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Fox 4

Jabiru sk fuel burn

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recently flew a mates jabiru sk , it went amazingly well and indicated an airspeed of 90knts + using around 2600 revs , burning 18+ litres. + 100 knts+ using 3000 revs. ( pretty much flat out ). Burning 25+ litres

 

Not being overly familiar with the Jabiru , I was surprised with the quantity of fuel being burnt and would be interested if a fellow jab pilot could supply some comparison figures

 

 

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My LSA (same as SK but factory built) cruise is normally 95 knots at 2850 rpm and you can get 100+ if you sit the plane "on the step". Your fuel burn may vary dependent on carby jet sizes fitted.

 

 

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Around 15 litres/hour at 2850 in cruise sounds about right. If you got consistently less than this, then I'd be concerned about combustion temps, and if you are using less than about 18 litres/hour when doing Vy climb-outs, I'd be very concerned - you need to throw a bit extra fuel at the engine for cooling under heavy load at lower airspeeds.

 

FWIW - any Jab. 2200 installation should have the available fuel flow rate checked at 100-hourlys, to deliver AT LEAST 25 litres/hour from either the mechanical OR the electrical boost pump, used singly. - and in max. climb attitude i.e. around AoA of 15 degrees.

 

The Jab. Bing carby is simple to operate - there's no 'mixture' control other than starting choke. Rotax carby engines use the same carby - but Rotax engines have the operating latitude afforded by water-cooled heads. Jabs. are simpler, cheaper, and DO require more intelligent / observant operation to get reliable service. By 'intelligent' - I do NOT impugn Rotax owners - they have made a decision to pay the extra money for a more robust engine. Jab. owners should NOT expect to get a cut-price Rotax without having to pay their dues by way of careful engine management practices and attention to maintenance, any more than a farmer should expect to harness a Polo Pony to a plough and expect it to do the work of a Clydesdale.

 

I own a Jabiru that has spent almost all of its life as a training aircraft. The log-books record a number of engine failures - and I own it because an EFATO resulted in accident damage that has required well north of 1,000 hours of rebuild time!. ( Admittedly, I've done a huge number of changes/improvements in that time). It is entirely obvious that my (L2-maintained) aircraft was subject to some of the worst maintenance I've ever seen on anything, motor-mowers included. Yes, RAA has been informed..

 

Not ONCE in any of the 100-hourlys signed off, is there evidence of a fuel-flow check. However, there IS evidence of repeated engine failures at low hours - but from the evidence, there is no reason to believe that any work was ever done to check that the engine installation performed to Jabiru specs.

 

I have numerous examples of work done on my aircraft ( when I did NOT own it - it's never flown in my ownership - yet) that would be totally unacceptable for a ride-on mower. Some of those could have resulted in catastrophic failure to primary control circuits. Think rod-end fittings with the shank bent 15 degrees or more, to the nosewheel - and the effect on locking the rudder hard over..

 

Now - if things that could be seen on a relatively casual inspection were allowed to operate in that condition - what chance did the engine have to be operated in a responsible manner?

 

 

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AT LEAST 25 litres/hour from either the mechanical OR the electrical boost pump, used singly.

Don't know about the 2200 specifically but both pumps are nominally rated at 60 lts/hr on a 3300 and can be checked giving above 50 (engine driven pump at idle). I would be surprised if they are not the same, but may well be. Have done next to no maintenance on a 2200.

 

 

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