However, did the 787 truly fly supersonic relative to the air? The answer is no. The 787 is a widebody passenger aircraft capable of flying long distances at a cruise speed of 0.85 Mach (652 mph/1,050 kph).
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The sound comes from the rotary hydraulic motor situated in the wheel well of the jet which turns the drive shaft for the flap drive screw jacks.
For example, the speed of sound at 30,000 feet is about 670 miles per hour, but an aircraft must travel at least 750 miles per hour (Mach 1.12, where Mach 1 equals the speed of sound) for a boom to be heard on the ground.
Fifty years ago, the federal government banned all civilian supersonic flights over land. The rule prohibits non-military aircraft from flying faster than sound so their resulting sonic booms won't startle the public below or concern them about potential property damage.
Aircraft are put through extreme testing during their certification, but such limits are never intended to be actually faced. The 747 -100, for instance, was tested up to Mach 0.99, almost breaking the sound barrier. Other 747s, such as Air Force One, have approached the sound barrier but never crossed it.
The 747-100, for instance, was tested up to Mach 0.99, almost breaking the sound barrier. Other 747s, such as Air Force One, have approached the sound barrier but never crossed it.
The power, or volume, of the shock wave depends on the quantity of air that is being accelerated, and thus the size and shape of the aircraft. As the aircraft increases speed the shock cone gets tighter around the craft and becomes weaker to the point that at very high speeds and altitudes no boom is heard.