We are in tropical zone. The issue we face only during hot afternoons (86 to 104°F ). Fuel pressure goes down to lower red arc in startup and climb inclg partial power loss in P2008JC and P2006T Tecnam Aircraft

NO issue during night and morning (77 to 85°F ).
Corrective action taken as per maintenance manual line , no joy
1.Fuel line clean including vent found all cleared.
2. carburetor float chamber venting clean ,float weight check found satisfactory .
3. induction air filter replaced with new one and clean induction duct.
4. Spark plug replaced with new after test with spark plug tester .
5.Ignation system check for loose connections found satisfactory. 

The above issue is seen on all our 8 aircraft fitted with ROTAX 912 S2 and ROTAX 912 S3 engines.

Any suggestion please?

Thanks & Regards,


  • Re: Low (FUEL) pressure at hot ambient (86 to 104°F

    by » 4 months ago

    I’m confused. Is your issue with oil or fuel pressure?

  • Re: Low (FUEL) pressure at hot ambient (86 to 104°F

    by » 4 months ago

    Hi Sam,

    it's fuel pressure. Writing "oil" in the title line was erroneous. Thanks for pointing out.

    The title may please be read as below:

    "Low fuel pressure at hot ambient (86 to 104 °F)

    Sometimes, even RPM drop of about 300-500 is noticed. 

    Thanks for your attention. 


  • Re: Low (FUEL) pressure at hot ambient (86 to 104°F

    by » 4 months ago

    Do these aircraft have a fuel return line? If they do make sure the orifice is not blocked. What kind of fuel is being used.? You may have a vapor lock/gas boiling/bubbles developing.

  • Re: Low (FUEL) pressure at hot ambient (86 to 104°F

    by » 4 months ago

    I live in Eastern Australia. Summer day temps can reach  46C (115F) in the shade. I have experienced all what you describe BUT not often. 

    Why not often, because I take steps to manage the situation;

    Recognise that all systems have inherent weak points, that must be managed. Carburetted Rotax 9's have fuel lines that are vulnerable to "heat soak" from the engine, exacerbated by high ambient temperatures. 

    ALL Fuel lines within the engine compartment should be well insulated. Fuel lines that are close to exhaust component should have extra attention (shielding and/or better insulation).

    Avoid take offs above 30C. This can easily be done by starting your activity at dawn, in the cool of the day. Recommencing in the late afternoon.

    Lastly it's not very comfortable to fly above 30C - While on the ground you cook in your own little glass house, density altitude has a negative impact on your aircrafts performance and you usually have to climb/descend through turbulence - fly on another day!

    If take off above 30C are unavoidable;

    When parked face into wind to assist with static cooling. Open any engine inspection doors/hatches to help clear hot air.

    Extend run up times (particularly @ high power) to clear vaporised fuel (vapour lock) from your fuel delivery system.

    Run your boost pump from engine start to safe altitude.

    Plan for low/nil engine performance ie be prepared for an aborted take off. Use all of the runway available (no intersection take offs). Do not persist with a spluttering/low performing engine, stop & back track.

    Lastly, in high temperature periods, consider using AvGas with its lower vaporisation. It may be less likely to cause vapour lock in fuel lines.


    Thank you said by: RotaxOwner Admin

  • Re: Low (FUEL) pressure at hot ambient (86 to 104°F

    by » 4 months ago

    Many thanks , Griffin

    Awesome, you have hit the nail on the head. Being experienced with the similar weather condition as in India, this is definitely the best solution.  Although restricting flights till temperature comes down may not be practicable for all operators, but it could be made less vulnerable by other supporting measures. 

    We are confident that these are the best options. We would get back after giving it a try.

    Thank you very much.


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