Conversion Table
| Metric & U.S. Imperial systems conversion | ||
|---|---|---|
| 1 kg | 1 kilogram | 2.203 pounds |
| 1 kN | 1 kiloNewton | 981 Kg |
| 1 L | 1 litre | 0.264 US gallon |
| 1 m | 1 meter | 3.279 feet |
| 1 m2 | 1 square meter | 10.76 feet squared |
| 1 mm | 1 millimeter | 0.039 inch |
| 1 km | 1 kilometer | 0.622 miles |
| 1 km/h | 0.622 mph | |
| Mach 1 | Speed of sound (depends on altitude, see below) | |
Speed of Sound at Different Altitudes
Mach 1.0 represents the speed of sound in air, and when a plane reaches Mach 2.0, it’s traveling at twice the speed of sound. It’s important to understand that the speed of sound isn’t a constant; instead, it varies depending on altitude, specifically, the temperature at that altitude. For instance, at sea level, an aircraft flying at Mach 1.0 is moving at approximately 1,225 kilometers per hour (661 knots or 761 miles per hour). However, as you ascend to higher altitudes, like 30,000 feet, the speed of sound decreases, causing Mach 1.0 to correspond to roughly 1,091 kilometers per hour (589 knots or 678 miles per hour).
In aviation, we classify speeds as follows:
Subsonic: Speeds below Mach 1.
Transonic: Speeds ranging from Mach 0.8 to 1.2.
Supersonic: Speeds above Mach 1.2.
These distinctions help us navigate the diverse aerodynamic challenges posed by different flight regimes.
| ALTITUDE | TEMPERATURE | SPEED OF SOUND | |||||
| Feet (ft) | Meter (m) | Celcius (°C) | Kelvin (K) | mph | knots | km/h | m/s |
| 0 (sea level) | 0 (sea level) | 15 | 288 | 761.1 | 661 | 1,225 | 340.3 |
| 5,000 | 1524 | 5.1 | 278 | 747.9 | 650 | 1,204 | 334.4 |
| 10,000 | 3048 | -4.8 | 268 | 734.5 | 638 | 1,182 | 328.4 |
| 15,000 | 4572 | -14.7 | 258 | 720.8 | 626 | 1,160 | 322.2 |
| 20,000 | 6096 | -24.6 | 248 | 706.9 | 614 | 1,138 | 316.0 |
| 25,000 | 7620 | -34.5 | 239 | 692.6 | 602 | 1,115 | 309.6 |
| 30,000 | 9144 | -44.4 | 229 | 678.1 | 589 | 1,091 | 303.1 |
| 35,000 | 10668 | -56.0 | 217 | 660.7 | 574 | 1,063 | 295.4 |
| 40,000 | 12192 | -56.6 | 216 | 659.8 | 573 | 1,062 | 294.9 |
| 45,000 | 13716 | -56.6 | 216 | 659.8 | 573 | 1,062 | 294.9 |
| 50,000 | 15240 | -56.6 | 216 | 659.8 | 573 | 1,062 | 294.9 |
| 55,000 | 16764 | -56.6 | 216 | 659.8 | 573 | 1,062 | 294.9 |
| 60,000 | 18288 | -56.6 | 216 | 659.8 | 573 | 1,062 | 294.9 |