Jaba-who

I'll have to check the number but I have a sensenich prop on mine ( in fact it is the same prop that was used on jabiru 's own demonstrator (VHBNP) for several years.

 

I have had some extensive experience with jabiru props and after two went to the sensenich. The issues I had (and as have all the jabiru owners here in Cairns) is that the props are too coarse. We have several jabs here and none of them could get the required static RPMs. I also had issues with high fuel usage. When I put the sensenich on I immediately got 250 Revs higher and the fuel usage dropped from high 30s back to 24 l/hr.

 

I had extensive discussions with jabiru about it and they initially stated the pitch stats were the same as the sensennich but after research jamie cook said the method of measuring the pitch was not the standard and conceded they were more coarse.

 

The sensenich is a way better prop from pitch point of view but there are some negatives.

 

The prop is more fragile than the jabiru. It's made from harder timber (maple vs pine) and isn't covered with a layer of glass. So we have found them to be more prone to cracks in the tip. We have had two Sensenich props get fine cracks in the tip. In fact mine has been repaired three times since I got it. Admittedly the first was a stop gap repair and the second was an almost negligent repair (the repairer used polyester resin not epoxy) and it shredded the glass layer in the first rain I flew through. The last repair was actually done properly and has lasted well.

 

The other issue is because it has only a thin layer of varnish it needs more frequent retourquing (especially here as we have long periods of high humidity). The torque tensions are a bit higher than the jabiru one because it is harder timber.

 

On balance I much prefer thevsensenich prop.

 

 

Haven't seen that. I'll let him know and he can chase it up. Thanks.

 

 

All of the above are correct but I guess there are some comments to be made.

 

On MRX - XRX difference. MRX is about 1/3 the price. But XRX tells you where the conflicting ACFT is ( direction, distance height and whether it is climbing or descending into your bit of airspace The MRX gives that except the direction and I can tell you from 2 near misses (which is why I spent the money on a PCAS ) that you don't always have time to wonder which direction the conflict is coming - you need to be told so you can look immediately. I have a friend who has an MRX who is looking to offload it to buy an XRX because he's found having no indicator of direction a problem. He has a low- wing with bubble canopy with great views up but poor down. I have a jab which has pretty good views in some directions but there are plenty of directions where you have no vision. And All ACFT have blind spots somewhere so relying on the conflicts only ever being where you can see them is being optimistic.

 

After over ten years of flying on aero club tours around Oz i reckon that relying on the Mark 1 eyeball alone is a fools paradise. We fly often ten + aircraft in company and we talk to each other and tell each other exactly where we are (using GPS ) and you often just can not see small GA ACFT even when you know they are there.

 

The XRX will also connect to a number of screened avionics displays to incorporate the returns on the display. I'm not sure if the MRX will do the same. I don't think it does.

 

 

In the context of your original post about crossing ocean being safer with floats - knowing my luck there wouldn't be anywhere smooth to land.

 

I think my friend said the buccaneer was limited to waves of less than 1 foot. So essentially in the open waters of say Bass Strait I would have thought that there would be lots of days where floats or floating hull would be not any better than wheels.

 

Not that I am thinking Bass Strait anyway. I am from Cairns so the warmer but no less choppy waters of the Barrier Reef were more where I had mind. There are more days where you can't land a float plane than can up here.

 

But

 

 

Guess the best way is to have floats when crossing then remove them once back home, much saver option

I have no personal experience of floats but have a friend who has owned a Lake Bucaneer and now a C 206 on floats and I have heard him say that floats are actually quite restricted - can't land when there is more than a very light swell or waves.

 

 

Was thinking more about ditching.

 

Anyone had to ditch a jabiru?

 

Did it flip over on wheels touching the water?

 

 

Looking at the image of the Jabiru floating in the floods - it appears the left wing is barely in the water and the right one not at all. All the buoyancy needed to keep it afloat appears to be in the fuselage. I am assuming the cabin isn't water-tight (mine certainly isn't - but maybe the builder was more meticulous than I am :-) ) Given that the wings are also made up of lots of foam sandwich I would assume there is total buoyancy is waaaay in excess of that needed to keep it afloat if you ditched. Makes me feel a little more comfortable about flying over water.

 

Now what about techniques for getting safely from air to water?

 

 

Yep. Sources of interrogation can be either ground or air based (TCAS). Much of my flying is in company with other aircraft so if there is an interrogation source I have had opportunity to see by company aircraft.

 

You can sometimes get a hint it might be aircraft based. I have been flying in company with another aircraft way out in the boonies - no signal seen. Then suddenly he comes up on the PCAS and my own transponder is seen to be responding as well. Then disappears after a while. Not anywhere near a ground station so assume it was an over flyer.

 

If the signal is solid for long period of time it is probably a ground station that's triggering.

 

When ATC calls you well you know it's ground based. :-)

 

My biggest problem with PCAS has been false positive signals. Ghosting is quite common. Have to look at the distance and height of the threat. If they jump around it's probably a ghost ......... Probably. But I look hard anyway!

 

 

Since the actual thread was hijacked and closed down before I got to add my 2 cents I have to start a new one:-)

 

I have to add my support for a transponder (and PCAS).

 

The technical stuff has been mostly correctly posted by several people but what they haven't really stated was the extent of coverage by ground stations (you don't need radar, just ground based transponder interrogating equipment) which is very widespread across even outback Oz. I do lots of outback flying and I am regularly noticing the transponder replying to interrogations in some very outback locations. Basically if you are in the vicinity of an RPT route between towns there us a good chance it is serviced by transponder equipment.

 

I can also vouch that the entire eastern seaboard, lots of the inland around regional cities and even lots of parts of Cape York Peninsular are serviced by transponder interrogating equipment. Our group got called by ATC in western NSW one year asking were we a group together as they were receiving a bunch of returns.

 

I have a Zaon XRX and it is quite interesting watching it pick up people even when you would have thought the transponder interrogation was minimal.

 

 

I think it must be a left over from years ago. Haven't heard anything about a recent one.

 

 

I'm not sure of your terminology. If by barrel nuts you mean the nuts on the through-bolts you're right....partly. It's even more complex than that.

 

To get to the rear upper nuts you also have to remove the starter motor. To get to the lower ones you also have to remove the exhaust and inlet pipes.

 

I started doing mine (actually two of us planned to do two 3300s) and decided I could better spend my time doing other stuff and have booked both in at the factory at the same time as the Wide Bay Air Show. SO we'll go to the show, hang around an extra day and get the two done by jabiru for free.

 

One Jabiru service guy near here has said he just pulls the whole engine out and puts the engine on a swivel bench mount. Jabiru factory allocates a full day and two blokes for them to do one engine.

 

So all in all it is not a simple job.

 

 

Which service advisory is that?

 

So far I have read all that have come my way but maybe haven't seen them all.

 

So far all that has been mentioned in the ones I saw are fretting (which is due to movement (often micromovement) and happens usually without any change in shape of the parent structure) and thread failures on either the bolts or the nuts (I'm not sure which but the assumption seems to be the thread on bolts rather than the nuts.)

 

I'd be keen to see an official statement showing the engine blocks have actually twisted.

 

 

Hi Nev.

 

The set up already includes finger filters in the main tanks (that's standard in Jab main tanks ) that would trap such things as bits of chain and other foreign objects that get into the main tank. What I am pretty sure is involved here is an extra paper filter between the main and header tanks.

 

What Jabiru currently uses (apart from the aforementioned finger filters) is a single paper filter (Repco z15, I think, model) between the header tank and the engine, usually just after the electric fuel pump.

 

I have pulled apart a couple of the fuel filters in the past when I replaced them and never found anything in them. Also never heard of them clogging up on anyone else's machine. Have a talk to Jabiru but I am confident they will say it's OK to just remove that extra filter and run on one filter.

 

 

If the fly wheel always turns in the same direction you wouldn't expect bending back and forth would you?

 

 

I have a vague recollection that the old construction manual (before about 5 years ago) had two filters fitted in the line in one of the several conflicting diagrams so maybe this one was following the book?

 

Mine is in the same spot as jetjr's and every 100 hourly I swear I am going to move it somewhere more easily got at. It's a real problem where it is.

 

 

I have my J430 set up with a Dynonavionics D180, Garmin 296, AP 74 module and both pitch and roll servos.

 

It was reasonably easy to install and flies the aircraft very nicely, although like someelses comment about turbulence, it is not as good when it gets knocked around.

 

Have a look at my website. Http://www. jabiru430.com and follow the links though the work done since completion of the build.

 

 

I think Nev's use of "substantial" is reasonable, even though they are, in static terms, pretty minimal, they would load up pretty heavily at high revs.

 

I'd be interested to see the bolts that have fractured and where they have fractured. Wonder if they have all fractured at the level of the flywheel/crankshaft interface (which would suggest shearing forces at the flywheel as Nev suggests.)

 

But if the fractures are occurring deep in the threaded sockets then you might think that the forces were following a different path, especially if the holes (either in the flywheel or the crankshaft) show no deformity.

 

I can only assume the reason the prop bolts don't break is the timber allows for some deforming to absorb the vibrations. But also the bolts themselves are further encased in the drive bushes where they go through the metal flange. So I guess there is a fair bit of protection of the bolts in the forward end.

 

 

Nev,

 

I understand you are not a Jabiru engine owner so maybe you are unaware of the 10 paged document (JSB 012-2 ) that Jabiru have released that includes discussion about the causes of the bolt fractures. They outline 10 causes of bolt fracture of which only two are related to the flywheel itself. All the other 8 are related to transmitted vibration/shock through the crankshaft from the propeller.

 

What tests did you have in mind, and do you have any evidence they have not already done them?

 

I can't say how they arrived at this information but one has to assume they haven't just dreamt it up.

 

 

Though Jabiru's supposition that the problem is due predominantly to propellor issues would make this mod not applicable to some engines.

 

Will the same issue of transmitted forces still have the same potentially destructive effects even with the plates?

 

 

Can you give a breakdown of how many had full suite of EGT and CHT sensors and what their temps were like in the lead up to the problems?

 

If they had a full set of each and the temps were all good then it gives a different indicator of reliability (or lack thereof) compared to if they were just running in an unknown state or if they were known to be high.

 

 

Yep. I did the same. They said they are setting aside a full day for each engine. But they are not able to start them till mid May. They are taking bookings for dates after that. As already stated cost is free.

 

I also asked if they could put the new plenum chamber on at the same time. The guy I spoke to said they were about $600 - $700 for the parts. They are not yet a recommended replacement but the engines with them on were getting better narrower spread of figures so were probably going to be recommended soon. I have till the end of the year so will probably wait to see how the plenum chambers go and get them done at the same time.

 

 

I have just added some stuff to my webpage about the baffle experiments.

 

Try looking at http://www.jabiru430.com/EngineCooling.html

 

I have pages of figures for the various combinations that I have graphed in Open Office. But I have to work out how to show them on a webpage. At least the final graphs that show the better combinations that is. Basically they show:

 

The best combination seems to be:

 

A crossed baffle in the carby intake

 

Tilt the carby away from the hot side (if one side is hotter than the other)

 

Run at higher RPMs

 

 

We aren't talking about issues that are always major. Or What's major to one person may have been nipped in the bud as a minor change by someone else, who never realized it had the potential to become major. Plenty of people fix things, wonder whether it is worthy of reporting, then forget or don't bother.

 

Often people hear of an issue, fix it and assume the whole world knows about it and doesn't need to hear about their encounter with it.

 

 

Quote "I don't believe Jab or Rotax know the true stats. I reckon most people that have problems probably just fix it and get on with it without mentioning the issue to the manufacturer or RA-Aus."

 

Yep. Agree entirely. I know for a fact that plenty of minor problems get fixed or worked around and then never mentioned to Jabiru. Can't imagine it would be any different for Rotax.

 

 

"Just because you "haven't seen" them doesn't mean they are not out there."

 

I have to agree with bushpilot.

 

Like everything, the problems and the unhappy comments are the things that get published or talked about. The mundane and happy get kept quiet. Seems from what I hav heard there are a lot that do get full time. Mostly hard workers being used commercially. The ones that get treated very gently(which is a lot of the total) tend to play up. But I can assure you that happens in Lycomings and Continentals as well. I paid a fortune to get all the cylinders flexihoned out on a Lycoming because it sat in the hangar too much. A friend just got his R44 helo all new cylinders cos he didn't use it enough.

 

I was on another forum a while back where someone made a similar comment that Rotaxes never gave problems. That was followed by pages of comment from rotax owners that that was not the case. They give lots of trouble to some people, in some situations. Some people had very little trouble but there were enough people with problems to be able to say that they aren't immune either. Though just what the stats really are I can't say. Would be interesting to have an accurate survey.