<< >> NASA ASRS Report 551136, May 2002

A B737-300 was dispatched in non compliance with captain's and first officer's altimeters exceeding allowable maintenance manual split limits.

Attributes
ACN	551136
Time
Date	200205
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zzzz.artcc
State Reference	US
Altitude	msl single value : 37000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tower : fmn.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Qualification	technician : powerplant technician : fcc technician : airframe
Experience	maintenance avionics : 34 maintenance technician : 34
ASRS Report	551136
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : critical maintenance problem : improper documentation maintenance problem : improper maintenance non adherence : far non adherence : published procedure
Independent Detector	aircraft equipment other aircraft equipment : #1 #2 altimeters and standby ind other flight crewa other flight crewb
Resolutory Action	none taken : detected after the fact other
Consequence	other
Factors
Maintenance	contributing factor : schedule pressure performance deficiency : fault isolation performance deficiency : non compliance with legal requirements performance deficiency : logbook entry
Supplementary
Problem Areas	Aircraft Company Maintenance Human Performance
Primary Problem	Maintenance Human Performance

Narrative:

On may/wed/02, aircraft X came in with a write-up that there was a 140 ft split between the captain's and first officer's altimeters at FL370. I called maintenance control and asked if the split chart for this aircraft was available. I recall that he consulted the chart and told me that you were allowed a 220 ft split between #1 and #2 altimeters at FL350. Since I had 140 ft at FL370, I decided this was well within limits and signed off the write-up accordingly. The chart actually states that the limit is 95 ft and the 140 ft split was well out of limits. Clearly, I should have consulted the chart myself.

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Original NASA ASRS Text

Title: A B737-300 WAS DISPATCHED IN NON COMPLIANCE WITH CAPT'S AND FO'S ALTIMETERS EXCEEDING ALLOWABLE MAINT MANUAL SPLIT LIMITS.

Narrative: ON MAY/WED/02, ACFT X CAME IN WITH A WRITE-UP THAT THERE WAS A 140 FT SPLIT BTWN THE CAPT'S AND FO'S ALTIMETERS AT FL370. I CALLED MAINT CTL AND ASKED IF THE SPLIT CHART FOR THIS ACFT WAS AVAILABLE. I RECALL THAT HE CONSULTED THE CHART AND TOLD ME THAT YOU WERE ALLOWED A 220 FT SPLIT BTWN #1 AND #2 ALTIMETERS AT FL350. SINCE I HAD 140 FT AT FL370, I DECIDED THIS WAS WELL WITHIN LIMITS AND SIGNED OFF THE WRITE-UP ACCORDINGLY. THE CHART ACTUALLY STATES THAT THE LIMIT IS 95 FT AND THE 140 FT SPLIT WAS WELL OUT OF LIMITS. CLRLY, I SHOULD HAVE CONSULTED THE CHART MYSELF.

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.