There is evidence to support the notion that VVS fighters were superior in the horizontal to any of the main LW piston engined types before 1944. In the summer of 1943, a brand-new La-5 made a forced landing on a German airfield providing Luftwaffe with an opportunity to test-fly the newest Soviet fighter. Test pilot Hans-Werner Lerche wrote a detailed report of his experience. He particularly noted that the La-5FN excelled at altitudes below 3,000 m (9,843 ft) but suffered from short range and flight time of only 40 minutes at cruise engine power. Further, all of the engine controls (throttle, mixture, propeller pitch, radiator and cowl flaps, and supercharger gearbox) had separate levers which served to distract the pilot during combat to make constant adjustments or risk suboptimal performance. For example, rapid acceleration required moving no less than six levers. In contrast, contemporary German aircraft, especially the BMW 801 radial engined variants of the Focke-Wulf Fw 190 front line fighter, had largely automatic engine controls with the pilot operating a single lever and electromechanical devices, like the Kommandogerät pioneering engine computer on the radial-engined Fw 190s, making the appropriate adjustments.
Due to airflow limitations, the engine boost system (Forsazh) could not be used above 2,000 m (6,562 ft). Stability in all axes was generally good. The authority of the ailerons was deemed exceptional but the rudder was insufficiently powerful at lower speeds. At speeds in excess of 600 km/h (370 mph), the forces on control surfaces became excessive. Horizontal turn time at 1,000 m (3,281 ft) and maximum engine power was 25 seconds. In comparison with Luftwaffe fighters, the La-5FN was found to have a comparable top speed and acceleration at low altitude. It possessed a higher roll rate and a smaller turn radius than the Bf 109 and a better climb rate than the Fw 190A-8. The Bf 109 utilizing MW 50 had superior performance at all altitudes, and Fw 190A-8 had better dive performance.
Lerche's recommendations were to attempt to draw the La-5FN to higher altitudes. This has been misreported post war that the LW was issued orders not to engage below 5000m. no such order existed, but the LW did try to avoid low altitude combat against all single engined fighter types after the release of Lerches report. This was unfortunate, since most of the serious ground support operations by the VVS were conducted at tree top height. The LW reverted to BoB tactics, to escape attacks in a dive followed by a high-speed shallow climb, and to avoid prolonged turning engagements.
The La-5 had its defects which were gradually ironed out with the introduction of later types like the Yak-3 and La-7 and later the La-9. Perhaps the most serious of the criticisms that can be levelled against the La-5 is the thermal isolation of the engine, lack of ventilation in the cockpit, and a canopy that was impossible to open at speeds over 350km/h. To make things worse, exhaust gas often entered in the cockpit due to poor insulation of the engine compartment. Consequently, pilots ignored orders and frequently flew with their canopies open.