Fuel Pump Drain Hose Size?

Hi RW,

Clarification question. 

If you said fuel pumps should last to TBO then why does Rotax want them replaced at the 5 year rubber change. Of all the aircraft i work on every year I've never had a fuel pump go out. Most owners I've  worked with just leave them until the second hose change.

Just curious.

p.s.

Hope all is well.

Roger, you are correct.  

The 5 year requirement was a direct request from the fuel pump suppliers.  None of them will accept that they may last 15 years and 2000 hours.  That said the parts that fail from hours would be the diaphragms and mostly with auto fuels (more likely now than in the past due to relaxed requirements of the regulators on fuel production)  The pump shaft seal is another area that degrades, mostly from age and environment.  Long term storage actually is harder on the shaft seal than regular use.  Seals dry out and harden, one of the primary reasons they will not extend replacement times.  

For those who have worked on the Rotax pumps over the many, many years, we have seen 3 major pump design changes with the mechanical pump.   Within that there were sub plots of problems that caused Rotax to work with Corona for the last version.  Thankfully it has worked well since 2010 and we have only had a few minor issues.  

For those with experimentals you can run it as long as you like, however I recommend you have an electric inline back near your tank as boost pump/backup.  When you can back up a system you should in my opinion.

Cheers

Hi RW,

Provided everything stays in good condition i usually recommend every other rubber change (10  years) and so far all is well.

Hmmmm!

My first 912ULS (think 1998-9 model) had the non drain fuel pump. I replaced all "rubbers" shortly after purchasing aircraft.

I being new to Rotax, went several years without knowing that there was a recommended 5 year replacement on the fuel pump.

Eventually purchased a new pump, with drain. 

Old pump still delivering good pressure - put new pump on shelf.

Eventually at second 5 year interval (10 years since I purchased aircraft) I replaced the perfectly operating OM pump with the new model. The OM pump may have been close to 20 years old when replaced (service record a tad vague/incomplete)

Some time later, prop strike, had engine inspected by Rotax. Told off for not replacing pump (serial number gave me away) explained above - pump had only been in operation for 2 years.

Despite the above experince, I will be replacing the fuel pump, at the 5 year interval, on the new aircraft/912ULS - Why? because I see it as a critical component that should not be subject to penny pinching (one of my other pleasures)😈