Altimeter setting variation may have caused altitude discrepancy.

Attributes
ACN	294127
Time
Date	199501
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lrp
State Reference	PA
Altitude	msl bound lower : 16750 msl bound upper : 17000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	enroute airway : zny
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 130 flight time total : 10000 flight time type : 130
ASRS Report	294127
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 210 flight time total : 5000 flight time type : 210
ASRS Report	294129
Events
Anomaly	altitude deviation : excursion from assigned altitude altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Descent from FL200 to 17000 ft center gave altimeter 29.19. Apparently, leveled at 16750 ft. Called by center and reset level 17000 ft. Switched to approach and altimeter now 29.32. Differences in altimeter settings may lead to erroneous altitude. Vigilance necessary. Supplemental information from acn 294129: I was verifying iad ATIS and when I rejoined the crew I heard them discussing an altimeter discrepancy. Be alert when there are fast moving WX system for big differences in altimeter setting.

Original NASA ASRS Text

Title: ALTIMETER SETTING VARIATION MAY HAVE CAUSED ALT DISCREPANCY.

Narrative: DSCNT FROM FL200 TO 17000 FT CTR GAVE ALTIMETER 29.19. APPARENTLY, LEVELED AT 16750 FT. CALLED BY CTR AND RESET LEVEL 17000 FT. SWITCHED TO APCH AND ALTIMETER NOW 29.32. DIFFERENCES IN ALTIMETER SETTINGS MAY LEAD TO ERRONEOUS ALT. VIGILANCE NECESSARY. SUPPLEMENTAL INFO FROM ACN 294129: I WAS VERIFYING IAD ATIS AND WHEN I REJOINED THE CREW I HEARD THEM DISCUSSING AN ALTIMETER DISCREPANCY. BE ALERT WHEN THERE ARE FAST MOVING WX SYS FOR BIG DIFFERENCES IN ALTIMETER SETTING.

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.