Anatomy of a low frequency aviation radio beacon

Discussion in 'Amateur Radio News' started by KX4O, Aug 25, 2020.

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  1. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    What isn't mentioned the Tom Hanks Apollo 13 movie is that Jim Lovell created his own crisis through a bone-headed move. He jury rigged an unauthorized auxiliary light for the cockpit, and it shorted out his electrical system. That's how he ended up in the dark at night with no navigation or radios.
     
  2. W7IMM

    W7IMM Ham Member QRZ Page

    Yeah, I was in the military and read that report after it was published......They always blame the pilot when they cannot definitively find the reason (and it may very well have been the pilots fault as it frequently is) ADF approaches have never been as "safe" as other non-precision approaches..... especially at night when there's atmospheric effects (night propagation lightning etc) They're also very easy to jam.
     
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  3. W5UAA

    W5UAA Ham Member QRZ Page

    I was on the team who did the site survey to install an ILS on Tuzla runway 09 back in 1999.

    RIM00022.jpg
    (I'm the third one from the right)
     
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  4. W7IMM

    W7IMM Ham Member QRZ Page

    I had to go back and actually read the official report on the accident. They did in fact "know how to fly" an ADF approach.....but there were more than a couple of problems.

    The approach was a NON-DOD NDB approach to Dubrovnik. That wasn't a problem in itself but HQ USAF or major command DOV (like MAC) was supposed to approve it (in MAC/AMC we flew NON-DOD approaches all the time. [Jeppesen] But we were given approval along with the specified approaches)



    That (Jeppesen) approach was supposed to have been flown with 2 ADF receivers. That particular CT-43 (USAF 737) only had one. The pilots "fracked up" by not noticing that. It made them "NOT AUTHORIZED" to fly the approach from the getgo .......In general no MAJOR command, Wing or SQ Chief of DOV would ever waive that.

    They were 10 degrees off course which in many cases can still be still within the TERPS criteria for terrain clearance but the REAL BIGGIE was that they were 80 knots fast, not properly configured [gear/APP-flaps etc] and the killer was they didn't go "missed approach" at the missed approach point (which was identified as the second NDB......which the "second" ADF receiver would be tuned to if they had one)


    Flying that approach with only 1 ADF receiver would require the pilot not flying, once past KLP, the Final Approach Fix (FAF) to quickly switch (the single ADF) from FAF NDB frequency to the Missed Approach Point (MAP) NDB frequency!

    Screenshot_2020-09-03 ForeFlight Web.png

    If you're going say 220kts instead of 130kts that missed approach point can come and go before you even figure out you should have re-tuned!!! Which is why it was prohibited to have frequency changes on an approach in the final segment. (too easy to "frack-up"!!)


    It's quite common to have an NDB approach that only requires 1 receiver.......
    1. The NDB is usually located at the FAF (final approach fix)
    2. Once crossing the NDB, you "hack" the clock. knowing your ground speed, you then know how long (1min + 17 seconds etc) it should take to arrive at the MAP(Missed Approach point) . If you don't see a runway or are not in a safe position to land, YOU GO AROUND.

    It ain't rocket surgery!

    Cheers,

    Rick
     
    Last edited: Sep 4, 2020
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  5. K6CLS

    K6CLS Ham Member QRZ Page

    That is covered in the link I gave. And in Lovell's book. And every other telling of the incident. Thanks
     
  6. KE4IKY

    KE4IKY Ham Member QRZ Page

    If I remember correctly, a few weeks before the accident. HQ USAF said no exceptions to requiring approaches to be checked by TERPS. USAFE thought it could waive it, which brought up the whole thing of when does USAFE think it can over-ride HQ USAFE.


    In the report I read, if the approach it had been developed properly or checked by TERPS, they would have been well above the terrain where they impacted.

    I believe they also thought that they could fly it if they switched the NDB rx back and forth fast enough.

    Thanks
    Joel
     
  7. KE4IKY

    KE4IKY Ham Member QRZ Page

    I took care of it in the middle part of 2001. I was surprised at how brave the wildlife got. Walking on a gravel path, wildlife (rabbit.. etc) had no issue with being 4" off of the path while you walked by, or even tried to scare it, wildlife knew you weren't going off the path.

    There were also three NDBs in the area that apparently no one was taking care of. was able to get that contracted out.


    Thanks
    Joel
     
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  8. W7IMM

    W7IMM Ham Member QRZ Page



    That might be true that they thought that.............. but if they did, they were violating one of the most basic AF manuals that they were supposed to know and comply with!
    (emphasis mine)

    If you have any interest in USAF instrument flying procedures, have a look at the following PDF. Everything pretty much applies to civilian flying as well.

    https://code7700.com/pdfs/usaf/afman11-217v1.pdf

    The above manual is dated 2010 and I still have the one dated 2000 and it says the same thing although they renumbered the chapters......... In 1996, they might have been operating under the "old" manual (AFM 51-37) which was replaced by the newer designation somewhere in there..... but they still all said the same thing in this area.


    Bottom line: If they thought they could just tune back and forth after the FAF, they were violating a mandatory procedure. (Mandatory for a VERY good reason!)

    The accident report also said they were 80kts hot on final indicating to me that they were WAY behind the aircraft. If timing (to the MAP) was depicted on the approach, it would have been invalid since none of those approaches are designed for more than 180kts ground speed. They were probably doing well over 200kts
     
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  9. KE4IKY

    KE4IKY Ham Member QRZ Page

    I was a simulator specialist for years (F-16), yep, know the manuals. I didn't know they had a new one out though, thanks for the reference. I remember the one that also covered Omega, and I think Consolan.

    You also aren't supposed to land at the wrong airport, and that happens also :) and of course the main reason for RSO's (Runway Supervisory Officers) was mostly to let pilots know if they failed to put their gear down, which should happen without help on a routine basis.

    First hand experience with that one :), the only part I blew was that I could have fired the flare guns in addition to the radio call, probably would have set the airfield on fire though.

    Thanks
    Joel
     
  10. W7IMM

    W7IMM Ham Member QRZ Page

    Yeah......it has happened more than I'd like to admit!

    C-141 landed at Great Falls MT instead of Malmstrom AFB MT,
    C-17 landed at Peter O'Knight airport instead of MacDill , (I'm at a complete loss how one mistakes a 3600ft runway for a 11,400ft one in VFR though)

    Southwest 737 landed at the wrong airport in Missouri and more than a few airplanes have landed at Wainright Army airfield AK thinking they were landing at Fairbanks!

    Luckily, I was never one of them! I retired unscathed!!

    In MAC and later AMC it was policy to have the navaids (ILS, VOR, TACAN, FMC etc) dialed up to the landing runway. And if you did, you REALLY had to work at screwing it up!

    The aircrews above didn't have navaids dialed up and had accepted clearances for the "visual approach" when they (thought) had the "field in sight"

    It'll happen again.....
     
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