AOA Probe Failure

Discussion in 'Avionics and Upgrades' started by 455 Bravo Uniform, Apr 20, 2019.

  1. 455 Bravo Uniform

    455 Bravo Uniform Pattern Altitude PoA Supporter

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    Is a standalone AOA probe susceptible to plugging by bug guts?

    If so, what’s the failure mode? Reading high, low, or depending on which hole is plugged?

    Good to cross reference the ASI and stall warning, but will always be outside the envelope- stall horn blaring and ASI reading low and inaccurate due to angle.

    Just wondering, not trying to start an argument. I’d like to install one eventually.
     
  2. weirdjim

    weirdjim En-Route

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    Right now Boeing is trying to figure out an answer to that question.

    Jim
     
  3. Sinistar

    Sinistar Pattern Altitude

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    When reading about the 737 Max 8 AOA sensor problems, the FAA listed 2 of 3 companies with a notable amount of failures. They didn't list the 3rd but it's something like Thane or Thale?

    It seems that the failures are more related to precip (rain, ice, etc) than bugs.
     
  4. Sinistar

    Sinistar Pattern Altitude

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    ...oops last post really didn't help any...is the hole bigger than the pitot tube inlet? Maybe bugs are more likely to enter when parked than in flight...do they have covers like pitot tubes?
     
  5. Ravioli

    Ravioli Final Approach

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    If you've got airspeed indication and a stall warning horn, what exactly do you need AoA for?

    I mean really, the plane is already going to be telling you what's going on if your stalling, isn't it?
     
  6. 455 Bravo Uniform

    455 Bravo Uniform Pattern Altitude PoA Supporter

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    My stall horn is only on or off (at 44kts indicated), can’t tell how close to the stall I am once it turns on, then I have the ASI that I can use, but accuracy around 40kts is not great. Stall at 20-40 deg flaps is 35kts indicated. I’d just like to experiment with an AOA, with its precision, plus I like that I can have the sight on the glareshield (like @motoadve). My short field landings are not short enough (I’m greedy). Dumb? Maybe.
     
  7. Fancy

    Fancy Filing Flight Plan

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    You can use AOA for all sorts of stuff!! Max range, max endurance, min radius, max turn rate, best glide, best climb, and magnitude of control input to “break” a stall to name a few off the top of my head. Aoa flying needs to be trained to by someone that know what they’re doing however. But...assuming an accurate indication, aoa tells you more about the aerodynamic state of an aircraft than any other instrument.
     
  8. WannFly

    WannFly En-Route

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    The hole is about the same as pitot. Don’t know failure mode, haven’t had a pitot or AOA probe blocked...yet.



    Might have just jinxed it
     
  9. Sinistar

    Sinistar Pattern Altitude

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    @WannFly - does your AOA have small cover that you put on when parked?
     
  10. WannFly

    WannFly En-Route

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    I have been thinking about putting that cover on in summer for 2 summers now
     
  11. Sinistar

    Sinistar Pattern Altitude

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    Isn't 2 summers like as long as you've owned your plane :)
     
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  12. 455 Bravo Uniform

    455 Bravo Uniform Pattern Altitude PoA Supporter

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    I guess it’d be easy enough to test. Once with one hole covered with tape, next with the other (then both, if need be).
     
  13. WannFly

    WannFly En-Route

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    As tempting as it sounds, I am gonna pass
     
  14. GRG55

    GRG55 Final Approach

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    "Two summers" is about a total of four weeks in North Dakota. I am certain he's owned the plane longer than that. ;)
     
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  15. 455 Bravo Uniform

    455 Bravo Uniform Pattern Altitude PoA Supporter

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    Why not? As long as you fly with air-speed during the check?
     
  16. Hank S

    Hank S En-Route

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    So is Cirrus, there's an Emergency AD out on the AoA sensor for their fsncy new jet. "Before Next Flight", even . . . .

    Someone during assembly left loctite out of two set screws, and maybe didn't torque them right (or maybe they are loose due to lack of loctite). Results in undesired / unneeded / uncommanded nose down inputs with stall horn, stick shaker, etc.

    Sounds kinda familiar, doesn't it?
     
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  17. Sinistar

    Sinistar Pattern Altitude

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    Why not?

    I'm with @455 Bravo Uniform on this one, he will learn how it fails in all cases and it's my understanding that these AOA indicators that you 2 are using are not tied into any other systems right?
     
  18. WannFly

    WannFly En-Route

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    Yah it’s not tied to anything. I was referring to blocking both the probes and fly. Good skill to have but haven’t done a airspeed INOP flight since primary
     
  19. 455 Bravo Uniform

    455 Bravo Uniform Pattern Altitude PoA Supporter

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    Just to be clear, when I said “both”, I meant both holes of the AOA probe. ASI would remain fully functional.
     
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  20. WannFly

    WannFly En-Route

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    Ok. Yah that I can fly and report back next time I am up