Power Loss at 200'

Discussion in 'Lessons Learned' started by JohnAJohnson, Oct 11, 2016.

  1. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Friend with a Glastar/O-320 and I went for a flight this morning. He warmed the engine for 15 minutes (oil was 90 degrees), did a normal runup without problems, and had full power going down the runway. On initial climbout at approximately 200' AGL, the engine went smoothly from full power to no power in about 2 seconds. He lowered the nose and pulled the throttle back to prepare to land on the remaining runway. Once the nose was lowered, we both knew there was not enough runway to land on, or to even touch down on, so he pushed the throttle in and the engine went to full power. We climbed out and brought it around and landed. There was some light cloud layers/fog around us at ground to 300' or so but none in our flightpath. Conditions at takeoff:

    KFLP 111355Z AUTO 00000KT 10SM CLR 12/09 A3018 RMK AO1

    Could ice do this? He didn't use carb heat during the runup.

    Water in the fuel? He did sump as part of the preflight.

    Fuel starvation? He had 11 gallons in the left tank and 5 in the right, and both were feeding (both were in the ON position combining into one line and onto the carb). Each wing tank also has a gallon header tank. There is no pump on this plane, it is gravity only. He has flown with less fuel so it is unlikely both tanks unported.

    Your thoughts are appreciated.
     
  2. GeorgeC

    GeorgeC Pattern Altitude PoA Supporter

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    Obstruction intermittently flapping around in the air box?
     
  3. Dan Thomas

    Dan Thomas En-Route

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    The Glastar, as originally designed, had a Both position on the selector, and separate fuel tank vents, one for each tank. There was no vent crossover. This, for a FAR 23 or CAR 3 airplane, would be illegal. If the vents aren't providing exactly the same pressure to the tanks, the flow becomes uneven and if one tank has higher vent pressure and the fuel in it is low enough and unports in a maneuver like a climb, that air will get into the lines, exhaust the header tank on that side, prevent fuel flow from the other side, and the engine quits.

    §23.975 Fuel tank vents and carburetor vapor vents.
    (a) Each fuel tank must be vented from the top part of the expansion space. In addition—
    (4) Airspaces of tanks with interconnected outlets must be interconnected;
     
  4. Ryanb

    Ryanb En-Route PoA Supporter

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    Carb ice would be unlikely since you mentioned power was instantly restored by applying full throttle.
    Possibly an issue with the float in the carb?

    Glad everything worked out well for you.
     
  5. MAKG1

    MAKG1 Touchdown! Greaser!

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    It does sound like ice INGESTION to me. Application of full power melts ice, engine eats a chunk, stumbles HARD, pilot reacts instantly. The airplane probably would have gotten full power back on its own inside a second or so, and then flown normally thereafter.

    Conditions look quite good for carb ice formation, particularly if there is time spent at idle after run-up, say, waiting for landing traffic.

    I've had this happen. It's scary as hell. I made it up to 400 AGL, just past the end of the runway, in a 172 in similar conditions.
     
  6. Norman

    Norman En-Route

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    Temperature/dew point spread in post # 1 makes the humidity 82%. Could very well have been carb ice.
     
  7. Ryanb

    Ryanb En-Route PoA Supporter

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    If it was ingestion the engine would stumble for a few seconds with noticable roughness before power returns. It sounds like from what the OP stated, that full throttle was applied and full power was restored instantly without any hiccups.
     
    Last edited: Oct 11, 2016
  8. Dan Thomas

    Dan Thomas En-Route

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    Carb ice wouldn't take the power from full to nothing in two seconds.
     
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  9. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Disconnected the fuel line at the carb and got a good 35 gph out of the hose (as measured by the JPI FF paddle) with the tail all the way down. Gascolator screen is clear. Next we pulled the data from the JPI and that tells a story. We checked his previous flights and when he pushes the throttle in, the RPMs always go to ~2700 (CS Prop) and the FF always goes to 16-17 gph. Looking at the chart below, on the takeoff run the engine built full power (27 MAP and 2700 RPM) but was only pulling 12-14 gph. It is understandable why it quit. The supply wasn't keeping the bowl full. The chart below shows the same timeframe in all four frames, but I moved the cursor on each to show you the change in RPM and MAP (top row) and Fuel Flow (bottom row). The first (leftmost) box is before takeoff and shows 1561 RPM, 11.7" MAP, and 4.1 GPH. When the throttle is opened in the next frame, RMP goes to 2684 and MAP goes to 27.4 as they should. We are making great power and going down the runway but you'll notice FF is low at 11 gph and fluctuating. In the third frame, you'll see the sudden loss of power with RPM at 1694, MAP at 4.4, and fuel flow at 15. When power comes back in the last frame, we have full fuel flow at a normal (for this plane) 17.2 gph. The power outage lasted almost 10 seconds.

    [​IMG]

    It looks like it could have been a stuck float, or piece of crud in the float needle.

    Dan, the right tank was lower than he had ever taken off with before at 5 gallons (although he had run it dry many times before at cruise and it always continued feeding off the left tank without interruption). if it were sucking air out of the right tank (since both were on), how would the JPI FF paddle wheel act? Would it spin faster or slower with air passing through it instead of fuel?

    Could this still have been the result of ice?

    Thoughts on the graph? Full flight shown here at Savvy.
     
  10. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Me too! Thanks Ryan.
     
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  11. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Looked good. Thanks George.
     
  12. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    That was the setup. He idled for 15 minutes letting the engine warm up before doing the runup. I don't have ice problems in my Cardinal but on a long decent at idle power I always use carb heat just for GPs.
     
  13. MAKG1

    MAKG1 Touchdown! Greaser!

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    No.

    Traditional carb ice is like pulling the throttle out. The type I thought was going on here -- ice ingestion -- is more like sucking a whole lot of water momentarily through the fuel. If it messes with fuel flow, it also messes with MAP in a carbureted engine.

    This looks like a fuel delivery problem, possibly a carburetor problem such as a stuck float/needle, plugged vent, etc.

    I suppose you could have iced port vacuum, but I don't know if or how that's used in this particular carburetor. Sometimes that's used for spark timing, carb heat, or alternate air in automotive applications, but I don't think there is any of that here.
     
  14. Cpt_Kirk

    Cpt_Kirk En-Route

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    Gotta love JPI's. Glad to hear everything turned out well.
     
  15. orange

    orange Line Up and Wait

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    You went up with only 5 gallons of fuel in one tank? After 15 minute of running engine, it was even less. Were you flying to the next neighborhood?
     
  16. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Yes, flying to Mountain Home, AR, 6 miles away. He transferred 6 from the aux tank to the left tank adding to the left's existing 5 gallons, and with 5 in the right tank it should have been plenty, barring Dan's theory.
     
  17. Stewartb

    Stewartb En-Route

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    Warmed up for 15 minutes? I've never warmed up a plane that long.
     
  18. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Could that have been the cause?
     
  19. Dan Thomas

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    When I finished a Glastar for another fellow, that fuel setup bothered me. It had the cutoff nylon tubes facing forward under the wingtips, real scalp-scratchers. I noticed uneven fuel flow on most flights. It was a taildragger version with the folding wings, which let the fuel dribble out those vents when the wings were folded. I finally disconnected the vents, plugged their tank ports, and installed forward-facing vents in both fuel caps. I plumbed a vent crossover line between the two tanks to keep the tank pressures the same. It behaved itself after that.

    Carb ice can build during warmup and runup, but you will not get full power on takeoff if it's there, and if it swallows a bit of ice it will stumble, not quit smoothly.

    Air in the JPI fuel flow transducer won't drive the paddle and you'd see low or no flow.

    Something is affecting fuel flow in that airplane, and since it delivered 35 GPH on a ground test (hose off carb) and too little in the climb, it's either a clogged inlet strainer in the carb (yes, there's one in there, as part of the fuel inlet fitting), or something briefly got into the main jet, or the inflight airflow screwed up the tank vent pressures. I'd be opening that carb to check that there isn't something floating around the bowl, ready to do it again. I once had an engine quit in the takeoff roll; makes one thorough about looking for some cause.
     
  20. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Good info Dan. We suspect the finger screen at the carb inlet, needle, main jet, etc. The owner is pulling the carb as we speak.
     
  21. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    No problems found. From the Glastar manual: 34 gallons total in the wings, 24 usable. We had 5 in each wing (the 6 gallons in the aux tank didn't transfer to the left wing as we thought). Filled tanks and did high speed full power taxi (and slight flight). Fuel Flow went smoothly up to 16 and stayed there.

    Thanks all.
     
  22. BigBadLou

    BigBadLou En-Route

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    Glad the PIC did it right and lowered the nose without trying to turn around. It all worked out and you are here to tell the story.

    However, I am puzzled by the Glastar numbers. 34 full and only 24 usable? Is that a typo? That would mean 5 unusable in the tanks. Who on Earth would manufacture such a poorly designed tank? I sure hope it's a typo somewhere.
     
  23. Jay Honeck

    Jay Honeck Touchdown! Greaser!

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    My thoughts exactly. "Warming up" for that long (in anything but sub-zero winter weather, anyway) promotes nothing but fouled plugs.

    Which doesn't sound like the issue here, BTW.
     
  24. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    I can vouch firsthand that there really is 10 unusable :) Sometimes it pays to RTFM.

    Looking at the bottom of the wing, the sump/drain valve and pickup point are at the bottom of the tank, when the airplane is level in pitch. The tank's bottom is concave. The sump and pickup point are, however, about 5" fore of the back of the tank. So when the airplane is nose high, there is 5" of fuel behind the pickup point. And I guess that would be about 5 gallons.

    But I think there are airplanes just as bad if not worse. My friends A23/24 Super warns not to take off with less than 11 gallons for the same reason.
     
  25. ircphoenix

    ircphoenix Pattern Altitude

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    So the problem was taking off with essentially empty tanks per the manual?
     
  26. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Roger.
     
  27. ircphoenix

    ircphoenix Pattern Altitude

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    D'oh!
     
  28. SoCal RV Flyer

    SoCal RV Flyer Cleared for Takeoff

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    That's crazy. Most RVs have about one or two quarts unusable per side.
     
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  29. Dan Thomas

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    The typical Cessna SE has about a gallon and a half unusable per side. A designer can get the unusable way down by having outlets at the front and rear of the tank and teeing them together at some lower point. That won't work in a low-wing airplane. He can also lower the outlet itself in the tank, but that carries the risk of contaminants and water getting into the outlet.

    The Glastar has its outlets only at the rear, to accomodate the wing-folding feature. So on approach, with full flaps, the nose is way down and the fuel sloshed forward and unports if below the unusable fuel level.

    Aircraft design involves innumerable compromises.
     
  30. Jim Case

    Jim Case Pre-takeoff checklist

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    Glad to hear you are safe and sound. My best guess would be obstruction in the air box, or some kind of issue with the carb float. Other than that. I'm sure a more experienced pilot will get you something more concrete to go on.
     
  31. simtech

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    read post 26....its all good now
     
  32. Jim Case

    Jim Case Pre-takeoff checklist

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    I didn't realize how old this was.
     
  33. JohnAJohnson

    JohnAJohnson Line Up and Wait

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    Thanks Jim. And yes, I suspected the float circuit initially too.
     
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