Considering the Rotax 915

loftus

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from the above;
"Power was the main consideration.
redundancy was also a consideration; the engine will continue to run on only one carb, with enough power to keep the typical aircraft in the air."

I wonder if the gentleman who made that claim has ever tried it?
I have had an issue with one needle valve sticking, not a gyro and fortunately I have two engines, I doubt with the remaining engine a gyro would have stayed in the air indefinitely as max rpm was 2500 - 3000 RPM. I was near an airport so no issues returning to land. The electrical component is an issue with injected engines and a reason why the is engines have the added on alternator.
 

Tyger

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from the above;
" redundancy was also a consideration; the engine will continue to run on only one carb, with enough power to keep the typical aircraft in the air."

I wonder if the gentleman who made that claim has ever tried it?
I agree that claim is a bit suspect; on the other hand, it's probably pretty unusual for one carb just to stop working completely all of a sudden.
If you start to get a noticeable engine vibration, it's usually time to have a look at both carbs, before things get worse. A lot of times it IS just a matter of rebalancing.
 
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Tyger

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most cars and trucks cannot be maintained by your typical handyman anymore unless he/she can connect the vehicle with the latest computer software to tell what's wrong. Usually, the answer is to replace such and such a part rather than fix anything followed by a reboot of the system. Everything is moving towards greater complexity and deliberately short design life rather than durability and ease of maintenance.
If you want to see mechanics throw up their hands these days, try bringing them a car with a carburetor problem... a lot of today's car mechanics have never even SEEN a carburetor, much less thought about repairing one.
 
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WaspAir

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You've got it easy, guys. Classic Ferrari V12s have six two-barrel downdraft Webber carbs to balance.

early_ferrari_carb_assembly_1.png
 

WaspAir

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PS: I suspect that the "typical" aircraft to be kept in the air on one working carb as mentioned in that Rotax reference has fixed wings, not a gyro rotor.
 

Smack

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I had a FW buddy whose Rotax lost one carb; it had vibrated out of its rubber boot (maybe not properly synched/balanced).
He was able to circle back around and land, but I don't have any more details on the incident.

Yes, I recall working on a friend's 'Colombo' Ferrari V-12 project; I got my fingers smashed while aligning the intake manifold on those multiple studs. Seems that 250 GTE had only 3 Webers, but my memory is foggy on that.
 

XXavier

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PS: I suspect that the "typical" aircraft to be kept in the air on one working carb as mentioned in that Rotax reference has fixed wings, not a gyro rotor.

I once tried to take off with an ELA-914 that had a single working carb, due to a malfunction that I didn't detect in the pre-flight. With one working carb and fully open throttle, the gyro was unable to get unstuck after a run of 400+ meters on good tarmac. There was no noticeable extra engine vibration...
 

GyrOZprey

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A couple of years ago I had been requested to take each of a couple flying for their anniversary! After pre-flight brief I loaded the wife up & taxied out to 17 KEWK ...we had a great mag check & everything was normal ..pre-rotated & accelerated ...just before the nose wheel came up ...there was horrendous engine vibration & dramatic power loss! Instant abort & taxi off at next exit! ... at low revs / idle under 2500 ...everything seemed normal! I did some power-range tests after I unloaded my passenger ...and anything over 2500 ...ran super-rough & bad vibration!

When my wonderful local Rotax mechanic Michael at STOL creek aviation investigated opened up the top of the carbs - on the 2/4 side..he discovered the needle was missing- dropped down ...the Spring steel tiny clip & O-ring were gone! I was one of several Rotax owners who this had happened to about that time...and 9 months after filing a report to Rotax ... they issued ...a "defective manufacture" ...clip replacement service bulletin! The 200 hour carb-service now includes replacing these clips! (My machine was at about 179hours TTSN!)
2/3rds of the clip had fallen down in the carb dome area ... but the tiny 1/3 piece had followed the needle and continued into the piston!
Michael was thorough in his investigation ... checking for damages to piston, rings and turbo ...after a few pounds on the piston head ...it left about 5 small scratches and was expelled through the exhaust!
I hate to think of this happening in any flight ...away from airport vicinity! immediate outfield landing inevitable!
NO WAY to get ANY kind of power to continue flight in a gyro ...on ONE carb!
 

Abid

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Trust me I used to think that way about carbs in aircraft engines when I started out. That is one of the reasons early on in my flying I went to Suzuki conversions in trikes and then sold a dozen trikes with Suzuki conversions. To get the “benefit” of car technology into aircraft power plants for light aircraft. Sounds logical.

The problem is we are not flying cars. The application is different. The fuel injection that has to be done for aircraft has to be much more solid and redundant. The mile long wiring a lot more robust than in cars. Car conversions are not at that level. Car wiring isn’t at that level. Cars ECU and ECU like the Australian one used by Edge aren’t redundant. One loss of sensor or critical reading from a wire and you are toast. One computer chip malfunction and you are toast. So redundancy is quite important. But with that also comes required complexity. There is no two ways about it. You get some advantages but you also get some negatives. Nothing is ever free.
 
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Abid

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Chris. The carb problem you experienced is because of the great German Engineering from Bing. Bing basically makes nothing but carbs but you can’t hold a gun to their head to get the carbs of same quality as they did 10 years ago. I am sure they have outsourced a lot of the components to somewhere and that is what created the issue for floats and for other items. I do believe though not sure that Rotax does not buy carbs from Bing any longer. They have used some one else now to do those carbs for them.
 
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Burrengyro

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Chris, thanks for sharing your experience with carb failure. Happy you landed safely.

There is no way this carb problem could have been identified during the main daily inspection. Is this a good case to highlight the advantages of fuel injection over carbs?

Abid, do you know of any failures of fuel injection components in the new Rotax iS engines?
Thanks, John H.
 

Abid

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Chris, thanks for sharing your experience with carb failure. Happy you landed safely.

There is no way this carb problem could have been identified during the main daily inspection. Is this a good case to highlight the advantages of fuel injection over carbs?

Abid, do you know of any failures of fuel injection components in the new Rotax iS engines?
Thanks, John H.

Yes. Wiring harness. Also know of ignition coils that failed and fuel injectors getting clogged with partial power left and Rotax fuel pumps for iS in the 2019 and 2020 production failed quite a lot but usually right on the ground. That's another matter. 2018 and prior (made by AC Delco) and 2021 (made by new supplier) are fine because there is a difference in design. I have not seen Rockwell Collins redundant ECU failed yet but did hear of one lane failure in New Zealand on 912iS a few years back. Anything that is electronic just like anything that is mechanical can fail. I have training in Microelectronics and computer science. Nothing is fool proof. You can reduce chances with clever design with automatic redundant ECU failover in both hardware and software but you cannot eliminate everything. Wiring is one such thing (difficult to make redundant wiring) and certain sensors are another. Its the same with mechanical items but usually there are more mechanics available that can understand mechanical things and figure them out.

Actually a needle that is sticking like for Loftus and for Chris should be identifiable at runup to 3800 to 4000 RPM where you are supposed to do the mag check for Rotax 912 and 914. Usually its acting on the mid range so when you go from the 2500 warm up to 3800 RPM for mag check, you should feel really rough engine running and hesitation. This could indicate either main jet is clogged or carb bowls are leaky and sucking air or your needle is bent. That's about it.

In the iS world, you will need a $1200 dongle and BUDS software on a laptop which BTW you cannot download till you have taken a Rotax iS course, that can show you the logs with what's wrong. Most people find that they have a hard time reading the log and interpreting it and need help (and thus why Rotax wants training for people downloading BUDS software). I had no big problems interpreting the logs even without that training but I understand people's experiences are different. Once you know what the log says still does not mean you have completely pinpointed the problem. You just have an identification of what the computer sees and logs. Now you have to systematically eliminate things one by one that can cause that symptom and arrive at the actual root cause (and again this is why Rotax requires training for their iS mechanics specifically). Again I was able to identify problems without that training but again it depends on one's previous experience and skill at troubleshooting. Basically generally speaking mechanics will need specialized training to figure out iS issues if they are a bit complex. Some will naturally be better at developing that skill than others even after training.
 
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wolfy

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I have done lots of hours on engines that get the carbs balanced once in a blue moon, I had one engine that went about 1500 hrs before I re-balanced the carbs. To do it every few hundred hours is I think being a bit pedantic, they stay balanced for a long time if balanced well to start with. On two occasions I've had throttle return springs break, so that carb stays at pretty much full throttle and when idling back the other carb the thing runs rough as guts enough that I land straight away the vibration was horrendous.

wolfy
 

loftus

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I definitely agree that all systems have potential failure issues and whichever one chooses, strict adherence to the recommended maintenance requirements is key. With EFI electrical and fuel cleanliness issues seem to be the main potential problems. In my case with the Edge Performance System pre and post fuel pump filtration is essential. For single engine setups, the add on alternator is recommended. I have twin engines which provides some redundancy in this respect. I will likely add a dual battery system.
In my case the primary reason for switching to EFI was enhanced fuel efficiency to extend range. I followed Edge and checked with multiple owners over about 2 ½ years regarding reliability before committing.
BTW Abid, my runup when my needle valve stuck was fine and the issue occurred about half an hour into flight.
Wolfy, do you use the old standard guages to balance or the electronic one? I've found that with the standard guages balance between checks looks about the same. With the electronic one, there are always differences. How important these small changes are is again questionable.
 
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Burrengyro

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You have to buy a $1200 dongle, etc., and do a Rotax maintenance course to do your own maintenance on the 912iS / 915iS engines so the software can show you all the things that can go wrong??? o_O
Is this a mature/robust system yet?

Loftus, does your Edge system need as much work and $$ to keep it running?
 

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You have to buy a $1200 dongle, etc., and do a Rotax maintenance course to do your own maintenance on the 912iS / 915iS engines so the software can show you all the things that can go wrong??? o_O
Is this a mature/robust system yet?

Loftus, does your Edge system need as much work and $$ to keep it running?


Yes you have to have the dongle and it costs that much. Last I knew they would not let you download the BUDS software without training course.
 

loftus

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You have to buy a $1200 dongle, etc., and do a Rotax maintenance course to do your own maintenance on the 912iS / 915iS engines so the software can show you all the things that can go wrong??? o_O
Is this a mature/robust system yet?

Loftus, does your Edge system need as much work and $$ to keep it running?
It's too early for me to comment on reliability etc as I only have about 12 hours on the conversion. The Edge System appears to be much simpler than the Rotax is systems but as Abid says, at the cost of redundancy. The Edge system actually reduces the weight of the 912 ULS engine, whereas the 912is I believe weighs more (I think 20 lbs) than the ULS.
Except for changing the high pressure fuel filter every 100 hours and checking the filter in the fuel pressure regulator, there is no other maintenance. The Electronic Control Unit should not require any programming maintenance after the initial programming of Air/Fuel mixtures at various RPM which was done after the initial startup. It is recommended to change the 2 high pressure fuel pumps at 500 hours, though I'm not certain why it should be necessary to change the backup pump if it's not used.
 

Abid

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It's too early for me to comment on reliability etc as I only have about 12 hours on the conversion. The Edge System appears to be much simpler than the Rotax is systems but as Abid says, at the cost of redundancy. The Edge system actually reduces the weight of the 912 ULS engine, whereas the 912is I believe weighs more (I think 20 lbs) than the ULS.
Except for changing the high pressure fuel filter every 100 hours and checking the filter in the fuel pressure regulator, there is no other maintenance. The Electronic Control Unit should not require any programming maintenance after the initial programming of Air/Fuel mixtures at various RPM which was done after the initial startup. It is recommended to change the 2 high pressure fuel pumps at 500 hours, though I'm not certain why it should be necessary to change the backup pump if it's not used.


The 912iS adds 16 pounds to 912ULS. Its mainly redundant ECU, redundant generators and fuse box and associated wiring. Edge has no redundancy. If you take the external alternator option of Edge Performance (which produces more amps), it will come close to 912iS weight as well.

Edge uses a specific Bosch fuel pump model in their fuel pump manifold. Bosch makes very reliable and good fuel pumps. Edge can get those because they are small and Bosch does not know their fuel pumps are ending up in aircraft use. Rotax cannot do that because Bosch or anyone like that will not sell them their products because they know they will end up in aircraft. Its the typical western world problem of liability and sue city. I don't know why you should change working fuel pumps ever. If they are working they are working. You do your checks on the ground for each fuel pump. If they both checkout good, you are good. Bosch fuel pumps do run at 9 to 10 amps each. Rotax 912ULS or 914 produce about 18 to 20 amps total. You can see you can't really run both fuel pumps even for a short time without needing the external alternator option which robs a little horsepower and increases the weight of Edge setup. The Rotax fuel pumps run at 5 to 6 amps each.

There is no programming in iS ever. Its done at the factory and that's it. The only time you will have to hook a a dongle up is when there is Lane A or Lane B solid or blinking light that comes on to read the error logs and codes. If it never comes on you will never need it.
 

martin-av8r

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I Think Edge possibly.. use the Walbro GSL 393 , can depend on type of motor

normally aspirated or turbo and total boost psi...




GSL393-Flow-Chart.jpg
 

loftus

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Not doubting the Rotax IS engines at all or saying the Edge is better. If I were building again from scratch, I'd go with Rotax IS engines. When I started my build IS engines still seemed to be having some issues, and actually were discouraged by Lockwood in the Aircam at the time. In my case an Edge retrofit at about $6500 per engine was a lot more feasible than changing to new IS engines, both from a cost and of course work perspective. All the contacts I'd had with Edge customers were positive with regard to reliability. So I think the Edge conversion is a good retrofit option, but if one is considering a new engine, I'm all for the IS option. Remember I have two engines so there's some redundancy there.
 
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