The Diana 2 Experience

Updated: Jul 23, 2018

Diana's agent, Matthew Scutter from down under recently flown Diana 2 in Bielsko. This is his point of view, shared from his facebook page Matthew Scutter's Gliding :

The Diana 2 Experience

In the spirit of “If you can’t beat them, join them”, I’ve recently been flying the Diana 2 at the AVIONIC factory.

If you haven’t heard of the Diana 2 before, it’s a very unique glider. It has a monocoque wing (no spar!), with the strength coming from a thick carbon skin. It has a tiny, tiny tail, and a long and skinny tail boom. It has an empty weight of just 175kg - lighter than many 13.5 gliders, but it takes more water than the empty weight ballasting to 500kg, giving it the largest wing loading range of any production glider (~30-60kg/sqm).

It has a unique aerofoil designed by Prof. Krzysztof Kubryński, who has a track record of creating world championship winning aerofoils across a number of sports, and who’s software was used in the design of most modern gliders (V2, JS1, ASW27). It claims a best LD of 50:1 and a rate of sink at 110kts of 340fpm, which remains unmatched. It has dominated the 15m class since it’s inception, but due to production problems at the previous manufacturer only a few were made.

The factory has enlisted both the Polish Gliding Team and myself to provide critiques of the Diana 2 for future improvements, with the goal of turning the most uncompromising racing glider ever made into something you might see in a club one day, without sacrificing performance, just a few kg of minimum empty weight. The factories latest Diana 2-NG - their revision of the original Diana 2, had unfortunately already left for it’s new customer last week, but the factory was able to source me the famous BB - the SN#1 Diana 2, originally built by the designer for himself and flown to countless world championship victories by Sebastian Kawa. On the bright side this gave me the opportunity to see the factories point of view on why they have made the revisions they have.

Sitting in the glider the first time it all felt much like normal, with two exceptions: the side stick which sits just to the right of your thigh, and the flaps, which are inexplicably out of reach except for leaning forward and stretching - I couldn’t tell you why the original Diana 2’s were made like that, but it’s something that is changing on the Diana 2-NG. Also strangely is two identical controls on the left, the airbrakes and the undercarriage, with a matching trigger handles, except the undercarriage trigger is for unlocking it but the airbrake trigger is for the wheel brake. Utterly confusing and will inevitably cause a wheels up, the factory tells me this was their highest priority change for the Diana 2-NG.

The first flight was quite a handful - empty, on a 10m rope (10m - one zero metres!) behind one of the traditional Polish tugs (enormous radial that makes much less horsepower than you’d wish), into low level rotors. I left the flaps in +8 and the glider lifted off the ground quickly. The whole aerotow felt like walking on a knife edge while I tried to learn how to handle the glider while staying behind the tug in rotor. Once off tow I started to understand what was different about this glider - it has little to no control damping. On every other glider I’ve flown, especially larger gliders, there is a strong damping force that slows the response of the glider and smooths out your control inputs. It is this damping force that causes the hesitation in a glider when you move the controls and glider takes a moment to respond, and the same damping that causes PIO’s.

The Diana 2 doesn’t have this damping. Every movement elicits an instant response - I’m not sure if it’s the small tail volume, the ratio of the wing area to the control surface or just the aerofoil, but it took some getting used to. As I later came to appreciate, this is what gives the Diana 2 it’s agility and climb performance. I’ve often wondered how the Diana 2 pilots at worlds seem to be confident to turn inside me in very tight situations when no other gliders take the pass, was it just the uncompromising Diana 2 attracts a certain type of pilot, or did the glider offer the pilot I something I was missing out on?

It was tough climbing in the small rotors, but at a takeoff weight of 250kg (175kg empty + 75kg me) I was able to keep afloat in the shredded thermals. Landing was uneventful, good visibility from the head to toe canopy and easy to taxi on the ground.

My second flight was into a strong crosswind - everyone who has seen a Diana 2 at a competition knows this is a challenging situation for a Diana 2. Diana 2’s have a reputation for wing drops due to a number of factors; water tanks filling 100% of the wing creating a significant bend towards the ground at the tips, and flaps that are largely out of reach for the takeoff roll requiring you to pick a flap setting pretakeoff and stick with it until you’re comfortably airborne - or try and reach the flaps and risk a high speed ground loop if you’re not paying attention.

Both elements have been revised on the Diana 2-NG, the tanks are now sized to get you to MAUW rather than substantially beyond it, stopping the water flow to the tips and resultant bending. Despite my concerns, the glider wasn't a problem to manage with the crosswind and lifted off like normal. As I started to learn to thermal the glider I found myself needing to actively fly the rudder - the small tail feels a bit like small feathers on an arrow, less natural centring tendency so you need to fly the rudder much like you naturally fly the ailerons and elevator, as opposed to just using it for turn coordination and picking up the nose in thermals. This demands more attention than I was used to, but the light and responsive controls make it a breeze.

I hope that a bit more airtime in the Diana 2 will make me a better pilot going back to other gliders with more

awareness of the rudder. I had some opportunities on this flight to test out the performance and handling at higher speeds and flaps, with the rudder and the elevator remaining light as a feather but the ailerons feeling the speed more as you go faster and more negative. I’m not sure if this is by design or not - with the full span flaperons you only need very small movements to manoeuvre. My feedback to the factory was that this could be better harmonised, and the new designer said he will look into this when they reroute the control circuitry to suit the FES battery pack.

The end of the second flight was the only time I noticed the side stick - it uses a different set of muscles to what you’re used to, and my gym membership having expired I was now feeling it in my wrist and shoulder. I am indifferent on the side stick - it’s nice to have more space in the cockpit, and I think it helps with highly accurate flying in that you are manoeuvring the same left and right with a simple rotation of your wrist rather than a complex combination of muscles for a centre sick. The downside is an inability to change hands in flight, something I often do on long flights or while operating my instruments.

My third flight was beautiful - no ballast due to a wet runway (300m long…), but I was towed straight into classic lee wave at 2500ft, where I climbed straight to FL95, and never fell out of it the whole day. Even at 250kg takeoff weight I was easily able to penetrate into the 55kt headwind and the glider really felt rock solid and stable at these speeds. Immaculate sealing and a carefully designed wing/fuse intersection made for a whisper quiet flight.

I almost got myself in a bit of trouble at the end of this flight - there were bands of showers rolling through, and an all encompassing band appeared on the horizon so I started to head into wind towards the airfield. I misjudged the pace of the rainband, (55kt headwind remember!), and ended up finding myself in moderate rain and occasionally heavy rotor on the way to the airfield. The rain didn’t have much effect on the performance (apparently a design goal), but as it started to clear strange water patterns started forming on the wing! I tried to take some photos but they’ve come out very poorly - instead of globbing on the leading edge, the rain streamed to the back of the wing and then formed a clear line all the way along the span.

You could see the turbulent separation all the way back at 70-90%, even in the light rain! It was fascinating to fly along and change speeds/flap/airbrake settings and see the separation move around the wing like I’ve only seen in wind tunnels. The rotors worsened as I descended and were really quite violent on base and final but despite quite a few airspeed flickers below stall in the gusts the glider handled it nicely all the way down.

This glider is still primarily a racing glider. The performance claims are unmatched and validated by the track record of 10 WGC wins and counting. The handling is exceptional but unconventional because of the lightning fast response. It’s extremely slippery and accelerates quickly. I don’t see it, even with its revisions ever being a first solo glider. It trades a higher skill floor for a higher skill ceiling, but I would put it well within the abilities of a 300hr pilot, and with the new revisions in the Diana 2-NG I think it could possibly even be a club glider for experienced pilots.

For the future I am most interested in is the FES option - the Diana 2-NG is ideal for an FES with the very low empty weight making for a small impact on minimum wing loading while provided exceptional climb rates under power. The high nose clearance offers the possibility of a bigger bladed propellor for more efficiency than possible on other FES conversions, and probably self-launchable. There are two Diana 2’s coming to Australia in the next 6 months, one with an FES, so I look forward to seeing what is possible with this glider in Australia.