SonexBuilders.net

Morning Noel,

Win, lose, or draw this is going to be fun.

Yes, I have looked at MegaSquirt. I've downloaded the assembler source code for the old 6800 based system and the newer code written in C. I've stashed the code for reference. However ...

My experience is from the certified world. I haven't checked to see if there is a TSO for fuel injection but if there is it will almost certainly require the code be certified to DO178(B or C) Level A. If a design assurance level isn't given in the TSO, the producer will be required to conduct a "System Safety Assessment". I can almost guarantee the outcome of the assessment would be a Level A effort. And I couldn't argue with that.

A Level A assessment brings a lot of requirements. Here is some text from Wikipedia explaining the different failure conditions.

Catastrophic – Failure may cause a crash. Error or loss of critical function required to safely fly and land aircraft.
Hazardous – Failure has a large negative impact on safety or performance, or reduces the ability of the crew to operate the aircraft due to physical distress or a higher workload, or causes serious or fatal injuries among the passengers. (Safety-significant)
Major – Failure is significant, but has a lesser impact than a Hazardous failure (for example, leads to passenger discomfort rather than injuries) or significantly increases crew workload (safety related)
Minor – Failure is noticeable, but has a lesser impact than a Major failure (for example, causing passenger inconvenience or a routine flight plan change)
No Effect – Failure has no impact on safety, aircraft operation, or crew workload.

And here are the design assurance levels associated with the various failure conditions.

Level Failure condition Objectives[5] With independence Failure Rate
A Catastrophic 66 25 10−9/h
B Hazardous 65 14 10−7/h
C Major 57 2 10−5/h
D Minor 28 2 10−3/h
E No Effect 0 0 n/a

One failure every 1 billion hours!?!?!? At first blush you would think it impossible. But remember, there are three types of liars. Liars, Damn Liars, and Statisticians.

Anyway, all of this to say: The most recent code for the MegaSquirt ECUs runs totally counter to excepted norms in the aviation industry. The challenge we face is how simple and reliable can we make it. The challenge they face is how flexible can we make it to capture maximum market share.

You can't have a lot of unused options floating around in Level A code. In fact, you are not allowed a single line of "dead" code. If you want to water your eyes, have a look at the MCDC requirements for Level A.

Honestly, I would never leave the ground with a MegaSquirt.

Wes

I am in aerospace and i think your assestment is incorrect, This would be DAL B. An engine failure does not result in a crash it can result in an off field landing but not necessarily a total loss of aircraft. Its a borderline evaluation but very few things are DAL A and most things can easily be brought down in DAL level via redundancy. The Aeromomentum uses a microsquirt ECU for its control and has a fall back fail safe mode. All that being said this is the one place where i wish they had a second set of Computers and it will be something i probably tinker at my own risk even if its something as simple as having a second entire ECU system although at that point a common wiring harness would still leave you with a possible single point failure although given the 4 individual injectors and split coils it would have to be a catostrophic wirning failure.

Also technically you are not allowed any dead code at any DAL level you can have deactivated code but it needs to be tested to never be accessible or built into the binaries.

For refrence the coding and performance standards of all dal levels is the same and spelled out in DO-178 C, the only diffrence is the level of rigor of the validation and the related documentation required to prove you meet your stated function.

Keep in mind that is a very simplified analysis of DO-178 and the DAL levels but lots of people get paid lots of money to make sure software meets those validation standards and its the reason why Certified items are 3-10 times the amount of non cert items, is to produce the artifacts of compliance in order to meet the certification standard.

Wes,
I was advised by Mark Schaible in Feb 2020 (See below)

Are you speaking of the red anodized intake elbows that bolt to the cylinder heads? If so, you would be looking for part numbers ACV-M01-11 and ACV-M01-12 as shown in the AeroVee Assembly Manual: http://www.aeroconversions.com/support/ ... Manual.pdf
Price is $158.25 each.

This indicated the intake manifolds were available to purchase individually.

I have my Aerovee fitted with EFI using these same manifolds I will post an update of the configuration. Uses Microsquirt with full redundancy incorporating changeover to normally aspirated operation.

Hope this helps
Peter
Waiex #149

I've never seen a loss of all engines categorized as anything but catastrophic. Of course losing the engine can have a successful outcome, but it depends where and when it happens.

In a former life I was a helicopter fly by wire guy at Sikorsky. No way did we allow any dead source code whether it made it to the binaries or not.

For a hobby application like we are discussing here, the key thing is Wes's comfort and familiarity of the system. I do not think that DO178 is not necessary here and how would you do it as a one man show anyway? Unless the dog or cat can do peer reviews.

Wes I think this is a cool project. Good luck and keep us posted!

I think if I did it I'd add a second power source. Maybe something like a Kubota PMG. Makes no practical sense in a Sonex but I think this is more about play time than anything else. You know, fun.

Wes,

If you want to use your existing manifolds there are a number of options for mounting the injectors, below is a link to just one supplier with some examples.
https://www.efihardware.com/

Hi Guys,

Well, I'm back in the boonies with plumbing supplies. I'll be cleaning up the place and fixing leaks. So, for the next few days no keyboard. That means I can't argue with Jaun ;-)

Peter, Mark declined to sell me a set. Now my fealings are hurt. And please update us on your experience. Please feel free to use this thread so we can keep the EFI stuff kind of bunched together. My comments on MegaSquirt are just opinions, and you know what they say about opinions.

And Brian, you're right. There is no way to meet the independence requirements. I was just trying to draw a contrast.

Wes

Hi Peter,

Are you talking about putting bosses in the GPAS logs?

I found this:
https://www.efihardware.com/products/c382/Injector-Bosses-and-Mounts

Problem is I'm clueless. Not a machinist, welder, or gearhead. Is there a video or expinarion I could read?

Thanks,

Wes

As far as bosses you have two main options,

A machine the intake to work as the injector boss and seal with the built in injector o-ring
B drill and weld the injector boss into the intake

Pros and cons to both.

one you will need machined the other you will need welded really depends on what is possible with the aerovee logs i suspect that its pretty thin walled tubing so you will need to weld on some bosses the one disadvantage is you obviously have to remove the anodizing.

Have you thought about how you are going to solve the fuel rail? i feel like that is a bigger issue than the bosses hell you can get away with just drilling and sealing the bosses with RTV if you have a good attachment system for keeping the injectors pressed into the logs if you use a bar style fuel rail setup. of course you need to do this twice since you have intakes on both sides.

Hi Jaun,

No keyboard. Briefly, please go here http://www.sonexflight.com/58/index.html and listen and review tne show notes and you will see my starting point.

Wes

I have seen the SDS sonexflight pod cast, and that is a very valid starting point and they solved. you asked about how to install bosses so i was giving you a few options I really should have done a better job of reading since you did mention GPAS and i assumed you were talking about the aerovee logs thats my bad.

sepreatly on the power draw issue you can look at going to the lower ampreage draw coils and also there is an alternator install that was very interesting in the aerovee forums.