MD-80 Series (DC-9-80) Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Confusion; Situational Awareness; Workload
ATC Issue All Types; Aircraft Equipment Problem Critical
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Chart Or Publication; Human Factors; Procedure
While on the ground prior to our departure we reviewed our assignment of the new IAD GIBBZ1 RNAV arrival. We performed the basic math for descent rates; speeds and distances [necessary to comply with the multiple crossing restrictions] and determined that attempting to comply constituted an unsafe operation. As a result we asked center for [and received] a route change onto the DOCCS1 arrival.While en route we were reassigned the GIBBZ1. We informed ATC we could not accommodate the vertical descent profile and they assigned acceptable level offs. Most of the new RNAV arrivals into the DC area include descent rates and speeds compatible with Airbus and B-737s but not with MD80s. When the first iteration of the ELDEE arrival came out it had the same problems; it was changed twice before the distances; altitudes and speeds made operational sense. Please look at typical ground speeds and descent rates for non-FMS aircraft and give us an arrival that will not put our certificates at risk every time we fly. I spoke to the area manager this morning. We both agreed that we loved the ELDEE arrival. That should provide a good template for reengineering.
The reporter advised that while the aircraft in his MD-80 fleet were equipped with GPS positioning they did not have a full function FMS; most pertinently providing no vertical navigation planning and or guidance capability. Thus; complying with multiple complex--and sometimes demanding with respect to distance vice required altitude loss--crossing restrictions requires nearly complete flight crew attention. He believes that successful 'manual' compliance with the vertical navigation restrictions requires mentally reverse-calculating the crossing altitude at each waypoint based on where they have to be at the subsequent waypoint (starting backwards from the last waypoint on the STAR) and then establishing a rate of descent/speed combination that will satisfy the performance capabilities of the aircraft as well as the compliance with the charted restrictions.The reporter believes these complex STARs are incompatible with aircraft without fully functional VNAV capability. He feels the workload involved on an aircraft not so equipped is inconsistent with safety of flight considerations.
An MD-80 Captain refused to accept the GIBZZ RNAV STAR to IAD because his GPS equipped aircraft was not equipped with an FMS with full functional VNAV capability. He cited the complexity of the waypoint crossing restrictions as incompatible with flight safety.