Final answer:
True altitude is calculated by correcting the pressure altitude for temperature deviations from the standard atmosphere, with the closest option being 'Pressure altitude + temperature correction'. True altitude is crucial for maintaining aircraft safety by ensuring clearance from terrain and obstacles and for proper vertical separation with other aircraft.
Step-by-step explanation:
To calculate true altitude, one would need to take pressure altitude and correct it for non-standard temperature variations. This correction can be found in performance tables for aircraft or calculated using specific formulas that account for the temperature deviation from the standard atmosphere. The formula to calculate true altitude is not explicitly provided in the options given; however, part a) 'Pressure altitude + temperature correction' is closest to the procedure for finding true altitude assuming that 'temperature correction' encapsulates the necessary steps to adjust for actual atmospheric conditions versus standard conditions.
True altitude is the actual height above mean sea level (AMSL) and it is important because it allows a pilot to ensure that the aircraft is clear of terrain and obstacles. It also helps in maintaining vertical separation with other aircraft, as air traffic control typically provides separation based on flight levels and altitudes that reference the standard atmosphere. This is critical for flight safety.
Based on Figure A4 'Altitude-Air Density Relationship', as altitude increases, the air density decreases. Top of Mount Everest, for example, has an altitude of approximately 8,828 meters above sea level, and air density there is really low at 0.023 kg/cubic meter. Understanding this relationship is vital for calculating true altitude as it affects aircraft performance, engine efficiency, and lift.