Flying the LS10-st "LQ"
by Brian Du Rieu – LKSC – Australia
The LS10 is the new sailplane I should have bought in 2005 when I returned to gliding after a multi-decade absence. Instead I chose a TMG, thinking my wife would love seeing Europe by air. However I quickly realized her appetite for risk and excitement, flying in the French Alps, and marginal VFR transits was completely different to mine! So mid 2008 I started to look closely at the top 18m machines including ASG29, Ventus, JS1 and Antares. I wanted the sailplane based in Australia and a turbo to maximize independence but not the expense of a self-launcher. Miles Gore-Brown had previously written an excellent technical article on the LS10 for ‘Soaring Australia’ and this provided me with a high degree of insight.
In the end I decided if I was going to spend money on a turbo, the engine had to start reliably, be operationally foolproof and importantly produce an acceptable climb performance on a hot day rather than an unachievable manufacturer’s claim. Additionally I didn’t want a glider that required re-profiling the wings or drilling out a few hundred boundary layer blowholes every winter! On all these counts the LS10-st wins. The engine, exhaust and prop combination produce more than 21hp, the wing is unblown and has an immaculately durable surface finish. Annual maintenance should consist of only a buff and polish.
So what about performance?
Pre-production models had previously won the German Nationals in 2005 and the pre-Worlds in 2007. So in European conditions the LS10 is certainly competitive. The ASG29 has a 2kg/sq.m wingloading advantage at 600kg and in stronger Australian weather one would expect the LS10 to have inferior high speed performance. Not so.
Cruise:
I‘ve accumulated about 90hrs on ‘LQ’ since delivery late November 2009 and after close-range comparison on long final glides I can say the LS10’s high speed L/D at 100kts is as good as the other 18m types. At 105kts it’s even better!
Werner Scholz, the original LS10 design engineer told me he feels that this high speed performance is due to very good airfoil performance at low CL adding that the fuselage also ‘sits’ well in the airflow pattern. The design intention was to significantly enhance both low and high speed performance compared to the LS6 while retaining the low sensitivity to both rain and bugs. Additionally he feels the winglets don’t seem to have any unfavorable separation at high speed. The patented Mandl air extractor also helps bring performance close to the design theoretical maximum.
Flap operating technique is similar to the LS6; accelerate and simultaneously ‘float’ the flaps from 0 to achieve full reflex by 99kts (600kg). So 100kts is a sweet spot, and according to the LX8000 this gives a 1:36 L/D, equivalent to a MacCready setting of 4kts.
In weaker conditions 1:43 is achieved at 85kts (MacCready 2kts) at the same weight, so all in all the cruise speed range is at the high end.
Climb:
When the lift is weaker than 2kts dumping just a little water is necessary unless survival conditions prevail. During the Waikerie Nationals I dumped below maximum weight to 575kg just twice. Once to better work the day’s tight, broken thermals and the other to work weak lift at the end of what pretty much turned into a distance task.
Thermaling:
I prefer Flap 2 although I have experimented with Landing Flap in broken lift at 600kg. When comparing climb performance with other gliders in the same thermal I felt that sometimes it was better to circle at 55kts with the higher drag rather than Flap 2 and 59kts.
The wing flex/ stiffness seems about right and gives good feedback on thermal entry. In cruise the ride is always comfortable without a tendency to hit the canopy even in rough air at high speed. The control harmony is superb and the degree of controlability inspires confidence.
So enough of my subjective impressions; what about the practicalities?
Take-off:
Here the sailplane is simple to handle. Select Flap 1. Roll control is immediate with no tendency to drop a wing regardless of a partial waterballast load. The glider ‘pops’ off the ground when it’s ready to fly.
Landing:
Flap 2 on downwind, gear down abeam the landing point, speed 55kts (still air), speedbrakes as required reducing to half-brake in the flare. Landing Flap gives quite a steep approach so I’m happy with Flap 2 most of the time. The wheel brake operates at the end of the speedbrake travel.
Water Ballast:
The tank vents are located at each wing root. This means that with any amount of water loaded in any tank, one wing can be left on the ground. Leveling the wings will see a few drops vent but that’s all. No broomsticks required on the launch grid! Although capacity is over 190L split between the two independent systems I can only load 158L including 6.8L in the two fin tanks due to the installed weight of the Turbo.
The pure sailplane version on the other hand would usefully employ the full capacity. With a full load, dumping all the water in the inner tanks (System 2) reduces my AUW to 529kg (46.1kg/sq.m) and if the outer/ centre tanks (System 1) are dumped as well I’m back to my operating empty weight of 442kg (36.9kg/sq.m). The lever arrangement on the RH cockpit wall is such that the tanks can only be dumped or filled in sequence.
There are three water ballast valves under each wing plus two fin valves. I’d strongly recommend purchasing 2 filling devices from the factory and building a simple water ballast rig to reduce loading time.
CofG:
With the turbo & fin battery installed my minimum cockpit weight is 92kg. I offset this with three LS style weights in front of the rudder pedals which reduce my minimum by 15kg. If needed, an additional battery can instead be installed in the stowage area behind the headrest. This might be useful for a lighter pilot who can’t manage the minimum cockpit weight with the fin battery in place.
The independent water systems each have a corresponding fin tank. When water is dumped a proportionate amount jettisons from the respective fin tank to maintain the optimal CofG position. Simple.
Comfort:
The fuselage has a narrow profile and is almost identical to the LS8. The cockpit will accommodate a tall pilot but there are limitations on shoulder width. I did briefly consider stick-top controls for the LX but I can comfortably reach the instrument panel with either hand while having more than a centimeter clearance between head and canopy. This is helped by the DG dyna-foam seat cushion that is only about 1cm thick but highly supportive. The thighs seem to be slightly elevated compared to the LS6 and ergonomically for me at least this is more comfortable. All of the ancillary controls are perfectly positioned. The mechanical leverage required to lower and raise the undercarriage is optimal and the flap lever is at a height where the left elbow can support the arm’s weight while the hand moves the flaps.
This aircraft is quiet!
The canopy seals beautifully and the ventilation via the front vent is so good that even on the hottest 40 centigrade days at Waikerie the temperature under the tinted canopy remained totally acceptable at lower altitudes.
Externally the tail wheel has quite a high profile and combined with the 5” main wheel the LS10 has excellent gound clearance.
Electrics:
Both main batteries, wired in parallel reside under the pilots thighs and can be charged via a BSK plug on the rear cockpit wall. The additional tail-fin battery has to be removed for charging. However with the installed solar panel my batteries have so far stayed in place all summer! The solar panel regulator charges the lowest battery first. I reserve the main batteries for engine starting and use the fin battery for the avionics.
Stowage:
A large storage area behind the pilots head allows easy stowing of my 3L Camelbak, canopy cover, extra fluids and other odds and sods, all in front of the 13L fuel tank. My tie-down kit and MH KF-011 kevlar O2 bottle (9.27cm diam.) both fit into their respective recesses.
Engine:
The Solo 2350 sustainer drives a 2 bladed composite prop developing 21hp.
Preflight:
Open the fuel cock, select DEI Master ON and ensure the fuel pump is gated in the AUTO position.
Airborne:
Select engine ON, when the LCD shows the engine fully deployed, pull the Decompression Lever, accelerate and at about 70kts release the lever and the engine roars to life. My personal minimum altitude for starting is 900’ agl unless I’m well positioned on downwind at an airfield and then I might consider pushing it to 700’. The L/D reduces to 1:25 with the engine deployed but not running. So far I haven’t used the turbo in anger but it does inspire confidence to know it’s there and available.
The RPM limit is quite high so a level cruise in excess of 70kts is possible if low cloudbase prevents a saw-tooth profile. In this case the range is still acceptable at 164km. In saw-tooth mode the Flight Manual quotes a maximum range of 289km, a comforting thought when out ‘back of Bourke’.
Fuel Tank:
There is no need to remove the tank for refueling. Simply connect the fuel hose, insert the bayonet into a jerry-can of 2-stroke mix and press the refuel button. The system auto-stops when the maximum level is reached.
Instrument Panel:
I chose the LX8000 mainly because my previous sailplane had an LX installed and I like the system logic. In Australia we don’t have a lot of airspace or significant terrain to deal with so I find the screen size perfect. The 3 main screen pages scroll L to R; Nearest Airfield, Turn Point (I set this scale to 0.2km for the thermal track) and Task (scaled to whatever is appropriate for the phase of task being flown).
The AAT feature of the Task Page allows movement of any TP to optimize task distance. Nice.
The colour LX screen is readable in ALL sunlight conditions and now that I’ve figured out how to change the font size of the FLARM targets, I can read them as well. I can plan a task on my laptop using SeeYou and then save directly to the LX SD card. Vice versa to down load the .igc file from the Logbook page. Ditto for updating firmware, waypoints, airspace, airports, FLARM .fw and .obs and just about anything else. The preloaded airfield and airspace databases are worldwide and multi TP/ Task files can be stored and merely line selected when going from comp. to comp. A PDA is redundant.
I did have to settle on a 57mm altimeter but that was the only compromise. I still have a blank space for a transponder that I plan to install when I retire and can spend the winter wave flying! The easily reachable engine DEI control panel is located at the base of the control column and is separate from the main instrument panel.
Club Ops.:
In my opinion this glider is so vice free near the ground it would be quite suitable for club operations. As long as pilots paid attention to their individual CofG and water ballast limitations, and received conversion training in the areas of loading and engine use, risk could be managed at an acceptable level. Engines do add complexity though and a minimum start altitude should be mandated.
Status:
‘LQ’ (s/n 19) represents the production standard of the LS10, and what a standard! LBA type-certification was issued in December 2009.
I was fortunate to see my sailplane under construction at the factory in Bruchsal, Germany during several vists last year. All of the DG staff were very open and forthcoming with information, especially Holger Back, Volker Halbe, Stephan Goeldner, Clemens Mandl and Stephan Doernemann.
Thanks also to Tom Gilbert, Scott Lennon & John Viney in Australia who had the Form 2 and Experimental Certification completed in less than two days after the ship arrived; just in time for the first contest day of the NSW State Comps. What an effort!
For me personally the LS10 has been magic, albeit a learning curve. During my summer of 23 flights I’ve flown a couple of 750’s, bagged two 2nd places on the first and last days of the Australian Nationals at Waikerie and flown a PB of 168.6kph over nearly 500km on another.
If you love the LS6 or LS8 you’ll be besotted by the LS10!
Other Articles of Interest: | |
| |
| |
| |
| |
| |
| |