An EMB145's LGA STBNZ TWO RNAV DEPARTURE FMS database contains two STBNZ waypoints at 0 DME distance which caused the aircraft to transition from the FMS procedure to a roll mode. The crew selected the heading mode after overshooting the BIGGY transition.
Synopsis
An EMB145's LGA STBNZ TWO RNAV DEPARTURE FMS database contains two STBNZ waypoints at 0 DME distance which caused the aircraft to transition from the FMS procedure to a roll mode. The crew selected the heading mode after overshooting the BIGGY transition.
Narrative
[Recently] LGA began implementing RNAV departures. We were assigned the STBNZ 2 to BIGGY. We noticed that the FMS duplicated the STBNZ waypoint in the middle of the procedure. It showed 0.0 NM between the duplicate points. This seemed strange; and I would have normally deleted the duplicate waypoint; but there is a prohibition in the Pilot Handbook against manually editing waypoints in an RNAV procedure. The airplane flew to STBNZ; failed to anticipate the turn to MUNNZ; and then went into roll mode. We switched to HDG and started turning immediately but there was no way to avoid overshooting the course from STBNZ to MUNNZ. This procedure is coded incorrectly in the database. It was SW NZ5.2 with the DB dated 23 SEP to 20 OCT 2010. I took pictures of the 3 pages of 'Procedure Review' that show the coding error and emailed them. After investigating further; I discovered that there is a similar coding error (duplicate waypoints) in 3 of the 5 new RNAV departures for LGA. I also tried loading the new RNAV departures for PHL but did not see any errors on these procedures. Furthermore; I spoke to another Captain and he was able to duplicate it in another airplane; so based on this; I believe this is a fleet wide problem. My recommendations would be 1) a memo stating no RNAV departures out of LGA and 2) have dispatch file all flights out of LGA as unable RNAV departures until Honeywell fixes the coding of these procedures.
NASA callback
The Reporter stated the FMS RNAV loading procedure is standard and that no route discontinuity was seen in the transition from the common waypoint STBNZ to enroute transition to BIGGY. However STBNZ is in the procedure twice and if he manually deletes the second STBNZ the procedure appears to remain operable although he did not try to actually fly it because of his company's prohibition of modifying an FMS RNAV. He checked four other aircraft and found the database error in all four. Also there are two other new LGA FMS Departure procedures with the same issue; one is the NTHNS and he is uncertain without looking what the third is. His company has issued a bulletin to pilots and they are not longer allowed to fly these procedures. A recent database cycle change did not correct this error.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.