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Hello to everyone!

My name is Gottfried and I am new to this forum. I just registered, because last Friday we had an incident that really caught our attention.

We were departing for a 1-hour cross-country flight and were still flying in the vicinity of the field at 3.000 ft when the low oil pressure caution warning light came on. Oil pressure was just slightly below normal (1.9 bar) and oil temperature was normal. So we decided to land back and let it get checked. The engine ran totally normal. When starting the approach we switched on fuel-pump and carb heat. At about 2.000 ft I set LDG flaps and had to apply a little power to stay on the approach path. The engine ran smoothly all the time and first responded normally but about 2 seconds later it suddenly went to idle. The prop was still spinning. I pushed the throttle forward but nothing happened. About 20 seconds later the engine came back to life in an instance and ran with full power (because the throttle was full forward). Again there was no rough running or sputtering. It ran perfectly.

After landing we taxied to maintenance and they found nothing. Now the theory is, that there was condensation in the airbox that got sucked into the carburetor. I find that hard to believe because all 4 cylinders died at the same time without running rough and came back to life in the same way. Did anybody ever hear about such a scenario? Is it plausible? Or is there any other explanation? Another even more important question is how to prevent such an incident in the future.

  • Re: Temporary Total Loss of Power

    by » 5 weeks ago


     

    Here are my thoughts:

     

    1. I guess that your theory is referring to carburettor icing. I would imagine that you would get rough running rather than the engine rpm dropping to idle.

     

    2. Could it have been a fuel starvation problem?

     

    3. What if the fuel tank vent was blocked and that built up a vacuum in the tank as the fuel was used until the engine was no longer able to pull enough fuel into the carbs?

     

    4. Did you happen to note the fuel pressure during the time when you had the problem?

     

    5. Could there be a blockage in fuel line or fuel filter?

     

    6. Have you had any work done on the plane recently that might explain the problem?

     

    7. Could the fuel have been contaminated with water?


  • Re: Temporary Total Loss of Power

    by » 5 weeks ago


    Hi,

    Thanks for your answers

    1.) No, the theory is not referring to carb icing. We basically did a climb to 3.000 ft, then a couple of minutes in level flight, and finally a descent with carb heat on. Furthermore, if we had ice, then activating carb heat would have initially caused a rough running engine. Nothing of that. The engine ran fine during the first part of the descent, then went suddenly to idle and 20 seconds later back to full power. So I think we can exclude icing.

    The theory refers to water (condensed) in the airbox. Did anybody hear of something like that? I didn't until now.

    2.) Fuel starvation as a no fuel condition - no. We were 3/4 full on both tanks. Fuel starvation because of something else - maybe. But if so, it went away by itself. And it occurred - I think - in both carbs at the same time. Although: Would we have noticed 2 cylinders going away in our low power setting?

    3.) The vent wasn't blocked. That's in the preflight checklist. Furthermore, it went away by itself.

    4.) No, as far as I can remember, we had no low fuel pressure warning at this time.

    5.) No low fuel pressure warning - so most probably not.

    6.) No, the aircraft had about 7 hrs since the last inspection.

    7.) I drained the tanks and the port below the engine as part of the preflight check and then again after refueling. So, I guess no.

    I thought about this the whole weekend long and I'm pretty puzzled. And I very much would like to prevent this in the future. About 50 seconds longer and we would have been standing in the grass (hopefully).

    How would water (in the fuel or in the airstream thru the airbox) affect the motor? Would it run rough or would it go to idle and later came back on as if nothing had happened - like it did?


    Thank you said by: David HEAL

  • Re: Temporary Total Loss of Power

    by » 5 weeks ago


    If there had been residual condensation in your airbox, I imagine it would have all been sucked into your carbs much earlier in the flight.

    What I find most odd is that the engine would continue to run, but at idle speed only, despite the throttle being fully forward.

    Did you discover the cause of the low oil pressure?


  • Re: Temporary Total Loss of Power

    by » 5 weeks ago


    No, after the 20 seconds of idling it ran suddenly full power again. I pushed the throttle full forward after the power loss and it was full forward during the 20 seconds of idling.

    No, we didn't find the cause of low oil pressure (it was just 0.1 bar below normal and I doubt that it had anything to do with the power loss).
    The oil level was about 7 mm above min and was filled up to above 1/2 after this. It was in the morning of a very hot day, and we did some taxiing around before takeoff because we fuelled and had to check a tire at maintenance before. But the oil temp was in the normal range the whole time.

     


  • Re: Temporary Total Loss of Power

    by » 5 weeks ago


    Tyler Hathaway wrote:

    If there had been residual condensation in your airbox, I imagine it would have all been sucked into your carbs much earlier in the flight.

    What I find most odd is that the engine would continue to run, but at idle speed only, despite the throttle being fully forward.

    Did you discover the cause of the low oil pressure?

    IF it was residual condensation - would the motor react in the way it did?


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