The Aerocobra fighter is one of the most successful aircraft of the Second World War in its class, at the same time R-39 the most controversial fighter of that period, spears are still broken about its advantages and disadvantages in the United States. It was developed as a high-speed interceptor, hence the extremely powerful weapons - a 37-mm automatic gun, the high-explosive shells of which could ruin almost any aircraft into components. After flight tests of the prototype, the KhR-39 command of the US Army Aviation Corps allowed the turbocharger to be removed from the aircraft. At low and medium altitudes, this device did not bring tangible benefits, but at high altitudes it significantly increased the LTX of the aircraft. In the West, they attached great importance to the altitude of the fighters, so the decision to remove the turbo compressor looks rather strange. It is not surprising that many Cobra operators, especially the British, spoke poorly about the flight characteristics of the R-39 fighter. "Cobra" was not popular with pilots.