Communication Breakdown; Confusion
ATC Issue All Types
Chart Or Publication; Human Factors; Procedure
[Subject:] CLIMB and DESCEND VIA clearances and phraseology.Sometimes 'less is more' but the use of abbreviated clearances with something as complex as some of these STARS and SIDS is very likely to result in confusion and error for both pilots and controllers.Some of the bigger threats that these procedures contain:Similar language [with differing intent]:- '...MAINTAIN [FL/altitude XXX]...' deletes all charted altitude restrictions but '...CLIMB VIA; EXCEPT MAINTAIN [XXX IAS]...' requires compliance with published altitudes [but not published speeds].- Similar sounding clearances with opposite meanings. Example: 'RESUME PUBLISHED SPEEDS and RESUME NORMAL SPEEDS'Poor/contradictory charting: - Bold Print superseded by small print. Example: Top Altitudes may be lower than charted constraints and noted only in small print at the bottom of the chartCounter-intuitive procedures- Top Altitudes remain in effect even when cleared direct to a point beyond an intersection with a higher charted altitudeConflicting procedures- ICAO vs. FAA differences are a particular threat for long haul operations
A Boeing Widebody first officer addressed his concerns regarding ambiguity of abbreviated ATC/flight crew phraseology with respect to complex RNAV SIDs and STARs.