rotax 912is engine failure to develop full power

[bilby54]

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.

 

Maj....

These faults are so new that the engine supplier has not caught up with them yet. As you say, very difficult to diagnose anywhere especially when the diagnostic tool is not recognising any faults. Rotax has bit of doo doo to sort out

 

 

[facthunter]

Without being too hard, It was predictable. They should have anticipated the possibility,and had the resources there. You are buying a top line product .. Nev

 

 

[fly_tornado]

Rockwell software

 

 

[facthunter]

Boeing and Airbus use the same supplier but they specify variations of the systems to suit themselves. ( Or what they think their customers want). Nev

 

 

[Guest Maj Millard]

I believe Rotax did already send out a service technician to do a softwear upgrade on the first 912iS in the country. Maybe Hans needs to 'come on down' one more time !..

 

These engines like your modern auto fuel injected engine operates on sensors and the computer box (read softwear program) saying everything is fine...light the fire..or not. Could be as simple as bad fuel, old fuel, or even the wrong type battery.

 

No doubt the yanks have dozens operating over there already, so must be experiencing the same problems. I'm sure we'll hear about it on Rotax.com before long......................Maj...

 

 

[bluesky]

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.

[bluesky]

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.

Thanks for the advice Be it premium pump to plane or avgas ditto no change

 

 

[M61A1]

Thanks for the advice Be it premium pump to plane or avgas ditto no change

No problem, hope you get it sorted.

[bluesky]

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.

Thank you for response/advice. filter replace fuel system pristine, fuel either premium/avgas pump to plane no difference. regulator operation checked, however I am suspicious that there may be sensitivity to voltage drop on engine management system during periods of Higher RPM.

 

 

[seb7701]

I would have expected some greater action by the agents given the ridiculously low hours on the aircraft. Not a very good advertisement to one of my favourite brand names.

 

 

[fly_tornado]

the service comes free with the "Australian tax".

 

 

[Guest Orfboy]

Episode 1.

 

I had an episode where I loss power while crossing Bass Strait in my Pipistrel Virus SW with a fuel injected Rotax.

 

To correct the problem two components were replaced, the Key Box and the Fuse Box. All seemed well and the engine ran smoothly on the ground and initially in the air. I assumed that the aircraft was now serviceable and attempted to cross Bass Strait to return home.

 

Episode 2. (two weeks later)

 

Weather dictated an altitude of 2,200 ft to cross Bass Strait. I had been airborne for approximately 45 minutes and was 45 nm off shore when the engine suddenly seemed to labour and lost power. The revs had reduced from 5200 to 4500. and I noticed the Lane A light was flashing on and off.

 

The aircraft started losing height so I tried to increase power. I might add at this stage that failure of Lane A also causes loss of automatic control of the constant speed prop. I tried increasing RPM manually by changing the propeller pitch. It had no effect.

 

Next I increased the throttle in order to maintain altitude but instead of getting an increase in RPM the increased throttle setting resulted in a fall of rev to 4400. I then reduced the throttle setting and managed an RPM increase to 4600, sufficient to maintain an altitude of 1000 ft. and eventually, I was able to slowly climb to 2000 ft.

 

Voltage readings on both Lanes was 13.6 volts. Fuel pressure seemed extremely high (can't remember actual pressure) but I was unsure of what the reading should have been.

 

The EGT for the 4 cylinders were one and three in the green zone, albeit slightly lower that normal and two and four in the red zone marked by crosses (indicating the reading was not working and therefore, was inaccurate).

 

At this point I assumed that the engine was only operating an two cylinders.

 

I managed to get back to an airfield and land without further incident.

 

The engine log has been downloaded and I believe sent overseas by Bert Flood for analysis.

 

I now await a verdict as to the cause.

 

 

[Guest Maj Millard]

Mmmm, interesting that theses new engines are giving trouble already. It's the old adage...the more you complicate something, the less reliable it becomes. Please keep us informed and safe flying...............Maj......

 

 

[bluesky]

Episode 1.I had an episode where I loss power while crossing Bass Strait in my Pipistrel Virus SW with a fuel injected Rotax.

 

To correct the problem two components were replaced, the Key Box and the Fuse Box. All seemed well and the engine ran smoothly on the ground and initially in the air. I assumed that the aircraft was now serviceable and attempted to cross Bass Strait to return home.

 

Episode 2. (two weeks later)

 

Weather dictated an altitude of 2,200 ft to cross Bass Strait. I had been airborne for approximately 45 minutes and was 45 nm off shore when the engine suddenly seemed to labour and lost power. The revs had reduced from 5200 to 4500. and I noticed the Lane A light was flashing on and off.

 

The aircraft started losing height so I tried to increase power. I might add at this stage that failure of Lane A also causes loss of automatic control of the constant speed prop. I tried increasing RPM manually by changing the propeller pitch. It had no effect.

 

Next I increased the throttle in order to maintain altitude but instead of getting an increase in RPM the increased throttle setting resulted in a fall of rev to 4400. I then reduced the throttle setting and managed an RPM increase to 4600, sufficient to maintain an altitude of 1000 ft. and eventually, I was able to slowly climb to 2000 ft.

 

Voltage readings on both Lanes was 13.6 volts. Fuel pressure seemed extremely high (can't remember actual pressure) but I was unsure of what the reading should have been.

 

The EGT for the 4 cylinders were one and three in the green zone, albeit slightly lower that normal and two and four in the red zone marked by crosses (indicating the reading was not working and therefore, was inaccurate).

 

At this point I assumed that the engine was only operating an two cylinders.

 

I managed to get back to an airfield and land without further incident.

 

The engine log has been downloaded and I believe sent overseas by Bert Flood for analysis.

 

I now await a verdict as to the cause.

Very interesting would love to hear what response you receive and any outcomes. Would very much appreciate if you could let us know.

 

 

[Bruce]

Regarding the negative comments from seb7701 and bilby54 following bluesky's attempt to seek advice from forum members, the following are the facts

 

• Trouble shooting was carried out on the engine by a Rotax qualified L2. Bert Flood supplied two new fuel pumps.
   
   
  
• At this point the owner felt that the power issue had not been resolved and contacted TECNAM Australia. Copies of the printouts recovered with the dongle were forwarded to the TECNAM factory. Response back from the Rotax factory was that they were aware of the problem through Bert Flood and that they were working with Bert Flood to resolve it.
   
   
  
• It is important to note that TECNAM warranty covers the airframe constructed by TECNAM along with standard instruments. It does not cover the engine (Rotax or Lycoming) and third party avionics which are all subject to their own specific manufacturer warranties. This does not mean that we do not provide support and owners throughout the outback have first hand experience of our support.
   
   
  
• Arrangements were made for the owner to bring the aircraft to Southport (YSPT) for inspection by a well qualified LAME organisation.
   
   
  
• Their engineers went over the engine from front to back and spent hours on the phone with Bert Flood. A number of test flights were conducted by myself and the engineers using different prop settings and also fitting an original Tonini prop. With a Tonini prop we were able to demonstrate cruise at 106 knots and a fuel burn of 16 litres per hour.
   
   
  
• For each flight we split the Dynon Skyview screen showing half with flight instruments and half with engine instruments. A GoPro camera mounted immediately in front of the RHS screen recorded the flights. A dongle was used to download data from the Rotax ECU.
   
   
  
• With the Sensenich prop back on at #3 setting and flying 'on the step' we achieved 106 kts indicated and 16 litres per hour at 5200 rpm (all duly recorded by the GoPro).
   
   
  
• We concluded that the engine was now performing as per specification.
   
   
  

 

 

bluesky is right to be concerned as to why the power loss happened and this forum is an excellent source of feedback from 912iS owners such as orfboy and others well qualified to comment. As Nev comments, the engine is incredibly complex.

 

Bruce

 

TECNAM Australia

 

 

[fly_tornado]

Bruce you could run a blog on your website about this issue and other like minded and suitably qualified people could read and comment on it. The rest of us can stay here!

 

 

[Yenn]

Major.

 

Please explain how better combustion produces higher EGT temps. I was under the impression that higher EGT was caused by incomplete combustion within the cylinder and still burning gases going out the exhaust. Hence a higher EGT when a plug goes bad in a 2 plug cylinder.

 

 

[Guest Maj Millard]

Well I would imagine its because its a more complete burn with fuel injection because the fuel is atomised fully, being squirted into the cylinder under pressure. This might create a more explosive mixture that burns quicker. What other explanation would you have for the standard exhaust systems only lasting about ten hours, over those of a standard carbed 912 ?........................Maj.....

 

 

[facthunter]

An upping of the total power produces a proportionate increase in heat. If the exhaust system is not larger to cope the Temperature will rise

 

 

[bilby54]

Regarding the negative comments from seb7701 and bilby54 following bluesky's attempt to seek advice from forum members, the following are the facts

• We concluded that the engine was now performing as per specification.
   
   
  

 

 

bluesky is right to be concerned as to why the power loss happened and this forum is an excellent source of feedback from 912iS owners such as orfboy and others well qualified to comment. As Nev comments, the engine is incredibly complex.

 

Bruce

 

TECNAM Australia

Now that is interesting that you knew that it was a Tecnam that was giving trouble Bruce:cheezy grin:

 

That aircraft used to launch and could fly a circuit without leaving the airfield perimeter but now not the same. The interesting thing is that if it was a new motor vehicle, the supplier would have been all over it like a rash. My greatest concern was the aircraft had to be flown away while the engine was in a very suspect state putting the pilot/owner at some risk.

 

On a positive note, the P92 Eaglet is one of the best products made.... might have to come and talk to you about one

 

 

[DrZoos]

My greatest concern was the aircraft had to be flown away while the engine was in a very suspect state putting the pilot/owner at some risk.

Totally agree, nice gesture, crazy execution.

 

 

[bilby54]

Had a crack in an injected engine aircraft - the one that we don't know as a Tecnam - and all I can say is don't rush out and buy one.

 

They vibrate, change power settings without even loooking at the throttle let alone touching it and the egt's bounce the red line in every climb.

 

Did not enjoy it much at all and the "Rickety Fences" from China do a better job

 

Bring back the carburettor!!

 

 

[Ultralights]

whats the EGT redline?

 

and why would that be relevent to rough running? onvce it hits peak EGT, it will not go any higher.. hence "Peak"

 

 

[bilby54]

The problem is that the fuel management system used to compensate for high power settings and the egt red line was never reached as that is how the engine management system should work.

 

Now it is a battle to maintain constant power settings as it will just change several hundred rpm up or down during cruise. As for the vibration, your guess is as good as anyone's because it has been looked at by more qualified techs than me

 

 

[Guest Orfboy]

Episode 1.I had an episode where I loss power while crossing Bass Strait in my Pipistrel Virus SW with a fuel injected Rotax.

 

To correct the problem two components were replaced, the Key Box and the Fuse Box. All seemed well and the engine ran smoothly on the ground and initially in the air. I assumed that the aircraft was now serviceable and attempted to cross Bass Strait to return home.

 

Episode 2. (two weeks later)

 

Weather dictated an altitude of 2,200 ft to cross Bass Strait. I had been airborne for approximately 45 minutes and was 45 nm off shore when the engine suddenly seemed to labour and lost power. The revs had reduced from 5200 to 4500. and I noticed the Lane A light was flashing on and off.

 

The aircraft started losing height so I tried to increase power. I might add at this stage that failure of Lane A also causes loss of automatic control of the constant speed prop. I tried increasing RPM manually by changing the propeller pitch. It had no effect.

 

Next I increased the throttle in order to maintain altitude but instead of getting an increase in RPM the increased throttle setting resulted in a fall of rev to 4400. I then reduced the throttle setting and managed an RPM increase to 4600, sufficient to maintain an altitude of 1000 ft. and eventually, I was able to slowly climb to 2000 ft.

 

Voltage readings on both Lanes was 13.6 volts. Fuel pressure seemed extremely high (can't remember actual pressure) but I was unsure of what the reading should have been.

 

The EGT for the 4 cylinders were one and three in the green zone, albeit slightly lower that normal and two and four in the red zone marked by crosses (indicating the reading was not working and therefore, was inaccurate).

 

At this point I assumed that the engine was only operating an two cylinders.

 

I managed to get back to an airfield and land without further incident.

 

The engine log has been downloaded and I believe sent overseas by Bert Flood for analysis.

 

I now await a verdict as to the cause.

It is now more than two months since I posted my problem and I am still waiting for it to be fixed.

The aircraft did fly again (not by me) and it is now at my local airport. It was flown for about an hour in the vicinity of the airport where it was gathering dust with no problems being indicated. The agent then thought the aircraft was fully serviceable and flew it across Bass Straight. About one hour into the flight the engine again lost power. Several airborne tests were carried out and the pilot diagnosed the problem as a faulty fuel pump or fuel pump bypass valve.

 

He even shut down the engine and restarted it, which reset all computers, and carried on.

 

I am now waiting for Bert Flood's engineer to come and replace the fuel pumps and re-flash the ECU with the new software that has at last been released.