Sport Pilot Talk

howardnmn · Posted: Fri May 06, 2011 11:12 pm Post subject: rotax 912 fuel pump failure mode

i have heard that it's relatively common for 912 fuel pump to fail. question: what is the mode (or modes) of failure?

e.g., fuel pressure drops to zero and engine stops? most LSA have electric b/u pumps but not everyone can diagnose engine stoppage quickly. anyone have it quit on take off? in cruise? does fuel tank in high-wing gravity-flow suffice? partial starvation =rpm drop?

a eurofox CFI once told me he's seen fuel pump leaks at "dome" crimp. i would guess most leaks are small and caught on visual inspection or by nose on ground. large leaks = fire risk? wouldn't electric aux pump make things worse? [fuel press =zero & hit aux pump = more loose fuel in eng compartment]

i read somewhere that rotax is replacing pump with new model. but in meantime ...what to do?

roger lee · Posted: Fri May 06, 2011 11:41 pm Post subject: Rotax

The new fuel pump should be out by the end of the month or sooner, but no one really knows. Rotax said by the end of May. The pump fails open. If you have a high wing you may be able to fly from a gravity feed, but not at full throttle. If you have an electric pump turn it on. You won't know at that moment if it is a fuel restriction or a pump failer. Some pumps have been known to leak, but it's finding a good Rotax mechanic that knows where to look at what they are looking for. As far as landing and take offs. Do what you need to do to stay in the air long enough to come about and land with the proper altitude. If you are too low then your landing spot is more or less straight ahead. Don't panic, don't forget to fly the plane and try to pick the best carsh landing spot you can.

RyanShort1 · Joined: 17 Aug 2010 Posts: 101 Location: San Antonio, TX

In the Fox that I fly, it gave some warning - showing a low fuel flow indication several flights before it actually went out. I'm glad it went out with another instructor on board, instead of one of my solo students...
The pump in our case failed on takeoff - and the instructor had the presence of mind to hit the fuel boost pump, which was sufficient to get them to pattern altitude, where he turned it off to see if it was a fluke or not - and it wasn't. He flipped the boost pump on, made a normal landing, and grounded the bird until we got the replacement in.

Ryan

Jack Tyler · Posted: Sat May 07, 2011 8:30 am Post subject:

"In the Fox that I fly, it gave some warning - showing a low fuel flow indication several flights before it actually went out."

Howard, there's been some interesting discussions on this point on the Vans Air Force forum, in the RV-12 section, and with the same reported 'indication' mentioned above. Some builders, post-certification, have relocated the fuel pump to reduce the vibration it sees. You might want to 'search' that forum for the details...

Jack Tyler · Posted: Mon May 09, 2011 5:01 am Post subject:

howardnmn, as a follow-up here's a current thread on your topic that you may find useful reading:

http://www.vansairforce.com/community/showthread.php?t=66775

In one summary statement, Jetguy notes:
"I really like the Rotax engine but some of the accessories seem to be weak. It’s hard to know the exact data on failures of these types. As with the Honeywell oil sensor failures sometimes the things last for hundreds of hours and then sometimes they fail right away."

You'll find multiple threads at VAF that report on this same issue.

3Dreaming · Joined: 10 Jan 2010 Posts: 301 Location: noble, IL USA

Jack Tyler wrote: "In the Fox that I fly, it gave some warning - showing a low fuel flow indication several flights before it actually went out."

Howard, there's been some interesting discussions on this point on the Vans Air Force forum, in the RV-12 section, and with the same reported 'indication' mentioned above. Some builders, post-certification, have relocated the fuel pump to reduce the vibration it sees. You might want to 'search' that forum for the details...

Jack, this post is about the fuel PUMP. They are talking about the fuel (oil) pressure sending unit over on VAF. Tom

"edited for spelling and to add oil."

roger lee · Posted: Mon May 09, 2011 10:15 am Post subject: Fuel pressure sending unit

The fuel pressure sending unit should be mounted completely off the engine and mounted some where else like the firewall with and extension hose. Vibration will kill this these senders and cause them to be erratic. I have remote mounted many. You should also have a fuel pressure dampener devise in the pressure out line. Dynon sells a nice little fuel pressure dampening devise that looks like a little metal bulb. This issue has been discussed on other forums and other Mfg's follow these practices.

Jack Tyler · Posted: Sat May 21, 2011 4:10 am Post subject:

3Dreaming, thanks for the correction. I'd meant to send:
http://www.vansairforce.com/community/showthread.php?t=66775

In lieu of the above earlier link on the fuel PUMP which I'd meant to send, here is a more current one. (Inbedded inside it is an even earlier link discussing fuel pump failures). One interesting thing about this link...

http://www.vansairforce.com/community/showthread.php?t=72330

...is that, as this owner is going thru the process right now of trying to identify whether he has a pump failure or not, he offers readers some graphs of downloaded data (off his Dynon EFIS) on the pump's performance, both when the pump was performing correctly and when fuel flow was out of spec. Very slick...and yet in his case, it's still unclear if it's a faulty pump or winter additives in his fuel. He (and we) will know more soon...

Tad Olmsted · Joined: 28 Feb 2011 Posts: 34 Location: Sebring,FL

Hi Jack, I learned at a very early age the following:

Do not poke a skunk!

These pumps are horrible and I just replaced one that only had 60 hours on it since the last time it was replaced. When the very first CTLS came to the US, I replaced the fuel pump after its maiden voyage.

616jim · Joined: 13 Sep 2011 Posts: 1

THE LATEST 912 FUEL PUMP SEEMS WORSE THAN ITS PREDECESSOR. DOES ANYONE KNOW IF THERE ARE PLANS TO CONTINUE WORK ON IT?
I HAVE NOT HAD THE ENGINE QUIT BUT WATCHING THE FUEL PRESSURE DROP IS NOT A COMFORTING SIGHT. I HAVE AN AUX PUMP AND TURNING IT ON OR OFF SEEMS TO CORRECT THE SITUATION BUT NOT INSTANTLY. (PROBLEM OCCURS WHEN THE AUX PUMP IS ON OR OFF, -- BOTH MODES.) FLY AN AER0TREK 220, (EUROFOX) TAILDRAGGER.

roger lee · Posted: Wed Sep 14, 2011 2:58 pm Post subject: New pump

Haven't heard a lot bad except people not putting the vent tube in the right place and causing problems. Many have reported slightly higher pressures over the old one.