915Is ECU ISSUE

It is a 12 volt system.  I'll see if I can find a wiring diagram.

Here a response from Rotax in Brazil that explains their thinking when I challanged them on the checklist. Caution long read. However, they are redoing the POH.

***********************************

I would like to convey some critical information shared with me by Montaer HQ regarding your aircraft's Rotax 915iS engine installation and its systems. This process was meticulously supervised in person by Nino Tavio, Eddie Ronveaux, and Bruno Scotton. (Please feel free to share these names and information with the ROTAX experts you are consulting.) These gentlemen, top-notch professionals esteemed within the Rotax community, came from overseas and were physically present at our facility during the installation and testing phases, ensuring the highest standards of quality and safety for your aircraft.

Regarding the Rotax Manual "Notice," which is designed to capture the operator's attention towards essential operational considerations or efficiency enhancements, distinct from "warnings" that address immediate safety concerns, this specific notice advises against simultaneously activating both fuel pumps due to potential adverse effects on starting behavior. However, during our production and testing—carefully aware of this—it was determined that your aircraft's fuel system maintains optimal pressure levels when both pumps are operational. Consequently, based on empirical evidence and Rotax's consultation and backup, MONTAER has decided that activating both pumps concurrently eliminates the risk of operators neglecting to activate the second pump later, thereby enhancing operational safety and efficiency.

Addressing the second paragraph, which reads: “Most manufacturers only want minimum loads when starting, typically the PFD, the ECU lanes, and one fuel pump. I don't understand why your manufacturer would want the MFD, aux fuel pump, beacon, and Aux alternator on. The PFD is important to monitor the engine functions as you start the engine, but it would start without it.”

As the aircraft manufacturer, our main concern and philosophy is to harmonize straightforward engineering with technicalities and rules compliance with human behavior in an intuitive manner applied to our aircraft. This said, as the manufacturer's prerogative, strictly following the highest ASTM standards and intending to comply with FAA rules, MONTAER understands:

Why the MFD?
Operators often tailor the G3X display configurations to their personal preferences, which may alter the display of the engine instruments on the screens. Moreover, a routine series of verifications on the EFIS precedes engine ignition, encompassing checks on navigation data, radio frequencies, and occasionally, clearance for engine start-up. Despite preferences being debatable, we advocate for activating the MFD as this approach represents what we believe to be the most prudent and logical procedure.

Why the Aux fuel pump?
As mentioned above, during our production and testing—carefully taking this subject into consideration—it was determined that your aircraft's fuel system maintains optimal pressure levels when both pumps are operational. Consequently, based on empirical evidence and Rotax's consultation and technical backup, MONTAER has decided that activating both pumps concurrently eliminates the risk of operators neglecting to activate the second pump, thereby enhancing operational safety and efficiency.
Additionally, the load on the system will only be for a few seconds until it starts to run, therefore, benefiting from the aircraft’s overall optimal design and converging to safe operation procedures, it was the manufacturer's prerogative, again, backed up by the Rotax technical team.

In high consideration of your questions and with the intention of providing you thorough clarification and peace of mind on these subjects, today our CEO reached out by phone to Nino Tavio—who is considered one of the foremost authorities in the Rotax community (the Rotax experts you are talking to will know who he is). Nino, who oversaw the installation of your aircraft's engine, reassured us that, despite the ROTAX notice, it remains within the aircraft manufacturer's scope to ensure the best engine behavior.

Our team consists of esteemed in-house engineers and technicians, enriched with a deep understanding of aviation culture and extensive experience. We also maintain a robust technical partnership with our suppliers, including Rotax, collaborating closely on our projects. In 2024, Montaer was the largest Rotax purchaser in all of Latin America.

The perspectives of our customers are incredibly important to us; we take them very seriously. YOUR FEEDBACK IS ALWAYS WELCOME, GENE. We have considered many of your feedback for future revisions and updates in our manuals, some of them to be released soon.

Gene

It would appear they are butt hurt by some comments.  The comments were to help and no way to criticize what they perceive to be correct.  My comment stands, there is no reason to start on both pumps.  If the engine can not maintain pressure without 2 pumps on it suggests some restriction in the system.  Each pump is designed to pump to at least 125% of the required volume and pressure necessary to run the engine.  This is the same as standards for certified installations.  The load on the system is critical only for the first few seconds till the engine runs.  Fuel pumps such as this have a huge draw and the only time we have a risk of low power is at the start.  Given the pump draws something like 5 amps on cranking it is a big consideration.  As long as you have a healthy battery then great, start on 2 if it makes you feel good.  

As a note, the FAA or ASTM have nothing to say about how many pumps or the start process is, that is up to the OEM.  Out of all the things switched on the biggest draw will be the fuel pumps, hence the note in the operators manual that Rotax supplies.  I am rather surprised they yell at you about feedback, seems odd. 

Anyway as long as you're happy and the plane starts and runs great thats the main point.  This started out with questions about the ACC on the switch so everyone was trying to understand what was happening.  Nobody is questioning the that Montaer can do what they want to with the installation, we just did not understand  the load put on everything before you generate any energy.  The answer for me is a bit weak in thinking a pilot is not smart enough to turn on a pump or marker lights for example.  Perhaps they are different there. 

I can understand the opinion but it seems a bit over the top to answer you in that way, just my view so don't worry about it. 

Cheers

Yes they were butt hurt.  We called thier baby ugly, but welcome to the real world.  They are targeting flight schools and it makes financial sense for the school to get something like an MC-01 since the ROTAX is proven and bullet proof. I agree with you and they agreed that one pump would work (it does, and I tried it when I started the plane today.). However, in thier defense I think they were trying to make it as close to idiot proof as they could.  However, they never explained "why" even in footnotes for those of us that were curious.  

From my perspective, the comments that I've gotten here have increased my understanding and shows just how valuable a forum like this is.

Thanks

Gene,

I never intended on offending the manufacturer, of course they can design the aircraft however they please. I’ve never flown one, but the MC-01/915 appears to be a very nice aircraft.

Regarding their response, it screams out “don’t question us”.  Simply put, they spent more time assuring you of their expertise than they did on reasonable explanations. They are the final authority on their own aircraft, that’s what the ASTM rules require, but there are good reasons for the guidance Rotax provides.  I predict some forthcoming changes to the Operating Manual for your aircraft. So good job on moving the issues forward.  

In your original post you were getting lane errors on startup. This was seemingly because the start power scheme was not well understood, or maybe because of low battery voltage. Now they have provided a nine paragraph response, yet somehow avoided any possible solution for this issue or even an explanation of how the system works.

Anyway, it sounds like you now have a method to start the aircraft without lane errors, so go have some fun.