Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 40; Flight Crew Total 18150; Flight Crew Type 6500
Troubleshooting; Training / Qualification; Human-Machine Interface; Confusion; Distraction
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Flight Crew Overcame Equipment Problem
Equipment / Tooling; Human Factors
We had just departed CNO on RWY 08R and were complying with the departure procedure on the back of the 10-9 chart for obstacle clearance. I was the pilot not flying and the First Officer (FO) was the pilot flying. We were assigned 7000 ft MSL which we were maintaining. The first fix was the PDZ VOR. When we got to the VOR; a newly installed GTN 750 touch screen dual GPS unit gave conflicting information as to the next course out of PDZ for NIKKL intersection which was our next checkpoint. The GTN750 Flight Plan screen was accessed on the FO Unit at this point. The magenta highlighted fix after crossing PDZ was showing a next course of approximately 062 degrees magnetic for fix NIKKL. In actuality; NIKKL was more like a 100 degree magnetic course. The controller at So Cal queried us as to what our routing was and I verified that what she said was correct as what was programmed into the GTN750. The controller said; 'Just fly direct NIKKL' which we did and she was very polite. I honestly don't know what went wrong with the GTN750. The VOR and COMM radios are set up in the unit and the VOR frequencies were set properly. I have seen the GTN750 fail to sequence to the next waypoint and as a result of being able to scroll through the Flight Plan seeing all the waypoints with the touch screen panel; it sometime happens that when you cross a waypoint; the screen seemingly hides the waypoint you just crossed and will sometimes jump ahead to a waypoint that is further down in the flight plan rather that the waypoint that is immediately following the one you just crossed. In any event; it is a very confusing situation and the design of the Garmin GTN 750 was evidently made for light aircraft instead of a transport category aircraft. We have had all types of problems with it from the day that we got it out of the avionics shop. The first flight that we ever flew with it; we found out airborne that one DME receiver was counting up rather than counting down to the navigation fix that we were proceeding to. Maintenance at our base ascertained that the avionics shop had not even hooked up the DME. As a result; it took a team on avionics specialists approximately 3 weeks to figure out how to connect up the DME from the GTN 750 to our DME indicators. As well; there are no warning lights to alert the pilot that when the ILS is selected; the pilot needs to switch the CDI from GPS to VLOC. So it would be completely possible to shoot an ILS approach with the CDI needle in the GPS position and possibly have a horrible accident as a result. Our approach checklist is the only fail safe item preventing this from happening. Our training on the GTN750 was an interactive video that we did on our home computers and although we had a very short hands on school in the general office; the interactive video was woefully inadequate. There are a lot of unusual things about the installation. Number one; when the GPS mode of the CDI is selected; the RMI needles point to the waypoint selected in the GTN750; not the VOR selected on the NAV screens of the GTN750 as would be in a 'normal GPS installation'. Also; the company has placarded the GTN750 as 'VFR ONLY'. We were VFR at the time of this occurrence; but as always in the IFR environment. Another problem is that the installation of the GTN750s is all the way back to the end of the pedestal making it very hard to see and hand fly the plane at the same time. At the time of this occurrence. The FO was hand flying the aircraft. When the course change required to go to NIKKL intersection was depicted as approximately 062 degrees after the PDZ VOR; both myself and the flight engineer called this out to the FO and in actuality; he was correct in thinking the course was approximately 100 degrees and the information in the GTN750 was incorrect. I am very sorry for this mistake and we are going to have to study the GTN750 more carefully to learn of its tendencies to elicit incorrect information at the most crucial times.[Additionally] we were having difficulty with an amber CDI light that was illuminated on the overhead indicating that our compass system was in error. As well the Vertical Gyro light illuminated and I looked up at my horizon and saw that it was in error with the Standby Horizon and the FO Horizon. Positioned Captain on Alternate which bootstrapped me to the FO vertical gyro and this extinguished the light. The CDI light went out on its own but this caused confusion and the FO went approx. 3 or more miles south of NIKKL before starting an aggressive turn back to get on the East Bound airway that we had filed. Cannot remember the exact airway. The controller queried us about our course and I stated that we were; 'In the turn'.
Captain of a large transport category aircraft reported the GPS provided wrong heading to fix information which resulted in flying off course.