The D4Y Suisei combined roughly 1,400 horsepower with a cited top speed of 300 knots and a designed bomb load of half a ton. Its first flight came in 1940, but it entered service in 1942. This was a good aircraft whose late arrival reduced its operational value. Had it been ready for Pearl Harbor, it could have been much more destructive than the dive bombers available for that attack.
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The D4Y's delayed arrival reduces its early-war value
The D4Y offers higher speed and substantial engine power, but its 1942 service entry comes too late for Pearl Harbor.