The results vary with different airplanes: some wing over and dive while others dive gradually.
At speeds of 950 to 1,000 km/h (590 to 620 mph) the air flow around the aircraft reaches the speed of sound, and it is reported that the control surfaces no longer affect the direction of flight. Speeds of 950 km/h (590 mph) are reported to have been attained in a shallow dive 20° to 30° from the horizontal. On page 13 of the "Me 262 A-1 Pilot's Handbook" issued by Headquarters Air Materiel Command, Wright Field, Dayton, Ohio as Report No. Recovering from the dive and the resumption of severe buffeting once subsonic flight was resumed would have been very likely to damage the craft terminally. Computational tests carried out by Professor Otto Wagner of the München Technical University in 1999 suggest the Me 262 was capable of supersonic flight during steep dives. Chuck Yeager's Bell X1, the F-86 Sabre, and the Convair Seadart seaplane exceeded Mach 1 without area rule fuselages. The lack of area ruled fuselage and 10 percent thick wings did not prevent other aircraft from exceeding Mach 1 in dives. However, this claim is widely disputed by various experts believing the Me 262's structure could not support high transonic, let alone supersonic flight. Mütke reported not just transonic buffeting but the resumption of normal control once a certain speed was exceeded, then a resumption of severe buffeting once the Me 262 slowed again. Hans Guido Mutke claimed to have broken the sound barrier on April 9, 1945, in a Messerschmitt Me 262. There are, however, several claims that the sound barrier was broken during World War II. Flutter due to the formation of shock waves on curved surfaces was another major problem, which led most famously to the breakup of de Havilland Swallow and death of its pilot, Geoffrey de Havilland, Jr.Īll of these effects, although unrelated in most ways, led to the concept of a "barrier" that makes it difficult for an aircraft to break the speed of sound. The P-38 Lightning suffered from a particularly dangerous interaction of the airflow between the wings and tail surfaces in the dive that made it difficult to "pull out," a problem that was later solved with the addition of a "dive flap" that upset the airflow under these circumstances. This problem was solved in later models with changes to the wing. In the case of the Supermarine Spitfire, the wings suffered from low torsional stiffness, and when ailerons were moved the wing tended to flex such that they counteracted the control input, leading to a condition known as control reversal. The Mitsubishi Zero was infamous for this problem, and several attempts to fix it only made the problem worse. These included the rapidly increasing forces on the various control surfaces, which led to the aircraft becoming difficult to control to the point where many suffered from powered flight into terrain when the pilot was unable to overcome the force on the control stick. This led to numerous crashes for a variety of reasons. Propeller aircraft were, nevertheless, able to approach the speed of sound in a dive. This problem was one of the issues that led to early research into jet engines, notably by Frank Whittle in England and Hans von Ohain in Germany, who were led to their research specifically in order to avoid these problems in high-speed flight. The power needed to improve performance is so great that the weight of the required engine grows faster than the power output of the propeller.
It is due to these effects that propellers are known to suffer from dramatically decreased performance as they approach the speed of sound.
This was undesirable, as the transonic air movement creates disruptive shock waves and turbulence. This was particularly noticeable on the Stearman, and noticeable on the T-6 Texan when it entered a sharp-breaking turn. The tip of the propeller on many early aircraft could reach supersonic speeds, producing a noticeable buzz that differentiated such aircraft. Many forms of ammunition also achieve supersonic speeds. Similarly, a flag in strong wind may create a crackling sound produced when its edge goes supersonic. The tip of the whip breaks the sound barrier and causes a sharp crack-literally a sonic boom. Some common objects such as the bullwhip, or sparewhip, are able to move faster than sound.
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