Fuel pump pressure drop

Hi Jeff....I cant see anywhere in the MML where you have to replace the main pump at 1000 hours.  It clearly calls for a check of both pumps at 1000 hours nothing more.  The hose change at 5 year is based on time only.  

In a dual electric system I would run both pumps personally.  With a 3 bar, 45 psi system, any failure of the running pump the engine will stop.  With both running you will not lose power at all.  If you are only on one pump you must now do a restart, this starts to get stressful in my opinion.  I know that for the 915 and 916 engines the same verbiage exists and at about 3k per pump people will not replace them at 1000 hour.  

Perhaps i am missing something, I looked at the latest (2023) MML in the scheduled maintenance.  

Cheers

Still since the 912is came out is there no documented failures? Can’t believe certification wouldn’t have required even bench testing till failure. 

They’ve had some leaks, but haven’t heard of any total failures. Maybe Rotax folks will chime in on any failures.

RW,

My bad, you are correct there is no requirement to replace the pump at 1000 hours.  I accidently looked at the 914 MML this morning and that does require the main pump change at 1000 hours.  The 914 has a similar pump set up to the 912iS (same form factor) but the pumps are lower pressure.  Do you know what drives the 1000 hour replacement of the 914 pump?  The below page is from the 914 manual. 

And as for failures of the 912iS pump, I saw one that pushed itself apart.  The internal pressure pushed the plastic end cap out past the retaining crimps in the housing.  This particular aircraft did not have a high pressure bypass on the return line and the main pump was accidentally started with the fuel selector in the off position.  More than one manufacturer missed the requirement for the high pressure bypass on the return line around the dual selector valve. I think I heard that later model pumps have an internal high pressure bypass to avoid this, but I don’t know for sure. 

I guess ROTAX will chime in at some point given multiple operational configurations and safety concerns…hope we hear something.