Created Tuesday, Nov 23rd 2021 19:04Z, last updated Tuesday, Nov 23rd 2021 19:04Z
A Zagros Airlines Airbus A320-200, registration EP-ZAV performing flight ZO-4012
from Ahwaz to Tehran Mehrabad (Iran), was on approach to Tehran cleared to descend to 6000 feet and intercept the localizer runway 29L about to turn from a heading of 020 degrees onto a heading of 330 degrees to intercept the localizer about 9nm before the runway threshold when the EGPWS activated issuing a "PULL UP! PULL UP!" alarm. The crew went around, climbed the aircraft to 8000 feet, positioned for another approach and landed without further incident about 15 minutes later.
Iran's CAA released their final report in Persian only (Editorial Note: To serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a Persian only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe).
The report concluded:
the incident was caused by the high capabilities of EGPWS in identifying obstacles in different directions and predicting them according to route, speed, rate of descent. The procedures were not in alignment with the minimum radar altitude permitted 1500 feet above the highest obstacle. The border line of two adjacent areas caused a complexity in the drawings of the procedure plates with respect to minimum required heights on approach to Mehrabad.
The CAA reported that the EGPWS alarm was triggered by the Bibi Shahrbanu Mountain about 1nm ahead of the flight trajectory (if the aircraft continued on a heading of 020 degrees) with its peak at 5036 feet.
According to the procedures established by experts and approved by the CAA the minimum vectoring altitude had been set to 6000 feet leaving a safety margin of 964 feet (usually 1000 feet). At least two other flights had received similiar alarms however did not report them.
4 safety recommendations were issued as result of the investigation.
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