Fw 190 A of 2/JG 51 Lt. Joachim Brendel Winter 1942 1943. Engine BMW801
Primary Concerns with the BMW 801 Engine
Overheating, particularly the rear cylinders: This issue was particularly prevalent during ground operations, especially after prolonged low-revs operation due to the minimal airflow for cooling. This overheating was so severe that cockpit temperatures could exceed 55 °C, posing a risk to the pilot. The rear cylinder overheating issue wasn’t fully addressed until the introduction of cooling slots on the Fw 190 A-2.
Frequent malfunctions and unreliability: BMW 801, particularly in its early iterations, suffered from a variety of malfunctions. These issues ranged from fuel and oil system leaks, problems with the Kommandogerät (automatic control unit) and the variable-pitch propeller, and issues with spark plug wear. The tendency for engine cowlings to open in-flight due to poor lock design and difficulties with emergency jettisoning of the cockpit hood at high speeds also contributed to the engine’s perceived unreliability.
High operating temperature: The BMW 801 generated an enormous amount of heat due to its design as a double-row radial engine, packing a high power output into a relatively compact space. This high operating temperature led to concerns about engine fires and necessitated armoring for the cockpit, oil tank, and cooler on production aircraft. This intense heat also contributed to the aforementioned issue of rear cylinder overheating.
High altitude performance limitations: The BMW 801’s performance degraded significantly at higher altitudes. This weakness became increasingly problematic as the war progressed and Allied fighters, like the Spitfire, gained better high-altitude capabilities. To counter this, designers explored several options, including the use of a turbocharger, nitrous oxide boosting, and a pressurized cockpit, but these efforts faced various setbacks.
Potential safety hazards: The combination of high operating temperatures and frequent malfunctions, such as fuel and oil leaks, led to concerns about potential fire hazards for the aircraft and pilot. The leakage of exhaust gases into the cockpit was another significant safety concern, especially if the pilot wasn’t wearing an oxygen mask.
It’s important to note that these concerns primarily pertain to the early models of the BMW 801 engine. The engine was continuously developed and improved throughout the war, and later models like the BMW 801D-2 addressed many of the initial issues, particularly the rear cylinder overheating. However, the engine’s fundamental design as a double-row radial continued to present inherent challenges, like high operating temperatures and limitations in high-altitude performance, even in its later iterations.