What is triple mix for INS?

Discussion in 'Flight Following' started by jonvcaples, Oct 1, 2019.

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  1. jonvcaples

    jonvcaples Pre-takeoff checklist

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    Can someone explain what is triple mix and how is it done? I know it is used in conjunction with INS systems to discover and minimize error but have not been able to find an explanation of it.

    Many thanks!
     
  2. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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    INS went away 20+ years ago.
     
  3. nauga

    nauga Pattern Altitude PoA Supporter

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    With all due respect, INS is still very much around, typically either GPS aided or GPS denied. That being said, I have no idea what “triple mix” is. Could he mean triplex?

    Nauga,
    pedaling his Schuler cycle
     
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  4. luvflyin

    luvflyin Final Approach

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    one part Triple Sec, one part Tequila....oh. disregard
     
  5. donjohnston

    donjohnston Line Up and Wait

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    When you have three separate INS there was a system which would take the three inputs and provide a single output averaging out the error.
     
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  6. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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    The old INS that were gyro backed are long gone from commercial aviation. Airliners and business jets today are using "IRS" (inertial reference system) that uses ring laser gyros and accelerometers to calculate positions. The IRS can be backed up with DME/VOR and GPS to enhance the position.

    The "triple mix" Mr. Caples is referring to has to do with having 3 IRS's (not INS) weighted average of three independent IRS to determine the “triple mixed IRS” position.
     
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  7. IK04

    IK04 Cleared for Takeoff

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    "Triple Mix" refers to the logic in the Kalman filters used to derive a single position solution.
     
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  8. Unit74

    Unit74 Ejection Handle Pulled

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    I got it Doc....:cool:
     
  9. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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    Really? In what?
     
  10. Unit74

    Unit74 Ejection Handle Pulled

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    Nevermind.... I though you were talking about INS.
     
  11. nauga

    nauga Pattern Altitude PoA Supporter

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    There's definitely some terminology differences here. There are some aspects of commercial aviation (maybe not 121, I wouldn't know) that are still leveraging inertial nav to be functional in the absence of GPS. What you refer to as the IRS I have always understood to be the IRU, intertial reference unit(s), or IMU, inertial measurement unit(s); that an inertial nav system (INS) uses to estimate a position and nav solution. KVH and iMAR are two examples of current COTS INS producers, each with their own IMU. The days of iron gyros may be long gone, but LRGs and FOGs are still used.

    I have some experience with Kalman filters/LQE in nav and other applications and have never heard any part referred to as 'triple mix' - maybe it's application-specifc or deeper in the weeds of the sensor fusion than I typically go or something.

    Nauga,
    tripley-mixed up
     
  12. Rgbeard

    Rgbeard Cleared for Takeoff

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    I'm thinking about Long Island Iced Teas.
     
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  13. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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    What aircraft still use INS?
     
  14. Unit74

    Unit74 Ejection Handle Pulled

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    You like to get LIIT? :cheers: Where's Bruce! :stirpot:
     
  15. nauga

    nauga Pattern Altitude PoA Supporter

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    Pretty much any airplane or weapon that has GPS-denied or GPS-unavailable capability. Most Navy airplanes (ASN-139), several civil/commercial airplanes (not 121) in development off the top of my head, I'm certain there are more.

    Nauga,
    and his niche market
     
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  16. weilke

    weilke Touchdown! Greaser! PoA Supporter

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    Now that we got the dick length comparison out of the way:

    How does the system decide if one of the sensors is too far off to contribute to a nav solution ?
     
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  17. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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    Back to the OP and his question:
    This is rather confusing as I've never heard "triple mix" reference used in INS installations. Now INS that most in the commercial airline world refer to are the old Litton units back in the day of the 747-100/200/300, L-1011, DC-8, etc.

    The 757/767 has 3 IRS's on the overhead. The A320 has 3 ADIRS. Never heard them referred to as "INS".

    And Mr. Caples has stated many times he was a systems instructor on the B757, so I'm a bit surprised he has the terminology incorrect, and he doesn't understand "triple mix" as it's explained in the FOM.
     
  18. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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  19. GeorgeC

    GeorgeC En-Route PoA Supporter

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  20. weilke

    weilke Touchdown! Greaser! PoA Supporter

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    If you consider condescending sniping about acronyms as part of that, sure then it was interesting.

    Thanks. Mentions the answer in passing. Looks like it takes the two that are closest together and ignores the third.
     
  21. Velocity173

    Velocity173 Touchdown! Greaser! PoA Supporter

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    UH-60. That’s one down. I think INS / IRS are the same, just a difference in terms based on what the manufacturer wants to call it. At any rate, INS is still being used in military parlance.

    https://www.militaryaerospace.com/sensors/article/14067685/ins-gps-aircraft
     
  22. Unit74

    Unit74 Ejection Handle Pulled

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    IBTL.....
     
  23. TCABM

    TCABM Cleared for Takeoff

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    Math or FM. I choose to believe FM is the answer.
     
  24. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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    This is an old INS unit that was common place years ago.

    [​IMG]

    This is an ADIRS used in Airbus:

    [​IMG]

    And the IRS used in Boeing:

    [​IMG]
     
  25. denverpilot

    denverpilot Tied Down

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    So the Shuttle was quadruple mix with a backup? :)
     
  26. Larry in TN

    Larry in TN Cleared for Takeoff

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    INS is a single inertial unit--Often called an IRU. Two, often three, IRUs are combined into an airplane's inertial reference system (IRS).

    Each flight management computer (FMC) takes inputs from the IRS. Not just position, but also acceleration, attitude, heading, etc. that drives the flight instruments. Each FMC also has inputs from DME/DME and (usually) GPS. Each FMC evaluates all the data it has available to procedure its best position. All two, sometimes three, FMCs together make up the Flight Management System (FMS). When the GPS updating is working, the position on all FMCs are very accurate and very nearly identical.

    These terms come mostly from Boeing airplanes. Different manufacturers use different configurations and terms.
     
  27. Silvaire

    Silvaire En-Route

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    Triple mix is an approval criteria for RNAV 10 operations in oceanic and remote areas. It really just means having 3 IRU’s but there are other methods of having this approval all with differing constraints and rules. Just Google “RNP 10” and spend the rest of the week reading about it.
     
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  28. luvflyin

    luvflyin Final Approach

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    Whoa! Careful, lest thy be banned. Might I suggest ‘Ricardo el largo’
     
  29. IK04

    IK04 Cleared for Takeoff

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    The aircraft I work with for RNP RNAV has as its primary navigator two EGIs. EGI= Embedded GPS/INS.
     
  30. IK04

    IK04 Cleared for Takeoff

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    That Litton system is a little newer than the ones we used in [unnamed country] for overwater missions.

    The one we used had a large, heavy slab platform in addition to the processor box.
     
  31. jonvcaples

    jonvcaples Pre-takeoff checklist

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    Thanks for the positive contributions!

    The question is based upon the DC0-10. My last job at UAL was maintaining the aircrew training material for that fleet. Way back in those pre GPS days the Diesel 10 used 3 INSs for overwater navigation and conventional VOR/DME fore domestic nav. Unfortunately the day overwater nav was covered in ground school I was out sick and was never able to attend a subsequent class. The concept has always been intriguing so thought it might spark a fun thread which it has.

    Extraneous but maybe interesting stuff follows.

    My first job at UAL was teaching systems for the B-757/767. There was no GPS (1991ish) at that time so long range nav used three laser ring gyros. The Flight Management System used the information from traditional VOR/DME and the inertials to derive and update itself (if memory is correct it used DME/DME fixes then other fixes such as VOR crossing radials for updating...but that's going back several decades). The initial, recurrent, and upgrade training focused on domestic operations. International operations was taught only by specially designated fleet Captains and one fellow Academic Instructor, as we were called back then, who flew C-141's in the USAF.

    Some of the fleet instructor cadre who had been around since day 1 of the fleet used to talk about how the software was modified to dilute the accuracy of the LRGs output because DOD was concerned that the gyros themselves or the system software might be exploited (stolen or copied). The system was supposedly based upon that used in cruise missiles (LRG combined with terrain mapping updates). Some of the folks from our Photo Interpreter pool in the reserves did targeting during the Desert Storm/Shield unpleasantness. They used to say that at the start they targeted buildings, then very quickly specific walls of specific buildings. By the end they were targeting specific corners of specific windows. I always wondered why the FAA wouldn't allow us to fly ADF and VOR approaches used ther laser ring gyro info which no doubt was far more accurate than traditional RF technology.

    Again thank you for the positive comments!! Be legal, safe, and smart...
     
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  32. jonvcaples

    jonvcaples Pre-takeoff checklist

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    Later, after much exposure to the FAA I understood why they insisted on sticking with the hammer and tong terrestrial RF systems...
     
  33. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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    It's explained in the FOM.

    So you understand the theory and operation behind this system, but you don't understand it on the older DC-10 because you were out sick that day it was taught and you couldn't read it for yourself in the FOM? o_O
     
  34. Velocity173

    Velocity173 Touchdown! Greaser! PoA Supporter

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    If they were C-141 guys they had Doppler Nav as well. Not sure if they kept it when they upgraded to INS. We started with Doppler in the Army but the newer aircraft are going with Embedded GPS INS (EGI).
     
  35. jonvcaples

    jonvcaples Pre-takeoff checklist

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    Doc when I was involved with the 757/767 GPS was not in use by 121 carriers. Back then it was still under development and not installed in any UAL aircraft! After leaving that fleet circa 1993 and UAL circa 1996 I no longer had access to the FOM or the UAL training manual for that family. If you want to share this material I'd love to see it. If not act like a professional and quit harping about my not looking it up!
     
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  36. jonvcaples

    jonvcaples Pre-takeoff checklist

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    Also the DC-10 training materials did not cover triple mix either. It was mentioned as a function of the system but not explained or expounded upon in any of our material. The International Ops course mentioned it but did not explain it. Kind of like most pilot training doesn't really explain how transponders, VOR and or DME work except in very high level non-technical language. I'll humor your silly game a little bit with three questions.

    1-What modulation is used for aircraft voice communications?
    2-Why?
    3-Why are their only 4,096 transponder codes?
     
  37. EdFred

    EdFred Touchdown! Greaser! PoA Supporter

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    because 8^4 = 4096
     
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  38. Caramon13

    Caramon13 Pattern Altitude

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  39. Doc Holliday

    Doc Holliday Pre-takeoff checklist

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    Jon,

    First, stop with the yelling.

    Second, are you not aware that this information is all in the public domain?

    Third, you stated you were out on the days it was discussed in ground school. Were you unable to go into your manuals (you did have manuals, correct?) and read up on it? Even the earlier INS type installations had a version of triple mix, and the non gps IRS installations had a version of it using the available VOR/DME backup.

    Fourth, you claim to have been a systems instructor on the 757/767. Did you not have access to the training materials from the course that would have covered this?

    Fifth, you posted this asking a question, yet you never stated why you needed this info. You also used the wrong terminology which is unusual coming from someone who was supposedly involved in air carrier operations.

    When you teach someone, do you spoon feed everything to them, or do you expect that they should develop the skills to research matters?
     
  40. Velocity173

    Velocity173 Touchdown! Greaser! PoA Supporter

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    Really? We went with the old school 4096 question. :rolleyes:
     
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