Another Jab bites the dust.

[Guest Maj Millard]

In respect to J230s post re: oil and filter changes.

 

Sounds to me like he was advocating that you must change the oil-filter every time you change the oil ?.......which is not correct, as it depends entirely how many hours the oil-filter has done.

 

For instance, I will change oil on my 912 every 50, but only change the genuine Rotax filter every 100 hrs, which is every second oil change. I have no idea what jabaru require in that respect. I use exactly the same schedual on my 600 Klms a week vehical with no dramas. Cutting open and checking the contents of the filters, show that they are more than up to doing 100 hours in service. If on the other hand you operate an engine type that is prone to failure, then you may want to check the contents of the filter every 50 hrs, or even every 25 hrs, to acertain wether that engine may be 'making metal' or not.

 

I have in the past gone 100+ hours on oil and filter, before changing both, due to a mandatory trip that came up at about 95 hrs which put me at around 115 hrs before I got a chance to change the oil or filter. Not a drama, the engine didn't suddenly come apart at 100.1 hours

 

The high quality of our modern-day oils, (and filters for that matter, if you use the genuine ones) allows us to stretch it a bit if we need to. In fact the NZ authorities allow 10% over the 100 hours point before maintenance in their country.

 

I do by the way use Valvolene Durablend 15w50, with genuine Rotax filter in my 912 as recommended by Rotax. Prior to that I used Castrol GPS only until it was not recommended by Rotax, and I always warm up the oil prior to dropping it......................................................................................................Maj...

 

 

[Thirsty]

I doubt many jabs stop due to anything inside making metal. It's mostly through bolts and exhaust valves. The jab bottom ends are pretty robust.

 

 

[Guest Maj Millard]

Not only bottom ends are capable of making metal. Reading your filter element can show ferrous and non-ferrous metals such as brass, bronze, aluminim or steel from a multitude of sources throughout the engine. Starter-drives, exhaust guides, drive cogs, and pistons/piston rings are common sources..Most engines will make some small amounts of metal in their normal operation cycle. it's when that metal become excessive that you've got a problem.......................................................Maj...

 

 

[Powerin]

For instance early ea falcons were overheating but it was people crossthreading the threaded water reserve bottle and the coolant was escaping under pressure. ( as an example)

This got me to thinking (a dangerous thing)....it is often claimed that Jabs fail more often because of poor maintenance. Why would this be the case with Jabs more than other engines?

In Nev's EA Falcon crossthreading example above, I would consider that a design fault. Why? Because the design made it possible for a regular maintenance item to fail often because of human factors.

 

Two examples from agriculture: regularly maintained greaseable ball bearings generally last longer than sealed bearings, they wear gracefully and rarely fail catastrophically. Sealed bearings have a limited life and often fail by completely falling apart. So why are sealed bearings mostly used on agricultural machines? Because they require no maintenance. They generally last longer because humans forget, or neglect to grease bearings, or use dirty grease, or don't clean the grease nipple before greasing. Human Factors.

 

Back in the day agricultural machines had no guards. Shafts, pulleys and belts were out in the open ready to take the fingers, limbs or life of the careless farmer. So it was decided to fit guards AND for extra safety make them very hard to remove. This didn't work. Why? Because when the time came to inspect or repair the component under the guard, it took so long to remove the guard that farmers rarely bothered to put it back on. Nowadays safety guards are very easy to open and are usually hinged and secured with a clip. Human Factors.

 

Is this one of Jabiru's problems?

 

As an aside, I am constantly surprised at how difficult it is to actually access the engine of many aircraft. Tecnams (and probably many others) at least have a hinged top cowl that is secured by a couple clips. Giving the engine a quick once over for loose wires/cables, oil/coolant leaks, exhaust springs etc at every preflight is a matter of a couple minutes. How many engines under a screwed on cowl get a look over at every preflight inspection?

 

 

[eightyknots]

....

As an aside, I am constantly surprised at how difficult it is to actually access the engine of many aircraft. Tecnams (and probably many others) at least have a hinged top cowl that is secured by a couple clips. Giving the engine a quick once over for loose wires/cables, oil/coolant leaks, exhaust springs etc at every preflight is a matter of a couple minutes. How many engines under a screwed on cowl get a look over at every preflight inspection?

The Piper Super Cub I'm training in has easily accessible sides so that an engine pre-flight inspection is easy. Some planes' engines are very difficult to get to.

 

 

[boingk]

My 'Cab has an easily accesible engine and panel...

 

...but you have to hand start the thing

 

Human factors?

 

- boingk

 

 

[facthunter]

Some of the reasons a 912 gives good service is that the engine

 

(a) is liquid cooled.

 

(b) has Nikasil barrells with close running clearances.

 

© has hydraulic valve lifters and good valves and seats.

 

So it doesn't need much fiddling with ( The basic engine) so it gets left alone. The Jab does need attention (Servicing) and the TOP won't go the full TBO. Some of the attention is not done and some of it is not done RIGHT. The Jabiru is always "on condition", much the same way as earlier motors were and two -strokes are. In the same way that you can pull your lawnmower out from under the house and it has no compression, so can some aircraft motors... Nev

 

 

[flyhi]

Jab valve failure on takeoff at YBAF last week. He managed to get back on the runway and stop before running out of room. Lucky!!

 

 

[eightyknots]

Jab valve failure on takeoff at YBAF last week. He managed to get back on the runway and stop before running out of room. Lucky!!

Very fortunate: another survivor.