B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 182; Flight Crew Type 6000
Human-Machine Interface
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Aircraft; Human Factors
We were climbing through FL310 on the YOKES4 RNAV Departure; just past the YOKES waypoint. ATC called and asked where we were going; he said we were off course and queried if we were on the YOKES4 Departure. This caught us entirely by surprise; as we had properly verified the YOKES4 RNAV Departure and all its waypoints per SOP while on the ground. ATC then queried if we had a Honeywell FMS; and said that they had been having this problem with other flights. ATC said that flights had been going directly to DEHLI waypoint after YOKES; skipping CHICI. This is apparently what our FMS had done as well. ATC said that this was putting aircraft into conflict with arriving aircraft to DEN; but that we had not been involved in a loss of separation conflict. While we had not seen it occur; apparently the CHICI waypoint was deleted by the FMS after it passed YOKES. We reported the issue to Dispatch via ACARS and the flight continued without further incident.As ATC admitted it was a known issue; a NOTAM could have prevented it. Also; ATC could have verbally warned us at any time prior to YOKES so that we could be extra vigilant.
Controller asked 'where are you going; you're off the YOKES Departure'. We responded that we were proceeding direct DEHLI. Controller then said we were supposed to be heading to CHICI. He added 'is your FMS a Honeywell? We're having that deviation a lot lately and were trying to figure out why.' We notified Dispatch of the deviation; and asked them to verify the make of the FMS/computer. The route was verified during the briefings; and during taxi out the FO scrolled through the route again as we approached the runway to depart on the RNAV. I believe CHICI must have dropped out approaching YOKES.
B737 flight crew is informed by ATC that they are off course on the YOKES4 RNAV departing DEN. The FMC was tracking YOKES direct DEHLI and should have gone YOKES; CHICI; DEHLI. The Honeywell FMC was implicated by ATC.