Air carrier small transport flew 400' below assigned altitude.

Attributes
ACN	96515
Time
Date	198810
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : msp
State Reference	MN
Altitude	msl bound lower : 3600 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : msp
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	other
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 : 150 flight time total : 9000 flight time type : 1600
ASRS Report	96515
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : clearance other anomaly
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:

We were level at 4000' with a company altimeter of 30.22 qnh. We set and flew the company qnh below 10000'. Approach control asked us our altitude and we indicated 4000'. He told us that he was showing us 400' low at 3600'. He also informed us that the new qnh altimeter setting was 29.82. That was the difference between our 4000' reading and his 3600' reading. Callback conversation with reporter revealed following information. Reporter stated that the altitude error was a simple matter of not cross-checking the ATIS/ARTCC altimeter setting with that supplied by his company. If the difference had been noticed, they would have checked with ATC and if that had been impossible, they would have used the ATIS supplied altimeter setting.

Original NASA ASRS Text

Title: ACR SMT FLEW 400' BELOW ASSIGNED ALT.

Narrative: WE WERE LEVEL AT 4000' WITH A COMPANY ALTIMETER OF 30.22 QNH. WE SET AND FLEW THE COMPANY QNH BELOW 10000'. APCH CTL ASKED US OUR ALT AND WE INDICATED 4000'. HE TOLD US THAT HE WAS SHOWING US 400' LOW AT 3600'. HE ALSO INFORMED US THAT THE NEW QNH ALTIMETER SETTING WAS 29.82. THAT WAS THE DIFFERENCE BTWN OUR 4000' READING AND HIS 3600' READING. CALLBACK CONVERSATION WITH RPTR REVEALED FOLLOWING INFO. RPTR STATED THAT THE ALT ERROR WAS A SIMPLE MATTER OF NOT CROSS-CHKING THE ATIS/ARTCC ALTIMETER SETTING WITH THAT SUPPLIED BY HIS COMPANY. IF THE DIFFERENCE HAD BEEN NOTICED, THEY WOULD HAVE CHKED WITH ATC AND IF THAT HAD BEEN IMPOSSIBLE, THEY WOULD HAVE USED THE ATIS SUPPLIED ALTIMETER SETTING.

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.