Yet another Jab down.....

[Captain]

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[Dafydd Llewellyn]

Rosshave a look @ LAA's safety newsletters about Jabiru distributors

 

http://www.lightaircraftassociation.co.uk/2014/Mag/June/safety spot June.pdf

In regard to the subject matter of this LAA engineering note:

 

If I were operating one of these engines, I'd replace the original permanent-magnet alternator with the CAMit belt-driven alternator. That has two important additional benefits, apart from the increased electrical power capability and the benefit of field-current regulation:

 

Firstly, it provides a substantial reduction in the "Flywheel" inertia bolted to the back end of the crankshaft. That substantially reduces the oscillating loads on those rear flange bolts, which is probably its greatest benefit. It also increases the natural frequency of the propeller/crankshaft/flywheel system, thus moving it further away from the excitation due to the firing impulses.

 

Secondly, it provides a measure of damping for torsional vibration within the crankshaft.

 

The 2200 engine that I've been running in the test cell, is fitted with one of these, and it's keeping the test-cell battery up with no more fuss than the alternator in a modern car. The installation in an aircraft may need a separate electrical approval, and heavier wiring between the alternator and the battery.

 

 

[Oscar]

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[Captain]

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[01rmb]

Certainly worth reading the July issue referenced above, especially if you own a Pioneer (and would rather not have the fuselage 'come to pieces in flight', or a Sportscruiser and not have the tailplane 'effectively fold in flight'). Rotax 9-series owners might find the information in the August issue useful to help ensure they don't get an engine fire from a cracked exhaust.

Useful information included there worth considering I thought people only needed to be told about Jabiru engines failing.

 

I recall on the RA-Aus incident list a Skyfox had an exhaust stub completely detach from its flange. Having an engine failure is one thing - going down with flames is a whole different kind of concern.

 

 

[Dafydd Llewellyn]

The common message seems to be run solid lifters and keep the engines temps down. Have you valve geometry right. Solid lifters need a camshaft change at the same time. Also putting those heat reading washes under the plugs could affect their heat range. Perhaps go one colder on affected plugs to be safe. . Nev

Are you sure about the change in camshaft? I thought - tho I may be wrong - that the hydraulic lifter engines that do not use roller-followers, used the same camshaft as the solid-lifter engines, and can therefore be converted back to solid lifters.

 

 

[Oscar]

In regard to the subject matter of this LAA engineering note:If I were operating one of these engines, I'd replace the original permanent-magnet alternator with the CAMit belt-driven alternator. That has two important additional benefits, apart from the increased electrical power capability and the benefit of field-current regulation:

 

Firstly, it provides a substantial reduction in the "Flywheel" inertia bolted to the back end of the crankshaft. That substantially reduces the oscillating loads on those rear flange bolts, which is probably its greatest benefit. It also increases the natural frequency of the propeller/crankshaft/flywheel system, thus moving it further away from the excitation due to the firing impulses.

 

Secondly, it provides a measure of damping for torsional vibration within the crankshaft.

 

The 2200 engine that I've been running in the test cell, is fitted with one of these, and it's keeping the test-cell battery up with no more fuss than the alternator in a modern car. The installation in an aircraft may need a separate electrical approval, and heavier wiring between the alternator and the battery.

If one is intending to run an iPad or iPhone (and I should imagine, any tablet, now that OzRunways and others are bringing out versions of nav. software that run on other operating systems), and /or a LiFEP04 battery, the CAMit alternator provides current regulation that is far less likely to cause problems up to and including fire hazards. The Jab. alternator was ok (if a bit marginal) for the systems of 20 years ago but if you are intending to use 'modern' electrical / electronic equipment, it's extremely worth examining all the elements involved in the power supply side. I think one could add 'safety' to the list of potential benefits of the CAMit conversion.

 

 

[facthunter]

Dafydd, It's always been the case that the ramps vary, from solid to hydraulic in general auto practice. I have heard it stated specifically the same applies to the Jab cams which I believe were outsourced. It might be possible to have a design that would work with both. I have no knowledge of this being the situation though. A call to CAMit will sort it out. Certainly anyone changing over should get the full story.

 

Just in passing, Roller followers are less critical on cam profile. Too rapid rise may result in the edge of the follower digging into the cam of a solid lifter, as it's essentially flat. (Very slightly spherical). Nev

 

 

[Dafydd Llewellyn]

Well, yes indeed, it does - but I was looking at the LAA note on the rear crankshaft flange bolts. Many people would not be aware that changing to the belt-driven alternator is of benefit to them; one thinks "Alternator - electrical system" not "Alternator - crankshaft flange attachment".

 

 

[turboplanner]

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[Dafydd Llewellyn]

Dafydd, It's always been the case that the ramps vary, from solid to hydraulic in general auto practice. I have heard it stated specifically the same applies to the Jab cams which I believe were outsourced. It might be possible to have a design that would work with both. I have no knowledge of this being the situation though. A call to CAMit will sort it out. Certainly anyone changing over should get the full story.Just in passing, Roller followers are less critical on cam profile. Too rapid rise may result in the edge of the follower digging into the cam of a solid lifter, as it's essentially flat. (Very slightly spherical). Nev

Nev, I'd agree this is normal automotive practice; however the power output of hydraulic lifter Jab engines with the flat-face followers was noticably down from the solid lifter engines that preceded them. My understanding is that that was a consequence of the cam profile NOT being altered to suit the hydraulic lifters. I think the roller followers were introduced to avoid the issues of cam profile/flat-face followers. As you say, anybody getting a conversion kit from CAMit would need to check this point, but I'm sure you will find that Ian Bent is two jumps ahead of you.

 

 

[facthunter]

Non hydraulic lifters both roller or flat faced need ramps to unload the inertia loads on the valve train. This makes them quieter and less wear on valve ends etc. I'm not surprised the hydraulic lifters gave less power. There could be several reasons for that. I'm not a fan of hydraulic lifters in aero engines. Some Continentals have them. I

 

I had an 0-300 lifter fail on take off, rendering the engine well down on power. In fact it would not climb with only 2 on board.( C-172.)

 

I still make cams now and did good work with a very nice man, Merv Waggott, in the early 60's. Nev

 

 

[Dafydd Llewellyn]

Non hydraulic lifters both roller or flat faced need ramps to unload the inertia loads on the valve train. This makes them quieter and less wear on valve ends etc. I'm not surprised the hydraulic lifters gave less power. There could be several reasons for that. I'm not a fan of hydraulic lifters in aero engines. Some Continentals have them. II had an 0-300 lifter fail on take off, rendering the engine well down on power. In fact it would not climb with only 2 on board.( C-172.)

I still make cams now and did good work with a very nice man, Merv Waggott, in the early 60's. Nev

Yep; I'm aware of that. I think Ivan Tighe was involved in the original Jabiru cam.

Almost all Lyconentals use hydraulic lifters.

 

 

[Oscar]

Merv Waggott - a legend. I had a 30/70 Waggott cam in a Peugeot 203 with a rather 'warm' 403 motor, a superb cam. I had the pleasure of taking to Merv about what would work best in that motor; he was a real gentleman and a fount of knowledge. Used Waggott cams exclusively in the race engines I built, they never let me down and always delivered exactly as promised.

 

 

[facthunter]

The cam I was working on was for a Peugeot 203/403 motor in an Elfin open wheeler chassis.. Bit of a co-incidence Oscar I'm sure there was some cross fertilisation there. My own 203 did 117 mph on pump fuel. Nev

 

 

[gandalph]

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[Oscar]

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[coljones]

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[facthunter]

The Elfin did the hill climb at King Edward Park with my car engine in it fitted hastily as the original had blown. No testing no gear ratio changes. Engine fitted with 2 SU's narrowly beaten by Doug Kelly Lotus 18. It was nowhere near the power of the original motor which was on alcohol and raced at OranPark ,Catalina and Warwick Farm?? near Liverpool, driven by Alan Fergusson from Wallsend, Newcastle. Formula Tasman Car.

 

The Bob Holden Peugeot (usually a 403) from Killara, Sydney North Shore, had the engines built where I worked. Robertson Bros in Newcastle, so I spannered many of them. I specialised in setting up the worm drive diffs after I moved to Melbourne. I detuned the "quick" 203 a bit and sold it to a TAA Captain Bob Elks in the 70's. I got clocked at 109 mph going to Essendon Airport one night, but didn't get booked by the policeman. It was nice and low with good rubber . I'd still like to have it.. It got written off at an intersection, unfortunately.Nev

 

 

[motzartmerv]

To deny that there can and should be improvements to the reliability of Jabiru engines (specifically) would be daft and counter-productive. .

Oscar, just to add some context to your points and relevance to your position as Jabiru defender, Exactly how many Jabirus have you flown/ owned/ operated?

 

I ask this with all respect, I just wish to know what experience base you draw your conclusions from, in a real practical sense.

 

 

[facthunter]

IF I was Oscar Merv, I would find it difficult to extol my virtues. I have never liked selling myself. I even get embarrassed when I'm flatteringly appraised.

 

I believe he IS in a position to have serious input to this matter. The quote you make seems to be something you would find reasonable? NO?

 

WE know your frustration and I for one don't dispute your feelings of frustration and desperation and also those others who have had personal experiences that are not good with these engines.

 

Proper statistics will show the picture, not emotions. (I'm not directing this at YOU, or anyone specifically). We know something must be done. HOW it is done is my concern.

 

It isn't a question of Jab haters or apologists. A level headed approach is needed, not taking sides.

 

Forgive me for cutting in if it isn't helpful. All Aviation related decisions need to be as correct as possible .Nev

 

 

[motzartmerv]

IF I was Oscar Merv, I would find it difficult to extol my virtues. I have never liked selling myself.

Not a problem in this case. :)

 

Stats as you say are a key to understanding, so stats on oscars experience with these aircraft is what I seek. And I do so without looking to point fingers or use name calling. I just want some context to his self described " jabiru defender" status.

 

I know already his brothers involvement in the design etc , so Daffyds views are incredibly valuable due to his experience.

 

 

[dutchroll]

All of the nuances of this debate aside, I could certainly see the Jabiru aircraft itself benefitting greatly from a more tolerant engine. Intolerant engines in the modern aviation age are normally the domain of NASA, various military forces, and other organisations who have the money, time and resources to expend on continually checking, maintaining, and repairing them to a degree far above normal GA/RA maintenance schedules. I just wonder when/if it will happen.

 

 

[facthunter]

I empathise with what you say there Dutch. I can only come from my perspective. Many of the so called Gurus' of this and other engines are a dime a dozen, legend in their own loungeroom types, these days. Not a lot of hands on experience and a sceptics view of established procedures, so we often get a smoke and mirrors presentation or view.

 

I'm disappointed in the general unreliability of a lot of the information. The Llewellyn's approach is formal and correct, often annoyingly so but in that direction is where we will end up. We have proven the need by some of our antics. A bit more discipline and a bit more reality, needed.

 

The owners and operators will suffer because of no fault of their own (in most cases.) We should bear their situation in mind when we make decisions or bring down rules.

 

There appears to be a disconnect between the CAMit and the Jabiru people. That can't be good for anyone, long term.

 

Both groups probably get more advice than they wish to cope with from dubious sources at times, so they appear to be somewhat reluctant to engage.

 

A camel is a horse designed by a committee, they say. so this doesn't need a cast of thousands or be done by a poll..

 

As has been said the Board doesn't design aero engines not does the CASA .Nor should they.

 

My view is the current engine(s) should be kept running with explained and tested updates to some critical parts. for the immediate future. The engine needs to be professionally evaluated.

 

Not anticipating any particular result AT ALL some engines have had this done and found to be operating well above the design permitted/ evaluated output, so no further development was done, on output .

 

Sometimes a modification to some clearances or oil hole location or such can achieve good results. The American Liberty engine was putting out too much power for the crankshaft to handle but they couldn't afford to redesign it so they machined the main bearing journals with more clearance at the edges. (Reverse barrelling) and continued to run them. Nothing of this is intended to apply to this situation directly but just an example. Nev

 

 

[johnm]

many must appreciate your moderation facthunter ...... most must agree that this is important for many and must be treated properly