Rotax gets us to Temora and back in fine style........

[Guest Maj Millard]

Recently did the trip Townsville-Temora in my 912 100hp powered GR lightwing. Picked up Donald Windsor (windsor68) at Mackay, so most of the flight, and all of the take-offs were full fuel and gear, and two bums heavy !!..........Flight time down was 14 hours via Mackay-Springsure(O/night)-Charleville-Bourke (O/night)-Naromine-Temora. Return in 12 hours was Temora-Dubbo-Moree (O/Night)-Chinchilla-Dingo roadhouse-Mackay-Townsville. Moree to Townsville was completed in the final day.

 

I did quite a bit of mechanical prep in the weeks prior to departure as you do, including oil/coolant change, new oil filter, clean fuel filter, wheel bearings etc etc. I also remover the muffler for a complete check and welding of some small cracks that had appeared. My muffler likes to crack occasionally, and had done so a couple of times in the past. I also did a real good inspection on the exhaust header pipes prior to departure, but no cracks were found.

 

The engine at departure had about 620 hrs TT. Because I knew we would be loaded all the way I also removed the 3-blade Powerfin and depitched it a little, for better take-off revs. It had been pitched prev for max cruise speed. This 'livening up' of the prop worked well, and still gave a good solid 600-700 FPM climb out even close to gross. Cruise RPMs were generally around 5200, with a slightly higher fuel burn than normal around 19-22 Lph. Around 80% of the time flown was on straight Avgas, the rest on 95/98 Mogas or a mixture thereof.

 

Did not put a drop of oil in the 912 the whole trip !!....checked it a few times, but no oil needed, there or back !...Only suffered two mechanical dramas: one a stuck fuel-drain just prior to departure from Temora. I always carry a spare one so a quick swap, and we were on our way.

 

Then about 20 nm out of Dubbo after leaving temora, she ran funny for a few seconds. We went to both tanks, boost pump on, and out the side windows for a terrain check. It cleared promptly, and we landed at Dubbo with no further dramas.

 

After refuelling however my calcs showed we had exprienced an unusually high fuel burn on that leg of around 32 LPH !!! Off came the top cowl and I straight away spotted a cracked foward LH header pipe about 4" from the exit point of the head. It had been directing hot gasses onto the oil filter and fwd coolant hose, which fortunatly was protected by firesleeve and Stainless protection plate. These were not standard but I had fitted them some time ago to protect against radiant heat from the nearby pipe, fortunatly !...Neither Don or I had noticed any rise in any temps.

 

Off came the pipe as we wern't going anywhere with it cracked .(happy it was a front one, not back) Don and a very helpfull Dubbo local ran into town, and back come the pipe beautifully welded. We departed again after loosing only 2.5 hrs on the ground. Thank you Dubbo !!.

 

The very high fuel consumption , and the slight splutter I put down to the escaping exhaust gasses going back and entering the LH side air filter and carb, which would have unbalanced the engine and had the effect of running on full carb heat on one side only. Even with that, the engine ran smooth and sweet into Dubbo except for that one momentary splutter. Other than that little area of concern, the 912 did extremly well the whole way, and even pulled us through when doing an unplanned downwind heavy takeoff out of Chinchilla, after a wind change after lining up.

 

I'm sure the 100 or so sailplanes lined up beside the runway for launch, enjoyed it as much as we did !. Still the 912 pulled us out of there with as much style as I could muster !

 

Since returning to home base I have replaced the oil filter damaged by the leakng pipe, and removed the protection from the coolant hose but the hose looks fine. Protection was replaced, and I will replace that hose at the next check. I have done around 10 hrs since and it still needs no oil !... Thank you nice 912.....See you all at Old Station later this month !....................................................................Maj...

 

 

[motzartmerv]

Sweet Maj.... Theres no doubt, they are a brilliant engine.

 

 

[Ultralights]

Yep, in 400 hrs, we have never had to add any oil at all between the regular scheduled changes.

 

The only issue I have had in the past has been a few cracks in the muffler. And maj, you might have a solution to this, just finished a 200hrly on the 912, but over the last 5 hrs it has developed a vibration between 3900 and 4200 rpm, outside this range she is a smooth as a Rotax can be, after the 200hr inspection and maintenance, the vibration is still there, so it's not carby balance issue, the only thing I can think of is, the throttle cable for the left carby is straight, and about 6 inches long, the cable for the right side carby originates next to the left hand cable, but is routed in a giant S turn and it's about 3 times as long as the left hand cable. Could flexing in the s cable be causing A imbalance in carby throttle position at about the 3900 to 4200 rpm range? Apart from that I can't think of anything that could be causing it! Maybe a spinner imbalance? Or a blade that's a few deg, or out of pitch with the other 2 blades cause it?

 

Apart from that, it's the most reliable and trouble free engine I have ever flown behind..

 

 

[Guest Maj Millard]

Ultralights,I feel your on the right track with the carb cables, I had a similiar prob recently and found that one of my cable housings had come loose at one end. Reattached again with lockwire, and now all good. If not that, by all means look at prop and spinner. Check that spinner is firm and tight. I would agree that the Savvy throttle linkage could be better designed in some areas. Maybe they could look at the Lightwing one, simplicity plus and it works..Why don't you throw that new lady of yours in the Savvy and come up to Old Station for a run on the 25-26th this month ?.............Cheers Ross

 

 

[flyhi]

Yep, in 400 hrs, we have never had to add any oil at all between the regular scheduled changes.The only issue I have had in the past has been a few cracks in the muffler. And maj, you might have a solution to this, just finished a 200hrly on the 912, but over the last 5 hrs it has developed a vibration between 3900 and 4200 rpm, outside this range she is a smooth as a Rotax can be, after the 200hr inspection and maintenance, the vibration is still there, so it's not carby balance issue, the only thing I can think of is, the throttle cable for the left carby is straight, and about 6 inches long, the cable for the right side carby originates next to the left hand cable, but is routed in a giant S turn and it's about 3 times as long as the left hand cable. Could flexing in the s cable be causing A imbalance in carby throttle position at about the 3900 to 4200 rpm range? Apart from that I can't think of anything that could be causing it! Maybe a spinner imbalance? Or a blade that's a few deg, or out of pitch with the other 2 blades cause it?

Apart from that, it's the most reliable and trouble free engine I have ever flown behind..

Also check that both chokes are fully off.

 

 

[Ultralights]

Yes, didn't think of choke position.

 

Another solution/upgrade/mod I'm thinking of is replacing both throttle cables with solid rods. Looks quite easy to do with very simple bolt on mods to the throttle bar that joins both throttles inside the cabin. The rods will practically be straight with a slight z for the approx 2inch height difference from the throttle cross rod and the carbies themselves. Threaded ends of course for easy adjustment.

 

 

[Guest Maj Millard]

As long as you had a bit of vibration/movement absorbtion in the system somewhere UL., to allow for engine movement...........................................................................Maj...

 

 

[damkia]

Yes, didn't think of choke position.Another solution/upgrade/mod I'm thinking of is replacing both throttle cables with solid rods. Looks quite easy to do with very simple bolt on mods to the throttle bar that joins both throttles inside the cabin. The rods will practically be straight with a slight z for the approx 2inch height difference from the throttle cross rod and the carbies themselves. Threaded ends of course for easy adjustment.

You need a link of cable at the junction of the engine and airframe to prevent engine movement/vibration translating into throttle movement (ie, isolating the engine movement).

 

There is also the issue of resonance/slack of the bars causing potential uneveness of delivery of fuel through changes in throttle, potentially leading to one cyl being leaned out.

 

I'm not saying don't do it, but consider bars for the fixed structures, and cables (enclosed bowden type to minimise effect of vibtation?) for the vibrating parts.

 

But hey, what do I know - I a noob here:wasnt me:

 

 

[Guest Maj Millard]

As I said prev the Lightwing setup is simple and very effective, and similiar in design to the Savvy.................................................Maj...

 

 

[winsor68]

I reckon... in my humble opinion... from within the cockpit the Lightwing has the best throttle set up I have seen or used. A nice simple T-bar in a box type thingy... Can't comment firewall forward but from a flying point of view it works brilliantly and perfectly.

 

Howard Hughes has got to be a bloody genius...