The Jabiru KitFox by Colin Richardson
I am not enthusiastic about 2 stroke engines. The Rotax 912 was a possible alternative to the Rotax 582, but it's expensive and heavy. Like the 582 it is high revving and water cooled. The Jabiru 2200 had a "Good Press" and seemed the ideal solution. The 582 was sold to a chap building a surface skimming vehicle, the first in the UK. It's not a hovercraft, it has stub wings and flies in ground effect a few feet above a calm sea.
The Installation of the Jabiru was carried out professionally by Richard Yates of Yates Aviation, and was very straight forward. The agents ST Aviation Ltd supply the engine mounting for the Kitfox together with the engine instruments and all the necessary bits and pieces. A new instrument panel was required due to the engine instruments (RPM, CHT and oil temp and pressure) being of a different size. The PFA requirments include a proper firewall instead of the original one made of bacofoil. The cowlings must be very closely and securely attached to the firewall. A beefier battery and heavier cabling is required for the starter motor. The two blade prop is heavier than the GSC, although the weight of the Jabiru is comparable to the 582 it is these things which have increased the weight of the aircraft from 495 lbs to 527 lbs. This includes 4 lbs of lead on the tailwheel spring attachment.
The biggest problem with the installation was the refitting of the original cowlings. The "radial engine" type cowlings are only just wide enough. In retrospect it would have been easier to use the original rear cowling, top and bottom from the firewall rearwards. Forwards of the firewall it would have been better to have used completely new cowlings designed for an air cooled flat four engine. Perhaps the skyfox gazelle cowlings (for the Rotax 912) might be thr answer.
The metered flow of oil to the rocker boxes was an inital problem, but the engines produced now have overcome this. Another problem was the firbreglass air ducts for the cylinder head cooling. The agent supplied the ducts for the Jabiru aircraft which is faster. They were not right. The agent then supplied ducts made for the Kitfox which open out at the front like trumpets, joining together in the middle. All such problems have been very speedily dealt with by Kevin, Jeremy and Valerie, who have always been MOST helpful.
After the "trumpet ducts" had been fitted, the vent to extract the cooling air had to be doubled in size, with a lip to encourage extraction. The CHT was still near the top of the green sector. Fuel consumpution was amazingly frugal. I made two flights of 2 ¼ hours and after each was unable to emply a 20 litre jerry can of petrol into the aircraft. That's less than 8 litres per hour, and would give me an endurance of over 9 hours! I have two 21 litre wingtanks and the 35 litre fuselage tank. incidently, the engine uses Avgas unless specially modified for mogas.
The spark plugs showed that the mixture was lean. The main jet was changed from 1.95mm to 2.1mm (all new engines have this now) and the needle raised one notch. The fuel consumption has increased a little, but the CHT is now comfortably in the green sector. Originally the oil temperatue was on the high side, but a progressive enlargement of the cooling air intake to the sump, and the enlargement of the extractor vent have done the trick. This is not the same vent as for the cylinder, Jabiru engines have ribs on the sump to enhance cooling. The dip stick has been recalibrated for the tail down attitude on the ground.
For the first 25 hours the engine was run-in on straight 80 oil. At operating temps the oil pressure was low, in the yellow sector. At 25 hours the oil was changed to Qualube 15/50, a high quality car oil. There was an improvement in the oil pressure. At Cranfield I then met Rodney Stiff, the Australian designer of the engine. He advised me to drain out the Qualube and replace it with Aeroshell 15/50. It is not easy to obtain, but I have now change to the Aeroshell and the oil pressure is now comfortably in the green sector. The oil vent pipe in the slipstream sucks oil out of the engine. Rodney Stiff advised drilling a ¼ inch hole on the top of the oil vent bottle. The oil filter supplied is Australian and unobtainable (not true use Toyota MR2 filters they are the same)
The Spark plugs (NGK D9EA) are available in any good motor parts shop if not they can order them for you. The Yates propeller is 60in x 28in which is too coarse to realise the engine's full power for take-off and climb. The max permitted rpm is 3,300 but only 2650 is obtainable. Power = torque x rpm. So the take-off run is a tad longer than with the Rotax 582, but flying solo the ground run is still less than half my 260 yard strip. Flying solo the rate of climb is a disappointing 600 - 700 ft per minute. The prop rotates in the opposite direction to the Rotax 582 so the other rudder pedel is needed in the climb. In the cruise 2000 rpm gives 60mph, 2150 rpm gives 70mph and full throttle gives 95mph.
Richard Yates, near Boston, Lincs, UK (01205 750601) is prepared to do any other conversions except for the manufacture of new cowlings.
So I am pleased with the conversion?
You bet I am!
The engine is whisper quiet and vibration free, even better than the lovely Limbach 2000. One of the bonuses is clear intercom and radio transmission. Previously the noise cancelling microphones filtered out all the noise except for the frequencies of the human voice. The noise of the Rotax 582 was in this range of frequencies and was not filtered out.
Written by Colin Richardson