ASG 32 – Launch Report

Finally! Schleicher decided not to leave the double seater class to Schempp-Hirth any more without a fight. Since the first flight of the Duo Discus, SHK has enjoyed sort of a monopoly with only limited interference from DG’s DG1000/1001. At the last FAI European Gliding Championships 2011 in Nitra, one sole LAK12 (!) broke the phalanx of 8 Duos and 7 Arcus gliders. To be fair I have to add, that for many clubs searching for a modern 2-seat training glider, the DG1000 has been the glider of choice. But when you were looking for an all-out high-performance glider, you ended up paying a visit to the company situated at the Schwäbisch Alb with a Minimoa inside the Logo.

General Layout

At the AERO Friedrichshafen, I had the possibility to have a look at the brand new fuselage and – coming back from a tour through the Hangars – talk to Michael Greiner, the ASG 32 chief designer as indicated by the “G” in ASG 32. The general layout of the new 2-seater reveals no surprises: With 15,7 m², the ASG wing exceeds the Arcus wing by only 0,1 m² and the overall configuration is sort of a definition of “conventional”: flaperons throughout the 20m, a tandem cockpit, a T-tail and – guess what – winglets!

Pitcture 1: Top elevation comparison between ASG 32 and Arcus

Once one gets a bit closer to the airplane, one notices some interesting details however. As has been expected since the rumor was out, that Schleicher is working on a 20m 2-seat-ship, the ASG 32 uses the ASH 30’s forward fuselage. Going further downstream however, one notices that the vertical tailplane looks different from that of the bigger sister. Talking to Michael Greiner, he confirmed, that he designed a new VTP for the one obvious reason: to save drag. 

 Pitcture 2: Side elevation comparison between ASG 32 and ASH 30

Schempp Hirth on the other hand uses one VTP on DD, A and N4D. The reason is simple: The Nimbus 4D has a quite small VTP with a VTP coefficient of only 0,16. Using the same VTP on the Arcus results in a VTP coefficient of 0,025, which is good but still not excessive. (The difference results mainly from the shorter span of the Arcus.) With a fuselage which is 34 cm longer that of the Arcus, Schleicher could considerably decrease the VTP which on the ASH 30 is big enough to give her a VTP coefficient of 0,021 and still get a VTP coefficient of 0,024. (I derived these values from 3-view drawings, so the official values may differ a bit.)

Pitcture 3: Side elevation comparison between ASG 32 and Arcus

While a smaller VTP on a shorter span glider is quite logical, it is more surprising to see a new horizontal tailplane on a glider with less wing area but a bigger mean aerodynamic chord, as these two effects should cancel each other out. (If you are unfamiliar to the term mean aerodynamic chord, just read “average wing chord length” though they are not strictly identical.) So why did Greiner design a new HTP with comparable span and area? As I couldn’t find an explanation, I asked Greiner himself, who told me that the ASH 30 HTP simply didn’t fit on the now smaller VTP chord at the top.

Attention to details

With revolutionary breakthroughs in aerodynamics and structures being in short supply these days, sailplane designers around the world keep improving their designs by focusing on details and the ASG 32 is no exception. Going tip to tail, on at first spots the cockpit ventilation. Whether or not they are really necessary is still subject to debate, the idea behind them however isn’t: Outside of the cockpit is a low pressure area. In case the canopy isn’t completely airtight, some air will constantly leak through the canopy slot and act like a blow turbulator as used on some gliders to make the boundary layer go turbulent on purpose. Others claim that the outlets around the rudder linkages are more than enough to ensure that the pressure inside the cockpit is kept below the outside pressure. In order to make sure this is the case for the ASG 32, Schleicher placed the cockpit ventilation in what is probably the lowest pressure area on the fuselage: right above the wing.

Pitcture 4:Cockpit elevation

A first in series production is the retractable tailwheel. Retractable tailwheels have been around before. The ASW22 prototype and Dick Butlers ASW22-DB already had retractable tailwheels. The tailwheel kinemematics of the ASB 32 is linked to the main landing gear kinematics, so both wheels are operated using the same lever in the cockpit. Michael Greiner managed to design the kinematics such that the steerable tailwheels extracts rotating forward while the internally mounted tailwheel cover rotates backwards without the two parts conflicting.

Pitcture 5: Retractable tailwheel

2 be continued…