Competition Dominance
The Akrostar made its competitive debut just three months after first flight at the 1970 6th World Aerobatics Championships at Hullavington, England, where it immediately placed fourth individually and generated orders for the 1971 European and 1972 World championships. The aircraft's revolutionary design approach paid dividends in competition, with pilots praising its ability to maintain consistent handling whether flying upright or inverted - a critical advantage in precision aerobatic maneuvers.
The aircraft's success stemmed from its unique "marco-flap-system" that enabled exceptionally tight turning radii and precise control during complex aerobatic sequences. Pilots found they could maintain a horizontal fuselage centerline in both normal and inverted flight, with excellent low-speed controllability near zero G conditions - essential capabilities for winning championship-level competition routines.
Revolutionary Design Philosophy
Swiss aerobatic champion Arnold Wagner led the design effort, sponsored by himself and three German ex-champions including Horst Gehm, Josef Hößl, and Walter Wolfrum. Their objective was singular: create an aircraft capable of winning aerobatic competitions through handling characteristics completely independent of flight orientation.
Professor Richard Eppler of Stuttgart Technische Hochschule headed the Wolf Hirth engineering team, beginning development work in summer 1969 with construction starting in December 1969. The team incorporated several groundbreaking innovations, including a thick symmetrical Eppler airfoil with a 20 percent thickness-to-chord ratio mounted at zero incidence angle.
The aircraft featured independent trim tabs on flaps for precise pitch and yaw trimming, plywood-covered wings with a single glass fiber spar and foam ribs, and forward-mounted main landing gear integral with the steel engine frame to provide drag opposition during vertical flight maneuvers. A distinctive fuselage strake provided additional fin area for enhanced directional stability.
Manufacturing and Variants
Wolf Hirth GmbH manufactured the Akrostar at their facility in Nabern/Teck, West Germany, producing exactly nine Mk II aircraft between 1969 and 1973. The company also developed one Mk III prototype that incorporated weight reductions, lightened control surfaces, refined wing root fairings, and enhanced engine cooling systems designed for glider towing operations without overheating.
By 1981, Wolf Hirth GmbH retained the tooling and materials for potential additional production but ceased manufacturing due to prohibitive costs estimated at $90,000 per aircraft. The company was linked to gliding pioneer Wolfram Kurt Erhard Hirth (1900-1959), who co-founded the renowned glider manufacturer Schempp-Hirth and was brother to Hellmuth Hirth, founder of the Hirth engine company.
Technical Specifications
The Franklin 6A-350-C1 six-cylinder horizontally opposed piston engine produced 220 horsepower, driving a two-bladed Hartzell constant-speed propeller mounted in a steel frame. The Mk III variant incorporated cooling and lubrication modifications specifically for glider towing operations, demonstrating the engine's reliability for sustained aerobatic operations.
The aircraft's empty weight was 485 kilograms (1,069 pounds) with a maximum takeoff weight of 700 kilograms (1,543 pounds). Fuel capacity was 50 liters (13 US gallons) with an optional 40-60 liter cruise tank for extended operations. The wing design featured an aspect ratio of 6.03 with straight tapered planform and slightly swept leading edges.
Pilot Experience
Pilots consistently praised the Akrostar's predictable handling characteristics and precise control response during aerobatic sequences. The aircraft's ability to maintain consistent flight characteristics regardless of orientation allowed pilots to focus on competition precision rather than compensating for handling variations between upright and inverted flight phases.
Dr. Urs Meyer, who owned serial number 4009 (registration D-EOIG, later HB-MSK) from 1981 through 2013, regularly demonstrated the aircraft at airshows across Europe, showcasing its capabilities to new generations of aerobatic pilots and enthusiasts.
Legacy and Preservation
As of 2010, at least four airframes remained in existence. The prototype D-EMKB flew actively until June 2009 before being preserved at the Deutsches Museum Flugwerft Schleissheim in Germany. F-AZJF (formerly HB-MSA) underwent restoration in early 2010, while EC-CBS is displayed at the Museo de Aeronautica y Astronautica at Cuatro Vientos, Madrid.
The Akrostar's brief but brilliant competition career advanced aerobatic aircraft design through its demonstration that thick airfoils could provide superior slow-speed precision control while maintaining structural integrity under high-G aerobatic loads. Its orientation-independent handling philosophy influenced subsequent competition aircraft development, establishing design principles still employed in modern aerobatic aircraft.