B737-300
Confusion; Distraction; Situational Awareness; Workload
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Aircraft
Two days in a row; flying two different -300 aircraft; we were unable to fly or determine where we were supposed to be while flying the same SSTIK RNAV Departure out of SFO. The aircraft did not appear to fly the proper arc to the first point and missed the turn after the first point on both occasions. Luckily ATC intervened and gave us vectors without our asking. They must know there is a problem with this combination (-00 and/or SSTIK Departure). Additionally; with VNAV selected on both occasions; the aircraft failed to fly the indicated VNAV speed above 10;000 feet. After holding 250 knots to 10;000 feet; the aircraft would lower its nose and accelerate past the VNAV indicated climb speed requiring Pilot intervention prior to the clacker. We were so surprised the first time that we took extra care checking the route the second time to make sure we had not created the situation. The results were identical.We should not be flying -300 aircraft in the new aircraft airspace. Its' inability to fly some RNAV departures combined with the lack of moving map produces stressful and additive conditions that puts Pilots in the RED. This distraction will lead to subsequent issues (flap overspends; missed crossing restrictions; etc.) and dangerous situations caused by the lack of capability of the avionics.
A B737-300 Captain reported his aircraft had difficulty tracking the SFO SSTIK RNAV route after takeoff and properly flying the VNAV path above 10;000 Feet.