Air data instruments
The airspeed indicator compares pitot (total) pressure with static pressure. The altimeter reads static pressure against a reference setting. The vertical speed indicator measures the rate of static pressure change and therefore lags by a second or two.
Gyroscopic instruments
The attitude indicator shows pitch and bank against an artificial horizon. The heading indicator gives a stable compass reading. The turn coordinator shows rate of turn and slip.
Glass cockpits
A Primary Flight Display merges all six into one picture, adding speed and altitude tapes, flight director bars and trend vectors. The information is identical; only the presentation changes.
Key points
- Six-pack: ASI, AI, ALT on top; TC, HI, VSI below.
- Altimeter settings: QNH gives altitude above sea level, QNE (1013 hPa) gives flight level.
- VSI lags — use attitude and power for immediate control.
Knowledge check