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Overheard

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weather radar

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A third-party weather service provider (data links graphical weather information directly into after-market avionics installed on the flight deck)

Scenario Continued 1645Z: Once established on the airway and climbing to the cruise altitude, the first officer uses the graphical weather display to bring up the DFW weather graphic. The airport situation looks good, but some precipitation is observed on the western edge. The first officer pulls up the national weather picture for another look, and sees scattered precipitation in a line through central Texas. No other weather appears on their route but he decides to keep and eye on the Texas situation. 1820Z: After routine hand-offs through numerous sectors, N123AB is now talking to ZFW. There appears to be some rerouting around weather west of DFW, and the graphical weather display helps to portray the situation to the flight crew in real-time.
How does replanning occur?
1840Z: N123AB is issued a vector taking it off the flight plan and asked to descend to FL290. Based on graphical weather data, it appears the controller is planning to vector N123AB northward around a cell blocking the route to BOWIE. The PIC estimates this will add 10-15 minutes to the arrival time and requests vectors to the Southwest arrival gate (Glen Rose). The request is denied. The first officer reprograms the FMS, adding a place/bearing/distance waypoint at a location which he guesses they’ll be turned inbound. The FMS shows a 14 minute arrival delay with adequate fuel reserves. 1920Z: ZFW notifies N123AB that the Bowie arrival gate has been closed due to weather. His is vectored to Glen Rose and instructed to hold there and plan a Glen Rose Three arrival. The graphical weather display shows heavy precipitation covering the Bowie arrival gate. The first officer programs the FMS as instructed. The arrival delay is now 19 minutes, but the fuel reserves are still within the legal minimum. 1955Z: Following successive descents in a holding pattern, N123AB is instructed to proceed with the Glen Rose Three arrival. 2020Z: N123AB lands on 18R following an ILS approach.
Conclusion and Commentary
By having current graphical weather information, the N123AB crew had information on the DFW situation, although the resolution, formats, and coverage of this third-party weather information is not necessarily adequate to support all flight replanning decisions. Had they been able to plan better, they would have saved perhaps 40-50 minutes off their flight, which arrived at the DFW fixed-base operator almost an hour later than expected. However, the situation awareness provided by the weather information justified the control instructions and avoided possibly of the PIC using the radio to request an explanation for the longer course.
They were victims of the ‘four-poster’ Metroplex arrival arrangement at DFW. When their destination arrival gate closed, they were required to wait in line for a slot at a different arrival gate, which by then was backed up.
　
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