page_title: FMA IAe 33 Pulqui II
section_title: Testing and evaluation
hierarchical_section_title: FMA IAe 33 Pulqui II / Design and development / Testing and evaluation
caption_attribution_description: English: Eva and Juan Perón during his second inaugural parade, June 4, 1952. The vehicle was a 1939 Packard Super Eight Phaeton.
context_page_description: The FMA IAe 33 Pulqui II was a jet fighter aircraft designed by Kurt Tank in the late 1940s in Argentina, under the Perón government, and built by the Fábrica Militar de Aviones. Embodying many of the design elements of the wartime Focke-Wulf Ta 183, an unrealized fighter project, the FMA envisioned the IAe 33 Pulqui II as a successor to the postwar Gloster Meteor F4 in service with the Fuerza Aérea Argentina. The Pulqui II's development was comparatively problematic and lengthy, with two of the four prototypes being lost in fatal crashes. Despite one of the prototypes being successfully tested in combat during the Revolución Libertadora, the political, economic and technical challenges faced by the project meant that the IAe 33 was unable to reach its full potential, and the Argentine government ultimately chose to purchase F-86 Sabres from the United States in lieu of continuing development of the indigenous fighter to production status.
context_section_description: To prove the soundness of the IAe 33 design, two gliders built under contract by another expatriate, Reimar Horten, were constructed and used for aerodynamics testing in 1948–1949, including flights by Tank himself. These tests revealed significant problems with lateral stability, resulting in modifications to the tail to address this problem before construction began on two prototype airframes. Due to the lack of modern machinery, the all-metal fabrication relied heavily on handcrafting, and fabricating the prototypes was a labor-intensive procedure. President Perón envisioned that a benefit of setting up an aviation factory in Argentina would be to introduce production standards comparable to world-class manufacturing facilities. However, Tank realized that production tools and jigs were not feasible at this stage and relied instead on essentially hand-built examples. The first airframe (No. 01) reserved for static testing, was subsequently destroyed during the tests.
  The first of the "flying" IAe 33 prototypes, (No. 02) built in 1950, completed its maiden flight on 27 June of that year, with Captain Edmundo Weiss at the controls. On the second flight, ex-Focke-Wulf test pilot Otto Behrens encountered severe lateral stability problems at speeds over 700 km/h (435 mph) and returned to the airfield as a precaution. Landing at very high speed, the aircraft bounced with sufficient force to cause the right main undercarriage strut to fail. During repairs to the aircraft, in order to rectify the "tricky" landing characteristics, the front undercarriage strut was increased in length, which served to alter the angle of incidence of the aircraft, while the shock absorbers were adjusted to have a greater "throw". Although never considered docile, the modifications improved the takeoff, landing and low-speed characteristics of the IAe 33. More serious aerodynamic problems persisted, stemming from tip stall— in which the wingtip stalled before the wingroot resulting in an unpredictable "rolling moment"— leading to a change in the wing leading edge near the wingroot, while the rudder was modified in an attempt to resolve the interminable lateral instability issues. In addition, the canopy was reinforced with two external frames and a small fairing was installed above the engine exhaust.
  Tank, himself a capable development test pilot, took over the test program to investigate the aircraft's stalling characteristics, although the requisite airframe changes took several months to complete, with the Pulqui II N. 02(m) so modified not able to undertake its third proving flight until 23 October. During the ensuing high-altitude test, on two successive occasions, the IAe 33 stalled inadvertently, although Tank had sufficient height at 9,000 m for recovery. Adding ballast to the nose of the aircraft cured the problem. On 8 February 1951, Tank publicly demonstrated the IAe 33 before Perón at the Aeroparque Jorge Newbery in Buenos Aires. The audience also included government officials, legislators and the foreign diplomatic corps in the military attaches of the embassies, along with a large crowd of spectators. Both the IAe 27 Pulqui I and IAe 33 Pulqui II flew during the demonstration.
  With the successful completion of the proving test flights, the Argentine Air Force requested a pre-production order of 12 IAe 33 aircraft. In 1951, the air force established a team of service pilots to test fly the new aircraft in a series of acceptance flights. The first flight by Commander Soto on 31 May 1951 revealed severe vibration at about 1,000 kilometres per hour (621 mph). Tank declared the sole prototype unserviceable pending an investigation into the problem, although this stricture appears to have been overlooked and the prototype continued to fly. On the eve of its 28th flight, Captain Vedania Mannuwal, assigned to the test program, was advised not to stress the aircraft, as the source of the vibrations experienced during the previous flight in the morning had not been discovered. Determined to "better" his team leader's recent performance, howe
caption: President Perón and "Evita" during his second inaugural parade, June 1952.
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