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Thread: PA-11 Oil Temp Capillary Air Shroud?

  1. #1

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    PA-11 Oil Temp Capillary Air Shroud?

    My PA-11 had an air duck from the rear of the left air inlet behind cylinder 2 running over to small air box around the oil temp capillary behind the C-90 engine.

    Mechanic removed it during annual and stated it didn't have an STC, but now the oil temp is reading 10+ degrees more without it installed, and tonight the temp was reading close to 200 degrees which is highest temp on the gauge.

    Does anyone have a PA-11 service manual that might indicate if this requires STC to keep it on the engine?

    Thanks,

    Dave
    Last edited by DavePA11; 07-18-2013 at 09:48 AM.

  2. #2
    d.grimm's Avatar
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    I bought one from Univair for my C85 powered
    Vagabond and it was a stock PA11 part.
    I think your guy needs to put it back on.

    Dave

  3. #3
    cubdriver2's Avatar
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    Dave your mechanic is wrong. Why do you need a stc for something that was original equipment. I thought you had some Cub guys over there. You and Rene need to find someone who knows what their doing.



    Glenn

  4. #4
    nesincg's Avatar
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    My PA-11 had it when I took it apart. My question is, does it cool the oil or just cool the indication of the oil?
    The aviator formally known as 89.

  5. #5
    cubdriver2's Avatar
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    Quote Originally Posted by nesincg View Post
    My PA-11 had it when I took it apart. My question is, does it cool the oil or just cool the indication of the oil?
    Jerry Burr will tell you otherwise but I always feel better with a lower temp on the gauge.Did I mention that my 11 had over 45 lbs oil pressure at 2200 hrs.

    GlennGlenn

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    Where do I get documentation to show the mechanic? Thanks.

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    cubdriver2's Avatar
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    Quote Originally Posted by J3Flyer02m View Post
    Where do I get documentation to show the mechanic? Thanks.
    You shouldn' t have to.If you had someone who knew what he was doing you would' t have to hold his hand. Make him show you it needs a Stc.. Now you know why I do my own repairs.

    Glenn

  8. #8
    fancypants's Avatar
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    No instant gratification, but the parts manual might help:

    http://univairparts.com/shopping/pro...oducts_id=7110

  9. #9

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    Thanks! I ordered the PA-11 Parts Manual form Univair.

  10. #10
    RaisedByWolves's Avatar
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    Dave, bring that cub up to lwm and we'll get you squared away

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    JP's Avatar
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    Don't waste your time. It cools the temp bulb, not the oil.

    If you want to cool the oil a bit more install the spilt duct air intake on the nosebowl. If you really want to cool it run scat from the spare split down to the sump, but you likely won't need that.

    I flew in 93 degree humid weather, heavy and at high rpms with lots of climbing, for over five hours the other day and the temp never went over 205. Oil pressure was 5 degrees above redline most of the day, but that's it.
    JP Russell--The Cub Therapist
    1947 PA-11 Cub Special
    www.bloomerrussellbeaupain.com

  12. #12

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    JP

    Last flight was 198 but gauge only goes to 200. It was 95 outside with high humidity too. Tom mention top temp for c90 was 225 so it was under this temp. Not sure how he knew top temp for c90 while flying.

    dave

  13. #13
    RaisedByWolves's Avatar
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    Thats why i get paid the big bucks

    I have a c90, that's what my red line is. I also checked the TCDS, and it said the same thing.

  14. #14
    cubdriver2's Avatar
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    Quote Originally Posted by JP View Post
    Don't waste your time. It cools the temp bulb, not the oil.
    .
    I don't agree. If its cooling the housing and bulb then its removing some of the heat from the oil that's inside the housing. Might not be the 20 degrees that show on the gauge but if its lowering it only 5 its still helping to lower the temp.

    Glenn

  15. #15
    RaisedByWolves's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    I don't agree. If its cooling the housing and bulb then its removing some of the heat from the oil that's inside the housing. Might not be the 20 degrees that show on the gauge but if its lowering it only 5 its still helping to lower the temp.

    Glenn
    Even if its cooling the gauge it gives the pilot a little piece of mind. Seems like it will do a little something.

  16. #16
    skywagon8a's Avatar
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    I have seen this type of shroud on several different types of planes. It's purpose is to BS the gauge so that the temperature reading will pass the FAA flight tests.
    N1PA

  17. #17
    Steve Pierce's Avatar
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    Here is some data that Jerry Burr got on his Cub showing what the blast tube is actually doing. http://www.shortwingpipers.org/forum...be-Blast-Tubes

    As far as your mechanic removing it, does he have a parts manual? Obviously not. Sounds pretty arogant to remove something and he has nothing to prove it is not supposed to be there. There is plenty of documentation that that is a factory part. Sorry for the rant but I really get ticked off when a mechanic does something like this. Makes those of us who research and find answers to the questions we don't know look bad.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  18. #18
    JP's Avatar
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    Quote Originally Posted by RaisedByWolves View Post
    Thats why i get paid the big bucks

    I have a c90, that's what my red line is. I also checked the TCDS, and it said the same thing.
    My Amp goes to 11.....my gauge has a broader range and is red-lined at 225.
    JP Russell--The Cub Therapist
    1947 PA-11 Cub Special
    www.bloomerrussellbeaupain.com

  19. #19
    nesincg's Avatar
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    It is not in the parts manual. I checked last night.
    The aviator formally known as 89.

  20. #20

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    Quote Originally Posted by cubdriver2 View Post
    I don't agree. If its cooling the housing and bulb then its removing some of the heat from the oil that's inside the housing. Might not be the 20 degrees that show on the gauge but if its lowering it only 5 its still helping to lower the temp.

    Glenn
    Also the claim that the sender is conducting heat to the shroud directly is incorrect, as there is no substantial heat path from the sender to the shroud. The shroud is only loosely held in place by the retaining nut. It is not clamped up tight to the sender.
    All of the oil that the engine sees runs through that screen housing. if you cool the screen housing, you will certainly cool the oil. it's just not a very efficient heat exchanger.
    As well, there is a substantial amount of oil surrounding the bulb, giving it a much better chance of actually measuring the temperature of the oil and not the surrounding metal as would have occurred by introducing a temp sender into one of the oil passages.
    Unless great care was taken to isolate the temp probe thermally from the crankcase, It would likely be seeing heat conducted directly to the probe from the surrounding metal.
    DaveG

  21. #21
    Steve Pierce's Avatar
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    Quote Originally Posted by DaveG View Post
    Also the claim that the sender is conducting heat to the shroud directly is incorrect, as there is no substantial heat path from the sender to the shroud. The shroud is only loosely held in place by the retaining nut. It is not clamped up tight to the sender.
    All of the oil that the engine sees runs through that screen housing. if you cool the screen housing, you will certainly cool the oil. it's just not a very efficient heat exchanger.
    As well, there is a substantial amount of oil surrounding the bulb, giving it a much better chance of actually measuring the temperature of the oil and not the surrounding metal as would have occurred by introducing a temp sender into one of the oil passages.
    Unless great care was taken to isolate the temp probe thermally from the crankcase, It would likely be seeing heat conducted directly to the probe from the surrounding metal.
    DaveG
    Dave, Did you read what Jerry Burr posted?
    Oil Temperature Test.26 Jan 2010

    OAT. 37deg F.Alt. 1000’MP. 23.5MPH. 92.

    A two inch scat tube was used between the outside ram air and the oil screen shroud. It was modified with an air shutoff for the tests.
    The oil galley on the left rear of the engine where the oil cooler mounts was modified to accept a temperature probe.
    Two cameras were used to monitor the screen oil temp and the galley oil temp.
    These were fed to a common screen on tape and uploaded to computer to do the final comparison.
    10 minute runs were used as the temps seemed to normalize at that point.

    Time. Galley temp Screen temp Cold ram air
    10 min 207 183 Off
    10 min 207 152 On
    10 min 207 180 Off
    10 min 207 152 On

    Land
    approach
    202 150 On
    Touchdown
    195 152 On
    Park 193 162 On

    Slow flight
    1 notch flaps 200 180 On

    Oil temp in the galley seems to be affected mainly by power setting and not much else. The cooling of the screen had no effect what so ever on the galley oil temp.

    Jerry
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    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  22. #22

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    Yes I did...My concern with that test is the possibility that the sender he installed is also seeing heat conducted to it from the metal it's attached to. If he had used a thermally isolated mount for that probe I'd be more inclined to believe the data.... I just feel that that the capillary bulb in the screen housing has a better chance of reading the actual oil temperature.
    DaveG

    Quote Originally Posted by Steve Pierce View Post
    Dave, Did you read what Jerry Burr posted?


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  23. #23
    btracy's Avatar
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    Note: This is for the PA-18-95. The IPC illustration, isnt very realistic. But I think this is it. IPC sec VI, fig 30, Item 36/37. P/N 12230-00. It is on page 100 of my Univair Parts Manual.
    Last edited by btracy; 07-19-2013 at 05:49 PM.

  24. #24

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    Whether or not it does anything the Oil well baffle is listed in Piper Service Memo 13 in the list of parts required to convert PA-11 65 HP to 90 HP.
    Attached is a copy of Service Memo 13 and the parts manual corrections and additions page.

    Jim
    Attached Files Attached Files

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    RaisedByWolves's Avatar
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    PerryB's Avatar
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    Quote Originally Posted by skywagon8a View Post
    I have seen this type of shroud on several different types of planes. It's purpose is to BS the gauge so that the temperature reading will pass the FAA flight tests.
    I tend to agree.
    After Monday and Tuesday, even the calendar says WTF !

  27. #27

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    Worked with another mechanic today, and we decided to leave the metal shroud off but leave the hose blowing on the oil bulb. The metal shroud was held on by the nut holding the oil sensor, and it was causing oil to leak. In any case, the temp is about 10 degress below the 200 max temp on the gauge now with ambient temp at 93 so it seems to be working.

    Found a hole in the blow out tube at the top where its feed into the engine, and oil is coming out of this hole into the engine compartment. Is this used for winter operations in case the lower tube end freezes? How is this typically plugged during summer operations?

    Thanks,

    Dave

  28. #28

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    Thanks for all the replies and information!

  29. #29
    n40ff's Avatar
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    Cool

    Quote Originally Posted by PerryB View Post
    I tend to agree.
    +1 Reminds me of my mechanic's suggestion when I had issue with high oil temp the first summer with my PA16, "If it bothers you, put a black paster over the gage"

  30. #30
    Steve Pierce's Avatar
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    Sounds like you are talking about the whistle slot in the crankcase vent. It is there to allow crankcase pressure out in case the end of the vent freezes. It should be pointed in such a way where the oil will not leak out of the slot. Here is an illustration from a Cessna Safety Advisory Information Bulletin. http://www.cessna.org/documents/publ.../ace-99-05.pdf
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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