Microburst - Vy or pitch angle?

Discussion in 'Flight Following' started by rt4388, Nov 5, 2018.

  1. Fearless Tower

    Fearless Tower Touchdown! Greaser!

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    The danger of auto throttles when flying near microbursts is that if you get caught in one and experience the period of rapidly increasing airspeed, the autothrottles will pull power to idle. So if that happens, you are at a significant disadvantage when the moment comes where you need to push the power up. It’s that lag that can kill you.
     
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  2. tspear

    tspear Pattern Altitude PoA Supporter

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    Ok. Never flew jets so did not think of that. Does that still apply with newer engines? I recall reading somewhere the spin up speed in the 80s was often approaching 10 seconds while today it is closer to 2 or 3 seconds (new planes of course).

    Tim

    Sent from my SM-J737T using Tapatalk
     
  3. Cooter

    Cooter Pattern Altitude

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    I think the AT guidance will be aircraft specific. Some systems recognize increasing performance wind shear and the will advance throttles to go-around power (with FD guidance) when TOGA is selected.
     
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  4. Kritchlow

    Kritchlow Final Approach

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    In the Bus we just firewall it. That won’t turn off the auto thrust per se, but it will override it.
     
  5. jordane93

    jordane93 Final Approach

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    What are these auto throttles you speak of?
     
  6. Hacker

    Hacker Pre-takeoff checklist

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    At my company, flying the A300, just in the last year our procedure changed to keeping the AP and autothrottle on in a windshear escape maneuver -- which was apparently the procedure recommended by Airbus.

    It amazes me that a decade after they stopped rolling A300s out the doors of the factory, the procedures are still changing.

    That being said, I like Warren's video in the OP.
     
  7. Hacker

    Hacker Pre-takeoff checklist

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    I never understood the "relax" part.

    The stick shaker *is* the max lift AOA, thus being *in* the shaker is producing max lift.
     
  8. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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    Oh, the reason I am told is that the shaker will rattle from stall speed plus 5kts (in this airplane).....right to full stall.
    So you have no way of knowing where you are in that continuum (unless you are sharp enough to refer to the AOA during such an emergency) til a wing falls off and you are plummeting....for reasons other than a microburst.
     
  9. Hacker

    Hacker Pre-takeoff checklist

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    So, the technique is to be right at the front end of it, since it is an "area" rather than a "point".

    Plus, various aircraft have additional things that happen at the actual stall (e.g. stick pusher), as well as there being dynamic indications of stall AOA/airspeed on the gauges, that can help from getting into actual stall AOA or the performance results like wing drop and increased sink rate.

    When I need to get away from the dirt, I'm gonna be living in the shaker...I guess a career of flying fighters at the top end of the G limit, in the double rate and single rate beepers, doesn't have me as gun-shy of living right at that limit than others.
     
  10. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    Yep. If you try to hold altitude in wave, you're pulling the nose up during the downdraft portion, slowing you down and keeping you in it longer. Conversely, in the updraft portion you're pushing the nose down and getting out of it faster. Probably better to ask for a block of altitudes, trim for the right airspeed and just go for the ride.

    Those glider guys are pretty smart about this kind of thing. :)

    It occurs to me that no turns are necessary to be 90 degrees to the wind. It's going straight down, you're flying horizontally, you're already 90 degrees to it.
     
  11. Sluggo63

    Sluggo63 Line Up and Wait

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    Agreed. Here in the 757, if the autopilot/autothrottles are on, we leave them on and let it fly out with WS guidance. If the autopilot is off, we also click off the autothrottles and hand fly the whole evolution with WS guidance provided by the FD/HUD.
     
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  12. NoHeat

    NoHeat En-Route

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    From an Avweb article in 2000:


    Escape Maneuvers...
    Once you are in the grips of a microburst, the maneuvers required for escape may seem extreme, but they are your only hope. Apply full throttle IMMEDIATELY and pitch up to a climb attitude — or an attitude that will arrest your rate of descent. You may have to fly on the edge of a stall — in a jet, you should pitch up to the point of stick-shaker activation — to escape. It's best to think of this maneuver as an escape maneuver so you don't confuse it with a normal go-around or missed approach. This is a far different and more critical maneuver and you are trying to escape danger, not simply abandon an approach. This is not the time to be "smooth and gradual" in your application of power — firewall it! If you escape the microburst you can worry about your engine later!

    ...The Key Is Avoidance
    The key to successfully dealing with microbursts is awareness and avoidance. Be aware of the weather conditions that can cause these powerful phenomena and avoid them at all costs. Remember, an escape maneuver may or may not work. Luckily, thunderstorms are not too stealthy and there are usually ample warnings that they are in the area.

    https://www.avweb.com/news/safety/182986-1.html
     
  13. jordane93

    jordane93 Final Approach

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    Our windshear warning kicks off the AP after 2 seconds in the CRJ. We don’t have a choice. We have to hand fly the escape maneuver.
     
  14. orange

    orange Line Up and Wait

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    I think the lesson here is to stay far away from storms to avoid it all together.

    I was once flying a Cherokee from Hartford, CT back to Farmingdale, NY. I'm guessing I was at 4500 feet since I was going south. Somewhere near Bridgeport, CT, there were some nasty looking clouds. Mind you, I was still very new and didn't know/recognize storm clouds, etc. I was VFR (no FF) so tried to go around one. As I got abeam it, I felt a very strong and quick downdraft and the plane just started sinking. This was a couple of years ago, so I don't remember the facts, but I think I lost something like 800-1000 feet in about 10-15 seconds. The old sphincter muscle got a good workout. Scared the bejesus out of me.
     
  15. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    I'll bet! I'm glad my only encounter with an uncontrollable change in altitude was in the opposite direction (flew into a cloud just as it decided to become a T-storm). Idle power and pointing the nose down into the yellow arc and I gained about 4000 feet in maybe 30 seconds.

    Oddly enough, there wasn't even a bump. The parcel of air I was in just decided to become upwardly mobile, I guess. VSI rose up slowly for a second but then slammed into the peg.

    I sure don't want to experience any of that in the opposite direction. It was scary enough going up...
     
  16. Hacker

    Hacker Pre-takeoff checklist

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    That is certainly an important factor but it is not always possible, especially in scheduled commercial service.

    My airline flies into airports with "windshear advisories" and "windshear alerts" in the ATIS regularly. Different companies have different limits as to what's acceptable in terms of the magnitude of the shear (my company says anything 15 knots or less is okay to fly into), but crews listen up to PIREPs of aircraft landing before them and controllers are good about passing reports from the LLWAS sensors to arriving aircraft, and then make decisions about continuing, going around, holding, diverting, etc.

    So, I've held short of the runway for an hour while arriving aircraft reported experienced airspeed losses/gains of greater than 15 knots on final. I've also gone around (in places like Denver, frequently) when I'm on final and the tower controller says the equipment was reporting windshear at the approach end of my runway. Likewise, I've also held for 30 minutes waiting for conditions to improve, and also just plain diverted to my alternate. It just all depends on actual conditions on that day.

    But, if we are just talking GA flying, then you're right: there's no reason to go anywhere near it.
     
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  17. tspear

    tspear Pattern Altitude PoA Supporter

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    Many years ago, flying United back from Pheonix to DC, our flight was canceled so we re-booked through Denver. Ended up on 757 I think, and it was the most exciting takeoff in a passenger plane I have ever been in :D
    Listening to channel 9, ATC, you hear a couple planes landing with beeping in the background as they report wind sheer at roughly 500ft AGL causing a 50-100 altitude loss.
    The two planes in front of us decided to return to the terminal. Our pilot I think was ex-military; he gets on the PA and says the takeoff is going to rough, but once at altitude should be a smooth ride. He also said we will be close to the ground a bit longer than usual, this is to have more speed before we hit the speed bump (I do not every think I will forget that description of wind sheer as a speed bump).
    So we pull onto the runway, he stands on the brakes and brings the engines to full power (or4 what sounds like it, and I have not see that in decades). And then we are off down the runway, we lift off, and then seem to pause there for a few seconds at what appears to be just off the ground and get faster as the gear starts to come up. Then nose up, way above any angle I have ever felt in a commercial airline except Aeroflot in Russia back in the 90s. Just as you hear the loud thunk from the gear doors closing we hit the speed bump. The whole plane shook, and sort of felt like it stuttered, and then just climbed on normally. One of the shortest east bound flights I have ever had.

    Tim
     
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  18. Challenged

    Challenged Pattern Altitude

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  19. Sluggo63

    Sluggo63 Line Up and Wait

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    Yeah, if you think about it the places you are most likely going to encounter WS are also the places that you’re most likely to be hand flying anyhow. Takeoff and approach. Although I will say that if there’s a likelyhood that I’m going to encounter wind shear, I’m turning the AP on sooner on takeoff or leaving it on longer on approach. I’ve hand flown enough wind shear recoveries to know that probably the best thing I can do is let the automation fly it and monitor.