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Threat and Error of Iran Aseman Airlines Pilots
“Threats are defined as “events or errors that occur beyond the influence of the flight
crew, increase operational complexity, and which must be managed to maintain the margins of
safety.” (Maurino, 2005) one of the flight crew roles before and during a flight is to assess any
threats that may present or may appear. Some of these threats may be adverse meteorological
conditions, any terrain that could possess a danger to the flight like mountains, or aircrafts
malfunctions. When the flight crew detects a threat, they must make a decision on how to avoid
or alleviate the hazards of said threat minimizing the errors. “Errors are defined “actions or
inactions by the flight crew that lead to deviations from organizational or flight crew intentions
or expectations.” (Maurino, 2005) Errors could be due to various reasons, some of these reasons
could be lack of experience, having expectation bias, or being ill prepared for the flight. When
analyzing the accident involving an ATR 72-212 operated by Iran Aseman Airlines that occurred
on February 18, 2018, the threats and errors that occurred during the flight can be easily detected
when reading the report. The crew may have been able to avoid the accident that happened on
that day. However, it is hard to blame the crew as no one knows what was really going on
through their minds at the time of the accident.
The Iran Aseman flight 3704 was scheduled to fly from Tehran to Yasuj, Iran when it
impacted Mount Dena range just 15 kilometers from Yasuj Airport. There were 66 total
occupants including 6 crew members that did not survive the accident. The weather report
mentions that there were clouds with ceilings at a height of 15,000 feet, mountain wave
turbulence of up and down drafts reaching 3,000 feet per minute, isolated cumulonimbus clouds,
as well as icing conditions were present. The aircraft was initially flying at flight level (FL) 210
and requested a descent to FL170 which was approved by the locations area control center
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(ACC). Despite them requesting FL170 they programmed the autopilot to descent to FL150
which was below the minimum safe altitude (MSA) of 15500 feet. The aircraft first experienced
an updraft which the autopilot tried to correct for. As the aircraft autopilot system was correcting
for the updraft the aircraft entered a downdraft which again the autopilot system attempted to
correct. At this point the aircraft’s calibrated airspeed had dropped from 205 knots to 130 knots,
the pilot in an attempt to fix the issue selected FL140 as the altitude to maintain. The CAS
dropped even more to 118 knots. The aircraft stall warning came on causing the autopilot to
disconnect, the pilots re-engaged the autopilot and again chose FL150 as the altitude to maintain.
The aircraft then got close to mountainous terrain and the autopilot disengaged again as the
aircraft continued to descend. The flight crew saw the mountain ahead and unsuccessfully
attempted to divert away from it impacting the side of the mountain.
According to the Risk management handbook, “Some common threats include:
Malfunction of aircraft systems, engines, flight controls, or automation, Various unforecast
weather hazards, Collision hazards, including wildlife on airports and birds in the air, unexpected
sudden reduction in visibility.” (Risk management handbook 2022) When taking this into
account we can see that there were many threats in this flight. One of the threats that is quickly
noticeable is the collision hazard, flying in a mountainous terrain at near or below the height of
the tallest summit is a very serious threat. This could lead to a control flight into terrain (CFIT),
which is when a pilot unknowingly is in a stable flight flying directly into terrain like a
mountain. Another threat that is noticeable in the report but with no SIGMET issued making it
an unforecast weather hazard is the mountain wave phenomenon (MTW). As mentioned above
MTW could have up and down draft of 3,000 feet per minute similar to that encountered in a
thunderstorm. This could be very problematic as it could cause loss of control in-flight (LOC-I),
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which according to the analysis report of 2019 conducted by IATA, “LOC-I was the most
frequent category of fatal accidents, representing 60 fatal accidents or about 44% of fatal
accidents.” (Loss of control in-flight accident analysis report 2019 ... 2019) These threats were
not dealt with correctly, causing errors in the flight ending in an accident.
“Unmanaged and/or mismanaged errors frequently lead to undesired aircraft states.
Errors in the operational context thus tend to reduce the margins of safety and increase the
probability of adverse events.” (Maurino, 2005) In the case of this accident there were many
errors that made the adverse event occur. The very first noticeable error is programming
autopilot to a flight level that was not approved. When they descended to FL150 they were
below the MSA by 500 feet. Although, MSA during instrument flight rules give a 1,000-foot
separation from the highest obstacle they were 500 feet below the MSA or closer to the
obstacles, in this case the mountains. Any fluctuation as the ones since due to the MTW placed
them well below the MSA and at the height of the mountains. When the aircraft first experienced
the updraft, the pilots left the autopilot attempt to correct and descend back to the programmed
altitude, instead the pilot flying should have disconnected the autopilot, lowered the speed to
maneuvering speed (VA is 175kts for the aircraft of the accident) so that the load factor would
not cause structural damage, and maintained straight and level flight without using abrupt
maneuvers. The crew instead let the automation use abrupt maneuvers to return to FL150 and
encounter a downdraft which placed them in a stepper descend. Another situation where the
same decision was made was when the aircraft stall warning sounded and the autopilot
disconnected, the pilot should have again taken control of the aircraft and not let automation
which had no idea why it was climbing and descending so abruptly attempt to fix the issue.
These pilot errors ultimately resulted in the lives of all of those in board to end.
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There are many ways this may have been mitigated; however, no one will ever know if
this would have been enough to prevent an accident from occurring on that day. One thing they
should have done was flying the authorized flight level, this may not have prevented the draft of
the MTW but may have prevented them from going to low below the MSA. They should have
also placed the airplane to the prescribed VA disconnected the autopilot and attempted to
maintain straight and level flight. Unfortunately, this was not the case, the pilots failed to have
good cockpit resource management, aeronautical decision-making, they did not anticipate bad
weather when analyzing their weather brief, and lastly, they failed to follow correct stall
recovery procedures as well as checklists. The flight crew bad threat and error management led
to the catastrophic accident that occurred. Pilots must use these unfortunate events to learn from
them and find possible solutions so that they can avoid or correctly manage similar situations.
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References
Islamic Republic of IRAN Civil Aviation Organization Aircraft Accident Investigation Board.
(2020, June 15). https://reports.aviation-safety.net/2018/20180218-0_AT72_EP-ATS.pdf
Loss of control in-flight accident analysis report 2019 ... IATA. (2019).
https://www.iata.org/contentassets/b6eb2adc248c484192101edd1ed36015/loc-i_2019.pdf
Maurino, D. (2005, April 20). Tem in practice - faasafety.gov. FAA Safety.
https://www.faasafety.gov/files/gslac/courses/content/670/2028/TEM by Captain Dan
Maurino.pdf
Risk management handbook. (n.d.).
https://www.faa.gov/sites/faa.gov/files/2022-06/risk_management_handbook_2A.pdf
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