Glaser-Dirks DG-300

Glaser-Dirks/
DG Flugzeugbau DG-300

A DG-300WL at Évora, Portugal
Type designation	DG-300
Competition class	Club (formerly Standard)
Number built	511
Crew	1
Length	6.80 m (22.31 ft)
Height	1.39 m (4.56 ft)
Cockpit width	0.63 m (2.07 ft)
Cockpit height	0.81 m (2.66 ft)
Wingspan	15 m (49.21 ft)
Wing area	10.27 m² (110.5 ft²)
Aspect ratio	21.9
Wing profile	Horst & Quast HQ21/II
Empty weight	ca. 245 kg (540 lb)
Water ballast	190 kg (419 lb) or 130 kg (287 lb)
Tail water ballast	5.5 kg (12 lb) optional
Gross weight	450 kg (992 lb)
Wing loading	43.8 kg/m² 9.0 lb/ft²)
Maximum speed	250 km/h (135 knots)
Maneuvering speed	175 km/h (94 knots)
Stall speed	65 km/h (35 knots) at 32 kg/m²
Minimum sink rate	0.59 m/s at 78 km/h (116 ft/min at 42 knots)
Best glide ratio	41 at 100 km/h (54 knots) 42 for DG-300WL
Roll rate (−45 to +45 bank)	4 seconds at 95 km/h (51 knots)

A DG-300 at Sintra Air Force Base, Portugal

The DG-300 is a Standard Class single-seat high-performance glider built of glass-reinforced plastic. The DG-300 was designed by Wilhelm Dirks and manufactured by Glaser-Dirks Flugzeugbau's Slovenian partner company Elan (company). A total of 511 of all versions were built since production started in 1983. Representative contemporary types from competing manufacturers are the Rolladen-Schneider LS4 and the Schempp-Hirth Discus.

General description

The DG-300 has a flapless wing with triple taper based on the Falcon designed by Hansjörg Streifeneder, and employs the HQ 21/II, a relatively thick profile (ca. 17.5%). This wing is 'blown' on the underside by 900 small holes to achieve a controlled transition from laminar to turbulent flow. As with any racing glider, the thickness of the wing makes it relatively sensitive to performance degradation due to contamination by insect impacts or rain drops.

It is agile and a good climber, but slightly underperforms compared to its competitors in cruising flight, especially at higher speeds. The later DG-303 version with a new wing profile and winglets was developed that delivers higher performance at low to medium speeds plus increased aileron response. A fully aerobatic version (the Acro) was also sold, stressed for +7/-5g.

The DG-300 has typical DG features, which improve comfort and safety if at a performance cost. It has the large cockpit typical of DG giving excellent comfort, especially in high-altitude flight where the full-length canopy allows the feet to be warmed by sunlight. The view from the cockpit is superb, adding to the pleasure and safety of flight.

After the bankruptcy of Glaser-Dirks the newly founded DG Flugzeugbau GmbH took over the servicing of these gliders.

The operational limits were changed on April 2007 after a defect was detected on the main spar. Aerobatic flight since then is not permitted, even for the Acro versions.

Major features

• Wings: spar of GRP rovings, wing shell of GRP / foam sandwich
• Elevator: GRP shell
• Rudder: GRP / foam sandwich
• Fuselage: GRP shell
• Conventional T-tail with fixed stabiliser and moving elevator
• Retractable, sprung undercarriage in a sealed gear box
• Large 5"x5" hub main wheel, 200x50 mm tail wheel
• Parallelogram control stick
• Automatic control connections
• Self-trimming spring system for the elevator, with trigger release on the control stick
• Schempp-Hirth air brakes on upper wing surface
• Water ballast bags in the wings for 130 or 190 litres
• Large canopy with low sill giving excellent in-flight visibility

Variants

DG-300

Initial production version

DG-300 Club

With fixed undercarriage for club use

DG-300 Acro

Fully aerobatic (restricted from aerobatic flight after 2007)

DG-303 Elan

With a new aerofoil section and winglets; available in standard, club and acro versions, built by the Slovenian company AMS-Flight until end of 2005

DG-303 Club

With fixed undercarriage for club use

DG-303 Acro

Fully aerobatic (restricted from aerobatic flight after 2007)

Sources

• DG Flugzeugbau website
• AMS-Flight
• Richard Johnson, A FTE of the DG-300, Soaring, August 1985
• Sailplane Directory
• Main spar defect discussion
• Technical Note 359-24