An aircraft is cleared to climb to FL060 after take-off from an airport. The pilot levels off at FL060, but forgets to reset the altimeter. Local QNH 999 hPa remains set. What is the difference between the aircraft and other traffic at FL060? The aircraft is...
(Assume: 30 ft / hPa)
During climb, pilots change the altimeter to the standar pressure when passing through the transition altitude. Thereafter, the vertical position of an aircraft is controlled by reference to flight level.
It is important to note that the aircraft is not really flying at FL060 unless standard pressure is set (1013 hPa). Consequently, if the pilot does not change the altimeter setting and 999 hPa remains set => when you reach an altimeter indication of 6 000 ft and level off, you will not be at the same pressure altitude as the remaining traffic.
To solve this exercise, we must find out what altitude the altimeter would indicate if the pilot changed the altimeter setting to 1013 hPa (the aircraft’s Indicated altitude). We suggest that you use the following formula:
It is important to note that the aircraft is not really flying at FL060 unless standard pressure is set (1013 hPa). Consequently, if the pilot does not change the altimeter setting and 999 hPa remains set => when you reach an altimeter indication of 6 000 ft and level off, you will not be at the same pressure altitude as the remaining traffic.
To solve this exercise, we must find out what altitude the altimeter would indicate if the pilot changed the altimeter setting to 1013 hPa (the aircraft’s Indicated altitude). We suggest that you use the following formula:
TA = IA + 27 (Local QNH – Pressure setting)
Where; TA stands for True altitude, IA is Indicated altitude and 30 is the barometric lapse rate.
Where; TA stands for True altitude, IA is Indicated altitude and 30 is the barometric lapse rate.
- 6 000 ft = IA + 30 (999 - 1013)
IA = 6 000 ft + 420 ft
IA = 6 420 ft - The aircraft is 6 420 ft – 6 000 ft = 420 ft higher than remaining traffic.
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