rotax issues

[tecnamdave]

Just had my first splutter after takeoff today stick forward and landed straight ahead made it down ok

 

We had just finished replacing all the fuel lines in the Tecnam including emptying both tanks and replacing the fuel. checked out for any leaks and loose fittings all ok next turned on electric fuel pump every thing ok next fired up the trusty Rotax ran it for a couple of minutes all ok then proceeded to put the cowlings and final cleanup and DI befor taking it out for a check flight Approximately 5 or six minutes for warm up while taxing out all the pre take off checks including mags. check all ok lined up on the runway every thing running smoothly like all ways, lift of at 40 knots flaps up climbing at 65 knots then a splutter. after landing could not find any faults. Question is could it have been air in the fuel lines ? can any one give some input with the same experience

 

Next Day

 

Well we checked every thing out again this time holding the breaks on and running engine at full revs for app 2 minutes then the same again this time with electric fuel pump on as well. did not miss a beat so lined up and climbed out at around 300 feet the engine started to run rough with loss of power

 

once again stick forward throttle off almost through the boundary fence this time.

 

Another near death experience

 

 

[Ultralights]

Not sure about the Tecnam setup, but in our savvy, with 100hp uls, you do NOT take off with electric fuel pump on, as the pump over fuels the carby and floods the engine resulting in rough running usually just after take off.

 

 

[Guernsey]

Not sure about the Tecnam setup, but in our savvy, with 100hp uls, you do NOT take off with electric fuel pump on, as the pump over fuels the carby and floods the engine resulting in rough running usually just after take off.

Wow!! So when if ever do you use the fuel pump.

(not being sarcastic, just interested)

 

Alan.

 

 

[robinsm]

I thought the idea of having the fuel pump on at take off was to ensure a good supply of fuel to the engine when needed most. Carburetors are designed to limit the fuel delivered and control the line pressure by the use of floats and jets. I am wondering if you have the wrong fuel pump on and it is over pressuring the system, or the needles and seat need reworking.

 

 

[Ultralights]

we use the fuel pump at startup to get fuel pressure up to 5 psi before startup, then turn it off after starting, the engine fuel pump maintains pressure at 5 psi, but with the electric backup on it will rise to almost 9 psi. well into the red zone on the gauge. also, the fuel system being a high wing also has gravity on its side.

 

 

[tecnamdave]

we have sussed out what we think is the problem, do not think it to be a fuel problem after all, will confirm an Wednesday after we finish all the maintenance issues

 

Thanks for every ones input all the same

 

Cheers Dave

 

 

[Guest Maj Millard]

And.......ok, what was the real problem.....fuel filter in backwards ??..........................................................Maj...

 

 

[tecnamdave]

And.......ok, what was the real problem.....fuel filter in backwards ??..........................................................Maj...

I will confess all on Wednesday evening, after we have confirmed and remedied the problem, not as serious as first thought

Cheers Dave

 

 

[Guest Maj Millard]

I, and others 912 users no doubt, will look foward to that Dave..........................................Cheers Maj...

 

 

[turboplanner]

we use the fuel pump at startup to get fuel pressure up to 5 psi before startup, then turn it off after starting, the engine fuel pump maintains pressure at 5 psi, but with the electric backup on it will rise to almost 9 psi. well into the red zone on the gauge. also, the fuel system being a high wing also has gravity on its side.

This is a design fault which takes away an important safety back up, so should be remedied. I've had this with race cars, and given you wouldn't want to fiddle with an aircraft carby, the electric pump pressure needs to be reduced to the 5 psi engine specification, preferably by a different pump rather than a pressure regulator which adds complication.

 

 

[Guest Maj Millard]

No design fault. Just fit the recommended fuel pump as shown in the Rotax 912 parts manual (Pierburg) which only supplies 2-3 psi, and is suited to the rest of the fuel system as supplied. Then read Rotaxs' recommendations on not exceeding carb fuel supply pressure.....................simple..........................................Maj...

 

 

[Bryon]

I will confess all on Wednesday evening, after we have confirmed and remedied the problem, not as serious as first thoughtCheers Dave

It is almost thursday morning......where is the confession???

 

 

[tecnamdave]

It is almost thursday morning......where is the confession???

Duno wot part of the world you are in Bryon, but it is still only 3.30 am Wednesday morning here

 

 

[Bryon]

Duno wot part of the world you are in Bryon, but it is still only 3.30 am Wednesday morning here

Yeah, you are right Dave.....see what a 16 hour day does to your thinking.

I got a day ahead of myself, thought it was hump day

 

 

[tecnamdave]

I believe we have sussed out the problem just ran out of daylight today, so did not get to test fly the Tecnam. Me being a nervous pilot, who only fly's on very fine calm days, and having a bit of vibration on climb out at app 200ft with a bit of panic thrown in who immediately throttled of and pushed the stick forward and landing straight ahead thinking i had a fuel problem. putting it down to maybe air in the fuel lines, only to do the same again the next day after bleeding the fuel lines to make sure all would be ok and finding the vibration even more extreme. as i lift the flaps at about 2 to 300 ft and making that decision to land straight ahead once again as trained to do in the event of efato or any other event that would effect the the safety of self or the plane

 

we have come to the conclusion that it was the Tyre that i changed the other day causing one of the landing wheels to become out of balance and not doing its chronic boogie until well into lift off. this has now been rectified

 

Doh Dave

 

 

[rick-p]

Dave, just a word of advice lift off, stick slightly forward ground effect, pick up speed and climb out and in between doing all this, just after lift off, brakes on, stop main wheels rotating, less drag, vibration gone and the bigger the main wheels the better the result of your action, particularly with Tundra tyres.

 

 

[eightyknots]

Dave, just a word of advice lift off, stick slightly forward ground effect, pick up speed and climb out and in between doing all this, just after lift off, brakes on, stop main wheels rotating, less drag, vibration gone and the bigger the main wheels the better the result of your action, particularly with Tundra tyres.

Sounds like sound advice.

 

 

[Guest Maj Millard]

Dave , It is admirable that you have shared your recent P92 drama with us. I have experienced similiar wheel shake on P92s myself on past flights, and yes it can get one's attention. The fact that you had just done work on the fuel systems, makes it understandable that you believed it could have been engine related, and your decision to make a promt return to terra firma was an understandable decision in terms of safety, under the circumstances.

 

However had you promptly checked either the Tachometer or fuel-pressure guage, a normal operating engine would have been confirmed, as one or both of those would have been on the drop had the 912 not been happy. This would be followed no doubt by a normal scan of all other engine guages as appropriat.

 

Reminds me a bit of an accident around 1984 in Reno Nevada where a cargo carrying Lockheed Electra experienced a rattling loose minor external-panel just outside of the Captains window, shortly after a night take-off out of Reno. They had been experiencing problems with one of the props on that side, and he mis-diognised that the prop was again having dramas.

 

After the crew became preoccupied with shutting down things on the offending engine, the aircraft was allowed to descend in the dark night impacting in an auto wrecking yard, killing both crew. The cargo on board ironically was auto parts ! They probabily had not taken time to monitor engine guages either..The 912 fitted to your Tecnam by the way is in my opinion the most reliable engine available today to recreational aviators, and rarely fail if maintained correctly......................................Maj...

 

 

[tecnamdave]

Hi Maj

 

Thank you and every one else for there concern

 

My Mechanic Len checked out the plane this morning upon taking it for a test flight found the same problem, with a bit of vibration and definite lose of power. So back to the hangar and a thorough check of all the fuel system, we found the problem. The fuel line star that's a 4 way section that distributes the fuel to both carburettors and to the fuel pressure gauge had been inadvertently put back the wrong way, with restricted supply to one of the carburettors, instead of to the fuel pressure gauge

 

Once again a lesson learnt one cannot afford to not pay full attention to the smallest of parts This little 4 way piece of junction pipe has a restriction that can be easily overlooked at the best of times

 

Cheers Dave

 

 

[Guest Maj Millard]

The restricter is ment to be in the return line back to the fuel tank. Yes if it was in a carb-supply line it would cause dramas. It's also there to prevent over-pressurzation of the carbs with the boost pump on. The Rotax diagram in the Service and Maintenance manuals show this quite clearly. I'm sure once you get things sorted it'll all be sweet again !....there are always people on this forum who have been there before ready to help.............Maj...

 

 

[tecnamdave]

We have found two restricter one on a T piece just after the outlet from the fuel pump that goes inline with an outlet on one side to return back to the tank, the other one that we had problem with was on the four way, one side being the inlet one either side going to the carbs. and the fourth one going to the fuel pressure gauge being restricted. some how we did not pick up on this one in the manual

 

Dave

 

 

[tecnamdave]

There are two restricter the first one is on the side of a T piece on the outlet side of the mechanical fuel pump, that returns fuel back to the fuel tank, the one we had our problem with is a little further along the same fuel line it is a four way section with fuel going in from the line, an outlet on either side going to the carbs and the one going straight on restricted to the fuel pressure gauge. some how we missed this in the manual

 

Dave

 

 

[tecnamdave]

There are two restricter the first one is on the side of a T piece on the outlet side of the mechanical fuel pump, that returns fuel back to the fuel tank, the one we had our problem with is a little further along the same fuel line it is a four way section with fuel going in from the line, an outlet on either side going to the carbs and the one going straight on restricted to the fuel pressure gauge. some how we missed this in the manual

 

Dave

 

 

[tecnamdave]

The restricter is ment to be in the return line back to the fuel tank. Yes if it was in a carb-supply line it would cause dramas. It's also there to prevent over-pressurzation of the carbs with the boost pump on. The Rotax diagram in the Service and Maintenance manuals show this quite clearly. I'm sure once you get things sorted it'll all be sweet again !....there are always people on this forum who have been there before ready to help.............Maj...

We have found two restricter one on a T piece just after the outlet from the fuel pump that goes inline with an outlet on one side to return back to the tank, the other one that we had problem with was on the four way, one side being the inlet one either side going to the carbs. and the fourth one going to the fuel pressure gauge being restricted. some how we did not pick up on this one in the manual

 

Dave

 

 

 

[flyhi]

We have found two restricter one on a T piece just after the outlet from the fuel pump that goes inline with an outlet on one side to return back to the tank, the other one that we had problem with was on the four way, one side being the inlet one either side going to the carbs. and the fourth one going to the fuel pressure gauge being restricted. some how we did not pick up on this one in the manual

Dave

Yes Dave my Tecnam Super Echo also has two restrictors as you describe. I was aware of the one in the return line to the tank and noticed the one in the line to the fuel pressure gauge when I was replacing fuel hoses earlier in the year.

Flyhi