A319 captain experiences FMGC anomalies during descent on the SKNRD3 arrival to iah. Although the FM...

Narrative:

Cleared to descend via SKNRD3 arrival into iah. Prior to descent; both pilots checked the restrictions on the arrival with the FMGC. All in agreement. Descent started. First restriction at beatl was between FL240-280. However the pfd showed the constraint as FL280 and leveled off rather than descending through the altitude window. This was repeated at doobi and sknrd. Each time the constraint was double checked; but the airplane thought the restriction was a hard altitude. This caused doubt as to whether the airplane was going to meet the subsequent restrictions. Workload was increased and at one point; the flying pilot had to disconnect the autoflight and hand fly the descent. We even went to one of the restrictions and changed the window to a mid-altitude; for example: FL240-280 became FL260. Also during the descent we went out of des into open des. Which now meant the bottom altitude needed to be changed to the most restrictive altitude instead of the bottom altitude of descend via. It seems this is happening frequently into iah. It is odd; because the FMGC has the correct constraints; but the autoflight is flying it differently.

Original NASA ASRS Text

Title: A319 Captain experiences FMGC anomalies during descent on the SKNRD3 arrival to IAH. Although the FMGC shows the correct altitude window at each waypoint; the PFD shows only the upper limit and the autopilot choses to level off there at each fix.

Narrative: Cleared to Descend Via SKNRD3 Arrival into IAH. Prior to descent; both pilots checked the restrictions on the arrival with the FMGC. All in agreement. Descent started. First restriction at BEATL was between FL240-280. However the PFD showed the constraint as FL280 and leveled off rather than descending through the altitude window. This was repeated at DOOBI and SKNRD. Each time the constraint was double checked; but the airplane thought the restriction was a hard altitude. This caused doubt as to whether the airplane was going to meet the subsequent restrictions. Workload was increased and at one point; the flying pilot had to disconnect the autoflight and hand fly the descent. We even went to one of the restrictions and changed the window to a mid-altitude; for example: FL240-280 became FL260. Also during the descent we went out of DES into OPEN DES. Which now meant the bottom altitude needed to be changed to the most restrictive altitude instead of the bottom altitude of Descend Via. It seems this is happening frequently into IAH. It is odd; because the FMGC has the correct constraints; but the autoflight is flying it differently.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1244848
Time
Date	201503
Local Time Of Day	0601-1200
Place
Locale Reference	ZHU.ARTCC
State Reference	TX
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	A319
Operating Under FAR Part	Part 121
Flight Phase	Descent
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 24000 Flight Crew Type 8000
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy

A319 captain experiences FMGC anomalies during descent on the SKNRD3 arrival to iah. Although the FMGC shows the correct altitude window at each waypoint; the pfd shows only the upper limit and the autopilot choses to level off there at each fix.