Visual Approach Obstacle Clearance

Discussion in 'Cleared for the Approach' started by boydbischke, Dec 24, 2017.

  1. boydbischke

    boydbischke Filing Flight Plan

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    Merry Christmas all! I'm an instrument rated private pilot and just landed as a passenger on an airline flight to KBIS. There was a scenario in the flight that made me wonder.

    There are two towers that are about 1 mile apart and are 3392 MSL and 3425 MSL (so the towers are about 1200ft tall) about 10 miles southwest of the airport. The pilot was vectored by approach to a path directly toward these towers and asked to maintain 4400 MSL, which would be 975ft above the taller of the two.

    Then about 2 miles before these towers the Pilot was cleared for the Visual and began descending. The pilot was within 0.2 miles horizontally of the 3392 MSL tower and within 0.8 miles horizontally of the 3425 MSL tower. The plane altitude would have been about 4100 MSL at the time of crossing through, and so was within 675 feet of one and 708 feet of the other.

    It struck me as odd that the pilot and controller would come as close to these towers considering the next closest obstacles in the area are probably 1,000 ft lower. It just seems like if somebody made a mistake, it would would be much more likely to result in a tragedy, than if they had avoided the area.

    So, a few questions for the experts in the mix:
    1) What are the requirements for an approach controller in terms of maintaining obstacle clearance when vectoring?
    2) Are there any requirements related to obstacle clearance on a visual approach?
    3) Does this seem like an unnecessary risk, or is this type of situation very normal?

    Thanks
     
    Last edited: Dec 24, 2017
  2. Velocity173

    Velocity173 Final Approach

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    1) Minimum of 3 miles or 1000 Vertical (2000 mountainous). Vertical discontinued once passed. What device did you observe this position / altitude on?

    2) none, although ATC could give a shout out (safety alert) if they see fit.

    3) No. Yes.
     
    Last edited: Dec 25, 2017
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  3. midlifeflyer

    midlifeflyer Final Approach

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    1) none. The pilot was cleared for and accepted a visual approach. That means the weather was better than 1,000 and 3 and the pilot had the airport in sight. Unless the pilot was instructed to follow another aircraft the pilot didn't have in sight, vectoring and ATC responsibility for obstacle clearance was done.

    2) the pilot Is responsible for obstacle clearance. Although still under IFR, it's just the same process used by a student pilot when approaching to land at an airport.

    3) the 0.2 mile (if accurate) with no significant vertical would be too close for my taste; 0.8 mile sounds pretty normal for some pilots, less so for others,
     
  4. mscard88

    mscard88 Touchdown! Greaser!

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    :yeahthat: Here in BHM there's a mountain ridge with 3-5 tall towers, a couple 2000' , just east of the airport. Right downwind for runway 6 if you're on a visual approach one just waits to get by them and turns a right base for 6. I've flown it many times flying from ATL-BHM.

    http://155.178.201.160/d-tpp/1713/00050IL6.PDF
     
  5. Hank S

    Hank S En-Route

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    Sounds like downwind for 8 back where I got my license (KHTW, no approaches). Fly downwind outside the parallel ridgeline, keep steady when the runway disappears, judge when to turn base when the runway reappears with an eye on gaps in the ridgeline. In my Mooney, I always went one gap further than in the 172 . . . Out with one CFII, I had to prove that I couldn't land from the "normal" gap, went to idle, full flaps, slipped on final and everything--not even close!
     
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  6. aterpster

    aterpster Pattern Altitude

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    Answer 1: Assign not less than the MVA.
    Answer 2: Whatever the crew believes is safe and is not careless and reckless.
    Answer 3: Depends. Was it daytime? Did the controller point out the antennas? How familiar is this airline with this airport? (third is a rhetorical question)

    Attached is the pertinent portion of the BIS MVA chart. MVAs are required to have not less than 1,000 feet of vertical clearance and 3 miles lateral clearance. FCC licensed antennas are an exception. They may have as little as 950 feet of vertical clearance. The 4,400' MVA has 975' in this case.
     

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  7. boydbischke

    boydbischke Filing Flight Plan

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    All helpful information - thank you all for the education. To answer the questions:

    The altitude and position came from the track log on flight aware. I also saw it on iPhone GPS with ForeFlight.

    It was a night flight.

    The controller did not give a safety alert as per ATC archives.
     
    Last edited: Dec 25, 2017
  8. mscard88

    mscard88 Touchdown! Greaser!

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    Night makes no difference as long as the crew is visual and knows the towers are there. Usually ATC will query the flight if they're familiar with the towers. They do at BHM.
     
    Last edited: Dec 25, 2017
  9. midlifeflyer

    midlifeflyer Final Approach

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    Then the towers were probably even more visible than the are in daytime.
     
  10. Clark1961

    Clark1961 Ejection Handle Pulled

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    One thing about it is that the towers are unlikely to move much. Airline flight = pilots familiar with the airport = no biggie 99.9% of the time (usual made up statistic).
     
  11. Ravioli

    Ravioli En-Route

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    So there I was violating a regulation and it got me to thinking about whether the pilot was violating any regulations too.
     
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  12. mscard88

    mscard88 Touchdown! Greaser!

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    You're not in violation if the FAs don't catch ya! ;)
     
  13. Ravioli

    Ravioli En-Route

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    Or some Johnny Helper passenger. I've got a few prime examples of that dysfunction.
     
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  14. Larry in TN

    Larry in TN Line Up and Wait

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    Many airlines now allow passenger use of GPS devices inflight. You just have to have the cellular functions turned off.
     
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  15. Ravioli

    Ravioli En-Route

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    Oh... so the cross checking to the FlightAware happened after landing, not using the cellular? The in-flight WiFi would typically have been shut down by that time.
     
  16. luvflyin

    luvflyin En-Route

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    Be sure and have the volume turned down if you're using FF or some app that gives out audible alerts if it thinks the pilot is descending to fast and startles the passenger sitting next you. Yeah, that happened to me.
     
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  17. luvflyin

    luvflyin En-Route

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    So FFC antennas can 'round' at the halfway point, 50 feet. I was looking for the thing where if an obstruction was 'isolated' with a 3 mile radius circle, the rounding point was at 60 or maybe it was 80 feet. Is that still around for non FCC antenna obstructions?
     
  18. Cap'n Jack

    Cap'n Jack Final Approach

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    Which violation do you mean?
    Assuming the FCC reg about communicating with cell phone towers, on some airlines, they let passengers keep their tablets and other small electronics on, so long as the cellular functions (phone and data) are off. Since the use of ForeFlight was mentioned, I'm assuming the charts were pre-loaded so no communication with the tower was needed.
    If you mean some other regulation, apologies for my misunderstanding
     
  19. midlifeflyer

    midlifeflyer Final Approach

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    LOL. I keep my earbuds plugged in so no one else can hear. But I often do get a chance to give a ground lesson (is an in-flight ground lesson an oxymoron?) to the passenger in the seat next to me.
     
  20. Ravioli

    Ravioli En-Route

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    Post #15 might explain a bit of my question
     
  21. Larry in TN

    Larry in TN Line Up and Wait

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    I have no idea when he checked FlightAware. The context led me to believe it was after the flight but he wasn't specific.

    I fly 737s for United. Our wifi is available from pushback until arrival at the destination gate so it would normally be available during approach and landing. Other fleets, and other airlines, may differ.
     
  22. Hank S

    Hank S En-Route

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    I use Avare, not FF, and it works fine in flight (my plane or giant aluminum tube) with WiFi off and tablet set in Airplane mode. I do need to download / update the charts beforehand, though. Turn off everytning but the power, it works great as long as it can pick up the weak GPS signal. NOTE: my tablet is wifi only, not cellular.

    So what regulation(s) am / are I violating???
     
  23. Larry in TN

    Larry in TN Line Up and Wait

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    None.
     
  24. Ravioli

    Ravioli En-Route

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    Probably none. The question is how/when the OP got Flight Aware data to compare to what he was seeing on his handheld.
     
  25. Hank S

    Hank S En-Route

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    My guess would be later, like when he listened to the ATC tapes . . . .
     
  26. Ravioli

    Ravioli En-Route

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    I'd offer to @Larry in TN that the last thing needed in a professional pilot's life is a bunch ppl's monitoring every twist and turn in their iJunk for further report/discussion after the flight.

    Could be worse than being LoJacked by a "significant other."
     
  27. Cap'n Jack

    Cap'n Jack Final Approach

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    I see- I also looked at post #7. There is enough ambiguity in wording that I read it differently. I understand your question now.

    I was just geo-tagging some pictures and got a reminder that positions taken from a GPS within a vehicle might be more than just a little off- ForeFlight positions measured within a jet through those tiny windows may not quite correspond to the actual jet position.
     
  28. Larry in TN

    Larry in TN Line Up and Wait

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    I've been an airline pilot since 1990. If a passenger wants to talk about something they saw or heard during the flight I'm happy to explain it to them.
     
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  29. Ravioli

    Ravioli En-Route

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    In this case, the guy is asking SGOTI. Quite different than asking you at the cockpit door during deplaning. And much more different than asking people who will ask more questions and review more data if it becomes "an official inquiry."

    Just doesn't sound like a good thing to me. But you're the professional.
     
  30. midlifeflyer

    midlifeflyer Final Approach

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    I'd offer that professional pilot doesn't give a crap and would treat it the same way as passengers griping after a bumpy flight to their Facebook friends.
     
  31. aterpster

    aterpster Pattern Altitude

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    Typically, an isolated obstacle is a single FCC-licensed antenna. If it is a mountain peak, for example, 200 feet of assumed adverse obstacle (AAO) must be added to the elevation of the peak. If it were a very tall building, the actual elevation of the building could be used, plus its accuracy code. But, no rounding down except for FCC-licensed antennas. This is why there are lots of tall towers that are XX49.
     
  32. luvflyin

    luvflyin En-Route

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    Hmm. I was sure there was a 'rounding point' at either 960 or 980 for something.
     
  33. Palmpilot

    Palmpilot Touchdown! Greaser!

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    I don't know about the FCC, but in general If you're rounding off to the nearest 100 feet, the standard rounding rule in mathematics is that 950 or above would round to 1000 feet, and less than 950 would round to 900.
     
  34. aterpster

    aterpster Pattern Altitude

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    Could have been when MVA charts were done in a haphazard manner. That all changed perhaps 10 years ago when NBAA pointed out all the errors in MVA charts that used to be drawn on sectional charts by the facilities. The result was better standards and a computer design system similar to that used for instrument approach and departure procedures.
     
  35. aterpster

    aterpster Pattern Altitude

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    In the World of TERPs there is no rounding down. The FCC-licensed antenna rounding down is for MVA charts only. No rounding down of those antennas for IAPs or PDs.
     
  36. aterpster

    aterpster Pattern Altitude

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    There's no requirement in the 7110.65 to do that. At BHM it is likely local policy.
     
  37. luvflyin

    luvflyin En-Route

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    Yeah. It was awhile ago. It would have come from the days of building MVA maps from sectionals.
     
  38. mscard88

    mscard88 Touchdown! Greaser!

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    I know it's not in the .65, was only stating that BHM asks if you're familiar, or in sight, works great as no one has hit them. ;)
     
  39. aterpster

    aterpster Pattern Altitude

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    I didn't know until I looked it up. Seems like another broken chain in the system.
     
  40. aterpster

    aterpster Pattern Altitude

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    This thread got me to looking at all the obstacles around Bismarck. On a clear night, there must be red and/or flashing antenna strobes all over the place.