Looking at 912 failure modes......

[Kyle Communications]

Yes Ross I stuffed the air pressure one up I remember now it was to push the oil through the engine. I did it when I first got the engine

 

 

[Guest Maj Millard]

No dramas Kyle.......seasons Greetings to you and your family, and all the gang down that way..... Cheers......................................Ross .........

 

 

[Kyle Communications]

Same to you and yours Ross....this next year I am looking forward to attending flying getting there in my own aircraft now instead of driving

 

 

[eightyknots]

I wouldn't assume that you have to use the starter motor - it can be started by hand

Wow!

 

(good to know in case of starter motor or starter circuit failure.....)

 

 

[Teckair]

Wow!(good to know in case of starter motor or starter circuit failure.....)

I second that wow I had no idea that you could hand start a 912 maybe it is the foot swing move that is the secret???

 

 

[Head in the clouds]

Most of the fancy Euro cars use Pierburg pumps such as Porsche, Mercedes, BMW etc etc............their's is an interesting website by the way.................................................Maj...

Can anyone tell me what type this fuel pump is on the 912 I am fitting to my current project? And do they have a history, good or bad?

 

 

 

 

 

 

[skyfox1]

Hi it looks like the latest fuel pump that rotax have just bought out CPS sell them

 

l have heard that some of them over pressurize the fuel system .

 

l was going to replace mine with one of the new ones but decided to go with the original peirberg pump.

 

cheers Geoff.

 

Here is the link http://www.rotaxparts.net/scripts/prodView.asp?idproduct=1333

 

 

[Guest Maj Millard]

Yes that is the new style pump. I have purchased one from Floods, but haven't fitted it yet. Still running my Pierburg. I chatted with Gary a couple of weeks ago, and he said they are doing fine. There was some discussion on US forums about these pumps producing too much pressure, but I haven't heard much lately. It always wise to fit a fuel-pressure guage as you don't want to produce too much pressure for the Bing carbs..................................Maj...

 

 

[Head in the clouds]

Thanks so much for the feedback Geoff and Maj. I bought the engine a year ago, so those pumps have been fitted at least as long as that.

 

Never considered a 'too much pressure' scenario so I'll check the manual about max pressure for Bings (unless anyone wants to enlighten me...).

 

So what's the failure mode of the carbs with too much pressure? Flooding obviously... due to...? Pressure overpowering the float needle?

 

And - how to reduce the pressure if necessary?

 

Your experience much appreciated gentlemen, and ladies!

 

 

[Guest Maj Millard]

Range on the Bing carb is 2.2-5.8 Psi. If they get too much pressure, yes you can overpower the floats which leads to a richer mixture , possible rough running and fuel being pushed out through the equalization tubes. Some installations have overpressure-orifices in the fuel system which bleeds off excessive pressure and takes the un-needed fuel back to one of the tanks. The Rotax installation manual should show various fuel-system set-ups..My boost pump tends to give me around 7Psi on the guage when it's on, but it is only on for a short time at takeoff, and just before landing ..........................Maj...

 

 

[Head in the clouds]

A 912 in USA stopped unexpectedly, I'll post here the thoughts of a very knowledgeable gentlemen on another forum -

 

The carb.ice issue in the Rotax 912 has some interesting thoughts. I am working on a Rans S12 equipped with a 912. It was damaged in a forced landing when it flipped over. The engine suddenly failed. the owner was told that it was caused by carb.ice. The Lockwood Aviation people sell an after market carb. heat kit to install that uses cooling water circulating to warm the carburetors. I called Rans and talked to one of there engineers about the carb. icing with this 912 engine and he told me that it is a non issue and the carb.heat kit is a wast of money. The Lockwood people told me that the engine is dangerous with out the carb. heat. The owner insisted that he have the carb. heat kit so I put it on. I can't see that it could heart any thing. The Rans instructions rough the fuel line from the fuel sump to the fuel pump up over the top of the engine. I suspect vapor lock was the cause of the engine failure. I routed the suction line under the engine and got as far from any source of heat as I could. We probably never know the real cause of the failure. The owner sent the engine to Lockwood for a complete rebuild and they said that after dis assembly they found there was nothing wrong with the engine, carbs. or ignition at all.

 

Anyone here have any thoughts about the way the fuel lines are/should be installed regarding vapour-lock possibilities? I note from the angle of the fuel delivery lines to/from the pump (see post 56 above) that it would appear that you are intended to run the lines above the engine...?

 

 

[Guest Maj Millard]

Yes that's correct. Rotax prefer the fuel lines to be routed on top of the engine. Everything is set up for that...refer to the installation manual. Most 912s if not all that I have seen, have the lines on top, and fuel vapor-locks due overheating is unheard of.

 

The engines run cool anyway, plus those fuel lines should be protected from heat by protective fire-sleeve.

 

By going against Rotax recommendations you are out on the garden path, and my well create your own set of problems by routing underneath, such as an airlock at the lowest point etc.

 

Many aircraft installations using the 912 do have provision for a carb heat set-up, but it generally heats the incoming air, not the carbs themselves, which sounds a bit dodgy Bros to me. If your fuel lines on top were protected as recommended by Rotax, and set up per the installation manual then I don't think that was the cause of your failure.....if your engine is making enough heat out of the top of the case to cause vapor lock than you have a serious problem elsewhere. I suggest you look at the coolant and oil cooling systems for the problem..........................................Maj...

 

 

[johnm]

Engine stoppage due to carb-mount rubber failure or leakage

 

(Maj (or someone)) The 750 hr 912 we have has had the carbs off and the rubbers appear sound, pliable and sealed - irrespective of that should they still be replaced ?

 

thanks

 

 

[Guest Maj Millard]

Johnm, If you have had a complete look over those mount rubbers, inside and out, and they appear sound, with no cracks or deteroation, then basically they are servicable, and it's your call if you refit them or not. The earlier rubbers had a harder compound than the later ones, which appear softer. I have had a new (softer) set crack like they had been "cut with a razor" (Garys' words at B Floods). I currently have my old (harder) spare set on the plane, until new ones arrive.

 

As covered by Rotax in their Service Bulletin on the subject, I feel it is very important to ensure carbs are mounted correctly, with all but minor movement eliminated.........................................................Maj...

 

 

[Kev]

Engine stoppage due to carb-mount rubber failure or leakage(Maj (or someone)) The 750 hr 912 we have has had the carbs off and the rubbers appear sound, pliable and sealed - irrespective of that should they still be replaced ?

 

thanks

Johnm

912 carb sockets should be replaced at 5 yr/500hr iaw Rotax Time Limits.

 

 

[Downunder]

What 912 spares/tools should be kept:

 

1. In the aircraft?

 

2. In the hangar ?

 

 

[metalman]

I've had a Eurofox stop on me just after takeoff.

 

The guys I rent it offhand in the ops to clean up around 500agl ,which is pretty standard in most things I've flown ,flaps,fuel pumps,CSU setup, so it seemed pretty standard in the Fox .

 

At around 700agl ( I'd left it a bit later as the circuit was busy ,departing Natfly) I cleaned up the flaps, and switch the electric pump off,,,,,sh1t it started to sputter and stop,,,,after the a second of WTF I undid my last action and it came good,,,,I still did an emergency landing as I wasn't sure what had happened .

 

On the ground I couldn't get it to do the same thing ,it seemed fine, after I shut down Mick Poole and another eurofox pilot came over and the first thing they said " you turned the elec pump off " , yeh since then the school has the pump on till established in cruise , and I've since flown it and watched the fuel pressure as you switch to mech pump, the needle hits the stop and bobs around there for a good 10-15 seconds before the mech pump gets going.

 

The only thing I can think of ( and I'd be happy to hear otherwise) is the elec pump is forcing the fuel through faster than the mech pump, when you switch it off the mech pump cavitates for a while before it can get the pressure back up,,,,,

 

Met

 

 

[Guest Maj Millard]

Met, Do you know what type electric pump and what pressure does it product when on (max). It is annoying and uneccessary when poorly, or incorrectly designed fuel systems, cause engine stopages. The 912 is not that complicated in it's fuel requirement, and the mechanic pump does a good job most of the time. It is only when downstream systems (airframe) take things out of the Rotax recommended parameters, that you'l have any dramas. I do not agree that the elect boost pump should need to be left on to provide adequet fuel to the engine, for normal operations, that is what the mechanical pump is for. I suspect the boost pump in this case is producing too much fuel pressure when operating...Rotax recommended range is min 2.2 PSI-Max 5.8PSI...More is not better in this case with an ambient-pressure bowl type carb......................................................Maj....

 

 

[metalman]

Not sure Maj , I'll be taking it out next week and ill have a look, I do know I don't turn it off till I'm at height nowadays

 

 

[alf jessup]

Not sure Maj , I'll be taking it out next week and ill have a look, I do know I don't turn it off till I'm at height nowadays

My manual for the Tecnam Sierra quotes above 300 ft agl positive ROC flaps up & electric fuel pump off.

 

Alf

 

 

[Head in the clouds]

Unbelievable - never heard such rubbish. Never turn a pump off that's required for t/o or landing unless you're at safe height in the cruise. It's no wonder we've got a bunch of silly basic op problems happening.

 

And - if pumps are causing an overpressure - fix it on the ground...

 

 

[metalman]

The thing is I rarely post here anymore for just the above reason, Over and out

 

 

[alf jessup]

Unbelievable - never heard such rubbish. Never turn a pump off that's required for t/o or landing unless you're at safe height in the cruise. It's no wonder we've got a bunch of silly basic op problems happening.And - if pumps are causing an overpressure - fix it on the ground...

Sorry HITC,

 

Didn't realise you know more than the manufacturer, Sierra also has a mechanical fuel pump, maybe you should write all the manuals.

 

Alf

 

 

[Willborne]

My manual for the Tecnam Sierra quotes above 300 ft agl positive ROC flaps up & electric fuel pump off.Alf

Alf my Golf's manual states electric fuel pump must be on in all modes of flight. Go figure.

Willborne

 

 

[Guest Maj Millard]

My boost pump goes on and off just after I stow/deploy flaps which is around 4-5oo ft, been doing that for years with no dramas. In fact you can cause more problems by leaving it on too long with a 912....read the 912 operators handbook..........................................................Maj...