Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3
Situational Awareness; Confusion
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Chart Or Publication; Aircraft
I was working Final and cleared Aircraft X on the RNAV approach from a fix at 4000 feet. The next fix had a crossing restriction of 3000 feet. Aircraft X was not descending and I asked the pilot if his FMS shows the fix at 3000 feet; or at or above 3000 feet. The pilot said that his FMS shows that fix is at or above 3000 feet. I indicated that the approach plate has the fix AT 3000 feet and told them to descend. I told the Supervisor on duty about the situation. There have been multiple E175s having this issue where the FMS shows an 'At or Above' altitude on the approach; and the approach plate is an 'AT' altitude. Have [Company] double check their FMS to make sure it matches the approach plates.
We were flying the LINKK1 STAR into IAH with the GPS Z 27 approach transition. We were given a different descent clearance to 4000 expedited and slow to 210 kts. We were then cleared for the GPS 27 approach. After passing the fix SYYKO (the last fix before intercepting the final approach course) ATC asked us what our FMS read for the restriction at SYYKO. We stated that it read 'at or above 3000 feet.' ATC then informed us that it should read a hard altitude of 'at 3000 feet.' We were then given clearance to descend to 3000 feet and again cleared for the GPS 27 approach. We finished the approach and taxied to the gate without further incident. Once we got to the gate I called the Houston approach controller and spoke with him about the altitude deviation. He stated that this had been a reoccurring issue with our E175s flying the GPS Z 27 approach when crossing the SYYKO fix. We discussed the issue with the FMS database as well as the VNAV logic of the aircraft to want to stay high until it can perform a 3.0 degree glidepath to the next altitude restriction. He was very helpful and I told him I would send an email to the chief pilot to alert the rest of the pilot group to the FMS error and the need to manually input the 3000 foot restriction at the SYYKO fix. He also stated that there was no traffic in the area and we didn't cause any other disruption to the flow. Also I have never noticed this error using the same fix when on the ILS 27 approach.We always read through the arrival fixes and verify each waypoint restriction however on most approaches there are not the same kinds of restrictions so verifying each waypoint altitude is not a normal part of the briefing. Also considering that with the use of ATC radar vectors we don't actually fly over many of the points on an approach and our altitude and speed are constantly being amended by ATC. On our CAT 2 checklist though one of the required briefing items is to verify every point on the approach and the associated altitude. This kind of expanded briefing and just always double-checking the approach chart to make sure you don't miss something would help prevent these kinds of deviations. If we would have noticed the discrepancy between the FMS and the chart we could have queried ATC to verify that we should be at 3000 feet at SYYKO.
I90 TRACON Controller and EMB175 flight crew reported the E175s have an FMS anomaly where a crossing restriction is programmed as 'at or above' when it should be 'at.'