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Hi, 

We bought an Europa classic/XS with a Rotax 914 UL engine a couple of months ago. The seller did some maintenance on the engine before the plane was delivered, and everything runs smooth and looks good.

However, it feels like the engine is missing some power in take off. After getting of the runway, she doesn't want to climb and we need to fly low over the runway in order to gain speed, and then she starts to climb. I was wondering if the turbo is working, and did some checks.

During the self test (when powering on the TCU), the wastegate servo seems to travel fully and freely to fully  open and close. The bowden cable looks good, as well as the spring and  the free movement of the wastegate axle.

Because the previous owner did maintenance, I asked if he re-calibrated the throttle position sensors on the TCU, but he didn't. The TCU model that we have  is an old model which requires a special dongle cable from Rotax, which we don't have.

Before we bring the plane to a  Rotax service center, is there a way to see if the turbo is actually working ? The  control lights don't indicate any error, but that doesn't say anything if the turbo is  working or not.  Perhaps the  throttle sensors in the TCU calibration are off.

On the ground, with the prop in the minimal pitch setting and full power (throttle  in 115% position), we get 5200 max 5300 RPM. In flight, with the same pitch, after climbing and gaining speed, we  get +/- 5700 up to 5750 max.

Any ideas on how we can check if the turbo is kicking in or not would be welcome,

Thank  you,

Johan.

  • Re: Rotax 914 Turbo missing power in takeoff

    by » 4 weeks ago


    Everything you need to know about the Turbo Status is shown on the MAP (Manifold Air Pressure) gauge.

    At a full WOT (Wide Open Throttle) takeoff, you should be getting close to 39" MAP.

    The Turbo is Always fully engaged unless it reaches a limit, and then the waste gate opens.

    It doesn't "Kick-In", it is always "IN", unless it isn't

    If the Waste gate isn't closed and sealed, you will never make full power.

    It will not be just a little power loss either.

    This isn't a 100hp engine that is Turbo Boosted to 115hp.  (+ 15%)

    This is an 80hp engine being Turbo Boosted to 115hp.  (+ 44%)

    With the Waste Gate in the Open position,  88hp is the limit.


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


    Thank you said by: RotaxOwner Admin

  • Re: Rotax 914 Turbo missing power in takeoff

    by » 4 weeks ago


    Bill is correct.

    If the Europa does not have a MAP gauge you need to install one.


    Thank you said by: RotaxOwner Admin

  • Re: Rotax 914 Turbo missing power in takeoff

    by » 4 weeks ago


    In re-reading your original Post.

    You can reach 5700+ rpm at cruise, so, assuming the prop was originally setup this way, you are making full rated power as intended.

    In the climb at 5200 rpm you are making about 90hp (78%) which is why climb performance is suffering.

    What you appear to have is a prop set up a race-plane or at least the previous owner had chronic Get-There-Itis.

    I suggest that if you are more concerned with clearing the trees at the end of the runway than getting to the destination ASAP, you should Remove 2-3° of Pitch OUT of the prop.  Flatten the Prop.

    You want to be able to make ~5800 rpm during a Vy climb.

    This would allow you to put that 25 Hp back into the climb.

    At 500KG (1100lbs) that 25hp would add 3.8m/s (750ft/min) to your initial climb.

    - - -

    Remember that this will also increase the cruise rpms and you will need to be mindful of Not over-revving the engine In level or Descending flight.

    This should not be a major problem as most pilots tend to reduce throttle in level flight naturally.  It isn't a race!

     

     


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


    Thank you said by: Johan, RotaxOwner Admin

  • Re: Rotax 914 Turbo missing power in takeoff

    by » 4 weeks ago


    Thank you very much!

    We did some more testing.

    During take off roll (so while on the ground), we need the full runway length (480 ~ 500m) to get from the ground. The RPM doesn't go higher than 5250 RPM, and +/- 33 or max 35 inHg. But once we get airborne and fly slightly (<1m) above the ground, the RPM increases, the MAP increases quickly to 39 inHg in +/- 3 seconds and we are able to climb out at Vy or Vx.

    We have an older type Airmaster prop, AP308 with an old controller AC100, and slightly adjusted the fine pitch microswitch so that we are able to adjust the fine pitch a little more. We now get 5650 RPM on the ground while standing still with +/- 36 inHg and power at 115%. 

    This looks better to me, but we couldn't make a test flight yet. Unfortunately the constant speed unit is broken and it's not for sale anymore. This means we need to be very careful with our RPM, because with this fine pitch we now might go over the 5800 once airborne. I think this won't be much of an issue if we just put the nose in the climb position though.

    Thank you for reply, it's appreciated. Will update this forum with the new results.

     

     


    Thank you said by: RotaxOwner Admin

  • Re: Rotax 914 Turbo missing power in takeoff

    by » 4 weeks ago


    Sounds like you have an old TCU? check the part number, if it is not the new 4.6 version 966741 it will spool up much slower.


    Thank you said by: RotaxOwner Admin, Johan

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