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  1. #1
    siddus74's Avatar
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    Mercury air start problem . . .

    Hi guys I was wondering if any of you can offer me some advice before I speak to AMT heres my problem . . .

    I started my Air start Mercury turbine started it today as normal with no problems and then after use used the ASU to run the cool down as normal. On the second start some 45 minutes later the turbine failed to start. All the transmitter calibration was completed successfully as normal and the air pressure and gas pressures were good, they were connected as normal, the ESC was put into start mode as normal using the 3 position switch and the sequence began as normal however the air supply delivered to the turbine via the ASU unit was constant as apposed to sequenced bursts, the turbine failed to start.

    There were no error beeps during the start procedure? (it has the first generation ECU as pere picture at the start of the thread)

    I checked the battery for the ECU and also the leads and wires connecting the glow plug / RPM sensor etc an all was fine, nothing had changed from the previous start up / shutdown procedure.

    Please can you offer me some trouble shooting advice?

    Scott :-(
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  2. #2

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    RE: Mercury air start problem . . .

    Hi Scott,

    Did you look at the EDT for start clearance. When the glow plug fails it stated at the EDT as "No start clearance".

    Please check cables and glow plug.
    Cheers,

    Ray Struik
    AMT Netherlands
    Electronic Control Designer

  3. #3
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    Hi thanks for the reply . . . I dont have and EDT :-(, ive checked the glow plug , thats fine . . .

    Connect Cord
    Calibrate 3 position switch . . .
    Calibrate throttle
    Fuel on
    Gas valve 1 turn
    Air on
    3 position switch to go . . .
    ASU supplies air, more air, constant air . . . thats it . . .

    Normay the air supply would stop and the turbine spins and the gas it supplied . . .

    ??? I dont know, RPM sensor? Can we check this component or does the ECU do this?

    Anybody have and EDT for sale? Im pulling my hair out!


    Scott.


    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  4. #4

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    RE: Mercury air start problem . . .

    Hi Scott,

    It seems that you have every thing correct. I suggest that the RPM sensor is not functioning anymore. Therefore the air sequence is not stop if it hits 5K RPM.
    This can only been seen on a EDT. Some try to find somebody with an EDT. Can you see if the sensor is not damaged. The surface must be clean at the compressor side. So no very small copper lead, just some (white) epoxy resin.

    What is the engine number of your turbine.
    Cheers,

    Ray Struik
    AMT Netherlands
    Electronic Control Designer

  5. #5
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    Thanks for the reply . . .

    Can the RPM sensor be tested with a multimeter on and ohms setting . . does anybody know what the values should be . . . I dont know anybody with an EDT, looks like Ill have to purchase one if i wanted to get this sorted ok.

    I think I read the the RPM sensors were the achilies heel of the AMT's? Ive only owned this Jet / Turbine for 2 days :-(

    Saw it start and stop twice when I bought it, and I started stopped it once correctly myself yesterday then this . . .

    Scott.
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  6. #6

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    RE: Mercury air start problem . . .

    I would try to start without the ASU this is very easily achieved. Also check the ASU and glow connection for dirt or corrosion.

    Florent

  7. #7
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    RE: Mercury air start problem . . .

    The EDT is nice to have as you can watch the start sequence and visually confirm any malfunctions. Changing the rpm sensor is easy to accomplish, loosen a couple of screws, remove, insert new sensor (be sure to confirm the proper depth from the company but I think the width of a standard business card will suffice) tighten the screws and voila' you'll be all set.

    I would also recommend you smear a light dab of Goop or silicone adhesive etc to the rpm sensor after tightening the bolts. What has likely occurred is the sensor has shifted slightly and has possibly been nicked by the compressor wheel, hence the lack of rpm reading by the ASU.

    good luck but simple fix.

    I recommend getting two sensors keep one as a spare. you'll probably never use it but......
    baby please.....I am not from Havana.

  8. #8
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    We have tested the Hall sensor with a Multimeter and even on 200m ohms it suggests an open circuit, How much are these bad boys and where can I get a couple from?

    Being that you purchased 2 im hoping that they are not allot of money?

    Before and after cleaning . . . runs perffectly well though . . . FOD Guard is the future but can you use them with Air start AMT's?

    Here are the detail from the sensor wire HoneywellUK0048 921FS0.8

    Here is a PDF I round, even looks the same Sensor PDF

    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  9. #9
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    New sensor is about £85 . . . wounded . . . One ordered as well as some FOD meshing from ebay . . .

    Scott.
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  10. #10
    yeahbaby's Avatar
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    RE: Mercury air start problem . . .

    You most certainly can run a fod guard on an airstart engine. couple of ways to do it:

    purchase an appropriately sized strainer from your local grocery store or English equivalent of Walmart, then fasten it to the face of your engine after routing your air, fuel, propane lines through the screen

    or

    in a fully enclosed bypass set up, you can insert the fod screen with the bowel facing forward. envision it such that you would be inserting the fod screen into the back side of the intake(s) forward of the engine. the engine must be in a fully enclosed bypass for this technique to work.

    good luck but you should be good to go as soon as you insert a new sensor and don't forget to purchase an EDT, even if you're using the ASU.

    cheers



    ORIGINAL: siddus74

    We have tested the Hall sensor with a Multimeter and even on 200m ohms it suggests an open circuit, How much are these bad boys and where can I get a couple from?

    Being that you purchased 2 im hoping that they are not allot of money?

    Before and after cleaning . . . runs perffectly well though . . . FOD Guard is the future but can you use them with Air start AMT's?

    Here are the detail from the sensor wire HoneywellUK0048 921FS0.8

    Here is a PDF I round, even looks the same Sensor PDF

    baby please.....I am not from Havana.

  11. #11
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    thanks for the advice, there is not anough room to get a fod guard on the front of the turbine (it is realy close to the ducting . .. it is fully ducted.

    I have purchased some mesh (1mm appertures 50% through put) as advised by AMT . . . I was going to use it half way down the air intakes on the F15 what do you think? (shape the mesh to the ducting and epoxy it neatly in place)

    Scott.
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  12. #12
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    RE: Mercury air start problem . . .

    placing the mesh screen in the intake will work just fine amigo. I did something similar with my SM F4.

    periodically check the screens for security but if you ingest any grass etc. you can easily stick a vacuum cleaner hose down the intake and remove any debris that may be lodged in there.

    you won't notice any reduction in power from the engine btw

    cheers


    ORIGINAL: siddus74

    thanks for the advice, there is not anough room to get a fod guard on the front of the turbine (it is realy close to the ducting . .. it is fully ducted.

    I have purchased some mesh (1mm appertures 50% through put) as advised by AMT . . . I was going to use it half way down the air intakes on the F15 what do you think? (shape the mesh to the ducting and epoxy it neatly in place)

    Scott.
    baby please.....I am not from Havana.

  13. #13
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    Thats sweet, the reduction in thrust was what I was concerned about . . . ill post some pictures when Ive done it . . . thanks for the supprt.

    Scott.
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  14. #14

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    RE: Mercury air start problem . . .

    The best way to check your sensor, Use the RX1 or ohms scale on our multimeter then place the sensor infront the compressor and spin the shaft nut. You should see a open and short (1-0)reading.

    We have tested the Hall sensor with a Multimeter and even on 200m ohms it suggests an open circuit, How much are these bad boys and where can I get a couple from?
    It's a hobby - keep it simple

    www.332ndredtail.com

  15. #15
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    Thanks, ill double check my old one later . . .

    Scott.
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  16. #16
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    Checked my sensor as previous post and nothing . . . New one has yet to materialize :-(

    Done the best I could with the FOD guards in the ducts, not enough room where the turbine fits I felt . . . Oh, well its an old cheap bird anyway :-)

    Scott.

    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  17. #17
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    Replaced the RPM sensor and installed the AMT PC software (I dont have and EDT) . . . After downloading the ECU log it suggested the reason for stop was RPM low (see pictures), not sure if that was the from the last successful run or the last attempted run can anybody confirm how this should be read?

    If I spin the turbine by hand I can get a 700rpm reading, but nothing inbetween and nothing more . . . possible 700rpm increments? Can any body confirm this as well?

    Software looks good though eh? :-)

    Scott.
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  18. #18
    yeahbaby's Avatar
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    RE: Mercury air start problem . . .

    Man that's some sweet software!!!

    inlet screens look good amigo, well done. If you haven't restarted the engine then the data you are looking at should be the last run for the engine. A quick call to Bennie ought to clear things up. Love his motors and you're gonna enjoy flying the F15 with this engine.

    it won't have blistering speed but will fly wonderfully.

    believe it or not years ago I built and heavily modified a JHH licensed version of this bird and managed to stuff an AMT Pegaus in there.

    glad you got the sensor sorted out.

    cheers
    baby please.....I am not from Havana.

  19. #19
    Dr Honda's Avatar
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    RE: Mercury air start problem . . .

    I just bought an Early (v1) ATM USA at180, but I got the ATM Netherlands software to work... and yes... it seems to have a 700 RPM increment.
    Tony

  20. #20
    siddus74's Avatar
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    RE: Mercury air start problem . . .

    Guys,

    Thanks for clearing up the 700 rpm thing and for the reasuring words about the F15 . . . Im doing this whole Jet thing on abit of a shoestring compared to most, so I need to double check everything . . .

    Thanks again for the support, Ill post again after I test it for real over the weekend.

    Scott.
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  21. #21
    yeahbaby's Avatar
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    RE: Mercury air start problem . . .

    Shoestring? LOL

    my avatar (kangaroo) is my first jet, couple cans of Krylon paint (that's a trash can lid for a smiley face btw), one of the first airstart mercury's, and a Futaba Super 7 at the controls. it was perfect!!!

    look forward to hearing about the first flights
    baby please.....I am not from Havana.

  22. #22
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    RE: Mercury air start problem . . .

    Just a quick update, first chance I got to test the new RPM sensor . . . it fired up first time and a ran beautifully . . . how chuffed am I!

    Scott.
    siddus74

    http://www.leenvalleymodelflyingclub.co.uk

  23. #23
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    RE: Mercury air start problem . . .

    The correct clearance between the RPM Sensor and the tip of the compressor blades is 2 "Post-It Notes". I like to scuff the sides of the sensor with some sandpaper to give it some roughness to grip the mout bracket when tightening and I put a drop of blue Locktite on it as well. I too agree that the RPM Sensors are the Achilies Heel of the AMT design. I have been flying AMT for lots of years all models, and have changed my share of sensors. Out of all the ones I have had fail, It has never happened in flight.... Don't ask me why...[sm=confused.gif] Lucky I guess.........

    Danno


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