New Life for Bushbaby

[Trikenut]

Well done

[Boet]

Chris,
Sal jy die enjin aanbeveel? Dink mooi voor jy antwoord.

[Chris Liebenberg]

Hi Boet
Sal ek die Jabiru Engin aanbeveel?

Om te begin, ek het geen verwysing om mee te vergelyk nie. Hierdie is my eerste Bushbaby, my eerste 3-as vliegtuig en my eerste engine. (Behalwe my Rotax 503 op my trike)

Ek wens iemand wat ‘n Bushbaby 912 of so iets het wil my BB kom vlieg en dan sy mening gee oor die performance.

My ervaring sover:

Omdat dit Jabiru ‘n direkte krukas aandrywing het, kan ek nie ‘n groot prop swaai nie.
Ek het ‘n 64” Brent Thomson prop wat my maksimum 3000 rpm gee. Die Jabiru kan maksimum 3300 rpm doen, so ek kom nie by 100% krag uit nie. Dit maak dat ek 400+ meter nodig het vir take-off. Dit is my grootste beperking.

My vliegtuigie doen 80~83 mph teen 2800 rpm. Dit beteken dat ek heeltyd omtrent 90% krag gebruik. Ek het weinig reserwe krag as ek dit sou benodig.

Ek het getoets, met 430 kg totale gewig, kon ek 300 ft/min handhaaf. Ek moet byvoeg, ons begin op 5000 ft hier in Lydenburg. Hierdie toets was gedoen bokant 5500 ft.
Bokant 7500 ft moes ek redelik trek aan die stok om gelyk te vlieg. Ek weet nie of dit normaal is nie.

Ek het een cross country gedoen na Secunda en terug. My brandstof verbruik was 16.6 liter/hr.

Wat die engine self aanbetref, ek het baie gemoedsrus met die 85HP Jabiru as kragbron.
Dit is ‘n low rev engine met min fieterjasies. Lugverkoeld, een carburettor, 2000 hr TBO, betroubaar, liggewig. Die manne in ons omgewing met die Bantams doen honderde ure sonder moeilikheid.

Hoop dit beteken engiets vir jou.

[Chris Liebenberg]

It is now time to replace the original instrument panel with a new one.
Since the Rotax 912 engine was replaced by a Jabiru, some of the guages, like vacuum guage, is not needed any longer.
Also, the two analogue CHT meters on top have been replaced by a single MGL electronic meter, and they are now just covering the holes in the panel.

I did an Autocad design, and send it to Aluminium Trading Company for lazer cutting.

Although I still use round analogue meters, I designed the new panel with cut-outs for MGL electronic meters for future.
Cover plates with analogue meter sizd round cut-outs were made, so I can still use the existing meters, and then just remove the cover plate and install MGL meters in future, without cutting, filing and fitting on the installed panel.

The center console is also designed to be a loose segement.
Re-doing the center piece is all that is need should the radio or GPS need to be replaced.
Removing the center segment provides easy access to wires and piping behind the panel.

With PhotoShop it was possible to determine the best colour by experiment with different shades of colours.

Photos of the completed instrument panel will be posted once installed.

[Pine]

Baie geluk Chris.

Dis baie netjies

[Chris Liebenberg]

The final product, ready for installation.

[Uncle Spud Murphy]

Dankie and very well done.

I really enjoyed reading this post as it unfolded as I am sure everyone else has.

Outstanding achievement to be proud of. Puff out the chest with pride.

Avdb

[justin.schoeman]

Hi Chris,

I don't suppose you are going to be experimenting with various props on your installation? I would be really interested to see just how well a Jabiru could be made to work on 'slower' airframes.

From the numbers you give, it seems as though your prop may be marginally too long, and too fine pitched to get the most out of the engine. Here is a nice document from Sensich on choosing props for these engines (and a wide variety of airframes):

http://www.sensenichprop.com/sen_html/p ... -adv-4.pdf

From this, it seems as though the ideal prop would be around 62"x44" (using the Kitfox IV as a reference, and an airfield altitude of 5000').

Also, do you have a manifold pressure guage? Jabiru recommends using one to set up a new prop - the target would be 2850RPM (75%) at 26-27" MP in the cruise, increasing to at least 3000 at 30" (not that you will ever see 30" at that altitude!).

Would be great to get some more info on the performance of this engine option!

Thanks,
Justin

[Chris Liebenberg]

Thanks for your valuable input Justin.

A guy in Groblersdal fitted a similar Jabiru with Sensenich prop on his Skyranger, a heavier aircraft than the BB, and the performance he claimed to get from his toy is to be envied.

Jan Loedolff, the test pilot (who also test flown my BB) suggested I should also go for a Sensenich prop, because it is the only difference between the 2 aircraft, and the performance difference is significant.

Your comment confirms this.

I would like to experiment, but I just havn't got the recourses for that.
If I know it will improve the BB's performance I will buy a Sensenich tomorrow, but then I must be sure.

Thanks in any case.

I will let you know when I did it.

[justin.schoeman]

I would like to experiment, but I just havn't got the recourses for that.
If I know it will improve the BB's performance I will buy a Sensenich tomorrow, but then I must be sure.

Seems to be a common problem setting up a new engine on an airframe. There is a lot of theory, but until you actually try something, you will never know. Most of the builders I have spoken too end up begging, borrowing (and hopefully not stealing) props from all their friends to test various combinations.

It would be really nice to see a Jabiru powered BB outperform a 912 powered one for half the price :D .

(Who knows - maybe some kind souls at the agents could help with testing and experimentation to find the optimal Jab power system for the BB? hint hint!)

-justin

[Bushbaby Aircraft]

Good news Chris is that we are building the first factory Jabiru powered Explorer. I can see no reason why the combanation won't work. There is a lot of kitfoxes and Apollo foxes flying with the same setup. I think the two major factors influancing performance is the cowl design and the prop. We will concentrate on these.

[KFA]

Prop spec's op 'n Kitfox 4 met 'n 80hp Jabi
Chris, ek hoop hierdie help as jy dit nog nie gesien het nie. I can see no reason why this installation cannot work. These spec's are for a 80hp Jabi

http://www.kitfox.eu/technical/proptest.html

[CFD]

Nice rebuild there - good to see the BB back in the air again. Interesting to see how it performs with the Jabi motor. It seems a little on the sluggish side though, especially climb performance being only 300ft/min.
My BB gets 550ft-600/min at 3000ft @ a.u.w. and that is with a Rotax 582! Seems your prop/engine combination is not ideal as it should perform much better than that. Do you know of any other Jabi powered BBs?
It will be interesting to see if you can get some more oomph out of it!

Good luck and keep us informed.

Richard, Cape Town

[Chris Liebenberg]

Hi Richard

Thanks for our interest.
I do not know of any other BB’s flying with a Jabiru engine.

I know I do not have the correct engine prop combination, but at the moment I also do not have the resources to experiment.
I saw a spec sheet of a Kitfox using a Jabiru engine, and with different props and their respective performances, and my BB is performing according to the specs on that sheet.
According to the spec sheet, I do not have the optimal length and pitched prop on my BB.


A guy at Groblersdal uses a Jabiru on his Skyranger, a similar aircraft to the BB, with a Sensenich prop of different pich and length to mine, and the performance he is getting from that combination is superb. If I a can remember correctly, +- 800 ft/min.

I must also mention the fact that I am operating at 5500~7500 ft here in the Lydenburg area. I can remember that when I took off from Hippo Pools (1200 ft), I managed 600 ft/min @ 70 mph easily.

The new agents of the BB in Komatipoort said they were going to experiment with Jabiru and different props on the new Safari, and will let me know what they found to be the best combination.

What I love about the Jabiru is the low cost of maintenance.
2000 hours TBO, 95 octane unleaded fuel, 16 liters/hour fuel burn, oil filter and spark plugs from Midas.

I love my BB and I enjoy the Jabiru engin.

[Morph]

You really need a ground adjustable prop in this case to get the perfect pitch