Flight crew set wrong altimeter setting descended below assigned altitude.

Attributes
ACN	287165
Time
Date	199411
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lrp
State Reference	PA
Altitude	msl bound lower : 16000 msl bound upper : 16000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : zdc
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 10500 flight time type : 1500
ASRS Report	287165
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X descending from FL240 to 17000 ft MSL and the altimeter was very low, 29.34. We were deviating around thunderstorm, in the clear, passing 18500 ft when we were given a frequency change and encountered moderate turbulence. I called out the altimeter setting, noticed that the change in altimeter coupled with our descent rate had suddenly put us 500 ft above level off altitude. I called '500 ft above' and then changed frequency and started to check in with ZDC. It was then I noticed my altimeter at 16000 ft MSL and the captain's was at 17000 ft. He had misset his altimeter to 30.34 and indicated 17000 ft. I immediately told him to climb. I checked in stating that we were climbing back up to 17000 ft. ATC asked what our altitude was and I again said we were returning to 17000 ft. Nothing, no other targets were on the TCASII and ZDC asked no questions, nor made any further remarks about our altitude. A combination of extremely low altimeter settings, radio frequency change, moderate turbulence, and my not checking the correct altimeter setting lead to a smooth, but low level off, but the altitude deviation lasted only 30-45 seconds and we discovered the error before ATC was required to make any corrections.

Original NASA ASRS Text

Title: FLC SET WRONG ALTIMETER SETTING DSNDED BELOW ASSIGNED ALT.

Narrative: ACR X DSNDING FROM FL240 TO 17000 FT MSL AND THE ALTIMETER WAS VERY LOW, 29.34. WE WERE DEVIATING AROUND TSTM, IN THE CLR, PASSING 18500 FT WHEN WE WERE GIVEN A FREQ CHANGE AND ENCOUNTERED MODERATE TURB. I CALLED OUT THE ALTIMETER SETTING, NOTICED THAT THE CHANGE IN ALTIMETER COUPLED WITH OUR DSCNT RATE HAD SUDDENLY PUT US 500 FT ABOVE LEVEL OFF ALT. I CALLED '500 FT ABOVE' AND THEN CHANGED FREQ AND STARTED TO CHK IN WITH ZDC. IT WAS THEN I NOTICED MY ALTIMETER AT 16000 FT MSL AND THE CAPT'S WAS AT 17000 FT. HE HAD MISSET HIS ALTIMETER TO 30.34 AND INDICATED 17000 FT. I IMMEDIATELY TOLD HIM TO CLB. I CHKED IN STATING THAT WE WERE CLBING BACK UP TO 17000 FT. ATC ASKED WHAT OUR ALT WAS AND I AGAIN SAID WE WERE RETURNING TO 17000 FT. NOTHING, NO OTHER TARGETS WERE ON THE TCASII AND ZDC ASKED NO QUESTIONS, NOR MADE ANY FURTHER REMARKS ABOUT OUR ALT. A COMBINATION OF EXTREMELY LOW ALTIMETER SETTINGS, RADIO FREQ CHANGE, MODERATE TURB, AND MY NOT CHKING THE CORRECT ALTIMETER SETTING LEAD TO A SMOOTH, BUT LOW LEVEL OFF, BUT THE ALTDEV LASTED ONLY 30-45 SECONDS AND WE DISCOVERED THE ERROR BEFORE ATC WAS REQUIRED TO MAKE ANY CORRECTIONS.

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.