Metric Units

In the "book of the Autogyro", only metric units are used. When constants are used in a formula, they appear with their units. This way, it does not matter in what units you fill in the variables, because they are explicitly given for each term in the formula. For example:

eq A.1

There's no need to tell that D (the rotor diameter) should be in m or mm, because all units are given. This is also the way computer programs like MathCad work.

• Length: m
  1 mm=0.001 m,
  1 inch=25.4 mm, (1 inch is also denoted 1")
  1 ft=12 inch, (1 foot is also denoted 1')
  1 km=1000 m,
  1 mile=1609.344 m
  1 nmile=1852 m (nautical mile)
• Mass: kg
  1 slug=14.5939 kg
  Note: do not confuse mass and weight. Weight is a force and is regarded as a derived unit. To help you remember: in space you are weightless, not massless. Weight is related to the force of gravity and mass tells you how much force you should apply to give something a certain acceleration.
• Time: sec
  1 min=60 sec
  1 hr=3600 sec
• Temperature: K
• dimensionless units:
  1 deg=(pi/180) rad
  1%=0.01

Derived units

• Speed: m/s
  1 km/hr=0.277777 m/s
  1 mph=0.44704 m/s (=mile/hr)
  1 kts=0.5144444 m/s (=nmile/hr)
• Force: N=kg*m/sec²
  1 kN=1000 N
  1 kgf=9.80665 N (kilogram-force, ancient unit)
  1 lbs=4.44822 N
• Pressure and stress Pa=N/m²:
  1 kPa=1000 Pa
  1 MPa=10⁶ Pa
  1 GPa=10⁹ Pa
  1 bar=10⁵ Pa
  1 mbar=100 Pa
  1 Psi=1 lbs/inch²
• Energy: J=N*m
  1 kJ=1000 J
• Power: W=N*m/sec
  1 kW=1000 W
  1 hp=550 ft*lbs/sec
• Frequency: Hz=1/sec
  1 rpm=1/min
  1 kHz=1000 Hz
  1 MHz=10⁶ Hz
• Volume: m³
  1 liter=0.001 m³
  1 gallon=3.78541 liter