Mode C malfunction. Controller requested air carrier crew to turn it off.

Attributes
ACN	129892
Time
Date	198911
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ztl
State Reference	GA
Altitude	msl bound lower : 14000 msl bound upper : 14000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : ztl artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 14000
ASRS Report	129892
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 8500
ASRS Report	129893
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Mode C error. Callback conversation with reporter revealed the following: reporter states altitude correct, but mode C readout was incorrect. Controller requested crew to turn off mode C. At arrival mode C functioned properly. Reporter did not report malfunction. Decided better protect himself with this report. His captain felt no need to submit a report, so the reporter sent a captain's report. No address or phone # included for return of identify strip.

Original NASA ASRS Text

Title: MODE C MALFUNCTION. CTLR REQUESTED ACR CREW TO TURN IT OFF.

Narrative: MODE C ERROR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATES ALT CORRECT, BUT MODE C READOUT WAS INCORRECT. CTLR REQUESTED CREW TO TURN OFF MODE C. AT ARR MODE C FUNCTIONED PROPERLY. RPTR DID NOT RPT MALFUNCTION. DECIDED BETTER PROTECT HIMSELF WITH THIS RPT. HIS CAPT FELT NO NEED TO SUBMIT A RPT, SO THE RPTR SENT A CAPT'S RPT. NO ADDRESS OR PHONE # INCLUDED FOR RETURN OF IDENT STRIP.

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.