Jab down in riverland

[Tomo]

and discuss how many people abide by the requirement for any flight to have a fixed reserve of 45 minutes fuel, and, related to the Jabiru models with wing tanks, the difficulty of measuring the tanks.

And how many people actually know their USABLE fuel amount? Some aircraft it is quite significant, don't forget it. As it will ruin your whole day. (speaking from experience, fortunately I was pulled up in my calculations by someone else before I got off the ground, but I'll never forget it.)

 

Might sound simple, but you can't go wrong with a bit of dip stick - in most cases.

 

 

[Guest davidh10]

...Might sound simple, but you can't go wrong with a bit of dip stick - in most cases.

Me thinks it is often a dip stick in the left seat that seems to cause most problems

 

 

[Tomo]

Me thinks it is often a dip stick in the left seat that seems to cause most problems

You're only a dipstick if you aren't learnable from your mistakes I reckon, we're all human and will make them. Learn from others, and it may save some grief.

 

 

[eightyknots]

I'll make one suggestion that WILL make an improvement on reliability and that is high pressure injection moulding for the heads and cyls.

As long as there is very good quality control (perhaps x-ray diagnostics) that there are no little air bubbles in the injected metal.

 

 

[eightyknots]

Might sound simple, but you can't go wrong with a bit of dip stick - in most cases.

A dipstick -if used correctly- is one of the two most foolproof systems far better than gauges (although impossible to use in-flight).

 

The other is the use of a sight glass in the cabin, as used in some high wing planes. This is very useful in-flight as well.

 

 

[Vev]

Please explain?

 

Originally had the larger KFM engine. Then they were discontinued and Jab decided to make their own version. I'll make one suggestion that WILL make an improvement on reliability and that is high pressure injection moulding for the heads and cyls.

Hi Ozzie,

 

Don't get your statement about high pressure injected moulded heads and cylinder? The cylinder are machined out of a slingle billet of steel.. what wrong with that?

 

Cheers

 

Jack

 

 

[eightyknots]

Hi Ozzie,Don't get your statement about high pressure injected moulded heads and cylinder? The cylinder are machined out of a slingle billet of steel.. what wrong with that?

 

Cheers

 

Jack

It's a shame that Jabiru uses steel for their cylinders. They could lighten the whole engine by using aluminium for the cylinders and possibly employ stainless steel liners.

 

 

[Vev]

Hi 80knts,

 

Seriously.. do you mean that? I'm no expert in metallurgy but I would think the current 4140 chrome moly single billet cylinder is miles ahead of an aluminum/stainless combo any day.... wouldn't your suggestion just add weight, complexity and cost on a cyl that works fine?

 

Cheers

 

Jack

 

 

[Guest ozzie]

High pressure moulding produces a better cooling transfer and you can cast thinner and more cooling fins. so i read in a japanese bike engine book once. steel vs alloy best choice would be for what can unload the heat the fastest.

 

 

[Gnarly Gnu]

I believe Ozzie is right. The other thing is that at least one of the best companies in the world at this casting technology is right here in Australia, Jab should be going this way for the heads at least IMO.

 

 

[facthunter]

Industry Practice.

 

Standard industry practice for AIR COOLED motors is Steel cylinders with threaded and shrunk on heads of aluminium alloy, mostly high grade castings (sometimes forged alloy). The steel cylinders are often nitrided for wear resistance. The head and cylinder are more or less considered a permanent fixture. This gives better heat transfer and avoids cylinder distortion, and eliminates a high pressure joint that causes reliability problems. There are exceptions which I could list examples of but they are much in the minority. They are usually mounted by a base flange to the crankcase.

 

The jabiru looks similar but has a CNC'd alloy (machined wholly from a billet) head bolted by smallish bolts to a high tensile steel machined cylinder ..Nev

 

 

[Guest ozzie]

With pressure casting the density of the material is higher than billet drawn extrusion. This increased density allows for a more thougher and rapid transfer of heat. have a look at all those air cooled bikes and study the finning on them. thicker near the source and thinner near the extremities. this allows the heat to be drawn away and into the airflow. material that offers easy machining is usually too soft and unstable and has poor thermal stability. IE it moves around unevenly during the heating and cooling of operation. this will also affect the long term durability of the product. Different types of materials can be a problem as well, anyone ever own one of the iron block/ alloy head falcons in the late 80's? forever having cooling problems and warped cyl head.

 

 

[facthunter]

Falcon heads.

 

Mostly due to the length of the head and the fact that the two metals have a different rate of thermal expansion.

 

With repeated cycling. (Heating and cooling). The head gasket gets scrubbed away and lets the combustion gases into the water (Coolant) with consequent overheating and head damage. Cured by redesigned head gasket post 98.. The head Joint is a weakness in all motors that use them (especially highly tuned ones). Better not to have a joint there, if you want reliability seriously. Nev

 

 

[Tomo]

outcome

 

Jab should be going this way for the heads at least IMO.

What would it benefit from the original heads? They don't particularly have an issues with the heads do they?

 

 

[jetboy]

not sure what the type of heads has to do with the Jabiru in question, but do jabs in Oz have the same AD requiring fuel sight gauge verification since the 2 forced landings in NZ attributed to wrong labels being supplied with the particular model tanks here?

 

Ralph

 

 

[jetjr]

Tomo, a number of issues with valves and failures has been attributed to overheating. In adequate tension of head studs can be "maintenence" they are lacking.

 

There can considerable differences between CHT's accross engine. I feel CHT every cylinder is a very good safety policy (EGT too)

 

The alloy the heads are made from apparantly isnt that good for its application and it shrinks and expands too much. Easy to machine and cost effective to manufacture

 

As ozzie said cast or moulded heads can be made to move heat better. There is someone working on this currently

 

 

[turboplanner]

$100,000, $110,000, $120,000, $130,000, $150,000 - whatever manufacturing process you prefer.