Airbus first officer and center controller reported descent below cleared altitude. The aircraft beg...

Attributes
ACN	1433006
Time
Date	201703
Local Time Of Day	1201-1800
Place
Locale Reference	CLT.Airport
State Reference	NC
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Airbus 318/319/320/321 Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR CHSLY 2
Flight Plan	IFR
Component
Aircraft Component	Altitude Hold/Capture
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 13900
Person 2
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Radar 8.0
Events
Anomaly	ATC Issue All Types Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

Narrative:

At FL260 and with a speed restriction of 290 knots just before the fix bluej we were instructed to descend via the CHSLY2 south transition at burrz. Being that we were under the altitude for bluej we inserted a hard altitude for burrz of FL240 as per company policy on the special info message section of the release. We had 9000 ft selected on the MCP as the bottom altitude for the arrival. At some point before burrz the airplane began descending below FL240. We were briefing a possible runway change and did not stop the descent until FL236. At the same time ATC called and asked about our altitude. I replied that we were trying to control altitude and would call him back. The airplane was not responsive through the MCP panel at all. The controller cleared us to descend to FL230. At that time he instructed us to call washington center and gave us a phone number. I replied that we were busy trying to control the altitude of the aircraft and would call him back. We then received the phone number and switched to atlanta center and had an uneventful approach and landing. We wrote up the MCP and altitude hold in the logbook and contacted maintenance. I do not know the outcome as we had to swap airplanes for our next leg.the chsly arrival is all but unusable in the A320 series. There needs to be a software change and the controllers need to stick with their procedures and stop issuing so many speed and altitude restrictions in conjunction with the arrival.

Original NASA ASRS Text

Title: Airbus First Officer and Center Controller reported descent below cleared altitude. The aircraft began an uncommanded descent below FL240 and the crew could not stop the descent until FL236. Reportedly known Airbus FMGC anomaly on this STAR contributed to the early descent.

Narrative: At FL260 and with a speed restriction of 290 knots just before the fix BLUEJ we were instructed to descend via the CHSLY2 south transition at BURRZ. Being that we were under the altitude for BLUEJ we inserted a hard altitude for BURRZ of FL240 as per company policy on the special info message section of the release. We had 9000 ft selected on the MCP as the bottom altitude for the arrival. At some point before BURRZ the airplane began descending below FL240. We were briefing a possible runway change and did not stop the descent until FL236. At the same time ATC called and asked about our altitude. I replied that we were trying to control altitude and would call him back. The airplane was not responsive through the MCP panel at all. The controller cleared us to descend to FL230. At that time he instructed us to call Washington Center and gave us a phone number. I replied that we were busy trying to control the altitude of the aircraft and would call him back. We then received the phone number and switched to Atlanta Center and had an uneventful approach and landing. We wrote up the MCP and altitude hold in the logbook and contacted maintenance. I do not know the outcome as we had to swap airplanes for our next leg.The CHSLY arrival is all but unusable in the A320 series. There needs to be a software change and the controllers need to stick with their procedures and stop issuing so many speed and altitude restrictions in conjunction with the arrival.

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.

Airbus first officer and center controller reported descent below cleared altitude. The aircraft began an uncommanded descent below FL240 and the crew could not stop the descent until FL236. Reportedly known airbus FMGC anomaly on this STAR contributed to the early descent.