Instrument Rating Exam · Mock exam

Why does a pilot flying an ILS approach in very cold temperatures need to apply a temperature correction to the DA?

• A.Because the decision altitude on the chart is a true altitude, while the altimeter always displays an indicated altitude referenced to the ISA standard datum
• B.Because cold dense air increases the true airspeed on final approach, requiring a longer final segment and therefore a correspondingly higher decision altitude
• C.Because the altimeter over-reads in cold dense air: the aircraft is lower than indicated at the charted DA, so the pilot flies to a higher indicated altitude to keep the same actual height
• D.Because the ILS glideslope radio signal is refracted noticeably in very cold air and must be re-calibrated by ground staff, so a temporary buffer is applied until this occurs