Very low pressure set in the altimeter.

Attributes
ACN	290765
Time
Date	199412
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : anc
State Reference	AK
Altitude	msl bound lower : 18000 msl bound upper : 22000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zan
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 250 flight time total : 3000 flight time type : 1200
ASRS Report	290765
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot inflight encounter : weather non adherence : clearance non adherence : published procedure other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : became reoriented flight crew : returned to intended course or assigned course other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation
Situations
Airport	procedure or policy : unspecified

Narrative:

Anchorage altimeter 28.42. When passing through 18000 ft, captain called '29.92 set left' when in fact he set 28.92. I did the same. The back lighting in my altimeter was out and maintenance had installed post lights leaving a dark shadow over the area from 1-5 O'clock thus my meter was in the dark. I was careless in not double checking with a flashlight and glanced at captain's to 2ASSURE my accuracy, of course, this was wrong. 15-20 min later A222TC asks 'altitude?' we responded FL210. ATC informs 'check altimeter we show 220.' after which ATC started using the prefix 'low' when giving altimeter settings. No conflict with other traffic. Good lesson.

Original NASA ASRS Text

Title: VERY LOW PRESSURE SET IN THE ALTIMETER.

Narrative: ANCHORAGE ALTIMETER 28.42. WHEN PASSING THROUGH 18000 FT, CAPT CALLED '29.92 SET L' WHEN IN FACT HE SET 28.92. I DID THE SAME. THE BACK LIGHTING IN MY ALTIMETER WAS OUT AND MAINT HAD INSTALLED POST LIGHTS LEAVING A DARK SHADOW OVER THE AREA FROM 1-5 O'CLOCK THUS MY METER WAS IN THE DARK. I WAS CARELESS IN NOT DOUBLE CHKING WITH A FLASHLIGHT AND GLANCED AT CAPT'S TO 2ASSURE MY ACCURACY, OF COURSE, THIS WAS WRONG. 15-20 MIN LATER A222TC ASKS 'ALT?' WE RESPONDED FL210. ATC INFORMS 'CHK ALTIMETER WE SHOW 220.' AFTER WHICH ATC STARTED USING THE PREFIX 'LOW' WHEN GIVING ALTIMETER SETTINGS. NO CONFLICT WITH OTHER TFC. GOOD LESSON.

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.