Date: 201811
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: 10
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Communication Systems
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Workload; Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: The aircraft had the WiFi system deferred; which meant that our backup [performance system] would not be available in flight if needed. It was later needed and unavailable for landing. On several occasions during the flight the CDU message 'NO ACARS COMM' was displayed and as a result ACARS was unavailable several times throughout the flight for unacceptably long periods of time. As a precaution we obtained ZZZ ATIS and landing data early but as expected the ATIS would change just prior to our arrival and thus require us by company policy procedure and FARs to obtain the most current landing performance before landing. We had also seen early problems with getting [performance] data to properly send and receive because on more than one occasion we received the CDU message 'UPLINK REJECTED' and 'REQUEST TIMED OUT' The descent and arrival phase was very busy and we had a high task loading due to heavy air traffic and the corresponding high ATC instructions and constant clearance changes. There was also quite a bit of turbulence and associated coordination with the flight attendants to contend with. At this time ATC informed us that a new ATIS was current and to advise when we had the information. The new ATIS happened to coincide with this already busy phase of flight and as an additive condition the 'No ACARS COMM' message was currently displayed on the CDU. We were now forced to contend with one pilot obtaining ATIS data over the radio while the other pilot handled the high ATC volume and the Pilot Flying duties. The new ATIS had significant changes to wind and precipitation at the field and thus would require new landing data for the already restricted runway performance at ZZZ. At this point the 'ACARS NO COMM' message disappeared and I attempted to send a new landing data request. Several minutes passed with no response and I attempted to send another request realizing that we were in unacceptably futile situation of not knowing when or even if we would receive the required landing data in time. WiFi was inop so our [performance data] backup was useless. The only other recourse left was to try and contact Dispatch via ARINC to obtain the data. This was highly time consuming and put us in the very unnecessary and high risk situation of once again splitting our pilot resources at the worst possible phase of flight. As luck would have it the landing data came back just as I started the radio call to ARINC and just as we got our approach clearance from ATC. The required landing data was confirmed correct and the flight landed without incident. The reliability problems with ACARS and [the performance system] have been a constant threat to crews since its inception. This is not my first [report] concerning the Safety problems that ACARS and [the performance system] has caused on flights I have operated. In flight [the performance system] reliability is a serious threat to crew task loading as an additive condition that is not being addressed. It is unacceptable that as a pilot I am required by Company policy procedure and FAR to obtain performance data and then find out that the equipment I have been given to complete the task is unreliable. Unreliable to the point that I will never know for sure when or even if the data I have requested will be sent and received back. It is unacceptable that I need to use the words 'luck would have it the [the performance] data came back just in time' to describe the real life operation of our landing data system.




Synopsis: B737 Captain reported ACARS and performance data communications failures are a threat to safety and crew task loads.