ATSB report into light aircraft engine failures

[fly_tornado]

http://www.atsb.gov.au/publications/2013/ar-2013-107_research

 

 

 

[Kyle Communications]

Ouch that is pretty convincing evidence almost 4 to 1

 

 

[Bats]

Well I guess you poke the bear for long enough and it will eventually retaliate. Everyone from parliamentarians to forum members had been putting the boot into CASA and by extension the ATSB for supposedly getting it so wrong about the Jabiru failure rate; it seems that there is your reply. The usual apologists will no doubt be getting ready to rubbish the report and anyone who dares to comment contrary to their belief system, so I don't expect that there will be an end to hostilities any time soon.

 

 

[SSCBD]

My simple question is with the Rotax numbers "ONE FAILURE in 36" - is the majority of these due to high engine revs compared to GA engines? What is the major failure of Rotax?

 

 

[Bats]

I suspect that the 1 in 36 includes Rotax 2 strokes, which are anecdotally more prone to failure than the 91- series. I don't know of a common theme with the 4 stroke Rotax failures, my quick and unscientific snap survey turned up things like lifters, fuel pump and a carbie mounting. Other than modified (turbo etc) versions, hard work and high revs don't seem to be implicated, but I'm happy to be corrected.

 

 

[Nobody]

I suspect that the 1 in 36 includes Rotax 2 strokes, which are anecdotally more prone to failure than the 91- series. I don't know of a common theme with the 4 stroke Rotax failures, my quick and unscientific snap survey turned up things like lifters, fuel pump and a carbie mounting. Other than modified (turbo etc) versions, hard work and high revs don't seem to be implicated, but I'm happy to be corrected.

The report isnt catergorical but it appears to include Rotax 2 strokes, see the bottom of page 5.

 

Have a look at figure 10 in the report. It gives a breakdown of the failures by type of failure and engine. The only areas in that table where the Jabiru performs better than the Rotax as in "Corrosion" and "Other Technical Failure mechanism".

 

The other interesting graph is figure 5. It shows that RAAus is much safer than VH registered across both Rotax and Jabiru. Real trend or lack or reporting???? GIGO???? (Garbage in Garbage out)

 

 

[kasper]

The report isnt catergorical but it appears to include Rotax 2 strokes, see the bottom of page 5.Have a look at figure 10 in the report. It gives a breakdown of the failures by type of failure and engine. The only areas in that table where the Jabiru performs better than the Rotax as in "Corrosion" and "Other Technical Failure mechanism".

 

The other interesting graph is figure 5. It shows that RAAus is much safer than VH registered across both Rotax and Jabiru. Real trend or lack or reporting???? GIGO???? (Garbage in Garbage out)

or is it that GA fleet sit on the ground a lot more than RAA ... leave it unused and it goes bang more quickly?

 

And given the two significant areas of mechanical failure/discontinuity are through bolts and valves - bolts are a design/scheduled replacement issue while valves is an on test ... even reading this report with a size 9 steel cap on with intent to kick the $hit out of Jabiru why did not the regulator look at mandating changes to life on components known to be at risk as the hours accrue in stead of the instrument they put in place??? It really does appear that the core issues where known and if you could remove the failures of these two areas (or even halve them) the engines are then no worse than the comparative rotax 912s ... at half the price

 

 

[BLA82]

Anyone who now states that it is a witch hunt against Jabiru needs to pull there head out of the sand (or their ). This report is damming in every way and to be honest I would feel safer strapping a old Yamaha tz750 to the front than I would flying behind a Jab engine. It is just pure luck and good pilot actions that these engines haven't caused a fatality.

 

Let's hope they are continually monitored to ensure the fix their shortfalls. The argument of them making aviation affordable doesn't sit well with me. Yes they make great airframes, maybe they should just stick with that.

 

 

[kasper]

Anyone who now states that it is a witch hunt against Jabiru needs to pull there head out of the sand (or their ). This report is damming in every way and to be honest I would feel safer strapping a old Yamaha tz750 to the front than I would flying behind a Jab engine. It is just pure luck and good pilot actions that these engines haven't caused a fatality.Let's hope they are continually monitored to ensure the fix their shortfalls. The argument of them making aviation affordable doesn't sit well with me. Yes they make great airframes, maybe they should just stick with that.

two points:

If you read the report (and your post) R912s ARE killing people while Jabs (though failing at an unacceptable rate) are not ...

 

Your post and yout singature tag line are in conflict ... Jab pilots are doing the Woo Hoo what a ride yet your post is against that ...

 

Just saying

 

 

[Fishla]

Lumps malfunctions and failures together. Doesn't explain why. Doesn't break them down.

 

Explains that there are high, medium and low risk malfunctions. Doesn't explain how many of each engine type are which. The 18 examples of high risk mention Jabiru twice only and I am left to assume the other 16 are non-jabiru.

 

Says can't explain causes for malfunction for 25% of Jabiru incidents but rotax that is 51% and average is 44% (in other words more thorough reporting of Jabiru which doesn't necessarily mean more problems).

 

Puts much blame on though bolts which I thought have been fixed?

 

As someone who has now risked their life for about 40 hours in a Jabiru I'll continue to believe the biggest risk to me is not being fit and well and underestimating the weather.

 

The stats don't add up to me when I read in Sport Pilot that it's more likely a Tecnam will kill me than a Jab.

 

 

[Nobody]

Kasper and BLA82,

 

Just tone it down a little. Turing what could be a useful discussion into a slanging match wont lead anywhere. The report, if the data in it is accurate, isn't good for Jabiru but the report may not tell the full story either.

 

Kasper, You suggest that placing a life limit on the components that fail is a suitable outcome but given the failures in the histogram below wouldn't that mean that the through bolts would need to be replaced every 100 to 200 hours give or take to be reasonably certain. Is that realistic?

 

 

Edit, My post #6 above referenced figure 10 but it is now too late to go back and edit it. . It should have been figure 6 on page 15.

 

 

[kasper]

Using the histogram

 

How about 500hrs to replacement?

 

1. it gets rid of 2/3 of the raw total numbers of this failure

 

2. the raw numbers cover both the new and old through bolts (and yes even the new ones are in the lower section)

 

3. a broken through bolt rarely stops and engine .. it results in leaks and other stresses that are not nice BUT unlike a valve head or seat issue is rarely a high risk failure.

 

And if you are doing work at 500hrs on the case you are at an ideal time to look at the top end as well ... and in honesty it takes a fair few 500hr changes in terms of $$$ to cover the additional cost of a 912 ... cost and usability in an engine are keys.

 

the aim is not zero failures but an acceptable level of failures that expose you to risk ... I will take any day of the week a risk of 1 in 100 of a through bolt failing over a 1 in 1000 carb falling off (912s have two that really do like doing that) - 1/10th the risk of occurrence but in my opinion many more than 100 times the risk to me and the plane getting on the ground in 1 piece safely

 

 

[Nobody]

Kasper, Bolt replacement at 500 hours doesn't get rid of 2/3 of the failures but more like 25%.

 

You need to allow for the fact that the replaced bolts(without design changes) fail too. For example in the above graph in there are 7 failures less than 500 hours and 19 failures at less than 1000 hours. If you replace the through bolts at 500 hours in then it is logical that in the time between 500 and 1000 hours you will get another 7 failures for a total of 14 failures to get to the 1000 hours. Therefore the failure rate has dropped form 19 to 14 or a reduction of 5/19=26%.

 

Edited slightly to fix a few typos.

 

 

[kasper]

Nobody ... sorry but you are wrong ... the histogram of Jabiru failure in the through bolt is not cumulative but discrete failures against hours in service for the bolts as far as they know. 7 failures in bolts <500hrs and 13 > 500hrs ... thats 2/3rd above 500 and 1/3 below as near as makes not change ... and even IF the failure rate at under 500hrs runs at the current rate (may not, if all are changed per schedule all the old small ones still in use will get removed) its a relatively low risk failure

 

 

[Bruce Tuncks]

An air-cooled motor is fundamentally different from a liquid-cooled one. It is much easier to damage an air-cooled by incorrect operation.

 

What I would like to know is what the failure rate of Jabiru engines that have been properly operated.

 

To give an example... My Jabiru engine went for 13 years without missing a beat until I ran it at full power on the ground, in contravention of the manufacturers instructions. My reason was that I was trying out a prop balancer, but this does not change the fact that the engine was not being properly operated when it shed a valve seat.

 

I think it possible that the Jabiru engine, operate properly, is as reliable as anything else.

 

 

[Nobody]

Nobody ... sorry but you are wrong ... the histogram of Jabiru failure in the through bolt is not cumulative but discrete failures against hours in service for the bolts as far as they know. 7 failures in bolts <500hrs and 13 > 500hrs ... thats 2/3rd above 500 and 1/3 below as near as makes not change ... and even IF the failure rate at under 500hrs runs at the current rate (may not, if all are changed per schedule all the old small ones still in use will get removed) its a relatively low risk failure

Kasper I am not wrong. I might not be expressing myself clearly but on this point I am right.

 

I will try to explain again.

 

If you want to look at the failure rates over 1000. Under the current regime you get 19 failures which is the sum of all of the values added up.

 

If you replace all of the through bolts in the fleet at 500 hours, based on the above graph you would expect to get 7 failures. But in the next 500 hours, ( the 500 between 500 and 1000) you will also get another 7 failures. You need to add these two numbers together to get a comparable value to the number of failures over a 1000 hour period which is 14 failures versus 19.

 

What you are saying is that replacing the bolts at 500 hour you get the 7 failure sin teh first 500 and then no further failures in the next 500 hours which is not logical based on the graphs provided.

 

 

[jetjr]

Very few have said there wasnt a problem but many have said CASA action is not detailed and unjustified. If fed from this report its no surprise as it too doesnt differentiate models of engines either. Ill bet that amongst some shoddy info on the problems, the size of the engine (both makers) IS known.

 

This report doesnt breakdown engine type or even seriousness of problem

 

No doubt throughbolts are an issue, the upgraded 7/16 with o rings is a full tear down to fit Id expect. Hoping for owners this isnt whats required to release limitations.

 

The concept that resonance is involved.....maybe but surely that makes the data applicable to engine cylinder configuration

 

What the report does indicate is what a bad year of problems can do to a small data set. The previous >2013 report draft indicated failure rates the same for both manufacturers.

 

With some stretching it also might indicate something introduced into Jab engines around 2007/08 has brought in significant issues - any guesses?

 

 

[2tonne]

I just had a quick look at the report and so may have missed it, but where is the table showing the rate of engine related forced landings for each make of engine? Surely that would be the most relevant data to support CASA's safety position?

 

 

[facthunter]

Why have we got 2 threads on the same topic? Nev

 

 

[turboplanner]

Ask the person who started the other thread and the person who pasted it on the Jabiru thread?

 

 

[gandalph]

Why have we got 2 threads on the same topic? Nev

So there can be twice the opinions with half the undertanding?

 

 

[Nobody]

So there can be twice the opinions with half the undertanding?

Perhaps we need three. One pro jabiru, one anti jabiru and one to actually discuss the issue?

 

 

[facthunter]

What I'm suggesting is we combine them. They are all in response to the same report. Nev

 

 

[gandalph]

Yes Nev, that's the most sensible idea. I presume that function is within the power of the moderators? Is there a procedure for making that suggestion to the Mods or do we wait for them to notice and act?

 

 

[bexrbetter]

An air-cooled motor is fundamentally different from a liquid-cooled one. It is much easier to damage an air-cooled by incorrect operation.What I would like to know is what the failure rate of Jabiru engines that have been properly operated.

One problem there Bruce is the failure rate of Lyc, Conti and 2 stroke Rotax that are on the list, are also air cooled and well below the failure rate of the Jab.

 

Yes, air cooled engines can be more sensitive, but the engines need to be real world savvy as well, there are people who will treat everything badly and there needs to be an idiot factor built into everything, from washing machines and motorcycles, to computers (there's a good reason MS ask you if you really want to delete/change before you do), if the Jab isn't idiot proof then sadly this is the real world result because the world is full of idiots.