Date: 201811
Location: SEQM.Airport, FO
Flight conditions: IMC
Weather elements / visibility: Thunderstorm; Rain
Light: Night
Aircraft: Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Aircraft component: Weather Radar
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Fatigue
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Diverted
Contributing factors: Airport; Aircraft; Company Policy; Procedure; Human Factors
Primary problem: Human Factors

Narrative: The pairings that operate between ZZZ and Quito create high levels of fatigue and reduced safety margins while operating in a high threat environment. Night time flying into Quito's airport is considered high risk for several factors outlined in the company's [manuals]. Factors that include high mountainous terrain; low visibility approaches; low ceilings; language barriers; wind shear; etc.The company has identified several hazardous threats to operations while operating in South America clearly documented in the [manual]; but allows its scheduling of crews to happen with no regard for increased and unnecessary risk associated with fatigue.The current crew scheduling prevents any and all aircrew from being at their highest level of performance for the elevated risk present in ZZZ-UIO. Just being aware that the flight is conducted at night with only 2 crew members that have been on duty prior to their Quito flight speaks volumes about a disparity between managing high threat operations and safety.Current Quito crew scheduling should be considered a clear and present threat to conducting the highest level of safe operations in one of the highest threat environments. In addition the crew is asked to rest at a hotel with an elevation above sea level of over 9;000 feet; and expected to rest for another high threat event within 25 hrs. The travel time to and from the airport further diminishes scheduled rest time.Studies have shown that even the best athletes can take a minimum of 3-4 days to properly acclimate their bodies properly to high altitudes yet [company] schedules their crews to rest at an elevation of 9;000; above sea level and asks that it be done during daytime hours to prepare for ANF from the South America. While the current scheduling may be within Federal Guidelines; the facts clearly demonstrate that just scheduling within the FAR 117 guidelines is not properly mitigating risk. Quito is high risk; scheduling crews to fly there who have been on duty during the day and resting them at high elevation for a subsequent ANF event is an oxymoron with regards to operating safely.The flight that I was a part of dealt with fuel planning that was marginally adequate for the forecasted weather; a weather radar that failed in-flight; poor weather; poor communication from ATC; excessive navigation clearances that taxed an already diminished cognitive state due to fatigue; and an archaic navigation system in the [aircraft] that further diminishes situational awareness in a high threat environment.All of my above comments; and our crew operating on razor thin margins were a contributor to our flight diverting and landing with a fuel state of 3.7. This is should not be allowed to happen in a world where our company preaches safety as a way of life. As a crew we did everything [company] asked of us but it is my sincere opinion that our crew and many other crews that fly the ZZZ to UIO flight are operating on the razors edge with threats that are compounded by high risk scheduling. [Pilot] was on the razors edge and while I am thankful that we landed safe at our divert; I can assure you that the relevant facts of any mishap investigation would have called to attention all of the unmitigated risk and fatigue that is created by crew scheduling.




Synopsis: Air carrier pilot reported dangerous scheduling practices which lead to fatigue during a weather radar failure and diversion under less than desirable conditions.