lately. The 912 simply isn't known for loosing oil pressure in flight...........................................maj...

 

 

[Bluey]

Thanks for all your help everyone, I think the biggest issue may be the low pressure at start up. I'm going to run some tests to see how long it really lasts to see if it really is a real reading. At this stage, I suspect that it might be but need to try starting the engine with the instrument panel on to see how long it really takes for pressures to come up (something I never do in case of voltage spikes that destroy the electronics). I'll keep you all posted.

 

Bluey

 

 

[Bluey]

Spoke to Wal and he says it sounds like a sender unit on the way out. Wil still do some of my own checks to see if the symptoms I am seeing remain consistent with a real fault.

 

Bluey.

 

 

[cscotthendry]

Bluey:

 

Here's simple check you can try: pull the oil pressure sender and see if the hole in the end is clogged or blocked in any way. If the hole is restricted by dirt or something, it could explain the slow rise in pressure.

 

 

[Bluey]

Finally got round to replacing the oil pressure sender unit and while the new one is producing quite stable pressures that are higher than the older unit, I am still seeing low pressures at start up with a cold engine. Don't know if it is significant but the warning light flashes and the pressure is below minimum for around 5 seconds or so at start up. As I said it only happens when the engine is cold when the engine has sat for a day or more. When the pressure does rise, it rises quickly and goes to around 5.8psi or so. During cruise it hovers around 4.0psi or even higher. A start up from a warm engine sees low pressures for a second or so. What's more is that I checked a friends 912 with lower total hrs than mine and strangely his reads a pressure when engine is off. This has to be a spurius reading. Hi warning light came on for about 2 seconds or so and the pressure rose a little slower. His also warmed up at about 3.3 psi and stayed at about that level during flight. Any thoughts?

 

 

[Bluey]

I turn the prop over about 10 revolutions at the start of every days flying. I have the oil cap off and listen to the burping. Being an airborne trike at 2.5 years of age I think the design is the same as all other airborne trikes. Having said that, I'm not sure if the tank is below the sump. It probably is.

 

Bluey.

 

 

[Bluey]

I also forgot to mention that I have lately been turning it over on the electrics for about 5 seconds or so before flicking the switches. This helps circulate the oil and reduces the low oil pressure warning time. I don't like doing this for too long out of fear of flatening the battery.

 

 

[Outback Bob]

The 912 was designed to be used as a tractor engine, not a pusher. I did my flight training on the first XT912 from the factory, the aircraft had temperature reading issues, in pusher config, later came fibreglass cowling. along with having to crank engine to get oil pressure before switching the mags on.

 

fantastic engines, still finding its compatabillity with some aircraft configurations.

 

 

[Guest davidh10]

... I suspect that it might be but need to try starting the engine with the instrument panel on to see how long it really takes for pressures to come up (something I never do in case of voltage spikes that destroy the electronics)...Bluey

SkyDat is the first thing I always turn on. I figure being a computer based instrument, it may like to measure steady state sensor voltages before starting, but I don't have any facts on this. In any case, you have a really good voltage regulator, called a battery. A battery of this size and type has a very low internal resistance, so will smooth out any spikes.

 

The engine instrumentation is meant to be on and stable, when you start the engine. Also 2Bar oil pressure within 10 seconds, so you look ok to me. See POH Section 4.8.2

 

 

[alf jessup]

The 912 was designed to be used as a tractor engine, not a pusher. I did my flight training on the first XT912 from the factory, the aircraft had temperature reading issues, in pusher config, later came fibreglass cowling. along with having to crank engine to get oil pressure before switching the mags on.fantastic engines, still finding its compatabillity with some aircraft configurations.

Howdy Outback Bob,

 

Well rest assured the temp issues with the first XT 912 built have certainly been resolved as I currently own that aircraft and have so for the last 4 1/2 years.

 

I got it when it had 287hrs on it and now it has 771 on the skydat, it has been a super reliable aircraft ever since i have owned it.

 

Only thing I have had to replace other than routine maintenance was a shocker on the left side as it would lose a little pressure then stabilize making it squat a little left side down.

 

Brilliant engine so far be lucky to use 50ml oil between changes @50 hrs.

 

Just thought i would let you know where your training trike was these days.

 

Cheers

 

Alf

 

 

[Bluey]

Thanks for all your replies everyone. Very educational.

 

Bluey

 

 

[Bluey]

Well it seems as though the oli pressure issues I am having just won't go away. After a week of no flying, the oil pressure was zero for about 10 sec after a cold start. I did all the usual things and had the skydat turned on. I burped the engine about (8 - 10) rotations of prop. I even turned the prop over without the ignition switches on and still about 10 sec of zero pressure. The problem is not as bad when I fly more frequently but it still occurs. As stated in previous posts, the oil pressure rises quite quickly when the engine is warmed (less than 3sec of low pressure at start up). I've spoken to Wal at Bert Floods and he suggested attaching an analogue dial that bipasses the skydat to see what is going on. I've ordered one and will get it tomorrow. If it is a real pressure problem, Wal hinted at possibly opening up the engine to see what is going on. I mentioned that the operations manual suggested that the pressure needs to be above 2 atmospheres within 10 sec for normal operations and Wal was still concerned and suggested that the issue needs to be investigated. Any thoughts and ideas would be appreciated.

 

Bluey