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Thread: Effects of wind shear

  1. #11
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    Effects of wind shear

    But its Scotland , not a real place ;-)

  2. #12

    Effects of wind shear

    Grateful for the observations chaps, and thanks for kind wishes.

    One message I take is that in an SSDR with a highish stall speed it would be good strategy to have airspeed in hand. It is however easy to balloon an SD1 because of the difficulty of getting airspeed within a critical zone before flaring and settling due to lack of airframe drag/slippery design and major ground effect from ultra-low wing. Just a few surplus mph will muck things up. For me the other deterrent factor of surplus airspeed would be the short strip at 280 meters or so, so a critical touch down point.

  3. #13
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    Effects of wind shear

    Rick

    Enjoy the plane and the challenge when it returns.

    I am sure you will find it one of the best experiences of your life getting to grips with your new toy, it looks like a lot of fun and if I had some money would be on my toy to have list.

    It took me 70 hours to consistently nail the Chaser which was the best thing I have done for a long time, lots of sideways out of control scary moments which took a bit of managing as I acquired the skill, all in easy stages, mind that was after a twenty year lay off so was a bit rusty ;-)
    I even got to brush up my engine failure practice.

    Fly safe

  4. #14

    Effects of wind shear

    hullo again Rick and returning to text of original post, there is the subject of calculating wind at circuit height using GPS/ASI.........whatever the aircraft track was at the time of your calculations, you would know only the headwind/tailwind component speed along that track at that height........it wouldn't inform you the actual wind vector, at any height. Hum,ho, is that right ? (I don't know).

    I suggest that circuit height figure might just give an idea as to perhaps the best direction in which to attempt to land but not of any value as to what to expect on short final approach.
    I have not read any words about a windsock so I presume there was not one there. As to what we might learn from this accident, you have written a few pointers today at 0958hrs.
    There is also a saying..."set yourself up for for success"......and I turn my thoughts to how to do that. Well, there could be a pre-flight search for forecast surface wind at the landing spot, there could be an inflight search for nearest METAR, there could be a search for smoke indications in the immediate area, there could be a mobile phone call to a nearby contact, e.g fellow pilot, farmer, nearby garage, etc for local wind info. In the absence of any definite wind info and faced with the prospect of approach to land to a very short runway, there is the possibility to utilise the preplanned alternate destination.

    And so on.

    Rick you have written the idea to have adequate airspeed in hand on the short final, but mitigated by the need for the right speed at point of touchdown. With benefit of hindsight would you have handled the circumstances surrounding the accident any differently?

  5. #15
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    Effects of wind shear

    Whitehill Farm is too short! :-)

  6. #16

    Effects of wind shear

    Patrick Burns wrote: hullo again Rick and returning to text of original post, there is the subject of calculating wind at circuit height using GPS/ASI.........whatever the aircraft track was at the time of your calculations, you would know only the headwind/tailwind component speed along that track at that height........it wouldn't inform you the actual wind vector, at any height. Hum,ho, is that right ? (I don't know).

    I suggest that circuit height figure might just give an idea as to perhaps the best direction in which to attempt to land but not of any value as to what to expect on short final approach.
    I have not read any words about a windsock so I presume there was not one there. As to what we might learn from this accident, you have written a few pointers today at 0958hrs.
    There is also a saying..."set yourself up for for success"......and I turn my thoughts to how to do that. Well, there could be a pre-flight search for forecast surface wind at the landing spot, there could be an inflight search for nearest METAR, there could be a search for smoke indications in the immediate area, there could be a mobile phone call to a nearby contact, e.g fellow pilot, farmer, nearby garage, etc for local wind info. In the absence of any definite wind info and faced with the prospect of approach to land to a very short runway, there is the possibility to utilise the preplanned alternate destination.

    And so on.

    Rick you have written the idea to have adequate airspeed in hand on the short final, but mitigated by the need for the right speed at point of touchdown. With benefit of hindsight would you have handled the circumstances surrounding the accident any differently?
    There is no windsock at the field. Circuit height was 500 feet or lower. Preflight check showed Cambridge EGSC were giving 12 knots from 240 at surface, runway was 21. Landed about 25 meters in from R21 threshold.

    Hindsight view: I would have come in with 10 mph more air speed and be ready for a go round if balloon takes place. I have made 2,000+ landings at my field and have never encountered these conditions before.

  7. #17
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    Effects of wind shear

    Sounds like a difficulty that is hard to square even for an experienced pilot like yourself; well meant advice is great but if you need speed in hand in case of an unexpected sudden reduction in headwind, and also have a short strip then the two factors are mutually exclusive.

    Wish I could contribute constructively, other than express that glad you're in one piece and shame about that beautiful machine; curious, was the 55 knots GPS or ASI sir? If GPS then if ground was flat calm, then you'd think you would be 15mph above stall.

    Cheers

    Kev

  8. #18

    Effects of wind shear

    Kev Armstrong wrote: Sounds like a difficulty that is hard to square even for an experienced pilot like yourself; well meant advice is great but if you need speed in hand in case of an unexpected sudden reduction in headwind, and also have a short strip then the two factors are mutually exclusive.

    Wish I could contribute constructively, other than express that glad you're in one piece and shame about that beautiful machine; curious, was the 55 knots GPS or ASI sir? If GPS then if ground was flat calm, then you'd think you would be 15mph above stall.

    Cheers

    Kev
    55mph ASI over the threshold, but I wasn't able to look at ASI just before the drop though

  9. #19

    Effects of wind shear

    Are we interpreting the effects of inertia correctly in this situation?

    We fly an approach at 60mph into a headwind of 15mph so our groundspeed is 45mph. We suddenly reach the layer of air on the ground which is at 0 mph relative to the ground so now we have a groundspeed of 45 mph and an airspeed of 45 mph.

    We loose lift and the plane turns sharply downwards. The plane accelerates and increases it's speed relative to the ground and the air.

    Surely the less inertia (mass) the plane has the more quickly we will recover airspeed and the ability to flare as we reach the ground.

    Laurie (2)
    (who has had this happen twice)

  10. #20

    Effects of wind shear

    I have had this happen to me twice. As many of you will know I fly a Quik in Competition. This involves trying to land and come to a halt in a 100 metre long box. In order to do this successfully I need to fly an approach at 55mph. At 55mph the Quik is uncomfortably close to a stall. If I come in at 60mph the approach is much safer and more controlled but it means that I touch down too fast and without a front wheel brake I cannot bring it too a halt in 100 metres.

    If you look at the results from the recent World Microlight Championships at Popham you see that in the only dedicated engine-off landing task we scored maximum points and were joint first on that task. For every other scored landing which was appended to the end of a navigation task we scored zero (because we ran out of the front of the box). For the engine-off landing task I was prepared to bring in it at 55mph. When I was tired at the end of a 2 hour Nav task I was not prepared to attempt that and we came in at 60 (or higher when it was really windy on Tuesday) and we could not stop.

    The 2 times I have crashed it doing this; one was practicing with “Concrete Mary” in the back at home when I flew a curving base approach in too high a wind at too slow a speed. I crossed over the hedge and immediately lost lift and got dumped into the ground and bent the forks and the pod.
    The second time was last year in Poland when there was zero wind. We flew an engine-off landing task and I actually tested the stall speed as we climbed up to 1000' (45mph indicated). I thought on the basis of this that I would be safe coming in at 55mph in zero wind so that's what we did. We were fine until we reached a layer of very hot air adjacent to the ground and the plane just fell out from underneath us and we hit the ground very hard.

    Everyone I speak to about this just says “well you can't do that 2-up in a Quik” but I keep trying. I think actually a front brake is the answer.

    Laurie (2)

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