A319 with ZNY descends below assigned altitude because of pilot altimeter functional error.

Attributes
ACN	602490
Time
Date	200312
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : mvy.vor
State Reference	MA
Altitude	msl single value : 28000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zny.artcc tower : phl.tower
Operator	common carrier : air carrier
Make Model Name	A319
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 14000 flight time type : 7600
ASRS Report	602490
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance non adherence : published procedure
Independent Detector	atc equipment other atc equipment : radar other controllera other flight crewa
Resolutory Action	aircraft : automation overrode flight crew controller : issued new clearance controller : issued advisory flight crew : returned to assigned altitude flight crew : overrode automation
Supplementary
Problem Areas	Aircraft Environmental Factor Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Flight to bos, just entered radar contact with center, just north of flynn intersection. Received a descent to FL280 from FL350. Started descent, very rough ride and it had been all day. Long day with almost 8 hours scheduled. During descent, received new bos WX on ACARS. Bos altimeter setting was high 30.48. On the airbus, you can preset landing altimeter by pushing altitude/setting knob, then pulling it back to 'standard.' I did this, but when I pulled the knob to go back to standard, it remained at 30.48 and I didn't notice. As the aircraft leveled at FL280, the captain and I noticed the discrepancy and my mistake. I climbed back up to FL280. We got as low as FL274. ATC noticed also and gave us block FL270-FL280. There were no conflicts and ATC didn't seem concerned. We had reported moderate turbulence and chop. I shouldn't have preselected altitude setting. Now I will wait till transition altitude/level. The airbus system with the push/pull knob is not the best automation and will allow this error.

Original NASA ASRS Text

Title: A319 WITH ZNY DSNDS BELOW ASSIGNED ALT BECAUSE OF PLT ALTIMETER FUNCTIONAL ERROR.

Narrative: FLT TO BOS, JUST ENTERED RADAR CONTACT WITH CTR, JUST N OF FLYNN INTXN. RECEIVED A DSCNT TO FL280 FROM FL350. STARTED DSCNT, VERY ROUGH RIDE AND IT HAD BEEN ALL DAY. LONG DAY WITH ALMOST 8 HRS SCHEDULED. DURING DSCNT, RECEIVED NEW BOS WX ON ACARS. BOS ALTIMETER SETTING WAS HIGH 30.48. ON THE AIRBUS, YOU CAN PRESET LNDG ALTIMETER BY PUSHING ALT/SETTING KNOB, THEN PULLING IT BACK TO 'STANDARD.' I DID THIS, BUT WHEN I PULLED THE KNOB TO GO BACK TO STANDARD, IT REMAINED AT 30.48 AND I DIDN'T NOTICE. AS THE ACFT LEVELED AT FL280, THE CAPT AND I NOTICED THE DISCREPANCY AND MY MISTAKE. I CLBED BACK UP TO FL280. WE GOT AS LOW AS FL274. ATC NOTICED ALSO AND GAVE US BLOCK FL270-FL280. THERE WERE NO CONFLICTS AND ATC DIDN'T SEEM CONCERNED. WE HAD RPTED MODERATE TURB AND CHOP. I SHOULDN'T HAVE PRESELECTED ALT SETTING. NOW I WILL WAIT TILL TRANSITION ALT/LEVEL. THE AIRBUS SYS WITH THE PUSH/PULL KNOB IS NOT THE BEST AUTOMATION AND WILL ALLOW THIS ERROR.

Data retrieved from NASA's ASRS site as of July 2007 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.