On the Design of Flight-Deck Procedures - Intelligent Systems ...

8. Change in operational environment. Example: Mountainous terrain.With mergers and acquisitions came new routes and new environments. For example, when Deltaacquired Western, it acquired routes into a large number of airports, some more adequate than others, inthe western U.S. This required a reexamination of Delta's procedures for approaches and departures toand from airports with high surrounding terrain.9. Cross-fleet standardization. Example: Shift to lower power radar sets.In a previous paper (Degani and Wiener, 1990) we discussed an airline which had a large fleet of DC-9s,and a small number of MD-80s (at that time DC-9-80). The -80 carried a radar set requiring much lesselectrical energy than the DC-9s. At that time pilots were allowed to fly both aircraft. Because of thelower energy set, the -80 radar could be turned on in ground operations without hazard to groundpersonnel; the DC-9 sets could not be. Fearing that pilots flying both models might inadvertently turn ona DC-9 set on the ground, the standards group decided to adopt a conservative procedure, and the MD-80 radar was operated in the same manner as the DC-9. The somewhat sub-optimal procedure for theuse of the -80 radar was a minor consequence.10. Marketing influences. Example: Better service for first-class passengers.The following example illustrates the extent to which marketing considerations can influence cockpitprocedures. In-flight service has advised flight management that better service can be provided to firstclass passengers if 2L (second door on left side of the aircraft) rather than 1L, is used for boarding anddisembarking passengers. This way the tourist-class passengers do not have to walk through the firstclasssection. The procedure instructs the B-757 flight crews to “start the APU after landing in order toshutdown the left engine as soon as possible after gate arrival 20 .” The procedure also addresses safetyimplications of having the jetway so close to the left engine -- “pay particular attention to the position ofjetway. If you think you are being told to taxi too far past the jetway and are concerned about the leftengine [hitting the jetway], don’t hesitate to stop and asked to be towed in or talked in.”11. New company policy. Example: Required use of flight directors.Airlines have had to strike a balance between requiring the use of certain automation features, and leavingthis choice to the discretion of the crew (see Appendix 1). This is one of the more difficult policy issuesin procedure writing today. On one hand management may feel that it has the prerogative to set policyfor the use of automation. On the other hand, flight crews generally feels that such decisions shouldremain in the cockpit (see Wiener and Curry, 1980, Guideline No. 5, p. 1009).One example would be a policy for the use of the flight director on takeoff. We have found a variety ofprocedures among the airlines on this issue. Many pilots prefer not to use it (presumably to de-clutter theADI display); some companies now require its use, principally for its availability for pitch guidance inwindshear encounters. One company specifies that the flight director not be used on takeoff untilreaching 3000 feet unless the aircraft is equipped with a windshear guidance program.12. New company philosophy. Example: “A captain's airline”Delta Airlines had once prided itself on being “a captain's airline.” There is no precise definition of whatthis means, but in general it reflects a view consistent with military discipline, namely that the captain issupreme in the cockpit, and the junior officers are there to carry out his commands. Following a seriesof serious incidents (fortunately no accidents) during the summer of 1987, Delta reconsidered thisphilosophy, and instituted a CRM course that stressed crew coordination and cross-checking (Byrnes20 The reason that the APU should be started before shutting down the left engine also involves passenger comfort. If theleft engine is shut down (and with it the left hydraulic pump) a power transfer unit (PTU), supplying hydraulic power to theleft hydraulic system, is automatically activated. However, the PTU is rather noisy and annoys passengers sitting in theback of the aircraft. To prevent the PTU from being automatically activated, the APU is started.66