"Jaberoo" down (Mildura this time)

[motzartmerv]

CHT tubz. 180 c max continuous.

 

Oil temps start freaking the instruments out at 110 C

 

 

[Dafydd Llewellyn]

We went down the rabbit hole once before this incident with oil temp indications in a different 3300 (230)An engineer ended up using a thermocouple down in the oil dipstick gallery to get a true oil temp reading. It ended up slightly hystereses, but within 3 or 4 degrees at operating temp. Mind you this was NOT in the engine mentioned above. But it confirmed the fears, the oil was indeed, too bloody hot!!!!. It was in spec, but bloody hot.

The instruments were Dynon EMS and factory installed.

Just an observation, here: You need to be aware of which oil temperature you are measuring - the oil INLET or the oil OUTLET. Aircraft engine oil temperature limits are normally specified as oil INLET temperature.

Rod has stayed with the oil temp. sensor in the sump, because for a long time he was trying to cool the oil by fins on the sump. In that situation, the sump temperature near the suction line inlet is the oil inlet temperature.

 

But when you install an oil cooler that picks up from an adapter under the oil filter, the oil going into the main gallery is no longer at the sump temperature; it's cooler. Just how much cooler I don't yet know. The oil temperature in the sump is in reality the oil OUTLET temperature, for any installation that uses an external oil cooler. The real oil INLET temperature should be measured in the oil cooler adapter, where the flow is returning from the oil cooler. This is one of the things I will be measuring in the test cell, and later in flight.

 

Unfortunately, the "oil inlet temperature" limits given in the TCDS - and hence in the POH - are still based on a sensor in the sump. I'd like to change that, for the CAMit engine, but the basis for approval may prevent that, at least until Ian can manage a supplemental type certificate. Until then, we're still stuck with the existing TCDS basis.

 

So your measurement down the dipstick tube would indeed show a high oil temperature. It may well differ from the value shown on the Jabiru panel instrument, because the short sender used by that instrument will be somewhat affected by the boundary layer of somewhat cooler oil due to the air blast on the underside of the sump.

 

There are all sorts of tricks for inexperienced players, in certification instrumentation; it's been, as I have said, the biggest single problem in the Type certification work in which I have been involved.

 

 

[motzartmerv]

Yea ok, that sounds logical. It was a few years back, but from memory we were acting on factory advice.

 

 

[Dafydd Llewellyn]

Yea ok, that sounds logical. It was a few years back, but from memory we were acting on factory advice.

Yes - well, for the models that were certificated, this work was handled by either Alan Kerr and myself, or Alan Kerr and Keith Engelsman; we used our own instruments, and we gave the factory advice, not vice-versa. Look up MS 28034-1 on the internet; that's pretty much the GA industry standard oil temperature probe, and that's what I used. It reaches much deeper into the sump than the normal factory probe.

 

 

[geoffreywh]

In my experience (24hr motorcycle endurance racing) "cooling fins" on a sump just don't work, they look good but, the oil at the finned surface cools considerably , thickens and effectively forms a barrier stopping any more oil reaching the cooling surface. Fins inside the sump worked better, but not by much. We reckoned that porcupine spikes inside/fins outside would have been the best solution, but , too dear.......

 

 

[fly_tornado]

I would think that oil coolers would be mandatory for air cooled engines

 

 

[David Isaac]

I suppose sump oil capacity is small to keep weight down and that adds to the oil cooling problem.

 

 

[deadstick]

Well we're talking about the old 3300 in my J230 here,

 

Oscar:- not sure where you are getting your info from but the factory were supplied with logbooks EMS data etc, the damage to the bottom end was as the factory put it due to the old thru bolts allowing fretting of the cases and the new ones (SB) closing the mains gaps to min tolerances. The thermal runaway incident had never been explained but one of the Jabiru techs (Don) thought it may have been due to an air leak where the intake runners meet the plenum as he had seen this exact problem before, the abnormal cylinder wear was attributed to the bottom end damage.

 

It certainly is hard to be across every aspect of operation with these engines especially in a school environment where other people are flying it, however this is one of the reasons why I fitted the 12 channel EMS system of which no over limits were recorded before that day, the other reason was that testing revealed that the single CHT was not up to par with different cylinders hotter under differing circumstance's.

 

In all accounts the engine was running very well and gave no indications to the abnormal wear in the bottom end until it was stripped, ( I still have it in a box ).

 

Further the insurance company replaced this engine and attributed the other damage to a manufacturing flaw ( Legal:- engine was never fit for purpose). This was the first Jabiru engine that the assessor had seen in his 30+ years in aviation, had never seen a main bearing eat a crankshaft before and was shocked with the lobe wear on the camshaft in such a short time hours wise.

 

The unwillingness to share EMS data that you elude to:- Completely different incident and I was willing to share up until I started getting differing opinions and multiple accusations and it became clear that Jabiru were just looking for a way to blame me rather than helping me.

 

This was the strange problems associated with 4 cylinder heads on my J160, all heads had signs of cracking between the intake and exhaust runners, one had dropped a valve seat at idle and all within 250 hours of a factory 'top end', I downloaded the EMS data on an old laptop at the time of removal and it showed no over limit indications but the laptop subsequently crapped itself (convenient I know), Sue woods was very interested and at her request I forwarded the heads but due to geographical distance (1000 km) I could not get the data again until in the area.

 

In the meantime I was fobbed off, Instead of working with me I started getting accusations and differing reasons why until finally after multiple requests an email from CASA and ultimately a legal letter from my solicitor to have them returned so I could get an independent inspection carried out I was given a one sided and rushed engineering report, (of which by the sounds of it you have been privy to).

 

Ultimately I was fed up and frustrated with the factories lack of assistance with an engine that had been plagued by problems since its top end and was tired of the finger pointing when all I wanted was some help, so no I did not forward the data, however

 

as you have indicated previously and I agree, the heads could be manufactured from a much better medium and given the EMS data not indicating an over temp I have come to suspect the cracking may have been from shock cooling from the flying school and hire environment, but I am certainly no metallurgy expert having only a 2 week intro when studying NDT.

 

I also forwarded the pictures to Ian for info.

 

Sure you can say that its maintenance, I didn't do this or didn't do that but fact is both engines were maintained by the book and with the advice of the factory at every turn backed up with EMS data and documented condition reporting! I am not one eyed and can forgive most and love the plane when its all going good before all this I was the most vocal supporter of the product and didn't believe other peoples first hand accounts, but slowly I had to pull my head from the sand. In 20 years of aircraft engineering I have never seen an engine with a guarantee that you will need to fix something before overhaul I am counting the days until I can fit a reliable and trustworthy power plant that isn't so delicate by all accounts. The latest roller cam engine seems to be a good product, however under 50 hours on it at the moment and I went to get in on Friday and could smell fuel, pulled the cowl and the mechanical pump screws had come loose allowing fuel under gravity to leak everywhere, this would be catastrophic in the air and I cant believe they aren't lock wired or even locked. Defect report being prepped for CASA.

 

 

[Dafydd Llewellyn]

In my experience (24hr motorcycle endurance racing) "cooling fins" on a sump just don't work, they look good but, the oil at the finned surface cools considerably , thickens and effectively forms a barrier stopping any more oil reaching the cooling surface. Fins inside the sump worked better, but not by much. We reckoned that porcupine spikes inside/fins outside would have been the best solution, but , too dear.......

Dead right, that's exactly what happens.

 

I would think that oil coolers would be mandatory for air cooled engines

They're not mandatory by regulation - remember Ralph Nader? (Legislate for the end, not the means) - but in a practical sense, they are essential.

 

I suppose sump oil capacity is small to keep weight down and that adds to the oil cooling problem.

The residence time in the sump doesn't seem to be a substantial factor; the flow velocity through the oil cooler passages keeps the boundary layer thin - and that seems to be the most important consideration.

 

 

[fly_tornado]

I'd love to see Ralph Nader meeting Rod Stiff

 

 

[bexrbetter]

I'd love to see Ralph Nader meeting Rod Stiff

A man with experience of flat 6 aircooled engines involved in crashes ....

 

 

[turboplanner]

Might pay to learn what the problem was all about rather than crap on with irrelevancies.

 

 

[DonRamsay]

I agree with the concept that you shouldn't have to be a flight engineer to fly a Jabiru engined aircraft.

 

I know it isn't strictly relevant but my newish Mazda doesn't even have a temperature gauge in the dash. Mazda are confident that their engine does not need constant monitoring for over temp by the driver. There is a warning light of course.

 

The thought that you should be monitoring (and recording) 6 x CHT & EGT as well as oil temp and pressure, etc. suggests to to me that we are dealing with a prototype not a mature product. And after all this time it should be a mature product.

 

 

[rankamateur]

The thought that you should be monitoring (and recording) 6 x CHT & EGT as well as oil temp and pressure, etc. suggests to to me that we are dealing with a prototype not a mature product.

And the fact that you need to, and the factory ask for the data, makes you a test pilot and part of the product developement program.

 

 

[coljones]

I agree with the concept that you shouldn't have to be a flight engineer to fly a Jabiru engined aircraft.I know it isn't strictly relevant but my newish Mazda doesn't even have a temperature gauge in the dash. Mazda are confident that their engine does not need constant monitoring for over temp by the driver. There is a warning light of course.

 

The thought that you should be monitoring (and recording) 6 x CHT & EGT as well as oil temp and pressure, etc. suggests to to me that we are dealing with a prototype not a mature product. And after all this time it should be a mature product.

Remind me not to buy a Mazda. The point of water temp and oil pressure gauges (or is that gage?) is to show that the engine is operating within its correct envelope. If you are in the middle of the desert in the middle of summer and the warning light goes red it would have been better to know if the temps were deviating from normal well before it all went pearshape.

 

 

[DonRamsay]

Initially, I kind of thought that way as well Col. But, I'm betting, as Mazda has, that on a probability basis it is so unlikely to suffer overheating as to make a coolant temp gauge unnecessary. The same judgement has been applied to come to the decision to not have an oil temp gauge, an oil pressure gauge or ammeter things that were once features of any well instrumented vehicle.

 

Mazda, wisely, does recognise a much more likely issue - the very real possibility that you could have a slow leak in a tyre. Mazda manages this risk with its Tyre Pressure Monitoring System. I'm comfortable with that risk management strategy.

 

Don

 

 

[fly_tornado]

Mazda make millions of engines so if they get it wrong they will loose billions.

 

 

[Guest Andys@coffs]

Nah not so much unlikely but the reality that the onboard computer will modify the engines behaviour/output power when in really hot locations so that the engine doesn't continue through to overheat and damage.....Those sort of decisions are normal for a product like a modern car engine where everything is instrumented and a reduction in power isn't likely to really impact the driver greatly, and very unlikely in a way that leads to demise, in fact in most cases they may not even be aware...take the commodore for example where I think its a six but it only runs5, 4 or 3 or whatever but less than the full complement of 6 when conditions don't require the full power..... as a means in that case of improving fuel efficiency, trouble with an aircraft is that when you need full power, you NEED FULL power and anything less may well be catastrophic...

 

Reality is that the computer manages the review of temp a billion times more often and never subject to interrupt or boredom....

 

 

[Dafydd Llewellyn]

I agree with the concept that you shouldn't have to be a flight engineer to fly a Jabiru engined aircraft.I know it isn't strictly relevant but my newish Mazda doesn't even have a temperature gauge in the dash. Mazda are confident that their engine does not need constant monitoring for over temp by the driver. There is a warning light of course.

 

The thought that you should be monitoring (and recording) 6 x CHT & EGT as well as oil temp and pressure, etc. suggests to to me that we are dealing with a prototype not a mature product. And after all this time it should be a mature product.

Not really a valid analogy, Don; your Mazda has EFI which, in effect, has a "flight engineer" in a black box, in the form of the system management computer. Adding an EMS to an engine such as either a carburetted Jabiru or a carburetted Rotax, is approximately an equivalent of this; it monitors the CHTs and EGTs and things like fuel remaining (if you want to use that feature) and brings up a warning if the pre-set limits are exceeded. You don't have to sit there squinting at it. What is doesn't do is make decisions in lieu of the pilot.

This sort of thing has been standard practice in the more modern GA aeroplane for several decades.

 

 

[Dafydd Llewellyn]

Remind me not to buy a Mazda. The point of water temp and oil pressure gauges (or is that gage?) is to show that the engine is operating within its correct envelope. If you are in the middle of the desert in the middle of summer and the warning light goes red it would have been better to know if the temps were deviating from normal well before it all went pearshape.

That's the fundamental difference between a pilot and a zombie. Me, too.

Being able to record the history of the last 100 hours or so is also becoming necessary to substantiate a warranty claim, as I understand it. No, it does not make you a test pilot.

 

 

[Oscar]

No, that's an EMIS: Engine Management INFORMATION System. A proper EMS is the next stage - making management decisions on the basis of pre-determined algorithms.

 

 

[DonRamsay]

I did say it wasn't directly relevant other than to assert that a mature product should not require constant monitoring over many variables.

 

The last car I had overheating problems with was in about 1980. And then it came about through coolant loss not the normal environment it was operating in.

 

The Jab engine, to my consumer view, is not (yet?) suitable for the application it is sold into.

 

Does anyone believe a Jab engine is cheaper over 2,000 hours than a Rotax?

 

 

[Dafydd Llewellyn]

Yes, well I was using the manufacturers' terminology. In aviation, we've tended to give the PIC the ability to make his own decisions. Admittedly, using the Bing CD carburettor has eliminated one of them - the ability to mis-manage the mixture. Now, if we could come up with something as simple and reliable as the CD carbie to eliminate the pilot's ability to mis-manage the carby heat . . .

 

There is a well-known intellectual conflict between pilots and designers over this; the pilots want to be able to control the damn thing; the designers - especially the ones who are not themselves pilots - want to remove as much decision-making as possible, so the pilot doesn't get it wrong. As both an engineer and a pilot, I find myself wanting the control, in the aircraft that I fly, but wanting to automate it as much as possible, in an aircraft that I allowed you silly buggers to fly . . .

 

 

[Dafydd Llewellyn]

I did say it wasn't directly relevant other than to assert that a mature product should not require constant monitoring over many variables.The last car I had overheating problems with was in about 1980. And then it came about through coolant loss not the normal environment it was operating in.

 

The Jab engine, to my consumer view, is not (yet?) suitable for the application it is sold into.

 

Does anyone believe a Jab engine is cheaper over 2,000 hours than a Rotax?

No, I would not argue that. As I said, there is a real point in what Ian Bent is doing.

The dilemma was very well expressed by an airline pilot friend of mine, who was confronted with the choice between the Boeing 737 and the A 320; he said: "Fly -by-wire is OK with me, as long as the wire is 7 x 19 . . ."

 

 

[Dafydd Llewellyn]

No, that's an EMIS: Engine Management INFORMATION System. A proper EMS is the next stage - making management decisions on the basis of pre-determined algorithms.

Remember the Airbus A 320 debut at Paris, where the fly-by-wire overruled the pilot? Yes, the French seem to have by now got most of the bugs out of the software. But if you look at the certification requirements for software, it will become very obvious why we are not likely to see that sort of autonomy in systems for toy aeroplanes; the cost of the proof-of-compliance for the software would put the cost of the product up by a factor that no manufacture could be competetive with. You all accepted the el-cheapo altimeters and airspeed indicators, didn't you? So are you going to accept el-cheapo automated flight hardware?

It's coming, in the form of being able to input a flight plan into a moving-map GPS and simply press the go-to button; but remember the issue with the autopilot trying to maintain height in the MU-2? The EMIS (if you want to call it that) is an iterative step that is currently acceptable, provided it has a TSO.