Training update....with a question ? | FerrariChat
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Training update....with a question ?

Discussion in 'Aviation Chat' started by FERRARI-TECH, Nov 4, 2012.

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  1. FERRARI-TECH

    FERRARI-TECH Formula 3

    Nov 9, 2006
    1,677
    Los Angeles
    Full Name:
    Ferrari-tech
    #1 FERRARI-TECH, Nov 4, 2012
    So today i got in a bunch more landings, and for sure they are better and more consistent, so I'm happy about that.
    My instructor had intended for today to be pattern work, more solo time and then some solo work in the practice area, but winds at Van Nuys would not allow that, so off to Oxnard we go..
    We get to Oxnard and winds are 7-10 on the nose on the ground and about 14-20 in the pattern, so crazy tail winds on the down wind..always fun, but i was happy with the way things where going, we did a few landings with the head/cross winds, then my instructor said one more like that and you can go up on your own for 2 or 3, then in the down wind, the tower changes the runway from 070 to 250, i make the right 180 to enter a right pattern, for 25 , then obviously have silly tail winds, and wind shear when landing 25. We did a couple of closed circuits for 25, and i Told my instructor after the first one, "you are not getting out here"
    My question here is knowing the wind conditions, With 14kts on the tail on final , wind shear at 300ft, why would the tower put you in that position ?
    Everyone else started calling in the wind shear, and difficulty with winds on landing !

    I understand that KVNY has to compromise its best solution because of the class C for Burbank, but why would Oxnard ( which is in the open ) change and make it harder, you might even say more dangerous ..All part of the training process i guess, but seams counter intuitive to my little brain !

    Any insight to that thought process ? and how do you get 172 with full flaps power at idle to desend with a 14-20kt tail wind..LOL crazy but fun..
     
  2. LouB747

    LouB747 Formula 3

    Apr 8, 2009
    2,123
    Huntington Beach, CA
    Full Name:
    Lou Boyer
    #2 LouB747, Nov 5, 2012
    Takeoff and landing runways are determined by the wind direction on the ground, not aloft. While these are typically the same, with the wind speed increasing with altitude, sometimes the wind is blowing a different direction at altitude. I'm not sure I'm reading your post correctly, but if I am, then you had a tailwind until around 300 ft or so, then shear, then a headwind for landing. Believe me, that's the best of the 2 possible scenarios. Imagine having a nice headwind until 300 ft., then a tailwind on landing. That shear at 300 ft. would cause your airspeed to drop. A 15 kt. tailwind to say a 5 kt. headwind would be a 20 kt. shear. Imagine your approach speed of around 70kts. in a 172 decreasing to 50 quite quickly. That's just about stall speed.

    Your descent rate is the same no matter the wind direction. But as you say, it's harder to get down with a tailwind as your descent angle flattens. You can start your descent earlier to compensate. If that's not possible and you become high, you can always slip it in. I'm not sure if you're been taught slips yet. And I don't remember if slips with full flaps in a 172 is recommended. That said, I've done plenty of them. It's a good way to lose altitude fast. Basically you cross control (ailerons one way, rudder the other) to slip and fly sideways, exposing the whole fuselage side to the wind. A lot of drag is created, forcing you to push the nose down to keep your airspeed. It's a lot of fun too!

    I once put a 747-200 in a full slip on approach at around 1000ft. Not because I had to, just to do it. Cargo plane, no passengers... As expected, it created a lot of drag and took quite a bit of power to stay on the normal glide path. After American Airlines lost the tail off an Airbus a few years back using "excessive" rudder, most guys (me included) don't really use the rudder much except for crosswind landings.

    Anyways, I hope this answers your question. Without being there, it's hard to really say. But ground winds control the runway, not winds aloft.

    Lou
     
  3. FERRARI-TECH

    FERRARI-TECH Formula 3

    Nov 9, 2006
    1,677
    Los Angeles
    Full Name:
    Ferrari-tech
    #3 FERRARI-TECH, Nov 5, 2012
    Lou, thanks for that, It makes more sense when explained that way, I think the wind on the ground had changed, but not that much. It was still on the tail on the ground, although it was more cross wind than tail. We didn't have any noticeable shear when we were using runway 7 but when we switched we got it, my instructor was a little confused why they changed it also. I have done side slip landings, and got to practice more of them yesterday LOL, fun as you say but a little disconcerting at first, all of the joys of learning i guess..
     

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