rotax 912is engine failure to develop full power

[bluesky]

engine failing to develop full power lane b running slightly rough, diagnostics indicate engine functioning and running correctly. would seek advice as to any engineers in Australia with diagnostic expertise with this engine. Thanks

 

 

[crashley]

hi will need a bit more info ie what does " lane b running slightly rough" actually mean and was loss of power gradual or sudden during flight taxi ground run etc

 

and what actual diagnostics were performed ie leakdown check plugs checked ignition checked but it could be anything from bad fuel to bad ignition module

 

Bert Flood in Melbourne is the Australian agent and would be a good place to start

 

 

[bluesky]

Thanks for your response. Ignition/fuel system divided into lane A lane B power loss first noticed on climb out from same runway under similar weather conditions and take off weight. Previously circuit altitude reached on crosswind with reduction in power required downwind to prevent over revving. First indications were in circuit where aircraft took to 25% downwind leg to reach circuit altitude and no throttle reduction required to prevent over revving of engine and continuing slight decline in performance up until now. engine diagnostics dongle information forwarded to Bert Flood with nothing to indicate any faults. fuel pumps replaced on advice from Floods with problem persisting. filters/plugs checked, leakdown test performed. Ignition modules exchanged, prop balance checked.

 

 

[Ultralights]

Carby balance? carby checked for air leaks causing one rich one lean?

 

 

[fly_tornado]

on a fuel injected engine? must be the carb heat stuck on

 

with all electronic stuff I'd start with the battery, then the wiring loom

 

 

[bluesky]

Thanks for the comments, yes it is the latest fuel injected motor

 

 

[facthunter]

Doesn't it have codes etc? Otherwise you just change things till it runs right and that would not be cheap. Like had to be done with early Kawasaki's with injection.. Nev

 

 

[M61A1]

engine failing to develop full power lane b running slightly rough, diagnostics indicate engine functioning and running correctly. would seek advice as to any engineers in Australia with diagnostic expertise with this engine. Thanks

Have you looked at your fuel? A LAME acquaintance recently was telling me about an aircraft he was involved with that had an EFI automotive conversion. This aircraft had slowly been losing power, after much stuffing about, they changed the fuel for some fresh stuff, with great results. Apparently, as the fuel goes stale, the octane rating drops, with all the knock sensors and stuff, the engine simply de-rates itself to run on lower quality fuel, just doing what it was designed to do.

 

 

[obad]

engine failing to develop full power lane b running slightly rough, diagnostics indicate engine functioning and running correctly. would seek advice as to any engineers in Australia with diagnostic expertise with this engine. Thanks

Bluesky, I have recently worked on a FOXBAT fitted with the fuel injection engine which suffered from symptoms similar the ones you describe. In this aircraft as the rpm passed approximately 4400 to 4700 Lane A & B voltage would start to drop -perhaps down to nine volts and RPM could not be increased until emergency battery power was switched into the circuit . Does your lane voltage do the same?. Also what fuel pressure are you reading? Check & clean your filter very thoroughly. M61A1 posts on fuel quality are also worth investigating. what type of aircraft is your engine fitted to?

Our voltage problem was solved by the replacement of the fuse box/regulator which was diagnosed from the downloaded data obtained by the aircraft agent.

 

 

[facthunter]

I'll stick to two magnetos and an adjustable carburetter thanks. Nev

 

 

[Guest Maj Millard]

Interesting to see these new problems popping up already, in what is a relatively new engine and system, on engines with only low hours on them. there is no doubt that fuel injection is smoother, more efficient, and more economical, that we know from our experience with modern Automobiles.

 

However when things aren't right, they can be a bear to diagnose and fix, unless you've got someone with the expertise/experience and the proper diagnostic tools. This is especially so if those problems occur away from home, or in the field.

 

Another big disadvantage to me is the fact that instead of a measly 5-7 psi of fuel pressure in the lines, with a carb system, you now have at least ten times that amount, so even minor leaks in or around the engine bay are going to be potentially large and very dangerous, with the potential of spraying high- pressure fuel over everything. Bad enough having that in a car, disaster in an aeroplane.

 

Plus the reliance on the two high-pressure fuel-pumps which must work to full potential, otherwise performance will not be there.

 

Then the absolute reliance on the systems battery, for a reliable and stable electrical supply which can't drop below a certain voltage.

 

Fuel-injection because of its complete burn, produces a much hotter exhaust temperature, and already the 912iS is requiring a new specialised exhaust system to handle the higher temps. The standard exhaust metals previously used were only lasting around 10 hours.

 

Then we have all the sensors and computerised controllers, which are responsible for all the efficiency when everything is happy, but a system with a mind of its own when it's not !.....and of course all these very specialised components cost big money when a replacement is required.

 

Automobiles with fuel injection engines have become very reliable as we know, however recently my Triton ute which had been absolutely reliable until around 200,000 Klms simply refused to start one morning, with no forewarning. The fuel filter was the obvious first stop. changed that, still no start. Checked fuel pressure...normal. Finally after having it towed to a shop which had the required diagnostic equip, it turned out to be either the crankshaft or cam sensors, both of which must supply the required info, or things just don't compute. Changed both at some expense, and now running perfectly again. Without the required diognostic tools forget the roadside fix up, you won't even know what is causing the problem !...

 

Time will tell if the computerised style of fuel-injection works well, and is worth the trouble on the new Rotaxs, in aircraft. Lycomings and Contenentals have used fuel injection for years. And except for a few starting problems when hot, have performed very well and reliably. They are however mechanical units without all the electronic magic................makes a couple of easy to understand, and adjust carbs look simple by comparison..Of course we must embrace new technology, however it must also prove to us that it will be as reliable, and as safe as the equipment we already use..........Maj....

 

 

[facthunter]

That's well put Maj. I think I posted wayback that this motor is not for tinkerer's. It's box it back to somewhere with the test equipment. A gravity feed float carb ( under the motor) with a drop from the hiwing tanks, and two magneto's is the nearest thing to foolproof you can get. You battery goes flat? Doesn't affect the engine ops whatever. No fuel pump needed.. Accelerator pump primes the engine. Carb heat YES you must do it. Nev

 

 

[Guest Maj Millard]

That's well put Maj. I think I posted wayback that this motor is not for tinkerer's. It's box it back to somewhere with the test equipment. A gravity feed float carb ( under the motor) with a drop from the hiwing tanks, and two magneto's is the nearest thing to foolproof you can get. You battery goes flat? Doesn't affect the engine ops whatever. No fuel pump needed.. Accelerator pump primes the engine. Carb heat YES you must do it. Nev

Yes that set up is hard to beat and well proven over many flight hours. When we have many people out there who already can't adjust, understand, or leave alone a simple carb without dramas, you must wonder what their future would be with a highly complicated, computerised, and expensive fuel-injected engine.

 

Just the potential for high pressure fuel leakage sceneroes alone, is scary in the extreme around folks with a bad case of tinkeritis.....and nobody needs a high- pressure fuel-feed fire at altitude, or anytime for that matter !.........Maj....

 

 

[fly_tornado]

Fuel pipe issue isn't that hard to fix.

 

 

[facthunter]

The trouble, f t is that when these things don't function correctly or intermittently fail you don't know where to start unless a code gives you the answer. Self test of function is needed. Often battery/system voltage is critical. sensor malfunction poor canon plug conductivity. High pressure fuel is dangerous around a vibrating engine ( and even jets do that. The worse kind. High frequency). FUN = 1/ complexity. Nev

 

 

[Guest Andys@coffs]

Fuel pipe issue isn't that hard to fix.

Except when at 9500ft doing 140kts while slowly trying to emulate an F111C Dump and Burn....could be challenging to fix at that point in time....while not scorching the paint finish......or your ar$e!

 

 

[fly_tornado]

I haven't heard of a 912is doing a dump and burn yet, installing aluminium fuel tube isn't rocket science. I'd rather deal with once off task of retrofitting fuel line than face exhaust valve failure every 250-400 hours.

 

 

[Guest Andys@coffs]

Well........yep.....led with my chin on that one......my 3300 is back in the aircraft waiting for its test fly when I finish wiring in the 12channel CHT/EGT monitoring kit. Hopefully I can get better than 200hrs for that $10k

 

Andy

 

 

[fly_tornado]

Still haven't heard of a 912is catching fire...

 

 

[Guest Andys@coffs]

but the point about having fuel rails running at pressures far beyond what is needed for gravity fed Carby's is true, in the event of a rail failure at any point in the high pressure run life would get interesting in a big hurry.......

 

The chances of it occurring might well be small but not zero

 

(All that said...would I swap one for my newly overhauled 3300....In a heart beat!)

 

 

[Guest Maj Millard]

On aircraft engine design, reliability and safety are the two things that guide certification. Fire potential is looked at closely which is why fuel lines are ment to have fire sleeve on them, or some other form of protection. All fuel components should be capable of enduring 2 minutes before failure, when exposed to fire.

 

On the Lycomings and Contenentals the fuel injection lines are stainless, and there is at least one AD requiring close inspection for any leaks or cracks in those lines. Don't know if I would like aluminium lines for high pressure as it does crack easily.

 

Next to throwing a prop blade, a fuel-fed engine fire would be a close second on events to be avoided at all cost !!.............Maj...

 

 

[bilby54]

There is a Tecnam with less than 100 out here with the exact same symptoms. EMS is saying everything is fine but has had the same fuel pump / filter / plugs replacement. Bert Floods have been very helpful trying to find the problem but cannot say the same for the agent

 

 

[facthunter]

I would not think copper or aluminium tube would be good enough. Stainless is used in GA and the pressure is not that high. Vibration does the damage.

 

I guess this all comes down to how you relate to technology. ( Not the IT kind) I don't need an engine to run forever. It would be nice but such a motor hasn't been made yet and I would happily drive a plane with a motor that had grease nipples on the rocker gear. Don't forget the early Gnome and Rhone engines did only four hours without repair sometimes.. Not suggesting we go back to that but I would still fly one of those given the chance. IF it needs more servicing so be it. I have flown a plane where the hot section of the engine had to be inspected on each turnaround, so it even happens with the best of them at times. Nev

 

 

[Guest Maj Millard]

We are way past the Gnome and Rhone engine stage by now, so other than looking back for some historical reference, there is no comparison to the modern aircraft engine. We have been used to engines that easily do 1200, 1500 and on up to 2-3000 hours as the norm now for decades.

 

Most mechanical developments were complete, or known by the end of WW2, with that event being a major stimulus for research and improvement.

 

Lycomings and Continentals used today were designed in the 20s and 30s, with only minor development changes to components etc. since.

 

We have every right to expect that our modern engines be easily capable of providing us with good reliability, and safety for at least 1000 + hours, with only normal maintenance and servicing............Maj...

 

 

[M61A1]

On aircraft engine design, reliability and safety are the two things that guide certification. Fire potential is looked at closely which is why fuel lines are ment to have fire sleeve on them, or some other form of protection. All fuel components should be capable of enduring 2 minutes before failure, when exposed to fire.On the Lycomings and Contenentals the fuel injection lines are stainless, and there is at least one AD requiring close inspection for any leaks or cracks in those lines. Don't know if I would like aluminium lines for high pressure as it does crack easily.

Next to throwing a prop blade, a fuel-fed engine fire would be a close second on events to be avoided at all cost !!.............Maj...

A properly installed fire sleeve will also divert the leakage flow to the ends of the hose/pipe, and hopefully away from the fiery bit.