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Landing site Selection


Patrick1
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Hi All,

I'm relatively new to the sport and am just finding my feet, I have a question on my recent landing site selection.

I was flying on Wednesday evening in pretty benign low wind conditions, after a relatively short flight, about 10 minutes, I landed on a cricket pitch with plenty of space. Happy to report is was a sound landing and no problems. However, I over-flew my anticipated landing spot by about 30 metres which meant I was landing within the rotor shadow of a tree line. Basically, I was landing into wind with trees in front of me.

I wanted to ask how dangerous this is? It was almost still air so the risk would have been reduced but if I did the same thing again in a slightly stonger wind, it strikes me that I could risk an asymmetric frontal collapse as I enter the rotor shadow when I'm pretty low?

I'm content that I should always avoid landing in rotor zones - that's not in question but I'm interested in measuring how much risk I'm exposing myself too in this context?

Before you ask, I have trained with a BHPA instructor and have also emailed him to ask advice and yes, will be doing some continuation training over the summer.

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Hi Patrick,

It all depends on wind intensity.

If it's still air or pretty still, you can reasonably be safe in landing close to potential rotor spots.

It is when the wind starts to pick up that you can be in troubles. How much and what does that mean? It all comes with experience, but if you are unsure of your judgement while in the air, its simply better to avoid such landings.

The good thing about this sport is that you always have a second chance, if you find yourself over.flying the target, push the throttle, get some height and try again, or choose a nearby field and be prepared for a little walk back to the car.

Regards,

dave

Hi All,

I'm relatively new to the sport and am just finding my feet, I have a question on my recent landing site selection.

I was flying on Wednesday evening in pretty benign low wind conditions, after a relatively short flight, about 10 minutes, I landed on a cricket pitch with plenty of space. Happy to report is was a sound landing and no problems. However, I over-flew my anticipated landing spot by about 30 metres which meant I was landing within the rotor shadow of a tree line. Basically, I was landing into wind with trees in front of me.

I wanted to ask how dangerous this is? It was almost still air so the risk would have been reduced but if I did the same thing again in a slightly stonger wind, it strikes me that I could risk an asymmetric frontal collapse as I enter the rotor shadow when I'm pretty low?

I'm content that I should always avoid landing in rotor zones - that's not in question but I'm interested in measuring how much risk I'm exposing myself too in this context?

Before you ask, I have trained with a BHPA instructor and have also emailed him to ask advice and yes, will be doing some continuation training over the summer.

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Sounds like you already took your lesson from the event.

Rotor may even have been the cause of your overshot landing as the headwind fell off and you entered ground effect.

It's not that rotor will smack you from the sky, but that it has no predictable nature within it.

Air can go down, up, sideways and every combination with varying degrees based on steady wind, gusts and the mixture of the two.

Always best avoided, but mountain wave is rotor - just on a scale that has predictable edges.

Sometimes it is better to pick a "windshadowed" spot then stay in a place where thermic turbluence is more likely to remove your support from an unrecoverable height. The best answer is the one that works for you and the conditions you're dealing with. Your latest risk paid off, and still is as you're learning more from it actively.

Good on ya.

Gratuitious link with pictures:

http://www.paraglidingforum.com/viewtopic.php?p=184959

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My general rule of thumb in light to moderate wind is to allow a minimum distance of 5 times the obstacle height for landing, and at least 10 times obstacle height for take off. This seems to work well for simple obstacles such as tree lines or buildings. The difference is because rotor affecting your wing on take off might extend your launch, bringing you closer to the obstacle.

In stronger winds I seem to recall that rotor effects quadruple as wind speed doubles, so a much greater margin is required.

Sounds like your overshoot was just the pronounced wind gradient when the light headwind disappeared below the tree line. Even if there had been rotor you would not be in much danger of a collapse. The worst that usually happens is a slight swing or roll which can knock you slightly off course. The main danger here is in overcorrecting which can cause a swing into the ground, so usually better to go with it and stay hands up for a strong flare even if you go a few degrees off course to the wind.

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