Originally posted by VO101_Isegrim
Something of interest I found a while ago :
American pilot Robert C.Curtis remembers :
"My flight chased 12 109s south of Vienna. They climbed and we followed, unable to close on them. At 38,000 feet I fired a long burst at one of them from at least a 1000 yards, and saw some strikes. It rolled over and dived and I followed but soon reached compressibility with severe buffeting of the tail and loss of elevator control. I slowed my plane and regained control, but the 109 got away.
On two other occasions ME 109s got away from me because the P 51d could not stay with them in a high-speed dive. At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. The P 51b, and c, could stay with those planes in a dive. The P 51d had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds"
It seems that Curtis was probably scared to dive the P-51. His "redline" figure applies only to altitudes below 9,000 feet. In point of fact, the P-51D was placarded at 300 mph IAS (539 mph) at 35,000 feet. That's Mach .81 and that ain't slow. Jack Ilfrey, who was decidedly not shy about pushing the P-51D reported seeing speeds in excess of 550 mph at just 5,000 feet chasing a 109, which he caught.
Also, Curtis was wrong about the wing thickness and his understanding that this and the bubble canopy induced compressibility at lower speeds than the P-51B. What did happen was as described by Sid Woods, a double ace.
"The D model was placarded at 300 mph IAS (539 mph TAS, Mach 0.81) at 35,000 ft. In a dive, the P-51D was such an aerodynamically clean design that it could quickly enter compressibility if the dive was continued (in reality, a pilot could, as a rule, catch any German plane before compressibility became a problem). But, say, in an evasive dive to escape, as the P-51's speed in the dive increased, it started skidding beyond what the pilot could control (this could be a problem in a dive onto a much lower-flying plane or ground target--couldn't keep the plane tracking on the target if speed was too high). As compressibility was entered, it would start rolling and pitching and the whole plane would begin to vibrate. This began about Mach 0.72. The pilot could maintain control to above Mach 0.80 (stateside tests said 0.83 (605 mph) was max safe speed--but structural damage to the aircraft would result). The P-51's quirk that could catch the uprepared service pilot by surprise was that as airspeed built up over 450 mph, the plane would start to get very nose heavy. It needed to be trimmed tail heavy before the dive if speeds over 400 mph were anticipated."
Since Curtis was flying over Vienna, he was likely flying with the 15th AF out of Italy. In all likelihood, they had just transitioned from the P-38J... And that plane made many pilots afraid to get into a high speed dive.
My regards,
Widewing
