Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling less than the minimums specified for visual meteorological conditions, requiring operations to be conducted under IFR.
Drag generated by the collision of airstreams creating eddy currents, turbulence, or restrictions to smooth flow.
The United Nations agency for developing the principles and techniques of international air navigation, and fostering planning and development of international civil air transport.
A model of standard variation of pressure and temperature.
The estimation of an intermediate value of a quantity that falls between marked values in a series. Example: In a measurement of length, with a rule that is marked in eighths of an inch, the value falls between 3/8 inch and 1/2 inch. The estimated (interpolated) value might then be said to be 7/16 inch.
An increase in temperature with altitude.
The feeling that the aircraft is tumbling backwards, caused by an abrupt change from climb to straight-and-level flight while in situations lacking visual reference.
Lines which connect points of equal barometric pressure.
Lines drawn across aeronautical charts to connect points having the same magnetic variation.
See instantaneous vertical speed indicator.