A321 pilot reported a loss of 400 feet of altitude due to autopilot failure; weather; and turbulence...

Attributes
ACN	1576728
Time
Date	201809
Local Time Of Day	1201-1800
Place
Locale Reference	ZKC.ARTCC
State Reference	KS
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	A321
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Total 17000
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence

Narrative:

While in cruise flight at FL350 in IMC with only green precipitation depicted on radar display; we encountered moderate turbulence causing an increase in airspeed followed by a sudden decrease in airspeed. The autopilot was unable to maintain altitude. We lost approximately 400 feet of altitude before the descent could be halted and a climb initiated to get back to our assigned altitude. ATC noticed our altitude deviation and queried us about it. We made a PIREP [pilot report] regarding the turbulence and inability to maintain altitude. ATC advised us that there had not been any separation conflict due to our altitude deviation. Unknown weather created moderate turbulence and loss of energy to maintain altitude.

Original NASA ASRS Text

Title: A321 pilot reported a loss of 400 feet of altitude due to autopilot failure; weather; and turbulence.

Narrative: While in cruise flight at FL350 in IMC with only green precipitation depicted on radar display; we encountered moderate turbulence causing an increase in airspeed followed by a sudden decrease in airspeed. The autopilot was unable to maintain altitude. We lost approximately 400 feet of altitude before the descent could be halted and a climb initiated to get back to our assigned altitude. ATC noticed our altitude deviation and queried us about it. We made a PIREP [Pilot Report] regarding the turbulence and inability to maintain altitude. ATC advised us that there had not been any separation conflict due to our altitude deviation. Unknown weather created moderate turbulence and loss of energy to maintain altitude.

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.