Set millibars versus inches on the captain altimeter, resulting in off altitude 600 feet.

Attributes
ACN	82483
Time
Date	198802
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : bvl
State Reference	UT
Altitude	msl bound lower : 24000 msl bound upper : 24600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zlc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 70 flight time total : 16500 flight time type : 1000
ASRS Report	82483
Person 2
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : overshoot other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Altitude clearance was FL240. At 17500 ft I reset the captain's altimeter to 29.92 and verbally called '29.92' as per company procedures. Shortly after level off, center asked us to verify our altitude. It was then noticed that my (captain) altimeter read FL240, while the first officer's read FL246. Center immediately cleared us to climb to FL290 and we then continued our climb. The problem was caused by my setting 992 in the millibar window on the captain's altimeter by mistake, instead of 29.92 in the inches window. A contributing factor to this was the fact that this particular aircraft is a nonstandard variant in the company fleet. Among several differences is the captain's altimeter which has the millibar and in hg windows reversed from most of the rest of the fleet. (The usual position is MB-lower left, and in hg-lower right. This aircraft has millibars-lower right and in hg lower left). Also, the 'MB' and 'in hg' captions above the respective windows are missing on this particular altimeter. Standardization of instrument face presentations would help prevent this type of incident, I would think. We tend to do things from habit patterns instead of actually noticing details which may differ from the norm.

Original NASA ASRS Text

Title: SET MILLIBARS VERSUS INCHES ON THE CAPT ALTIMETER, RESULTING IN OFF ALT 600 FEET.

Narrative: ALTITUDE CLRNC WAS FL240. AT 17500 FT I RESET THE CAPT'S ALTIMETER TO 29.92 AND VERBALLY CALLED '29.92' AS PER COMPANY PROCEDURES. SHORTLY AFTER LEVEL OFF, CENTER ASKED US TO VERIFY OUR ALTITUDE. IT WAS THEN NOTICED THAT MY (CAPT) ALTIMETER READ FL240, WHILE THE FIRST OFFICER'S READ FL246. CENTER IMMEDIATELY CLRED US TO CLIMB TO FL290 AND WE THEN CONTINUED OUR CLIMB. THE PROBLEM WAS CAUSED BY MY SETTING 992 IN THE MILLIBAR WINDOW ON THE CAPTAIN'S ALTIMETER BY MISTAKE, INSTEAD OF 29.92 IN THE INCHES WINDOW. A CONTRIBUTING FACTOR TO THIS WAS THE FACT THAT THIS PARTICULAR ACFT IS A NONSTANDARD VARIANT IN THE COMPANY FLEET. AMONG SEVERAL DIFFERENCES IS THE CAPTAIN'S ALTIMETER WHICH HAS THE MILLIBAR AND IN HG WINDOWS REVERSED FROM MOST OF THE REST OF THE FLEET. (THE USUAL POSITION IS MB-LOWER LEFT, AND IN HG-LOWER RIGHT. THIS ACFT HAS MILLIBARS-LOWER RIGHT AND IN HG LOWER LEFT). ALSO, THE 'MB' AND 'IN HG' CAPTIONS ABOVE THE RESPECTIVE WINDOWS ARE MISSING ON THIS PARTICULAR ALTIMETER. STANDARDIZATION OF INSTRUMENT FACE PRESENTATIONS WOULD HELP PREVENT THIS TYPE OF INCIDENT, I WOULD THINK. WE TEND TO DO THINGS FROM HABIT PATTERNS INSTEAD OF ACTUALLY NOTICING DETAILS WHICH MAY DIFFER FROM THE NORM.

Data retrieved from NASA's ASRS site as of August 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.