Supersonic planes travel faster than the speed of sound.
The speed of sound is about 1220 km/h at sea level at 15°C.
Sound travels slower higher up, so the speed of sound is about 1060 km/h at 12,000 m.
Supersonic plane speeds are given in Mach numbers. These are the speed of the plane divided by the speed of sound at the plane’s altitude.
A plane flying at 1500 km/h at 12,000 m, where the speed of sound is 1060 km/h, is at Mach 1.46.
A plane flying at supersonic speeds builds up shock waves in front and behind because it keeps catching up and compressing the sound waves in front of it. Energy, force and motion
In 1947 Chuck Yeager of the USAF made the first supersonic flight in the Bell X-1 rocket plane. The X-15 rocket plane later reached speeds faster than Mach 6. Speeds faster than Mach 5 are called hypersonic.
The first jet plane to fly supersonic was the F-100 Super Sabre fighter of 1953. The first supersonic bomber was the USAF’s Convair B-58 Hustler, which was first used in 1956.
Supersonic jet fighter planes are used by the military to intercept and attack enemy aircraft.
Spaceplanes of the near future may reach speeds of Mach 15.
The double shock waves create a sharp crack called a sonic boom that is heard on the ground. Two booms can often be heard one or two seconds apart.
In 1976 Concorde became the first supersonic aircraft to carry passengers on commercial flights. It was retired from service in 2003.
An aircraft’s wings or ‘foils’ are lifted by the air flowing above and beneath them as they slice through the air.
Because the top of the wing is curved, air pushed over the wing speeds up and stretches out. The stretching of the air reduces its pressure.
Underneath the wing air slows down and bunches up, the air pressure in this area rises.
The wing gains lift’ as the air around the wing is sucked from above and pushed from below.
The amount of lift depends on the angle of the wing – called the angle of attack – and its shape, and also how fast it is moving through the air.
Aircraft get extra lift for climbing by increasing their speed through the air and by dropping the tail so that the main wings cut through the air at a steeper angle.
If the angle of attack becomes too steep, the airflow breaks up and the win loses lift. This is called a stall.
Planes take off when air is moving fast enough over the wing to provide enough lift.
Airliners have ‘high-lift’ slots and flaps on the wings to give extra lift for sh take-off and landing speeds.
The 870 km/h German Messerschmitt Me 262 was the first jet fighter. It had straight wings like propeller planes.
The Lockheed Shooting Star was the first successful US jet fighter.
The Korean War of the 1950s saw the first major combat between jet fighters. Most now had swept-back wings, like the Russian MiG-15 and the US F-86 Sabre.
In 1954 Boeing introduced the B-52 Superfortress, still the USAF’s main bomber because of its huge bomb-carrying capacity.
In the 1950s aircraft began flying close to the ground to avoid detection by radar. On modern ground-hugging planes like the Lockheed F-111 a computer radar system flies the plane automatically at a steady height over hills and valleys. If the system fails, the plane climbs automatically.
The Hawker Harrier of 1968 was the only successful ‘jump jet’ with swivelling jets for vertical take-off (VTOI.).
Airborne Early Warning systems (AEWs) look down from above and detect low-flying aircraft. To evade them the Americans began developing ‘stealth’ systems like RCS and RAM.
RCS or Radar Cross Section means altering the plane’s shape to make it less obvious to radar. RAM (Radar Absorbent Material) is a coating that doesn’t reflect radar.
In 1988 the US unveiled its first ‘stealth’ bomber, the B-2, codenamed Have Blue. The F117 stealth fighter followed.
The 2500 km/h Russian Sukhoi S-37 Berkut (‘golden eagle’) of 1997 uses Forward Swept Wings (FSW) for maximum agility, rather than stealth technology.