Jabiru engines

[Guest ianymeany]

Hi all

 

I keep hearing stories of failures of Jabiru engines, and see an occasional report in the RAA monthly, but given the number of Jabs flying, I am getting the feeling that the number of failures may be exaggerated.

 

I like the look and feel of the Jabs, and am considering buying a second hand machine - would anyone like to venture their opinion on this subject please?

 

Regards, Ian

 

 

[Guest David C]

Ian ,

 

The question of aero engine reliability is always a bit of a personal thing . While one person will lambast and engine , another will praise the same motor . Me , I have flown about 110 Hrs on the Jab , always the LSA with the 85Hp 4 Cyl motor . I have never had a seconds problem with them . They need regular mntce , like all engines , and I think this is the key . If correctly maintained , at the correct time intervals and with the correct aero oil , plugs etc .they seem pretty reliable . They have a TBO ( time between overhaul )of 1000 Hrs . The present day 4 Cyl is quoted at 85 Hp , while some earlier engines had different tappets and were rated at 80Hp . This is just my opinion of course , and may be disputed by others , but lets face it , if you fly a KR2 from London to Sydney with a Jab 4 Cyl motor up the front , which has been done ,then they can't be too bad can they ..

 

Dave C

 

 

[Guest ianymeany]

Many thanks Dave for your well considered opinions. You own experience and the KR2 story are very compelling thanks mate. How do you find the LSA - it it the one with the throttle of dash?

 

 

[Coop]

Many thanks Dave for your well considered opinions. You own experience and the KR2 story are very compelling thanks mate. How do you find the LSA - it it the one with the throttle of dash?

As Dave says, well mantained Jab engines do pretty well. The problem is that a few owners don't understand very well what "well maintained" means. And a few others think they can run the engine with the throttle to the firewall all day.

 

Doesn't matter what sort of aero engine you consider- poorly treated engines will have poor outcomes.

 

Regards

 

Coop

 

 

[Guest David C]

Many thanks Dave for your well considered opinions. You own experience and the KR2 story are very compelling thanks mate. How do you find the LSA - it it the one with the throttle of dash?

The LSA has the throttle lever between the legs and under the seat cushion !!! ... I found it a little difficult getting used to the position , and add to that the control column and trim lever on the centre console and it all adds up to an ergonomic challenge . Imagine trimming the aircraft with the left hand crossing over the right hand which is on the control stick . Like all , though , when you get used to the quirks it feels "almost " normal .

 

I think all pilots who have flown the Jab LSA would say that they are easy to fly , but not so easy to fly well , and particularly in the landing stage .. You must keep on top of the airplane , they will bite you given half a chance !! , and like most light rec aircraft , you will have to get used to using the rudder to pull off balanced turns . I have only flown a few types , the Tecnam P96, Bantam , Lightwing and CTW , but apart from the Lightwing , which is a tail dragger , they would be the most challenging to land .

 

They cruise beautifully at around 95Kts at 2800 rpm , and consume around 14L/ Hr of fuel . They are not the roomiest aircraft around , offer little baggage space , and on standard tanks give around 4 hrs endurance , which I think is plenty for the average male , and particularly the average male bladder ...

 

If you have a chance , take one out with an instructor , you never know , you may love them ...

 

Dave C

 

 

[Guest ianymeany]

Many thanks mate

 

Congratulations on mastering ergonomics - I am still struggling with the small cabin and I am not large

 

I will certainly give the Jabs a try before I buy a LS, and would love to suport an OZ maker.

 

 

[Guest ianymeany]

Thanks Coop, you make very good sense. I went to a few flyins before starting to fly RAA, and was amazed at the poor air sense and machine care by many "pilots".

 

I very nearly did not bither, but am glad now I did.

 

 

[TAA Qwerty]

Iany

 

I have a heap of hours behind Rotax and was complacent and happy till I was faced with the prospect of purchasing a Jab powered machine. My thought process went something like this. There SEEMS to have been lots of jab failures but then there are thousands of them in the air. CASA wold not have certified them if they were not OK. Sure they have their fair share of problems but properly maintained and operated there should be no problems....and so far so good....I boought the aircraft and it is operating flawlessly.

 

Coop

 

Why not run the engine "on the firewall all day" If burning the fuel doesnt worry you and the temps are OK, why not run it at the firewall. What stresses could possibly be produced that could be a problem.

 

My engine won't stay cool for extended periods but I have a mate who, after a proper warm up, pushes the throttle to the fire wall and leaves it there till he reaches cruising altitude 10 - 15 or more minutes later. At first I thought this was hard on the engine but it isn't, why would it be, what is full throttle going to do to the engine.....nothing that I can think of.

 

Any thoughts, I would love to know if I've missed anything.

 

 

[Coop]

IanyCoop

 

Why not run the engine "on the firewall all day" If burning the fuel doesnt worry you and the temps are OK, why not run it at the firewall. What stresses could possibly be produced that could be a problem.

 

My engine won't stay cool for extended periods but I have a mate who, after a proper warm up, pushes the throttle to the fire wall and leaves it there till he reaches cruising altitude 10 - 15 or more minutes later. At first I thought this was hard on the engine but it isn't, why would it be, what is full throttle going to do to the engine.....nothing that I can think of.

 

Any thoughts, I would love to know if I've missed anything.

Running the engine flat out puts the maximum stress on all components, gives the greatest temperatures and pressures, and therefore increases the rate of wear, etc. Sure, your engine might be able to take it, but if there are any flaws, then this will bring them out. Cooling systems, for example, are designed to minimise weight, and could be marginal when at max power. Combine that with (say)a butterfly sucked into the radiator core on a hot day (not considered in the design) and you could get overheating, whereas at less power, the system might cope.

 

10-15 minutes isn't a long time. My Gypsy's oil temp doesn't stabilise until 20 minutes after a change in power. The manual for my engine states maximum times for given power settings, some as short as 5 minutes, some as long as 1 hour, depending upon circumstances. It certainly doesn't approve continuous operation at max power.

 

I also have operational experience on my side. I've always looked after the engine- given it plenty of warm-up time before opening up for take off; reduced power in the climb once the flaps are up; allowed the machine to accelerate in level flight before slowly reducing the power to cruise, and slowly reducing power for descents. There are always exceptions, of course- when a 'roo jumps out in front of you on short final the throttle gets opened promptly!! On my engine, 500 hours between top overhauls is considered about par for the course. We recently did our first top overhaul after 750 hours. That's a real saving, and I figure my careful handling of the engine probably contributed to it.

 

So that's why I think it is unwise to run an engine at max power all the time....

 

Coop

 

 

[GAJab]

It doesn't matter how well you look after a Jabiru engine, it will still do what jabiru engines do best and require a top end overhaul by 600 hours, particularly for the 6 cylinder models. It's the harsh reality and I can give you many examples ranging from 130 hours upwards where this has been the case.

 

 

[TAA Qwerty]

You are both entirely correct but the only real negative stated for the jab engine is increased wear, and this will only be a marginal increase. All the other comments while correct are not neccessarily bad for the engine. Higher stresses, so what. Higher temps and pressures, so what. The engine and its components are designed for this otherwise there would be a restriction on available power, smaller carby or what ever....or...there would (in the case of the Gypsy and the Rotax) a restriction on time at full power. It is my understanding the the restrictions on time at full power ar due to the cooling system. Rather than make the cooling system able to cope with continuous full power and therefore heavy, the designer opts for a lighter cooling system and uses the engine its self as a heat sink to allow for operation at full power for short durations.

 

Having said all this I don't operate either of my engines (Jab and Rotax) at full power for extended periods but the point I am trying to make is that as long as there are no over heating problems there is no mechanical reason to "baby" the engine. Jabiru engines actually perform better under load with a few revs. It seems that the load and revs maintain a better operational environment for the rings. I am told that running your Jab at low power at low rpm (2400-2600) will result in the engine burning more oil.

 

 

[Guest ianymeany]

Many thanks for your comments and experience mate, very much appreciated. I am very grateful for the very thoughtful responses received from this thread.

 

Regards, Ian

 

 

[biggles5128]

Spoke with one of the senior mechanics at Jabiru on this subject.... He had done a service on the demo 6 cyl Jabiru from Bundaberg, which included a leak down. The aircraft was then flown around Australia, the pilot running the thing flat out all the way. Not too worried about the extra fuel that would be used but keeping all temps in the green. On his return the engine was again serviced including another leak down, the interesting thing was that the engine was in better nick on his return than before he left. The moral I believe is do good and regular maintainance, use sound in flight engine management, trend monitoring, but don't treat it like a day old kitten.

 

 

[siznaudin]

I'll post in this discussion line as it's not worth starting a new one. That said, it may be of pleasure/interest to you Jabiru-ites out there.

 

I'm a non-pilot "enthusiast" (I like to watch, as the voyeur put it...) but have been lucky enough to have had flights in such things as Tiger Moths (with a barrel roll on one occasion!), Austers, Stearman DH Beaver and Chipmunk. Lots and lots of fun, as you might well imagine - and I really count myself fortunate to have had such treats.

 

Now Jabirus I have hitherto regarded as a sort of plastic streamlined tadpole modern "thing" of no great virtue. Somewhere I had picked up the belief that their rate of climb depended, like the fully laden B-24, on the curvature of the Earth.

 

Well how bleeding wrong was I !

 

A couple of weeks ago I got to fly in a 6 cylinder Jab: and simply could not believe it! Takeoff - vroom! Climb - zoom! Chuckability - whee!

 

As well as all this, the damn thing was smooth, sophisticated and civilised. Fan-bleeding tastic.

 

Looking behind, I see a cavernous space for the other two passengers/baggage: what a useful unit!

 

In short, I've been converted: while I just love the nostalgic vintage aircraft experience, it's obvious, like the canine dangly bits, that there has been a very great deal gained in the last 50 years or so.

 

As a post script, in the interests of exhaust valve temps the owner/builder runs his engine a little richer than normal - at a small increase in fuel burn - and at (?)hour intervals he changes out the exhaust valves; their price isn't prohibitive so for him it's a case of safety at a reasonable price.

 

Happy flying, Jab-ites! [ATTACH=full]1745[/ATTACH]