Widebody transport aircraft requested by ATC to secure mode C portion of transponder.

Attributes
ACN	294608
Time
Date	199501
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : lax
State Reference	CA
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute airway : lax
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 7600 flight time type : 1500
ASRS Report	294608
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe inflight encounter : weather other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : unable other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Instructed by ATC to cross fix at (and maintain) 11000 ft. Did so, and all cockpit altitude indicators showed 11000 ft. However, ATC showed us at 10000 ft and had us secure mode 'C' of transponder. No further problems. Contributing factor: experienced numerous static discharges from aircraft (st elmo's fire) during descent which caused minor electrical disturbances in cockpit. This may have affected the mode 'C' and thrown it off.

Original NASA ASRS Text

Title: WDB ACFT REQUESTED BY ATC TO SECURE MODE C PORTION OF XPONDER.

Narrative: INSTRUCTED BY ATC TO CROSS FIX AT (AND MAINTAIN) 11000 FT. DID SO, AND ALL COCKPIT ALT INDICATORS SHOWED 11000 FT. HOWEVER, ATC SHOWED US AT 10000 FT AND HAD US SECURE MODE 'C' OF XPONDER. NO FURTHER PROBS. CONTRIBUTING FACTOR: EXPERIENCED NUMEROUS STATIC DISCHARGES FROM ACFT (ST ELMO'S FIRE) DURING DSCNT WHICH CAUSED MINOR ELECTRICAL DISTURBANCES IN COCKPIT. THIS MAY HAVE AFFECTED THE MODE 'C' AND THROWN IT OFF.

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.