"Jaberoo" down (Mildura this time)

[David Isaac]

David, Read post # 109.

Well you certainly missed my point. I am aware of what Col Jones stated in post # 109. My question was simply why is this so necessary on a certificated engine if it is operating at correct temps. The symptoms Col Jones was describing are typically a result of running at over temps. So why is this happening with a certificated engine in a factory Jabiru installation and not happening with the other engine that is so popular in other ultralight aircraft.

 

 

[bexrbetter]

If there is an airframe out there that has an enclosed cockpit, decent performance in all aspects, genuine and demonstrated survivability in the case of a crash, and a better 'intelligent and informed' owner-maintenance potential than a Jab., I invite its nomination.

.

Next week.

 

 

[Dafydd Llewellyn]

Well you certainly missed my point. I am aware of what Col Jones stated in post # 109. My question was simply why is this so necessary on a certificated engine if it is operating at correct temps. The symptoms Col Jones was describing are typically a result of running at over temps. So why is this happening with a certificated engine in a factory Jabiru installation and not happening with the other engine that is so popular in other ultralight aircraft.

As a matter of curiosity, David, which Jabiru models are producing this - the certificated ones, or the LSA ones? I ask, because the certificated ones were flight tested, which includes engine cooling, by competent test pilots who were NOT Jabiru employees. I tested the early aircraft, and Keith Engelsman (ex CASA chief test pilot) tested the rest of them. And CASA normally does its own verification testing as well. The cooling test results have to be corrected to a condition of ISA plus 22.7 degrees (i.e. a 100 degree F day at sea level.)

 

 

[Guest Jablev2]

Can't blame the owners & maintainers all the timeTo many inconsistencies in the engines themselves

I very well agree. The problem is Rod Stiff and his stubbornness to fix well known issues. Its very easy to blame the maintainer.

 

 

[bexrbetter]

I heard Ian Bent is working on cowl mods to keep it all much cooler

I borrowed a set of heads from a forum member recently and had them flow bench tested in the hope that the exhaust port may be able to be reflowed to aid cooling but alas not enough mods within the current casting would be able to be made to make any major differences.

 

I haven't had time to continue with that pursuit at this moment but still hope to get a standard head and one modified to a porcupine finned head to see if that is effective.

 

 

[Teckair]

I very well agree. The problem is Rod Stiff and his stubbornness to fix well known issues. Its very easy to blame the maintainer.

I thought he had retired?

 

 

[bexrbetter]

I thought he had retired?

I have found a a retired 'overseer' is often a worse case scenario.

 

Killed the British automotive industry.

 

 

[Head in the clouds]

Some of the work done - and bloody well signed-off, in later cases by an L2 who is now manufacturing aircraft - was bad beyond reasonable belief. Replacement of the front leg, leaving a near-25mm hole clear through the firewall and the steering rod-end (which is part of the rudder control system) bending against the side of the new hole to the point where the rod-end shaft was seriously bent? The rudder cable attached with the rod-end on the wrong side of the control horn, stressing the rod-end fitting? The entire rudder control system box moving on its rivets? Annual inspection reports entered and signed off - by said L2 - without airframe hours being recorded? New main legs installed with old - and in some cases, not the correct size- bolts in contravention of the factory instructions - again signed off by said L2.

This is rather worrying Oscar, I trust you have filed a report with RAAus?

 

 

[Guest Jablev2]

I thought he had retired?

He is still there pulling the feeble strings.

 

 

[David Isaac]

As a matter of curiosity, David, which Jabiru models are producing this - the certificated ones, or the LSA ones? I ask, because the certificated ones were flight tested, which includes engine cooling, by competent test pilots who were NOT Jabiru employees. I tested the early aircraft, and Keith Engelsman (ex CASA chief test pilot) tested the rest of them. And CASA normally does its own verification testing as well. The cooling test results have to be corrected to a condition of ISA plus 22.7 degrees (i.e. a 100 degree F day at sea level.)

Good question Dafydd,

I don't know. Col made the statement in post # 109 and that was why I questioned the need. Rod Stiff also mentioned the need to do the hand reaming In his latest Jabbachat article as well, another reason why I was questioning its need. All these 'needs' point me to a fundamental over heat problem. Perhaps it is a systemic problem in engine cooling installation design or operator abuse. But then again if the engine installation does not include accurate CHT read out facilities, is that not a fundamental installation design flaw given the POH has CHT operating limits and the consumer should be able to rightly rely on the CHT instrument accuracy, especially on factory built LSA models.

 

In any case how do we know that the test bed cooling system is the same as the produced one? BTW I am not suggesting there is a difference, but I know what manufacturers have historically done with products requiring Listing verification.

 

 

[Oscar]

I borrowed a set of heads from a forum member recently and had them flow bench tested in the hope that the exhaust port may be able to be reflowed to aid cooling but alas not enough mods within the current casting would be able to be made to make any major differences.I haven't had time to continue with that pursuit at this moment but still hope to get a standard head and one modified to a porcupine finned head to see if that is effective.

Port flow affecting cooling? You are so far off understanding the physics of heat transfer that it is bloody laughable.

 

Sorry, edit - delete 'laughable', insert 'hilarious'

 

Oh, and just by the way, in regard to your claim - the heads are not 'Cast', they are CNC machined. If you had actually ever seen Jab. heads in the flesh, you'd know that. You are so much male bovine excrement, you'd overlay a Texas Rodeo paddock.

 

 

[gandalph]

Well you certainly missed my point. I am aware of what Col Jones stated in post # 109. My question was simply why is this so necessary on a certificated engine if it is operating at correct temps. The symptoms Col Jones was describing are typically a result of running at over temps. So why is this happening with a certificated engine in a factory Jabiru installation and not happening with the other engine that is so popular in other ultralight aircraft.

No David, I simply thought you may have missed that post. Just trying to be helpful.

 

 

[David Isaac]

Well with my experience with flow testing in high performance V8s, why would you bother with an engine that peaks at 3,000 RPM?

 

 

[Guest Andys@coffs]

He is still there pulling the feeble strings.

Umm I have no issue with what you say but it probably is worth disclosing your from Camit.......after all they aren't exactly on the sideline with this one.....

So....not saying dont comment, but if you do, let people know, then no one can claim your biased

 

Andy

 

 

[Old Koreelah]

I heard Ian Bent is working on cowl mods to keep it all much coolerStay tuned

The main problem with the Jab: the wing is in the wrong place!

Seriously, though, most cowls try to force cooling air out the bottom into a high pressure zone. Much easier if it exits into a low pressure area, like above the leading edge of the wing.

 

 

 

[David Isaac]

No David, I simply thought you may have missed that post. Just trying to be helpful.

Apologies Gadalph, seems I have misread your intent. Bloody hard sometimes with damn written stuff ...LOL

 

 

[bexrbetter]

Port flow affecting cooling? You are so far off understanding the physics of heat transfer that it is bloody laughable.

Ironic the ignorance to physics you have just demonstrated but I'm really not interested in your constant pissing contest.

 

Back on ignore.

 

 

[gandalph]

Apologies Gadalph, seems I have misread your intent. Bloody hard sometimes with damn written stuff ...LOL

No apology needed David.

 

 

[JimG]

So without reading though the whole 9 pages, has the actual cause of this engine failure been discovered..?

 

cheers

 

JimG

 

 

[SDQDI]

It has been determined that it was a dodgy engine with dodgy maintainers and dodgy pilot and poor engine design.

 

Well that's what I have got from the last nine pages:yes:

 

 

[Old Koreelah]

It has been determined that it was a dodgy engine with dodgy maintainers and dodgy pilot and poor engine design.

.....so nobody escapes the blame?

 

 

[JimG]

Well , it was a serious question.

 

JimG

 

 

[SDQDI]

Well , it was a serious question. JimG

Well on a serious note I don't remember reading an exact cause but as usual lots of ranting from both bashers and lovers if there was an exact cause it would be in the first 4 or 5 pages as after that it has turned more to talk of cooling issues

 

 

[PA.]

Heat extraction can be more effective is controlling heat than force cooling. Overheating is a big problem in Formula 1 this season and they have addressed this by increasing the heat extraction. The venting on the Jabiru does seem to be minimal. I do wonder how much better the heads would cool if there was cooling ducts in the cowl?

 

This is the McLaren sidepod.

 

 

Would love to see a plane designed by Adrian Newey.

 

 

[Dafydd Llewellyn]

Good question Dafydd,I don't know. Col made the statement in post # 109 and that was why I questioned the need. Rod Stiff also mentioned the need to do the hand reaming In his latest Jabbachat article as well, another reason why I was questioning its need. All these 'needs' point me to a fundamental over heat problem. Perhaps it is a systemic problem in engine cooling installation design or operator abuse. But then again if the engine installation does not include accurate CHT read out facilities, is that not a fundamental installation design flaw given the POH has CHT operating limits and the consumer should be able to rightly rely on the CHT instrument accuracy, especially on factory built LSA models.

In any case how do we know that the test bed cooling system is the same as the produced one? BTW I am not suggesting there is a difference, but I know what manufacturers have historically done with products requiring Listing verification.

Silly question - If you bother to think about it, it should be obvious that the engine test cell cooling system cannot be the same as the aircraft cooling system, because it's not moving through the air at 70 knots or so. Its function is purely to maintain the engine at the red-line temperature limits throughout the test, in order to prove that the engine can withstand those temperatures. Alan Kerr supervised the most recent J 2200 certification, and he used his own calibrated instruments, not VDO. (I used my own calibrated instruments for the flight testing I did, also; the calibration report is a required part of the test report. The instruments I used were standard aircraft hardware, not VDO; I had to get Rod to tap the oil temp probe hole in the sump for the MS 28034 probe). There was no question of cold-junction error in what I used.

 

All this test work, for a certificated aircraft, is done under CASA's beady eye. They sit in on the engine endurance run, all 50 hours of it, and they go through the results minutely. They critically observe the before-and-after engine power rating tests; and they are right there for the engine disassembly and strip examination. Their test pilot and flight test engineer re-do any parts of the applicant's flight test report they feel like (and they usually feel like checking the cooling test, because it's such a fundamental issue.)

 

Attached is a photo of the sort of thing that is involved in a test cell endurance run of an engine; it has a 5 HP electric centrifugal fan to supply the air.

 

So the test cell endurance run is a test of the ENGINE, not of its installation.

 

The test of the INSTALLATION is part of the required flight testing of each certificated model of the airfraft, and it uses the temperature limits that were established during the test cell running of the engine.

 

The flight test procedure for engine cooling is to get the engine hot in level flight at low altitude (like, 50 feet above the water, off the beach between Elliot heads and Burrum Head), reduce throttle momentarily to slow to climb speed, and pull it into a maximum-performance climb at Vy, with full throttle - and hold that climb until the temperatures hit their peak and start to fall as the outside air temp falls - which generally takes about six minutes. You record the engine temperatures and the outside air temperature, every thirty seconds (I use a set of instruments in a box with a video camera recording them.) The peak temperatures are corrected by a standard formula, to account for ISA plus 22.7C. This procedure is identical for all the design standards; they all use the same words.

 

I hope you are beginning to see why I am having difficulty accepting that the engines in the certificated models are running overtemp when they are operated in accordance with the POH, because all that, including what goes into the POH, is based on these tests. CASA is very fussy about the POH; if you look at it carefully, you will see that the operating limitations and performance sections of it are CASA-approved.

 

The LSA models are not supervised or oversighted by CASA; and I have no knowledge of exactly what was done in their case. So I do not understand why you say " the consumer should be able to rightly rely on the CHT instrument accuracy, especially on factory built LSA models." . If anything, the level of surety should be higher for the certificated models.