Which aircraft was designed specifically to investigate inverted flight?

The Albatros L 79 Kobold was a German single-seat aerobatic aircraft of the 1920s and 1930s. It was a single-bay biplane with wings of equal span and no stagger, whose symmetrical airfoil was intended to ensure performance during inverted flight. It was powered by a 93 kW (125 hp) Siemens-Halske Sh 12.

It measured 6.27 m (20 ft 7 in) in length, 8.80 m (28 ft 10 in) in span and 2.24 m (7 ft 4 in) in height, with a wing area of 16.6 m² (179 sq ft). The empty weight was 465 kg (1,025 lb) and the gross weight 640 kg (1,411 lb).

Its maximum speed was 165 km/h (100 mph, 87 kn), range was 2.5 hours and climb rate was 3.2 m/s (630 ft/min).