PeytonM Posted Tuesday at 02:38 AM Report Posted Tuesday at 02:38 AM Recently I’ve noticed that my electric cowl flaps (‘89J) are creeping from totally closed to about 1/4 open during cruise. I can close them, but they will creep 1/4 open after a few minutes. Is the cowl flap motor the likely suspect?
Hank Posted Tuesday at 02:46 AM Report Posted Tuesday at 02:46 AM Sounds like they are finding a trail position for you, all by themselves. Any idea how far they open? Many advocate for ~1/2" -- 3/4" gap when closed.
toto Posted Tuesday at 02:58 AM Report Posted Tuesday at 02:58 AM 18 minutes ago, PeytonM said: Recently I’ve noticed that my electric cowl flaps (‘89J) are creeping from totally closed to about 1/4 open during cruise. I can close them, but they will creep 1/4 open after a few minutes. Is the cowl flap motor the likely suspect? Are you seeing this on the indicator, or via some other means? I’ve never noticed mine move from fully closed unless I move the lever, but I’ve never really paid much attention to it.
toto Posted Tuesday at 03:55 AM Report Posted Tuesday at 03:55 AM 18 minutes ago, LANCECASPER said: On the electric flaps there's an LED indicator showing where they are. I have the same aircraft as OP - the indicator is just a little vertical gauge that shows the position (photo below). It’s not part of my normal scan, and I never really look at it unless I’m adjusting the cowl flaps. The flaps are infinitely adjustable with a little switch that controls the electric motor.
LANCECASPER Posted Tuesday at 04:35 AM Report Posted Tuesday at 04:35 AM I realized after I typed it that later in the 90's the indicator was LED. 1
Will.iam Posted Tuesday at 05:39 AM Report Posted Tuesday at 05:39 AM My indicator is like what is shown above. When i was testing the theory of fully closed vs open a 1/2 inch for better speed i found out there is some slop from the cowl flap and the linkages to the motor. The indicator followed the cowl flap itself so it would be a little maddening to have the motor run for a second and have the indicator show one thing on the ground and something else in the air as before i never really looked at the indicator except to fully open or fully close the cowl flap. Once i got out and at an intermediary position i just moved the cowl flap by hand and noticed that it would move about a 1/2 inch in play but the indicator inside followed that play. Then i noticed more closely when i start to close the cowl flaps the indicator does not move for the first second or so as the motor takes up all the slack in the linkage and play in the cable as the indicator jyst stayed where it was at then it started to move. Hope this helps in your understanding of the indicator vs the actual cowl flaps position. .
PeytonM Posted Tuesday at 01:08 PM Author Report Posted Tuesday at 01:08 PM Over the past couple of Annuals, my A&P has worked diligently to remove all play in the cowl flap mechanism. When I do a preflight and grab the cowl flaps, there is virtually zero play. When we started, both had a pretty good rattle to them; now there is nothing. Why would the cowl flap indicator and the cowl flaps move to 1/4 open when in cruise?
LANCECASPER Posted Tuesday at 01:57 PM Report Posted Tuesday at 01:57 PM 8 hours ago, PeytonM said: Over the past couple of Annuals, my A&P has worked diligently to remove all play in the cowl flap mechanism. When I do a preflight and grab the cowl flaps, there is virtually zero play. When we started, both had a pretty good rattle to them; now there is nothing. Why would the cowl flap indicator and the cowl flaps move to 1/4 open when in cruise? The pressure of the air you're taking in is finding the path of least resistance? 1
Ragsf15e Posted Tuesday at 06:06 PM Report Posted Tuesday at 06:06 PM Wasn’t there also the original Globe motor with a smaller gear train that could be backed up some? Do you know if you have had the electric motor oh ever? FWIW, my k has the same indicator and the newer globe and the indicator still slides to 1/4 open during cruise. It’s not just the indicator either, because i see an effect on oil temp and chts if I shut it again. The motor should not be able to back up…
PT20J Posted Tuesday at 11:54 PM Report Posted Tuesday at 11:54 PM It sounds like maybe you are putting the cowl flap switch in the off position after closing them. I leave my switch in the open or closed position unless I’m setting them to an intermediate position as described in the POH. With the switch in the closed position, the motor should close them again if they drift open. I had a flight today and put the switch in the off position after closing and they did not drift partially open, so I suspect there is something amiss with those that do.
Will.iam Posted Wednesday at 12:11 AM Report Posted Wednesday at 12:11 AM Yes i thought (incorrectly i found out) that the slip stream air pushing on the outside would keep the cowl flaps close but the air pressure from the air that comes into the engine compartment is stronger and therefore pushes the cowl flaps open or to put it another way the air pressure inside the engine compartment is greater than the air pressure outside the cowl.
PeytonM Posted Wednesday at 01:09 AM Author Report Posted Wednesday at 01:09 AM (edited) I flew again today and after setting up in cruise with the cowl flaps closed, and moving the switch to the center position/off, I watched the cowl flap drift to 1/4 open in about a minute. I then closed them. (I know that there was a change because I could hear a difference in sound.) I repeated the experiment and same thing. If I leave the switch in the closed position, the cowl flaps remained closed. Is that how it’s supposed to work? Edited Wednesday at 01:23 AM by PeytonM Clarification
Slick Nick Posted Wednesday at 04:56 AM Report Posted Wednesday at 04:56 AM 3 hours ago, PeytonM said: I flew again today and after setting up in cruise with the cowl flaps closed, and moving the switch to the center position/off, I watched the cowl flap drift to 1/4 open in about a minute. I then closed them. (I know that there was a change because I could hear a difference in sound.) I repeated the experiment and same thing. If I leave the switch in the closed position, the cowl flaps remained closed. Is that how it’s supposed to work? Sounds like it. See Skip’s screenshot above.
Ragsf15e Posted Wednesday at 05:36 AM Report Posted Wednesday at 05:36 AM 4 hours ago, PeytonM said: I flew again today and after setting up in cruise with the cowl flaps closed, and moving the switch to the center position/off, I watched the cowl flap drift to 1/4 open in about a minute. I then closed them. (I know that there was a change because I could hear a difference in sound.) I repeated the experiment and same thing. If I leave the switch in the closed position, the cowl flaps remained closed. Is that how it’s supposed to work? If you leave the switch in “closed”, it still opens slightly, but when the “uplimit switch” opens, the motor closes it again. You will end up cycling the motor the whole flight. I think it should be more like @PT20Js which stay closed. Alas, my K does the same thing and I don’t leave the switch closed as I want to control the “cycle”. It would be better if it stayed where you left it.
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