Is there a problem

[aro]

The first page of the current Rotax 912 series engine installation manual:"This Installation Manual for ROTAX® aircraft engines should only be used as a general guide for the installation of ROTAX® engines into airframes. It does not represent an instruction for the installation of a ROTAX® aircraft engine in a specific type of airframe or airplane.

True. Ultimately, it is the airframe manufacturer's job to deliver an uninterrupted supply of fuel at the correct pressure to the carb. How they do that is up to them.

 

Older 912 installation manuals don't have the instruction for the return line, unless you used an engine with the Rotax fuel manifold which included a return fitting. Obviously then you need to connect it to something.

 

Changes beget changes, so adding a return line if it wasn't originally fitted creates other complications. For example, some fuel is returning to the tanks, so obviously the fuel system has to be able (and tested) to deliver more fuel upstream of the return line. How much more? Well, now you might need to measure how much is being returned to the tank... and so on.

 

The solid-state Facet fuel pump fitted to the aircraft depends on a good fuel flow through it for cooling - hence the instruction to use the pump only for start up or in the event of a failure in the main pump. At other times, specifically during engine idle, it is possible there is not enough fuel flowing to cool the pump adequately - particularly in engines like the Rotax 912, which have a very low fuel flow at idle.

This I doubt... do you have any reference, e.g. Facet specifications or installation information? The Facet pump is automotive in origin, correct? No-one has a fuel pump switch in their car, they typically run continuously. A 912 at idle is still shifting a lot of air - I am sure it is using substantially more fuel than a similar size car engine idling at 1/2 the rpm without a big propeller on the front. I think the recommended fuse size is 3A, so that's only 40 watts or so of heat at 14V before the fuse blows. Shouldn't need much cooling to prevent damage.

 

 

[dan3111]

I have now work in the fuel and oil filter industry for petrol and Diesel engine for over 20 years .I have seen some pretty strange fuel line set ups in all types of engine boat trucks cars and some aircraft .

 

 

[dan3111]

I have now work in the fuel and oil filter industry for petrol and Diesel engine for over 20 years .I have seen some pretty strange fuel line set ups in all types of engine boat trucks cars and some aircraft . The manual of my Savannah is a classic case for what not to do in a fuel system they have changed it on later models still not right but . I would like to state the fact more often then not the person that designed the fuel system of a aircraft don,t even fly . Just work there for a living so don,t have the feed back of other pilots around the place because a job most likely not interested after hours . Good tips and safety wing tanks aircraft should have a small head tank and electric boost pump ,fuel tank return from highest part of engine fuel system and tap on that ,fuel pressure gauge . Now feed lines to and form header tank big as practical then first in line strainer electric pump fuel filter then engine pump then 4 way tee to carbs and return to tank pressure gauge . There needs to be a few taps in the system to shipmates off in case of fire etc . Now where people so wrong is venting ,venting and venting I should say it one more time . There is so many traps to get in between gravity and air pressure or lack of it . In a perfect world wing tanks and head tanks should have a balance vent pipe between them all . I could talk for hours on this as my paying job so will just drip feed you a bit at a time .

 

 

[dan3111]

My custom made Savannah fuel tee has 1 feed in and 4 ports out left and right carby ,return line at highest point at top of tee with 0.3 mm hole and fuel pressure port at back outer of view . All p clamps to cross over tube to support it .

 

 

 

 

[storchy neil]

spot on dan when that part has been a requirement from ROTAX SINCE 2004 according to the manual I got when I purchested my aircraft ( bert flood RIP mate )informed me 1997 or there about 2000 it was mentioned somewhere

 

those that quote the pages said had better read it again as it states air frames does not say that they do not attach return line to rotax motors in their airframes neil

 

 

[SilverWing]

There for had return line been in accordance with rotax installation manual that would not have happened.Facts are that foxbat did not install return line there for by your own admission you are at fault.

Get with it fuel under presure will boil stop making out that it's not happening ROTAX have had the return line to the tank for more years so for you to say it is not required is bulxxxx so sue me if you recond that that you know more than ROTAX.

 

I am talking ROTAX 912 series motors not bloody GA.

 

What size was the fuze ?neil

Oh dear Neil - no, the incident was caused by incorrect operation of the fuel pump. You can drive down the road at 100 km/h and slam the car into reverse. By your reckoning, the result would be the vehicle manufacturer's responsibility, not the driver's.

 

Inconvenient as you may find the truth - a fuel return line is not mandatory on 912 engines - right up front, the Rotax installation manual makes it clear that it should only be used as 'a general guide' and that the airframe manufacturer has the final say.

 

I know you think GA certified aircraft are irrelevant but many of them do not have a fuel return line. RA and LSA aircraft are certified to a lower standard than most GA types.

 

PS - the more expletives you use, the more hysterical you sound

 

 

[facthunter]

IF a fuel pump will overheat at low fuel flows that is a serious limitation of it's suitability. A fuse will NOT protect against overheat in these circumstances as the current may not have risen enough to blow or trip it as the motor is cooking due lack of cooling fuel flow. To protect this occurrence you would need a temperature sensitive trip feature or just increase the fuel flow If the pump is heating the fuel it's a good reason to have a return to tank facility downstream of the pump. Of course if the pump wasn't fitted it won't be heating fuel or overheating at low fuel flow situations. You might still have a problem with mogas on a hot day on a gravity feed system, especially with under cowl temps. If the carb Bowls get hot the mogas will work like a bottle of Coke when you first release the seal. Clouds of bubbles and the float sinks and the carb floods. Nev

 

 

[storchy neil]

So automobiles is the best solution to your argument that you can come up with just goes to show how wrong you are in your statement. Neil

 

 

[storchy neil]

Nev I do have a pump similar too what appears to be a fire risk pump I did set it up and run water through it then fuel

 

By letting the fuel run unrestricted no heat at pump when partly restricted small increase of heat when the flow was brought to a trickle there was significant increase in heat at pump also heating of fuel

 

Also the wiring to the pump also heated

 

Rotax have an AD that if your engine had fuel pump number xxxxxx to xxxx to replace it so the maker of the aircraft who installed the engine there way does not have to inform you of this AD

 

On a four wheeler bike That had fuel problem it was found that the manual fuel pump was pumping to mutch fuel and blowing out the carby seals changed pump problem solved

 

Experimenting to be done with extreme caution

 

To see how many litre are returned to the tank

 

Place plane in area safe

 

Anchor aircraft important

 

Have three observers

 

Have fire extinguisher ready

 

remove return line

 

Extend return line to a container well away from aircraft

 

Enter air craft

 

Start engine and run at idle for say five minutes

 

Measure quantity

 

Now use the same procedures as at 4800

 

Have a thermometer and check fuel temp

 

Whats the conclusion Neil

 

 

[dan3111]

Nev I do have a pump similar too what appears to be a fire risk pump I did set it up and run water through it then fuelBy letting the fuel run unrestricted no heat at pump when partly restricted small increase of heat when the flow was brought to a trickle there was significant increase in heat at pump also heating of fuel

Also the wiring to the pump also heated

 

Rotax have an AD that if your engine had fuel pump number xxxxxx to xxxx to replace it so the maker of the aircraft who installed the engine there way does not have to inform you of this AD

 

On a four wheeler bike That had fuel problem it was found that the manual fuel pump was pumping to mutch fuel and blowing out the carby seals changed pump problem solved

 

Experimenting to be done with extreme caution

 

To see how many litre are returned to the tank

 

Place plane in area safe

 

Anchor aircraft important

 

Have three observers

 

Have fire extinguisher ready

 

remove return line

 

Extend return line to a container well away from aircraft

 

Enter air craft

 

Start engine and run at idle for say five minutes

 

Measure quantity

 

Now use the same procedures as at 4800

 

Have a thermometer and check fuel temp

 

Whats the conclusion Neil

Well storchy is a bit like this you can only lead a horse to water , some people will never change and never see common cents . Like telling a smoker or over weight person to start looking after them selfs and there answer is "I never had a problem with my heath " we all know how that's going to end . So you get to a point of life where you stand back and watch with eating pop corn mind you and let people make there own mistakes after they have been well warned . There is a true saying learn by other peoples mistakes as you don't live long enough to make them all your self . Our sport is not for giving and until you have people die in front of you at you local aircraft you start to respect the sport and the advice given by a lot wiser people . I have been on the field with over 6 deads now and another 10 plus people I knew at other fields on the news.

 

 

[aro]

the incident was caused by incorrect operation of the fuel pump

I'm still looking for evidence that the fuel pump can be operated incorrectly.

 

I think the Vans RV12 also uses these fuel pumps, hard wired to run when the master is on. They state that the pumps are designed to run all the time, and there is a safety benefit when they are running and no benefit from turning them off.

 

 

[aro]

you think GA certified aircraft are irrelevant but many of them do not have a fuel return line

It is important to compare apples with apples... GA aircraft typically use avgas and (according to my understanding) the main reason for the fuel return is the greater likelihood of vapor lock when running mogas.

 

Avgas vs. mogas also affects GA aircraft, e.g. there are more mogas STCs for high wing aircraft than low wing due to the increased concern about vapor lock when drawing fuel up from low wing tanks.

 

 

[facthunter]

Plenty of pumps run immersed and die when they are run when dry. The fuel keeps them cool and safe. It's all too rich to burn. An inline pump that relies on fuel to cool it where in some common in flight circumstances does not get enough flow to do it is a problem going somewhere to damage you. I think it's poor design. Murphy's law will get you anytime you let it. If Boeing or Airbus did something like that in principle it would have to be made more fail safe.. Nev

 

 

[Yenn]

I disagree with the statement that there s no advantage to turning pumps off. If you have a mechanical pump and an electric pump, how are you going to know you have a pump failure until they both fail, if you don't turn the electric pump off before you go flying.

 

Mechanical pump failed, encine will start and run if electric pump on. Electric pump, failed engine starts and runs with mechanical pump output.

 

 

[M61A1]

I disagree with the statement that there s no advantage to turning pumps off. If you have a mechanical pump and an electric pump, how are you going to know you have a pump failure until they both fail, if you don't turn the electric pump off before you go flying.Mechanical pump failed, encine will start and run if electric pump on. Electric pump, failed engine starts and runs with mechanical pump output.

Pretty much the same way you check your mags. Start on both, turn the electric off, while taxiing and running up, ensure electric pump back on for takeoff.

I don't see any people saying they turn one mag off once airborne.

 

 

[facthunter]

On some planes with "impulse" magnetos you start with impulse only selected. This is for handswinging and also advisable for electric cranking. A magneto without impulse will fire (if it does) in the fully advanced position. When the impulse actuates it gives a delayed (retarded) spark. Nev

 

 

[M61A1]

On some planes with "impulse" magnetos you start with impulse only selected. This is for handswinging and also advisable for electric cranking. A magneto without impulse will fire (if it does) in the fully advanced position. When the impulse actuates it gives a delayed (retarded) spark. Nev

Yes Nev, that is correct, but what I was getting at is that these modern electric pumps have been designed for continuous operation, yet we stick steadfastly to 1940s operating procedures and turn the electric pump off during flight. At the first sign of trouble, or for anything other than straight and level, we then turn it back on again. We also have two magnetos or CDIs but leave them on at all times except for testing. It's not logical captain.

( disclaimer: except for fuel pumps not designed for continuous operation)

 

 

[dan3111]

It's a little harder to compare any GA aircraft unless they have a 912 fitted , all most aero engines have carby at the bottom of the engine and fuel lines lower in cowl as well . Jabs even has low carbys ,but 912 are one of the only engine with carby's and fuel lines in the worst spot for heat after engine stops .

 

 

[Geoff13]

When something potentially life-threatening happens, it's very scary, particularly in an aeroplane. Soon enough, those who experienced the event start looking for causes and those around them understandably want to support them. However, occasionally, comments can get blown into huge issues - sometimes based on a misunderstanding or an unintentional error.First of all, the Foxbat did not have a 'fuel pump fire'. The solid-state Facet fuel pump fitted to the aircraft depends on a good fuel flow through it for cooling - hence the instruction to use the pump only for start up or in the event of a failure in the main pump. At other times, specifically during engine idle, it is possible there is not enough fuel flowing to cool the pump adequately - particularly in engines like the Rotax 912, which have a very low fuel flow at idle. Nevertheless, I understand it was common practice in this aircraft to leave the back-up electrical pump switched on while in the circuit/pattern.

 

Second, the pump was fused and switched - the power to the switch (and thence the pump) clearly came via the blade-fuse box on the lower instrument panel. The pump in the incident aircraft did not experience any kind of electrical failure. It overheated because there wasn't enough fuel cooling it and as a result the heat started to melt and scorch the internal insulation. Perhaps through a misunderstanding, the pump was switched on at the top of a long (low fuel flow) descent or had been left on after starting. Either way the cooling effect of the fuel flow on an engine-idle descent was reduced. Because there was no electrical failure, power continued to the pump, which continued to overheat. The fact that the pump continued to run while overheating caused the operator to think there was no fuse - which in fact there was. In spite of the severe scorching on the pump, there was no fire. The pump cooled and the smoke stopped when the pilot switched the pump off.

 

Third, only three carburettor Rotax engine Aeroprakt aircraft in the world have ever been fitted with electric fuel pumps - all in Australia and all at the absolute insistence of the buyers, with considerable reluctance by the factory. In fact, Aeroprakt, in line with their earlier misgivings, will now only fit electric fuel pumps to fuel-injected Rotax engined aircraft. Of the three carburettor aircraft, the first suffered the fuel pump incident referred to. The second owner has, from the start, observed the 'use only at start up' and has experienced no problems. The third aircraft was optionally fitted at the owners' expense with a non-solid-state Pierburg electric fuel pump configured as for the injection engine, with dual return lines to each tank to alleviate excess fuel pressure, as required by Rotax.

 

I have considerable sympathy with those who experience serious incidents in aircraft. I have experienced some myself. However, the understandable wish to apportion some sort of blame - occasionally revved up by others with their own agendas - should not allow the facts to be ignored.

I agree in which case you should actually check the facts.

 

I am interested to know how you know what caused the pump to fail when you haven't even looked at it.

 

The fuel pump was not switched on when it failed, it had been off for several minutes and only ceased "burning" (When something fills the cabin with smoke that to me is a fire) after I had turned off the master switch not the fuel pump switch. And had been on for less than 2 minutes prior to that as per the check list for swapping from one tank to the other.

 

You quote the procedures for operating the fuel pump, I would like to know where you found them because I have the POH for that aircraft in my hand and there is no mention of the fuel pump in it. Nor is there a circuit for it in the wiring diagram. For me to get the wiring diagram that showed the fuel pump, I had to email the factory direct.

 

I agree the pump was switched, and there was a blade fuse there which was not wired in accordance with best practice nor the eventual wiring diagram.

 

The incident did not happen as you say during a long low fuel flow descent. So if you decide you want to bag the pilot before you do an investigation and find the "FACTS" you should first at least take the time to gather some evidence. Because I have plenty. Being a qualified Electronics Technician put me in good stead when I fault found the aircraft, and I find it interesting how quickly the factory determined to remove the fuel pump and evidence prior to a thorough investigation. But not quick enough to prevent me doing my own.

 

I have been sitting back waiting for the factories response and from what you have written here there will not be one. So if you would like the facts by all means ring me some time to discuss them.

 

 

[storchy neil]

Geoff13 shit I have read that 3 times and cannot believe what you have written used car salesman comes to mind

 

Unbelievable bloody unbelievable 4 read that's when my head stops rotating still can't get me head around it

 

As dan said you can lead a horse to water WE DO HAVE PROBLEM here Neil

 

 

[M61A1]

I agree in which case you should actually check the facts.I am interested to know how you know what caused the pump to fail when you haven't even looked at it.

 

The fuel pump was not switched on when it failed, it had been off for several minutes and only ceased "burning" (When something fills the cabin with smoke that to me is a fire) after I had turned off the master switch not the fuel pump switch. And had been on for less than 2 minutes prior to that as per the check list for swapping from one tank to the other.

 

You quote the procedures for operating the fuel pump, I would like to know where you found them because I have the POH for that aircraft in my hand and there is no mention of the fuel pump in it. Nor is there a circuit for it in the wiring diagram. For me to get the wiring diagram that showed the fuel pump, I had to email the factory direct.

 

I agree the pump was switched, and there was a blade fuse there which was not wired in accordance with best practice nor the eventual wiring diagram.

 

The incident did not happen as you say during a long low fuel flow descent. So if you decide you want to bag the pilot before you do an investigation and find the "FACTS" you should first at least take the time to gather some evidence. Because I have plenty. Being a qualified Electronics Technician put me in good stead when I fault found the aircraft, and I find it interesting how quickly the factory determined to remove the fuel pump and evidence prior to a thorough investigation. But not quick enough to prevent me doing my own.

 

I have been sitting back waiting for the factories response and from what you have written here there will not be one. So if you would like the facts by all means ring me some time to discuss them.

I have to ask...do you know which components in the pump let the smoke out? as the Facet pump is advertised as "solid state". I know of some serious smoke/fumes events caused by something as small as a capacitor dying, and such an event may not even blow a fuse. Also, unless the pump fitted is grossly overrated, the same amount of fuel will flow through it as the mechanical pump, so I don't understand why it wouldn't be adequate cooling. Such pumps are designed for automotive use, and spend much of their life in hot conditions at idle (low flow) without dying.

I am genuinely interested in what the fault is, and it may determine which pump I install in my aircraft, the Facet ones I have or anything else.

 

 

[dan3111]

Geoff you really know how to spoil all the fun with facts we all thought we have found the prefect plane which is the safest never made not a fault in the world . So all going to sell our aircraft and buy and foxbat but I'm a non smoker so mite be a deal breaker . So will have to check with Neil if he smokes . Ah well might have to buy a used car instead .

 

 

[storchy neil]

Yes ooooh sheep Neil

 

 

[jetboy]

Which type of Facet pump is the problem? I have only had experience with the traditional ones which do not draw power when there is no outflow therefore dont require flowing liquid for cooling. of the ones listed at ACS the posi-flow might be one that needs a return line for constant flow as is the case for most cars with the in-tank pump and EFI fuel pressure regulated manifold?

 

https://www.aircraftspruce.com/pdf/2017Individual/Cat17330.pdf

 

 

[Geoff13]

Actually guys and girls, don't get me wrong. The Foxbat is a brilliant little machine. But it is just that, a machine which means it was put together by humans and as such can have faults. The problem here is not that the machine is not perfect it is simply a matter of the factory and/or their distributors not admiting that there could be a problem and not even investigating properly to see if there is or how it could be fixed.

 

How anyone could make the conclusions posted in this thread or the thread that started this discussion without sighting either of the aircraft in question or any of the faulty components actually beggars belief and makes a mockery of the pretence of learning from others problems. In both instances IMHO there is evidence that refutes the conclusions drawn.