Dartmoor Gliding News-Saturday 24th February 2018

After a mostly dry week the airfield is finally drying out. Watching the forecast over the last few days revealed a potential for easterly winds and the formation of wave. The sounding forecast showed a sharp inversion at about 925 hpa ( the airfield was at 968 hpa today so the inversion was at about 1290 feet above the airfield ) and although the wind strength was not really increasing with height, the profile was really encouraging.
The soundings forecast for 1300 gmt
Early in the day there was 8/8th cloud but this cleared away leaving a blue sky day. The only cloud visible were some wisps indicating areas of wave rotors. At the east end of the airfield the windsock was hanging mostly limp with occasional gusts but experienced Dartmoor pilots know that on a wave day it often looks like this as the rotor back washes that end of the runway  So game on.

The Zugvogel 3B ready to fly
 This was a licensed pilots only day. Most of the assembled members were preoccupied with tasks around the airfield but the Zugvogel 3B syndicate ( Alan Carter, Roger Green and myself ) were determined to fly so we woke the glider from it's winter slumbers and reasonably quickly had it assembled and ready to fly. Allan Holland very kindly offered to drive the winch for us.

The other syndicate members bravely nominated me to fly first. I ensured that I was well strapped in and that everything was secure ( I had an idea of what might happen next ) and off I went. The ground run was a little long ( windsock still limp ) and the initial climb was unremarkable. At about 500 feet all hell broke loose as I flew into the rotor and keeping the glider climbing correctly took a lot of control input. Releasing the cable at 1000 feet the glider began a wild dance through the rotor. Don't fight it Stephen, work with it.

Thankfully I was climbing in this rough air and suddenly at 1200 feet the air went completely smooth. This is WAVE. After a short, slow climb, I made my first mistake. Convinced that the climb rates should be better than this, I pushed forward to the east looking for what I thought was going to be the primary wave. In my defence, remember that the sky was blue so I had no visual references to help me. I flew into violent rotor and deeply sinking air and had to do a quick about turn and head for the airfield arriving adjacent to the runway at 800 feet convinced that I was going to have to land shortly.

This is where fate took a hand in the events and I flew into very strong rising air. Turning steeply I centred what turned out to be a wave enhanced thermal bubble which propelled me skywards with the variometers off the clock. Four circles later I was passing 1800 feet when the air went smooth again. Turning south across the wind I followed the wave bar in smooth lift and promised myself to climb first before going exploring again.

Looking west towards Dartmoor
Climb rates were not remarkable, probably averaging a couple of knots and ultimately I topped out at 4800 feet. The visibility was not very good with some haze but this lent some enchantment to the view, which I know so well, with the sun shining brightly off the Tamar estuaries which would have otherwise been invisible through the haze.

Yours truely relaxing in the sun
( the left strap looks a bit dishevelled after the rotor )
The hazy view with this thin cloud layer quite invisible from the ground
I had promised Roger that I would be back in an hour so it was time to go. There was an area of smooth air with no lift just to the south of the airfield so it was here that I started my decent. With the glider at 60 knots with the airbrakes fully deployed, I flew large lazy circles down through the mostly smooth air. At one time I flew into the rotor again and even with the airbrakes fully out the glider started climbing strongly once more. Turning away soon sorted that out and after a few more circles I was able to start a circuit from what would normally be considered ridiculously high, but in these conditions you need to maintain lots of energy ( for energy read height ) to cope with the rotors that always populate the circuit area ). The circuit was very rough but uneventful with a nice landing. This flight had taken 1 hour and 15 minutes.

Roger ready to launch
Roger guides the Zugvogel up the wire.
( notice the limp windsock and the haze trapped as a cap cloud over Dartmoor beyond )
Roger Green was next up. After a short briefing from me ( It's very rough Roger! ) he had a similar flight to mine topping out at 4100 feet and landing back after 1 hour and 10 minutes. Our 3rd sydicate partner had already headed home so there was some time to spare before we needed to derig. We offered Rick Wiles the chance to fly the Zugvogel. ( Instructors are included in our insurance cover ). Rick flew for about 30 minutes topping out at 3500 feet.

Roger's View of the airfield from the south looking north
Roger topped out at just over 4100 feet
After rescuing Allan from the winch, we quickly derigged the glider and washed the mud from the fuselage ( Roger had managed to find a soft spot in the runway ) before returning to the clubhouse to thaw out. At ground level the temperature had stayed about 3degrees all day.

Our special thanks to Allan Holland for the winch driving and to Alan Carter for helping us to get the glider ready without flying it.

A great flying day for experienced pilots.



Rich Roberts said...

Great blog, great detail. Good to see some fun wave flying !
Well done guys.

hrf said...

Ohhhhh. I hope this weekend brings easterlies too!