Being in close proximity to Mam Tor, Lord's Seat, Rushup Edge, Treak Cliff and Longcliff, Rowter Farm has a relevance to all these sites.
The landing field at Rowter is the large triangular field to the West of the farm complex. It is bounded on its East side by the driveway from the main road.
It is sometimes used as an "over the back" option when Lord's Seat is flyable (that's planned, as opposed to running away if blown back). It can be used from Rushup if you can keep height and push into wind.
It's also a landing option from Mam Tor, Treak Cliff and Longcliff. If trying to avoid going to the bottom landing field, it may be a better option than Windy Knoll, because...
Windy Knoll is often seen as a benign place, and when landing there from good soaring on Rushup Edge, it most usually is.
Using Windy Knoll as an option for landing from Mam Tor in an Easterly - there is a high chance of rotor behind the spine that bounds the landslip face. This should only be attempted by experienced pilots fully aware of \ briefed on the risks (and how to avoid them) and prevailing conditions.
Using Windy Knoll as an option for landing from Treak Cliff in an Easterly - there is severe rotor behind Treak Cliff - you need plenty of height (site guide suggests the height of Mam Tor) to get over this rotor to reach Windy Knoll.
For all the above sites, the more Northerly component the wind has, the more the risk increases that the whole of Mam Tor and Rushup Edge will generate rotor directly on to Windy Knoll. These conditions are extremely dangerous, and you should not try to land at Windy Knoll - go to Rowter Farm (if height allows) or the bottom instead.
(Note that the Castleton valley may effectively funnel the wind, giving the impression that it is more Easterly than it actually is.)
The attached pictures are of the areas mentioned above - to give a general idea.
Caveat - it's doubtful anyone really knows exactly how far areas of rotor stretch back from that which generates them, or how high they reach. The pictures are just an aid to understanding the words. It's a complex area and there are risks - risks that change according to the conditions at any given time. There are far too many variables for simple pictures & words to convey & cover fully.
You, as the pilot in charge, make the decisions regarding your flight plan \ conditions \ risks \ your ability. You should gather as much information as you can, from a range of sources, to enable you to make informed choices.
There are no definitive "this is what to do every time and you'll always be safe" rules. There can be rotor off that spine. There can be rotor out the back of Treak. Windy Knoll can be very dangerous.
Fly Safe
SO
Thanks for the post. Hopefully this will prompt pilots to consider safe landing options and the effects of rotor at our sites. Is Bradwell bottom landing field safe in strong winds? What about flying at Bradwell when the wind is WSW? What areas on Eyam are subject to rotor? Rotor and associated pilot error is a significant cause of accidents.
Lord Seat. Join the club Join the fun. https://youtu.be/3NbOOv4LQMM
Windy Knoll & Rowter farm Landing Field, see attached file. Personally after my friend Neil died in the field on the left side at the top of the Winnets pass Road. I think approaching Rowter from Long Cliff or the South end of Treak over Winnets pass Could be doggy.
Facebook post by Gordon Rigg
Reposted from Facebook (always good to post here stuff gets lost on FB)
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I should add, obstacles unwind shed vortices that spill off and travel down wind. They vary in size and frequency and occasionally there is a bigger more violent one.... they diminish and smooth out and eventually die away. What this means is if you are a bit close to the thing that makes it rough, you might well have a nice smooth landing. But it's a game of chance, and it might eventually hit you with a big one. So you must play safe and make your judgement. If you think it would be iffy in one landing place, but you see someone have a nice landing there, they might have been lucky, you landing there in the past might have been lucky.It is worth walking these places and feeling the wind there. You can feel.the gustiness and the sudden calms,.or even wind reversals when the rotor comes. Go and have a walk about when it's a bit too windy and you are waiting for it to drop.
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Agree, great postGordon
. It seems some pilots are pushing the limits of the top speed of their wings and conditions they launch in and history is repeating itself with paragliding. Twice the wind speed (10 to 20) four times the possible turbulence (in the air or while landing) worth remembering.
Mark Busby
"I believe, despite the wind direction being NE yesterday (26/06/2021), there were still pilots who risked landing in Windy Knoll.
Why, when you know full well that there will probably be some kind of wind shadow or rotor there, don't people err on the side of safety and land in cleaner air?
The club now pays so that we can land at Rowter without having to hike up to the farm house and pay a quid - it is only a couple of hundred metre's walk to Windy Knoll from there...
Why become a statistic?"
Gordon Rigg
As wind increases vortices will begin to shed and will be powerful enough to persist some distance down wind.
So in stronger winds there will be randomly periodic horrible gusts persisting much further down wind of obstacles.
In the case of Mam tor land slip edge for example, this is compounded by convection in strong sun. So it's a double whammy. Thermals building and rising up the lee side and breaking off will drag a wind fueled vortex tail behind them across windy knoll in a north east wind.
Wind over a fairly round hill.
In lighter wind the flow will stay attached and it is safe to land in the lee. As the wind increases it has too much momentum to follow the slope and detaches, so turbulence forms in the lee.
As wind increases the turbulence becomes more violent, and persists further down wind.
The stronger the wind is, the more careful we must be about what is up wind of us when we land.
I believe this follows a square law same as parasitic drag. So twice the wind means 4 times the energy in the turbulence... So it goes 4 times further down wind.
I will land in windy knoll in an easterly in 25 mph. In 40 mph probably the turbulence from the edge of Treak will persist into that landing field...
Because some of the turbulence is a periodic vortex shedding, it can become a lottery. Maybe every tenth glider gets slammed into the ground.