Narrative:

During descent on the RNAV arrival we encountered wake turbulence from the preceding aircraft. The captain; without verbalizing it; decided to fly off to one side of the center of the arrival route ostensibly to avoid the wake turbulence. I noticed what he was doing and asked if he would prefer to offset to one side of the track within the rnp limits. He said no; he would manually do it to maintain his mental acuity. As soon as I turned back; I noticed and notified the captain that we were 500 ft below the minimum altitude for the next waypoint. He immediately climbed back to the correct altitude. As we approached the correct altitude; ATC asked us for verification of the altitude. No further comments were made by ATC concerning altitude. The captain chose to fly the aircraft off the RNAV course and refuse my recommendation to use the offset function that would have continued to abide by altitude constraints. If the captain had notified ATC of the wake turbulence; they may have allowed an alternate descent profile which would have required less monitoring. If he had verbalized his plan; I could have spoken up and made an alternate recommendation. There are some pilots whose complacency has become so ingrained that they become at odds with SOP's and choose to rationalize making up their own. Simply line checking on short hops doesn't catch the pilot who exhibits this behavior when they are tired or trying to expedite their last leg home. Line checks need to be done much more often and on a mix of long and short legs if they are to achieve any usefulness beyond checking a regulatory box.

Google
 

Original NASA ASRS Text

Title: A321 First Officer reports altitude deviation by the Captain flying when attempting to hand fly off the RNAV arrival to avoid wake turbulence.

Narrative: During descent on the RNAV arrival we encountered wake turbulence from the preceding aircraft. The Captain; without verbalizing it; decided to fly off to one side of the center of the arrival route ostensibly to avoid the wake turbulence. I noticed what he was doing and asked if he would prefer to offset to one side of the track within the RNP limits. He said no; he would manually do it to maintain his mental acuity. As soon as I turned back; I noticed and notified the Captain that we were 500 FT below the minimum altitude for the next waypoint. He immediately climbed back to the correct altitude. As we approached the correct altitude; ATC asked us for verification of the altitude. No further comments were made by ATC concerning altitude. The Captain chose to fly the aircraft off the RNAV course and refuse my recommendation to use the offset function that would have continued to abide by altitude constraints. If the Captain had notified ATC of the wake turbulence; they may have allowed an alternate descent profile which would have required less monitoring. If he had verbalized his plan; I could have spoken up and made an alternate recommendation. There are some pilots whose complacency has become so ingrained that they become at odds with SOP's and choose to rationalize making up their own. Simply line checking on short hops doesn't catch the pilot who exhibits this behavior when they are tired or trying to expedite their last leg home. Line checks need to be done much more often and on a mix of long and short legs if they are to achieve any usefulness beyond checking a regulatory box.

Data retrieved from NASA's ASRS site as of April 2012 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.