Speeds
IAS is what the instrument shows. TAS corrects for density and is higher at altitude. Ground speed adds wind. Mach number matters above roughly FL250. V-speeds label limits: V1 decision speed, VR rotate, V2 safety speed, VNE never exceed.
Altitudes
Altitude is height above mean sea level, height is above a datum such as the airfield, and a flight level is a pressure altitude on the 1013 hPa standard setting written as FL350.
Everyday shorthand
METAR is an observation, TAF a forecast, NOTAM a notice to air missions, ATIS a recorded airport broadcast, and squawk the transponder code assigned by ATC.
Key points
- IAS drives handling; TAS and ground speed drive navigation.
- FL350 means pressure altitude 35,000 ft on standard 1013 hPa.
- V1 is the last point at which a takeoff can be safely abandoned.
Knowledge check