Avianca A320 near Cali on Jul 3rd 2017, GPWS prevents flight into terrain
Last Update: May 1, 2020 / 23:30:45 GMT/Zulu time
Colombia's GRIAA rated the occurrence a serious incident and opened an investigation.
Colombia's GRIAA released their final report in Spanish 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 Spanish 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 probable causes of the serious incident were:
Loss of situational awareness by the crew, who failed to consider their position and the characteristics of the descent profile with respect to MSA before initiating the descent and accepted descent clearances by ATC to altitudes below MSA and airway minima, which resulted in a dangerous approach to terrain with associated risk of a controller flight into terrain (CFIT).
Erroneous clearance by Bogota Control Center, when ATC assigned an altitude enroute below the MSA as well as airway minimum altitude, as well as Cali Approach, who did confirm the wrong clearance assigning an altitude below MSA to the aircraft. Cali Approach did not react to the aircraft descending below MSA while heading towards CLO VOR.
Contributing factors were:
- accumulate fatigue by the captain of the flight which may have decreased his ability to properly analyse the operational environment and aeronautical decision making as well as may have impaired his ability to react properly to the GPWS alarm.
- Cockpit communication failure, no inflight briefing was conducted while flying along a rare route indicating complacency, lack of knowledge and experience of the route Leticia to Cali.
The GRIAA reported the captain (43, ATPL, 5,567 hours total) was pilot monitoring, the first officer (22, CPL, 2,235 hours total, 2070 hours on type) was pilot flying.
The aircraft had been enroute at FL380 and was cleared to descend to FL190 by Bogota Area Control Center while heading towards Cali VOR. However, the MSA for the area to be overflown was 19700 feet MSL. The clearance was not queried or rejected by the crew.
The aircraft was handed off to Cali Approach about 61nm from Cali VOR. Cali Approach advised to expect an ILS approach to runway 02 and cleared the flight to descend to 6000 feet MSL, although the aircraft was yet to pass over mountaineous terrain with MSA still at 19,700 feet. The crew did not challenge the clearance, but commenced the descent.
About 37nm from Cali VOR the aircraft descended through 14,070 feet MSL, both radio altimeters activated. At that point the rate of descent was 2800 feet per minute at 322 KIAS. Descending through 13,300 feet the radio altimeters reached 2500 feet AGL and shortly afterwards the EGPWS sounded the "TERRAIN! TERRAIN!" warning. The first officer disengaged autopilot 2 but continued the descent at 2900 fpm. 34nm before Cali VOR the flight reached 13,100 feet, the GPWS activated a second time calling "TERRAIN! TERRAIN!" for one second, then calling "PULL UP! PULL UP!" for 3 seconds and activating a visual alert to PULL UP for two seconds. The first officer now pulled the nose up and initiated an evasive maneouvre, the flight mode announciators continued to indicate DES/NAV modes however. The aircraft climbed at 2300 fpm and increasing with an airspeed of 314 KIAS decreasing. The aircraft continued the evasive maneouver for about 30 seconds, climbed to 14900 feet at about 32nm before Cali VOR, engaged the autopilot 2 again and coninued the approach to Cali descending to 6000 feet again. The aircraft completed a landing without further incident.
The GRIAA analysed that the aircraft was flying along an airway which had no connecting standard arrival route into Cali, the aircraft thus needed to vectored to the approach. When Bogota Area Control cleared them to descend to FL190, the crew trusted ATC would ensure both separation to other traffic as well as to ground and did not cross check their MSA. When the GPWS activated the crew initiated an evasive maneouvre however forgot one important item: to advance the power levers to TOGA power.
The GRIAA analysed the aircraft was tracking airway UL655, the minimum airway altitude was FL250. However, Bogota Area Control cleared the flight to descend from FL380 to FL190, which provided a false sense of safety. The crew did not inquire about the clearance, MSA and minimum airway altitude. It is evident that the instructions provided by ATC to flights without a standardized arrival are most likely to miss MSA and minimum airway altitudes. This condition, combined with lack of good cockpit resource management between crew and ATC, may prompt flight crews to enter unwanted flight scenario.
The investigation established that the Cali Approach Controller only learned of the event days later when the operator's safety message arrived. This allows to conclude that the surveillance and alert service by ATC was not provided to AV-9882 contrary to regulations.
Cali's radar system features an according monitoring and alerting system, this was however deactivate by default due to database issues. In addition, Cali approach did not notice the flight level change nor did the crew announce the descent.
With respect to human factors the GRIAA analysed that the first officer as well as the captain lost situational awareness, when they accepted and complied with ATC instructions to first descend to FL190 and subsequently 6000 feet without noticing the aircraft would fly below minimum airway altitude and below MSA. The captain, pilot monitoring, did not detect the danger until the GPWS activated with the "TERRAIN! TERRAIN!" call, at which point an incomplete evasive procedure was initiated.
This article is published under license from Avherald.com. © of text by Avherald.com.
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