Major weaknesses addressed

[DrZoos]

I am very reliably informed these test engines have been consistently producing 128hp. They have been test flying them in an accelerated testing phase. Not in the way we need as customers (1000+ hours reliability) but in the way they need to gather actual flight data on the engine in flight . A different head material has also been tested with continuous bursts of 5 min max power to see how it responds to the heat. Deliberate hot running on touch n goes of 170C and the 5min max sessions at 210C have so far proved no problems for the valves which apparently have improved cooling. And all with a dipstick to boot.

 

 

[Guest Maj Millard]

Well nice to see them doing some controlled testing at last..........bit like waking up an Elephant though. We have been on them now for about six years at least to fix things.....................Maj.....

 

 

[turboplanner]

Starting to do testing is a loong way from trouble free production; I've done a few hundred of those cycles and there have been surprises on every one.

 

 

[DrZoos]

In fairness though they are in a pretty advanced position due to experience with this engine....

 

But i agree .... Testing is a long way short of convincing punters to be to fly with one

 

People buy based on six main emotions. But in this case it will be greed , fear or pride.

 

The only way camit will steal a decent volume of sales will be to convince people they will be safer, save money or look smarter by having one.

 

Ultimately thats going to require a track record of reliability or a significant incentive to buy one. And not being able to shove it in club planes that might rack up the hours fast , they are going to either take a very long time to establish that reliability or they are going to have to fast track some engine lives.

 

I get the feeling after my source they will fast track it, but they are not ready for that yet.

 

Just as Mr Stiff probably wishes he did more testing early up these guys are actually trying to test it enought to get it to the stage they can do some longevity work...

 

Sounds to me like its very very very early days in terms of testing.

 

 

[Dafydd Llewellyn]

In fairness though they are in a pretty advanced position due to experience with this engine....But i agree .... Testing is a long way short of convincing punters to be to fly with one

People buy based on six main emotions. But in this case it will be greed , fear or pride.

 

The only way camit will steal a decent volume of sales will be to convince people they will be safer, save money or look smarter by having one.

 

Ultimately thats going to require a track record of reliability or a significant incentive to buy one. And not being able to shove it in club planes that might rack up the hours fast , they are going to either take a very long time to establish that reliability or they are going to have to fast track some engine lives.

 

I get the feeling after my source they will fast track it, but they are not ready for that yet.

 

Just as Mr Stiff probably wishes he did more testing early up these guys are actually trying to test it enought to get it to the stage they can do some longevity work...

 

Sounds to me like its very very very early days in terms of testing.

Well, as you say, they are working from a known base, and looking for an improvement. It takes time to evaluate how big the effect of an improvement will be on the longevity of the engine; but it takes a lot less time to quantify that there IS an improvement. Elevated temperature testing is likely to be pretty relevant in the case of the cylinder head; see the attached - it shows how the effect of time at elevated temperature affects the strength of a typical aluminium alloy; you can see how much faster it loses strength at the higher temperatures. So better cooling can be evaluated with some knowledge - or a change in the alloy. If one can measure the temperature of the exhaust valve guide and thereby modify the design to make it run cooler, you can be pretty sure of an improvement in durability. Some users can get quite acceptable lives from their Jabiru engines; some do not. The biggest single factor is the user; and that's not something the manufacturer can measure readily. All he can really do is try to provide a bigger safety margin.

 

 

[Marty_d]

Interesting thread. Thanks to all those imparting wisdom on here, from the perspective of someone who couldn't tell a valve seat from a dunny seat.

 

Seriously though as others have said it's going to be a hard run for any small company trying to sell "new" engines - like going for your first job, you need experience but you can't get it because no one will hire you without experience... recreational flyers will be looking for runs on the board before parting with their hard earned IMHO. In a couple of years (ok, an unspecified number of years) I'll be looking to buy an engine. Pretty sure I wouldn't buy any type that's only been in production a couple of years. They may not have had a single problem in that time, but they wouldn't have accumulated the hours that'd make a first time buyer like me feel safe.

 

This may get me stomped on by those getting excited about this engine, fair enough, go for it. But I'm just giving my opinion from my perspective.

 

 

[turboplanner]

Marty you've touched on some marketing reality. That's the way many people think and that's the challenge of any new product. Historically there have been some great cars which didn't catch on quickly and were scrapped on financial grounds. It takes a long time to get acceptance from the market place, and one of the best ways to kill a new product stone dead is to make outlandish claims before reasonable in-service performance is established beyond all doubt.

 

I was primed up by a major truck engine manufacturer once with test information on fuel economy three years before release, and kept my major fleet customers, some of Australia's biggest truck operators, informed month by month.

 

It was a 10 litre engine, but kept the 14 litre crankpin, con rod and piston size, so it would be unburstable - ideal conditions for Australia. It was a quarter of a tonne lighter than the 14 litre (which should have been a warning to me), and it attained a spectacular return of 10 mpg Los Angeles to New York with a tandem axle semi trailer fully loaded.

 

I had pre-orders waiting, and when it was released quickly sold 30 trucks with this great engine.

 

Almost immediately engine problems surfaced, fuel returns were about 6.5 mpg, and the fleets were demanding action on a particular problem.

 

On their behalf (and to have any chance of future business) I organised a meeting with the engine manufacturer, and can still remember the scene as I entered the car park and parked among PALLETS of replaced pistons stacked about a metre high.

 

As I entered the board room expecting to just be talking to my normal contact, five other people entered, were introduced, the screen lit up and a senior executive started to give me a power point on "where we are with the 105 issues found to date"

 

To their credit they worked with every one of my fleets, replacing components, in some cases complete engines and getting the fuel returns up to reasonable levels, but it was too late for the engine, it was gone within five years.

 

 

[facthunter]

Starting from a known engine and depending on what records of failures had been kept, and how they have been analysed, I reckon there should be immediate improvements available.. It won't require a complete redesign. IF it was proposed you would have an entirely different approach and it would be very expensive, so I can't see why endurance testing is particularly called for if the alterations make some parts better at their job and don't cause extra load on others in the process.. Shorter runs at high temps and RPM for example may be more indicative of the success of the modifications. than hundreds of hours of normal use. Nev

 

 

[Guest Maj Millard]

Test cell running and monitoring of engine performance parameters is the basic engine testing regime . Usually the biggest problem here is the constant noise produced, over a long period, plus keeping fuel, and cooling air up to the engine. The latter usually resolved with the use of large fans. A lot can be learn in a short time this way if conducted correctly.

 

I would expect this to be the very minimum level of testing for someone wishing to manufacture and supply a reliable aero engine, certified or not..................Maj...........

 

 

[Dafydd Llewellyn]

Test cell running and monitoring of engine performance parameters is the basic engine testing regime . Usually the biggest problem here is the constant noise produced, over a long period, plus keeping fuel, and cooling air up to the engine. The latter usually resolved with the use of large fans. A lot can be learn in a short time this way if conducted correctly.I would expect this to be the very minimum level of testing for someone wishing to manufacture and supply a reliable aero engine, certified or not..................Maj...........

That's exactly what happens in the required endurance run for engine certification. What would you consider to be a "short time"?

 

 

[DrZoos]

What would you consider to be a "short time"?

Well if you can manage to run it for 5-6 hours in a work day 5 days a week its going to be a lot of months before you have some good reliability numbers. Basically 100 hours per month or so. So what numbers are you wanting to see before you buy and on how many engines do you want to see it done on? Personally i would want to see 500 plus hours on several engines to establish some good credibility. And perhaps 1000+ on one engine. And if i was running the show and had the cash, i would want to do that before i sold any. Its easier to fix things in house then once they are all over the place or after you injure someone.

 

 

[turboplanner]

If you're at all serious you run it 24/7 under load, with heat cycles where a load is put on and temperature monitored and the cooling system adjusted until the temperature stabilises at an acceptable power on temperature. Then you start to do some fine tuning.

 

 

[facthunter]

I think you would want to have an aim in the test regime other than just accumulating hours which may prove little.

 

Military rated engines may have a service life of say 400 hours and the SAME engine run to lesser loads will have 2,000 or more hours life. Reliability is what is needed. This is achieved by having the engine nowhere near a limit that might cause a failure. You build in a margin of safety. You do the same with aircraft structures. The designer builds the margin in depending on the task the machine has to do.

 

If a motor was boosted say .5 atmos and run for one hour with the heads at 230 degrees C at 3500 rpm it would convince me more than 1,000 hours at 80% power. Some car engines run ice water through the hot engines to shock cool and distort them. They should be exposed to conditions more extreme than likely to be encountered but of the same nature as would be expected in service. Nev

 

 

[turboplanner]

To my knowledge we have never publicly seen a metallurgical report on a failed through bolt and associated area. Several of us have attempted over the years to try to come up with a solution, but without this basic information there's no starting point.

 

FH, I can't see where 230 degrees would take you when the chamber temperature could be anywhere from 1500 to 3000 degrees and the piston to cylinder wall performance from what I've read from owners seems to be good.

 

The exhaust valve issues also seem to have a separate cause which some people have put forward theories on, but that issue to me would seem to be relatively easily solved.

 

To me, it just needs a logical step by step analysis first, then some action after rather than any radical change.

 

 

[facthunter]

The 230 degrees C is an operating limit on the high side but affecting the material strength so it's worthwhile to run at that temp or higher in a test. The combustion effects are practical too as it's a possible situation to be encountered. These are only sample suggestions, but I hope you get the drift. Be nice to measure piston temps too because I've seen plenty of gudgeon pins coloured blue. as well as sections of the bores. Nev

 

 

[Dafydd Llewellyn]

Well if you can manage to run it for 5-6 hours in a work day 5 days a week its going to be a lot of months before you have some good reliability numbers. Basically 100 hours per month or so. So what numbers are you wanting to see before you buy and on how many engines do you want to see it done on? Personally i would want to see 500 plus hours on several engines to establish some good credibility. And perhaps 1000+ on one engine. And if i was running the show and had the cash, i would want to do that before i sold any. Its easier to fix things in house then once they are all over the place or after you injure someone.

Yairrsss . . .that would be nice, IF one had the money.

Let's see, now: CS-VLA calls for an endurance run of 50 hours, in 25 2-hour segments. Each of those segments has one hour of cold start, idle, full power, etc, and one hour at full throttle at maximum temperatures of CHT, oil, etc. This is quite separate from the various tests that must be performed for detonation, vibration, crankshaft torsional resonance, backfire testing, etc. All this has to be done with a "representative propeller" - you can't simply shove it on a Dyno. For certification, CASA has to be present for all of this.

 

For a 128 HP engine, that's going to consume around about 1000 litres of fuel, plus about 150 man-hours, plus 500 around KwH of mains power to run cooling fans, etc. - say $20,000 in direct costs, taking into accound transporting the fuel, etc. Then there's the cost of the test engine, which has to be fully "conformed" prior to the test run. It also has to be fitted up with thermocouples in all sorts of places. There's another $25K or so.

 

Then there's the cost of the test cell itself. Care to estimate what that costs? Workplace health & safety? Noise? And the engine has to be put through a power rating run before and after, because one of the aims is to show that 50 hours of torture at maximum everything, has merely run the engine in a bit - it should be producing more power at the end of the run than at the start of it. That means the test cell must be capable of running the engine at standard sea-level conditions

 

Once the final rating check is completed, the engine has to be stripped and inspected, also under CASA's surveillance. CASA charges around $180/hour currently.

 

You're looking at at least $ 100K to do just this much, and that's only if it all works perfectly the first time. You are asking for a procedure which - apart from the endurance run being increased to 150 hours - is appropriate for an engine to be used for carrying paying passengers in scheduled airline use. You want ten times this? AND you want an affordable engine?

 

BTW, test-cell running does not normally expose the crankshaft to propeller gyroscopic couples, or inclined airflow. The best way to include those effects is to put it in an aeroplane and fly it.

 

 

[Yenn]

That 230 deg is nowhwere near the combustion temperature, but it is the average heat of the cylinder head. there are several reasons why the head is lower in temp than combustion, such as the fact that combustion only lasts less than a quarter of the cycle and also incoming air and fuel are acting as coolant as well as the cooling airflow over the fins.

 

From memory to get an aero engine certified such as a Lycoming it has a test regime to follow, which includes some run time with no oil. I can't remember the exact requirements, but they are probably on the FAA web site.

 

 

[Oscar]

The whole test-cell thing used to be the way to go, but why would manufacturers do it this way nowadays? All they need to do is even just indicate they are thinking about building an engine and they will be told what they've done wrong, what they're going to do wrong, how to fix it, and why it'll never be half as good as a Rotax anyway, if they read some of the comments on this site.

 

 

[turboplanner]

You've got it wrong Oscar, we're just trying to inject some reality and counter some of the fantasy that had been posted. Some of us have built a few engines, experienced a few problems, and fixed them; others have worked in the industry week by week through good and and bad times and know the reality as against theory.

 

 

[DrZoos]

The whole test-cell thing used to be the way to go, but why would manufacturers do it this way nowadays? All they need to do is even just indicate they are thinking about building an engine and they will be told what they've done wrong, what they're going to do wrong, how to fix it, and why it'll never be half as good as a Rotax anyway, if they read some of the comments on this site.

Merry xmas oscar... Its a time to be happy

Personally i like this discussion and think its been very well behaved, not sure what got under your skin. Its a forum, its about discussion and opinions and if facts come along and spoil the party thats ok too:oh yeah:

 

I didnt see anyone saying anything was done wrong. Just a harmless discussion about some testing and possible testing. Im sure at the end of the day ian will do as he pleases. Personally i hope its ten times as good as a rotax.

 

 

[Guest Maj Millard]

Well if you can manage to run it for 5-6 hours in a work day 5 days a week its going to be a lot of months before you have some good reliability numbers. Basically 100 hours per month or so. So what numbers are you wanting to see before you buy and on how many engines do you want to see it done on? Personally i would want to see 500 plus hours on several engines to establish some good credibility. And perhaps 1000+ on one engine. And if i was running the show and had the cash, i would want to do that before i sold any. Its easier to fix things in house then once they are all over the place or after you injure someone.

I'm talking run them 24 hours a day continuous until failure, or 1000-1500 hrs...whichever comes first

 

 

[Guernsey]

I am sorry guys that I am not able to contribute anything to this forum discussion however, I had hoped to win that recent $70,ooo,ooo lottery and was going to donate $10,000,000 to Jabiru and another $10,000,000 to Camit to develop the newly improved engine plus what ever amount it would cost to pay a group of pilots willing to test fly the engine in five separate Jabirus for 1,500 hours each as quickly as possible. The offer still stands whenever I do win.

 

In the mean time Merry Christmas everyone..

 

Alan.

 

 

[DrZoos]

Lol If ya cant afford to test the thing you shouldnt be in this game. $50+k to test is peanuts if these guys are serious.and im sure they are.

 

 

[dazza 38]

These dudes have been making engines for over 20 years. They should have the bugs ironed out by now . Actually it has me stuffed how nobody has been thrown in jail by the multiple engine failures that have occurred with engine hours that are under 25 hours total time. Sorry guys but you can't blame owner maintenance when the owner hasn't even touched the engine with a spanner." Operator abuse under 25 hours" yeah that could happen but seriously, are these engines that fragile that they fail that early. ?

 

 

[fly_tornado]

Simple dazza, most of the jabiru customers have never heard of the trade practices act of 1974, gough's gift to the working man.