WAKE avoidance during instrument approaches

Discussion in 'Cleared for the Approach' started by WannFly, Nov 16, 2020.

  1. WannFly

    WannFly Final Approach

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    Last Saturday I was doing some practice approaches and while about 2 miles from the rny tower cleared a big iron to take off and issued me a wake turbulence warning to me (I was planning on going missed and setting up for another approach). To avoid an archer shape hole on the runway, I asked for and got side step to the right and climb to 3000 rny heading (my missed approach instructions as issued to me earlier).

    Which got me thinking, what do you guys do if this was a real IMC approach and you had to go missed in the soup? Would you do something similar ? I dont see much other option
     
  2. denverpilot

    denverpilot Tied Down PoA Supporter

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    In the real soup they likely won’t have you in as close a trail as when you’re VFR and they know you’re doing practice approaches / going missed.

    Have to separate you by wake turbulence class...

    That said... definitely kinda hard to plan to touch down somewhere appropriate in relation to where the other aircraft did, if you can’t see them.

    If you get a real wake warning in solid IMC, it’s a judgement call. If you’re visual, different story...

    Kinda depends on what I’m following and how low the breakout is. And how confident I feel about low level unusual attitude recovery today... ha.

    200 and a half, and I’m behind a 757? Screw it. Going around. LOL. :)
     
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  3. RussR

    RussR Pattern Altitude

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    Real IMC, I don't think the tower would be able to clear someone for takeoff with you that close, so the situation wouldn't come up.

    However, it's been a while and I would have to re-read the rules on that.
     
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  4. WannFly

    WannFly Final Approach

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    interesting, is there a rule for that separation ? in all VFR flight I have done, they just issue one and like go figure it out yourself. I think there was one instance long back when I was flying real IMC approach with a CFII from IAF and they cleared an MD-8 to go to FAF and essentially descend in front of me (I was coming from South and he was approaching from SE). I was doing 90 kts anyway and he was lot faster and I slowed down even more and it wasnt much of an issue. It wasnt hard IMC either, just lots of haze and every inbound was doing the ILS, I was doing RNAV
     
  5. EdFred

    EdFred Taxi to Parking

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    Yeah, they also leave more distance behind heavies.
     
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  6. denverpilot

    denverpilot Tied Down PoA Supporter

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    It’s in the controller regs not ours, but as @EdFred said, it’s why we have stuff like callsigns ending in “heavy”.

    My comment about the 757 was that I believe it was the first airliner that didn’t meet the weight requirements as a “heavy” but it generated so much wake turbulence AND at least a couple of accidents and near accidents for light(er) aircraft following it, that it’s had special separation rules similar to “heavies” for a long time now. Think I remember at least two 182s being flipped on final by the 75. Definitely one, was a CAP 182 in Utah.

    So eventually after the 75 became the oddball that didn’t follow the weight rules the whole thing was somewhat re-vamped to have a few aircraft cross those weight boundaries originally used but be handled as if they were in the higher weight class.

    In other words, different tables nowadays.

    Most... by weight. Some... by “that thing generates a stronger wake than it should for its size”.

    Tim has mentioned the specifics before for his airport. Runway lengths allowed, different visibility, stuff like that.

    In flight the in-flight separation rules apply. Even those aren’t enough sometimes in the right conditions.

    There’s a few YT videos of bizjets in trail of airliners descending on approaches that get smacked around and partially rolled. You also hear crews chatting about it when they see conditions setting up VMC for it to happen at altitude, and asking to move left or right laterally if someone in front of them had their descent stopped and they’re still cleared to descend behind them.

    Just off the top of my head the YT channel “Corporate Pilot Life” has one in the last year or so. I think “Captain Moonbeam” may also have one further back in his collection.
     
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  7. Radar Contact

    Radar Contact Pattern Altitude

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    If you’re simply an IFR arrival, it’s just runway separation. In the case of a heavy departing in from of your FLiB on the same runway, he only needs to be 6000ft down the runway and airborne before you cross the threshold. If they can’t see you in order to provide vis sep for the possible go around then it would be 2 miles increasing to 3 within 1 min after departure. There’s no protecting for the possible missed with wake turb. If you check on at the marker saying low approach, they would then make sure the heavy departure was an appropriate amount of miles or min ahead of you.
    *I didn’t look this up so no references provided. I’m no longer an expert on tower ops.
     
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  8. Jmcmanna

    Jmcmanna Pre-takeoff checklist

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    Like @radarcontact said, the spacing requirement is 2 miles increasing to 3 within one min after takeoff. The 3 miles doesn’t matter if you get an immediate diverging heading. If you were on a 2-mile final while the heavy was rotating at 140 knots (and increasing), there really isn’t going to be a lot in the way of wake turbulence by the time you reach his flight path. Wake turbulence also sinks over time, so by the time you flew the three miles and got to the point where the jet departure lifted off, you’re going to be several hundred feed above where their fight path, and they’ll be several miles ahead of you.
     
  9. SbestCFII

    SbestCFII Line Up and Wait

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    In IMC, you'll get more separation from traffic and wake-turbulence generally wouldn't be an issue.
     
  10. Radar Contact

    Radar Contact Pattern Altitude

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    What do you mean here?
     
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  11. MikeNY

    MikeNY Filing Flight Plan

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    For wake avoidance, a pilot needs to be in visual conditions and have visual contact with the traffic.
    Whereas in IMC, ATC remains responsible for traffic separation and wake avoidance.
    Is this understanding accurate, does it appear consistent with JO 7110.65, or any other thoughts?
    Thanks for help clarifying increased separation requirements in IMC, vs VMC.
     
    Last edited: Nov 20, 2020
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  12. N1120A

    N1120A Pattern Altitude

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    I'm not concerned landing behind an air carrier departure, into the wind. Even if you come down on the PAPI, there is plenty of time to get your plane stopped before their rotation point. If you have to go around or go missed, that's a different story - give me an early turn or whatever. Now, an IMC arrival is a completely different story, and ATC will keep that spacing for you.
     
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