In a simplified navigation calculation, an aircraft is at FL200 with OAT 0°C. An altimeter set to the QNH of a sea-level aerodrome indicates 19,300 ft. Use ISA temperature −25°C at FL200 and the 4%-per-10°C rule, assuming the ISA temperature deviation is uniform throughout the layer. What true altitude results, rounded to the nearest 100 ft? - ATPL Question Bank In English