AAIB report •Jab EFATO UK April '23

[Garfly]

 

 

 

Jabiru_UL-450_G-CDFK_08-24.pdf

 

 

Probable culprit:

 

 

 

 

As mentioned by The Flying Reporter here:

 

https://www.youtube.com/watch?v=NA0W0YHwdyY

 

[facthunter]

It doesn't take much to ruin your day. . That part is too unreliable to be on a plane. A backfire could cause that.  Nev

[BrendAn]

2 hours ago, facthunter said:

It doesn't take much to ruin your day. . That part is too unreliable to be on a plane. A backfire could cause that.  Nev

nothing wrong with them if they are changed out occasionally. they think that one has been there since 2006. or do you have a list of incidents where carb sockets have failed on jabiru engines. stick to the facts like you always say you do.

[facthunter]

Be Nice.  What is a non  fact on my post?  The equivalent on many motorbikes is far more substantial. Ideally the carburettor would be supported by more than  a rubber sleeve...Nev

[skippydiesel]

Interesting. If the Jab carb socket was new in 2006 and it had been a Rotax socket, it would have been replaced 3 times by now (assuming adherence to recommended practise) and due for another new one in a coupe of years.

Edited July 8 by skippydiesel

[facthunter]

Of course it's good to replace them at specified periods. I just don't think the design is good enough for aircraft practice. The weight should be taken at other places as well. I doubt the scrutineers would allow it on a race car either. Plenty of vibration  in reality and potentially to handle on an aircraft. ..Nev

[facthunter]

And a lot of extra "G" at times. Nev

[Thruster88]

It was a shame the carb socket split however the real problem here is the fact that the pilot stalled the aircraft which subsequently entered a spin. The pilot did not seem to understand how airspeed is controlled. Lucky not to die.

[BrendAn]

6 minutes ago, Thruster88 said:

It was a shame the carb socket split however the real problem here is the fact that the pilot stalled the aircraft which subsequently entered a spin. The pilot did not seem to understand how airspeed is controlled. Lucky not to die.

I thought it was odd. He had plenty of warning but kept the nose pointed up.

[BrendAn]

3 hours ago, facthunter said:

Be Nice.  What is a non  fact on my post?  The equivalent on many motorbikes is far more substantial. Ideally the carburettor would be supported by more than  a rubber sleeve...Nev

I meant what evidence do you have that carb sockets are a problem on aircraft. Think of how many jabiru and Rotax engines are flying around they can't be too bad. Although now I am going to fit a new one on mine. Otherwise your words will haunt me whenever I fly.😁

[facthunter]

Few other engines have such an inadequate carburettor attaching  set-up. They bolt straight on with a gasket. There's no other way THAT Motorcycle carb can be mounted easily. On the BMW bike it's from the pipe to the aircleaner helps steady it and it's pretty OLD (and cheap) model. Vibrating carburettors with floats can have frothing and flooding issues. Nev

[BrendAn]

37 minutes ago, facthunter said:

Few other engines have such an inadequate carburettor attaching  set-up. They bolt straight on with a gasket. There's no other way THAT Motorcycle carb can be mounted easily. On the BMW bike it's from the pipe to the aircleaner helps steady it and it's pretty OLD (and cheap) model. Vibrating carburettors with floats can have frothing and flooding issues. Nev

true but my jab has 399 hours on  it and there is no mention of problems with the carb socket in the log books since new in 2004. it has no support either.

[Red]

10 hours ago, BrendAn said:

true but my jab has 399 hours on  it and there is no mention of problems with the carb socket in the log books since new in 2004. it has no support either.

If you have no airbox and just filters hanging on the carb throats I'd reccomend removing the socket and inspecting at this point Brendan, I took the socket of my new to me Jabiru engine that had just 9 hours on it but years of sitting around waiting for the builder to complete and it was starting to split, they split internally.....it seems to be a quite rare occurence in Jabs but its so easy to remove and check its worth doing on your 100 hour checks imo.

Now if it was a Rotax 912  with no airbox...well Ive replaced them on one engine twice in a 1 year and actually had one split half way round and the carb fell right off luckily after landing, Jabs seem far more forgiving in this dept.

as Nev mentioned cantilever mounting on a stub of rubber with no support for the other end of the carb is far from ideal, maybe your aircraft has a rigid airbox that end..if so disregard my comment it'll probably last hundreds of hours mounted that way.

[BrendAn]

1 hour ago, Red said:

If you have no airbox and just filters hanging on the carb throats I'd reccomend removing the socket and inspecting at this point Brendan, I took the socket of my new to me Jabiru engine that had just 9 hours on it but years of sitting around waiting for the builder to complete and it was starting to split, they split internally.....it seems to be a quite rare occurence in Jabs but its so easy to remove and check its worth doing on your 100 hour checks imo.

Now if it was a Rotax 912  with no airbox...well Ive replaced them on one engine twice in a 1 year and actually had one split half way round and the carb fell right off luckily after landing, Jabs seem far more forgiving in this dept.

as Nev mentioned cantilever mounting on a stub of rubber with no support for the other end of the carb is far from ideal, maybe your aircraft has a rigid airbox that end..if so disregard my comment it'll probably last hundreds of hours mounted that way.

Mine is good.  Took it off and inspected 3 months ago. 

I am going to replace it anyway.

[skippydiesel]

"Now if it was a Rotax 912  with no airbox...well Ive replaced them on one engine twice in a 1 year and actually had one split half way round and the carb fell right off luckily after landing,"

 

Strange Red-

 

I am on my second Rotax 912 ULS. The first with basic conical air filters, no extra carby support,  had 900 hrs plus on it  - never had a problem.  Replaced all rubber at 5 years intervals.

New aircraft/Rotax 912 ULS (92 hrs) has air box (carby support). Yet to do a rubber replacement.

 

Interestingly: Had a story from a Europa/Rotax 912 ULS pilot. Carbys fitted basic conical air filters, no additional support. He & his wife (both very experienced pilot/instructors) were flying their newly completed/commission aircraft, when they lost a blade on the CS prop. The out of balance engine attempted to leave the airframe but stopped milliseconds after the prop lost . Aircraft landed in a paddock - no injuries. Such was the violence of the vibration, the whole of the front end of the aircraft had to be rebuilt. Pilot contributed the sudden stop of the engine, to the carburettors seperating from the rubber inlet manifolds. He was certain that he and his wife would have died, had the engine continued its vibration for milliseconds longer and departed the airframe.

[Kiwi]

23 hours ago, facthunter said:

It doesn't take much to ruin your day. . That part is too unreliable to be on a plane. A backfire could cause that.  Nev

I remember seeing a Drifter that one carb fell off on start up.

[facthunter]

Pure co-incidence Skip that a carb falling off helped. . You can't logically plead that one unless it was designed that way on purpose. Such designs do exist. The engine mount pins (3) are  designed to fail on a jet engine is the loads on it are high enough.  Nev

[BrendAn]

a friend of mine had the same thing happen on a thruster. the prop threw a blade and the 582 carbs came off instantly the vibration was so bad . he reckons it kept the engine from breaking off the mount before he could stop it. 

[facthunter]

A Chipmunk threw a prop blade over lake Macquarie and the engine came out..Nev

[BrendAn]

13 minutes ago, facthunter said:

A Chipmunk threw a prop blade over lake Macquarie and the engine came out..Nev

what happened after that.

[facthunter]

Pilot survived, I believe. The Much lighter and tail heavy plane didn't have a very high RoD stalled. Think it was near Coal Point.  Nev

[Red]

7 hours ago, skippydiesel said:

"Now if it was a Rotax 912  with no airbox...well Ive replaced them on one engine twice in a 1 year and actually had one split half way round and the carb fell right off luckily after landing,"

 

Strange Red-

 

I am on my second Rotax 912 ULS. The first with basic conical air filters, no extra carby support,  had 900 hrs plus on it  - never had a problem.  Replaced all rubber at 5 years intervals.

New aircraft/Rotax 912 ULS (92 hrs) has air box (carby support). Yet to do a rubber replacement.

 

Interestingly: Had a story from a Europa/Rotax 912 ULS pilot. Carbys fitted basic conical air filters, no additional support. He & his wife (both very experienced pilot/instructors) were flying their newly completed/commission aircraft, when they lost a blade on the CS prop. The out of balance engine attempted to leave the airframe but stopped milliseconds after the prop lost . Aircraft landed in a paddock - no injuries. Such was the violence of the vibration, the whole of the front end of the aircraft had to be rebuilt. Pilot contributed the sudden stop of the engine, to the carburettors seperating from the rubber inlet manifolds. He was certain that he and his wife would have died, had the engine continued its vibration for milliseconds longer and departed the airframe.

Strange indeed, over here its extremely commonplace to get splits, I think every rotax 912 sans airbox owner I know has mentioned it occuring to them at some point

I wonder if climate plays a part?, though I dont see how cold damp conditions could lead to this, especially as the splits always seem to start internally

Edited July 9 by Red

[skippydiesel]

39 minutes ago, Red said:

Strange indeed, over here its extremely commonplace to get splits, I think every rotax 912 sans airbox owner I know has mentioned it occuring to them at some point

I wonder if climate plays a part?, though I dont see how cold damp conditions could lead to this, especially as the splits always seem to start internally

All doing the 5 year rubber replacement on/close to, time??

 

The inside of the rubber manifold flange should only be exposed to air/fuel - I know the air is toxic 😎 so could UK fuel somehow have something to do with it???

[Red]

9 hours ago, skippydiesel said:

All doing the 5 year rubber replacement on/close to, time??

 

The inside of the rubber manifold flange should only be exposed to air/fuel - I know the air is toxic 😎 so could UK fuel somehow have something to do with it???

I can't see it being fuel as it seems to effect engines that were run on various fuels, ethanol free/laced/avgas.

I wonder if it could be hot cold cycles..hot when running then left getting cold soaked in hangers'''repeat every flight , quite temperature difference.

I don't imagine engines in your part of the world ever see  cold part of that cycle.

I'm just guessing here.

Edited July 9 by Red

[danny_galaga]

What sort of rego was it under? I don't suppose we'd see ANY kind of report if this happened in Australia...